Directory of Open Access Journals (Sweden)
Šulić D.M.
2014-01-01
Full Text Available Very Low Frequency (VLF and Low Frequency (LF signal perturbations were examined to study ionospheric disturbances induced by solar X-ray flares in order to understand processes involved in propagation of VLF/LF radio signals over short paths and to estimate specific characteristics of each short path. The receiver at the Belgrade station is constantly monitoring the amplitude and phase of a coherent and subionospherically propagating LF signal operated in Sicily NSC at 45.90 kHz, and a VLF signal operated in Isola di Tavolara ICV at 20.27 kHz, with the great circle distances of 953 km and 976 km, respectively. A significant number of similarities between these short paths is a direct result of both transmitters and the receiver’s geographic location. The main difference is in transmitter frequencies. From July 2008 to February 2014 there were about 200 events that were chosen for further examination. All selected examples showed that the amplitude and phase of VLF and LF signals were perturbed by solar X-ray flares occurrence. This six-year period covers both minimum and maximum of solar activity. Simultaneous measurement of amplitude and phase of the VLF/LF signals during a solar flare occurrence was applied to evaluate the electron density profile versus altitude, to carry out the function of time over the middle Europe. [Projekat Ministarstva nauke Republike Srbije, br. 176002 i br. III4402
Study of Ionospheric Perturbations in D-Layer Using Awesome VLF Receiver Data at Tashkent Station
Ahmedov, Bobomurat
2012-07-01
One VLF receiver and two SuperSID receivers were provided to Uzbekistan IHY cite by Stanford University and are operating in Tashkent, under the International Heliophysical Year (IHY). The results obtained at Tashkent IHY station are applied to earthquake electromagnetic precursors, lightning, and solar flares and to ionospheric disturbances originating from gamma ray flares of Soft Gamma-Ray Repeaters connected with evolution of strongly magnetized neutron stars believed as magnetars. Regular monitoring of the D-layer of ionosphere over Central Asia territory has been performed on the permanent basis. Few Solar flare events are observed during February in 2010-2011 years and the analysis showed that there is simultaneous correlation between the times of change of amplitude of the waves and the Solar flares. Features of the lightning discharge generated by radio atmospherics are studied and its effectiveness in D-region ionosphere diagnostics is explained. Assuming that earthquakes (EQs) can be preceded by the electromagnetic signals in the VLF bands detectable from ground-based measurements we have studied VLF amplitude anomalies related to the earthquakes occurred in 2009-2010 years with magnitude more than 5 on the path way from the VLF transmitters to the Tashkent station. For analysing narrowband data we have used the Nighttime Fluctuation (NF) method paying attention to the data obtained during the local nighttime (18:00 LT-06:00 LT). The amplitude data are analysed only for the reason that perturbations are identified more clearly in the amplitude data than in phase data. The mean nighttime amplitude (or trend) and normalized trend are found to increase significantly before the EQ with the same tendency as the NF and normalized NF. The obtained results have revealed a fine agreement with VLF amplitude anomalies observed in Tashkent VLF station during the strong earthquakes occurred on the path way from the transmitters to the receiver. Some of the initial
Tilt - ellips and rho - phase modelling of VLF EM and VLF R in Candi Umbul Magelang
Affanti, Adella Putri; Niasari, Sintia Windhi
2017-07-01
A research for geothermal energy is increased due to the need of green energy. The presence of geothermal manifestations indicate the existence of geothermal system. One of the geothermal manifestations is warm spring. CandiUmbul area which located in Telomoyo, Magelang has warm spring as the geothermal manifestation. Very Low Frequency (VLF) is one of geophysical method that can be used to map the subsurface in Candi Umbul, Telomoyo. VLF is a method using electromagnetic field that powered and transferred by the transmitter. The receiver read the electromagnetic signal which induce the rock and give information about the conductivity as the physical property measurred. In this research, after collecting and processing data, we modeled tilt-ellips data of VLF-EM and rho-phase data of VLF-R to explain the geothermal system of Candi Umbul. Both VLF-EM and VLF-R model were correlated for the interpretation. The model showed an anomalous conductive feature beneath the research area. The result of this research showed that the anomaly is oriented in NW-SE direction. This direction is assumed as a fluid path way of Candi Umbul which became the outflow of Telomoyo geothermal system. To prove the early deduction this research is still on going.
More evidence for a one-to-one correlation between Sprites and Early VLF perturbations
DEFF Research Database (Denmark)
Haldoupis, C.; Amvrosiadi, N.; Cotts, B. R. T.;
2010-01-01
Past studies have shown a correlation between sprites and early VLF perturbations, but the reported correlation varies widely from ∼50% to 100%. The present study resolves these large discrepancies by analyzing several case studies of sprite and narrowband VLF observations, in which multiple...... for this option to be resolved we need more studies using highly sensitive optical systems capable of detecting weaker sprites, sprite halos and elves....
Optimizing an ELF/VLF Phased Array at HAARP
Fujimaru, S.; Moore, R. C.
2013-12-01
The goal of this study is to maximize the amplitude of 1-5 kHz ELF/VLF waves generated by ionospheric HF heating and measured at a ground-based ELF/VLF receiver. The optimization makes use of experimental observations performed during ELF/VLF wave generation experiments at the High-frequency Active Auroral Research Program (HAARP) Observatory in Gakona, Alaska. During these experiments, the amplitude, phase, and propagation delay of the ELF/VLF waves were carefully measured. The HF beam was aimed at 15 degrees zenith angle in 8 different azimuthal directions, equally spaced in a circle, while broadcasting a 3.25 MHz (X-mode) signal that was amplitude modulated (square wave) with a linear frequency-time chirp between 1 and 5 kHz. The experimental observations are used to provide reference amplitudes, phases, and propagation delays for ELF/VLF waves generated at these specific locations. The presented optimization accounts for the trade-off between duty cycle, heated area, and the distributed nature of the source region in order to construct a "most efficient" phased array. The amplitudes and phases generated by modulated heating at each location are combined in post-processing to find an optimal combination of duty cycle, heating location, and heating order.
Subionospehric VLF perturbations of red sprites: 3D FDTD modeling and experimental results
Iwamoto, M.; Hobara, Y.; Ohta, K.; Minatohara, T.; Otsuyama, T.; Hayakawa, M.
2012-04-01
Majority of red sprites occurs in association with large positive cloud to ground discharges. Although the red sprite consists of highly ionized structure, physical properties of the ionization columns such as electron density and spatial extent have not understood well. In this paper 3D finite-difference time-domain (FDTD) method carried out to compute the subionospheric VLF signal perturbations due to the sprite ionization columns. Spatial scales of columns are determined by the sprite images obtained from our optical observations during winter lightning activities over the sea of Japan. Numerical results indicate that the multiple sprites generate the complicated scattering pattern of the VLF transmitter waves depending on special orientation and extent of sprite ionization columns. Spatial dependence of the scattered amplitude are compared with those from the experimental results of VLF observation network.
Haldoupis, Christos; Cohen, Morris; Arnone, Enrico; Cotts, Benjamin; Dietrich, Stefano
2013-08-01
Subionospheric VLF recordings are investigated in relation with intense cloud-to-ground (CG) lightning data. Lightning impacts the lower ionosphere via heating and ionization changes which produce VLF signal perturbations known as early VLF events. Typically, early events recover in about 100 s, but a small subclass does not recover for many minutes, known as long-recovery early events (LORE). In this study, we identify LORE as a distinct category of early VLF events, whose signature may occur either on its own or alongside the short-lived typical early VLF event. Since LORE onsets coincide with powerful lightning strokes of either polarity (±), we infer that they are due to long-lasting ionization changes in the uppermost D region ionosphere caused by electromagnetic pulses emitted by strong ± CG lightning peak currents of typically > 250 kA, which are also known to generate elves. The LORE perturbations are detected when the discharge is located within ~250 km from the great circle path of a VLF transmitter-receiver link. The probability of occurrence increases with stroke intensity and approaches unity for discharges with peak currents ≥ ~300 kA. LOREs are nighttime phenomena that occur preferentially, at least in the present regional data set, during winter when strong ± CG discharges are more frequent and intense. The evidence suggests LORE as a distinct signature representing the VLF fingerprint of elves, a fact which, although was predicted by theory, it escaped identification in the long-going VLF research of lightning effects in the lower ionosphere.
Kumar, S.; Kumar, A.
2015-12-01
Sub-ionospheric VLF signals from the NWC (19.8 kHz), NPM (21.4 kHz) and NLK (24.8 kHz) MSK VLF transmitters are monitored at Suva, Fiji, with a time resolution of 0.1s using GPS based timing and SoftPAL VLF system. Here one minute averaged amplitude and phase data have been used for analysis. We present perturbations in VLF propagation and D-region changes associated with 13 November 2012 total solar eclipse (SE) and 9-10 May 2013 annular SE using VLF observations at Suva, Fiji. During 13-14 November 2012 total SE, the totality shadow intercepted NWC-Suva path and NWC signal amplitude and phase decreased by about 0.70 dB and 23°, respectively. NPM signal amplitude during 9-10 May 2013 SE decreased by about 2.0 dB. The amplitude perturbation of ~1.8 dB on NLK signal was measured from the unperturbed level associated with 9-10 May 2013 SE. The decrease in the amplitude at the site can be understood in terms of destructive interference of modes converted at the discontinuity created by the eclipse intercepting the different Transmitter-receiver great circle paths (TRGCPs) and changes in the propagation conditions along TRGCPs. The decrease in the amplitude and phase of NWC signal for 13-14 November 2012 SE has been modeled using Long Wave Propagation Capability code to estimate the changes in D-region reflection height (H') and sharpness factor (β) which shows that H' and β were increased by 0.95 km and 0.01 km-1, respectively. The phase changes on NWC signal associated with 9-10 May 2013 SE have been used to estimate the recombination coefficient value, for 75 km height where electron density reduction due to SE was about 40%. The changes in the D-region parameters and the electron density are due to sudden decrease of the photo-ionization creating nighttime like conditions in the D-region ionosphere.
Titova, E. E.; Demekhov, A. G.; Mochalov, A. A.; Gvozdevsky, B. B.; Mogilevsky, M. M.; Parrot, M.
2015-08-01
In the studies of the data received from DEMETER (orbit altitude above the Earth is about 700 km), we detected for the first time electromagnetic perturbations, which are due to the ionospheric modification by HAARP, a high-power high-frequency transmitter, simultaneously in the extremely low-frequency (ELF, below 1200 Hz) and very low-frequency (VLF, below 20 kHz) ranges. Of the thirteen analyzed flybys of the satellite above the heated area, the ELF/VLF signals were detected in three cases in the daytime (LT = 11-12 h), when the minimum distance between the geomagnetic projections of the satellite and the heated area center on the Earth's surface did not exceed 31 km. During the nighttime flybys, the ELF/VLF perturbations were not detected. The size of the perturbed region was about 100 km. The amplitude, spectrum, and polarization of the ELF perturbations were analyzed, and their comparison with the characteristics of natural ELF noise above the HAARP transmitter was performed. In particular, it was shown that in the daytime the ELF perturbation amplitude above the heated area can exceed by a factor of 3 to 8 the amplitude of natural ELF noise. The absence of the nighttime records of artificial ELF/VLF perturbations above the heated area can be due to both the lower frequency of the heating signal, at which the heating occurs in the lower ionosphere, and the higher level of natural noise. The spectrum of the VLF signals related to the HAARP transmitter operation had two peaks at frequencies of 8 to 10 kHz and 15 to 18 kHz, which are close to the first and second harmonics of the lower-hybrid resonance in the heated area. The effect of the whistler wave propagation near the lower-hybrid resonance region on the perturbation spectrum recorded in the upper ionosphere for these signals has been demonstrated. In particular, some of the spectrum features can be explained by assuming that the VLF signals propagate in quasiresonance, rather than quasilongitudinal, regime
VLF signal perturbation due to the total solar eclipse of March 2015
Nait Amor, Samir; Bouderba, Yasmina
2016-07-01
On March 20 2015 a total Solar eclipse occurred and covered several regions in north America, Greenland, west of Europe and north Africa with different occultation rates. During this event, many VLF paths recorded at Algiers receiver were perturbed. In this contribution, we will present a qualitative analysis of two paths (GQD and DHO) which were disturbed differently since the occultation rate at the transmitter locations was different. In addition to the qualitative study, we determined the newly formed reference height and β values at different times during the eclipse transit. From these determined parameters the time profile of the electron density is then deduced. The results showed that the new reference height, β and the electron density are different from one transmitter analysis to other due to the occultation rate difference.
Solar flare induced D-region ionospheric perturbations evaluated from VLF measurements
Singh, Ashutosh K.; Singh, A. K.; Singh, Rajesh; Singh, R. P.
2014-03-01
The results of very low frequency (VLF) wave amplitude measurements carried out at the low latitude station Varanasi (geom. lat. 14∘55'N, long. 154∘E), India during solar flares are presented for the first time. The VLF waves (19.8 kHz) transmitted from the NWC-transmitter, Australia propagated in the Earth-ionosphere waveguide to long distances and were recorded at Varanasi. Data are analyzed and the reflection height H' and the sharpness factor β are evaluated. It is found that the reflection height decreases whereas sharpness factor increases with the increase of solar flare power. The H' is found to be higher and β smaller at low latitudes than the corresponding values at mid and high latitudes. The sunspot numbers were low during the considered period 2011-2012, being the rising phase of solar cycle 24 and as a result cosmic rays may impact the D-region ionosphere. The increased ionization from the flare lowers the effective reflecting height, H', of the D-region roughly in proportion to the logarithm of the X-ray flare intensity from a typical mid-day unperturbed value of about 71-72 km down to about 65 km for an X class flare. The sharpness ( β) of the lower edge of the D-region is also significantly increased by the flare but reaches a clear saturation value of about 0.48 km-1 for flares of magnitude greater than about X1 class.
Kawano, Tomoki; Hobara, Yasuhide; Tatsuta, Kenshin
2016-04-01
In this paper we perform the statistical analysis to study the response of the lower ionosphere prior to major seismic activities focusing on different earthquake types. The lower ionospheric condition is represented by daily averaged nighttime electric amplitude from various VLF/LF transmitter signals received in Japan by UEC team. Six-year record of ionospheric conditions are used for our data analysis. Over 200 earthquakes occurred around the VLF/LF transmitter - receiver paths during the time period of analysis. They are characterized into three different groups based on the Centroid-Moment-Tensor (CMT) solution such as reverse fault type, normal fault type and stress slip type. The ionospheric anomaly is identified by a large change (2 sigma criteria) in the VLF/LF daily nighttime amplitude. As a result, the highest occurrence rate of ionospheric anomaly is obtained for reverse type fault for both sea and ground earthquakes. The occurrence rate for these earthquakes are statistically significant because they are significantly large in comparison to those calculated from random test. The difference of occurrence rate of the ionospheric perturbations may indicate the coupling efficiency of seismic activity into the overlaying ionosphere originated from the pre-seismic condition of earth's crust. We also perform the trend-based earthquake prediction. Alarm threshold in nighttime VLF amplitude with -3.5 sigma is found to be most effective and significant for the earthquake prediction by using lower ionospheric perturbations.
Directory of Open Access Journals (Sweden)
M. Hayakawa
2011-02-01
Full Text Available Ionospheric perturbations in possible association with the 2010 Haiti earthquake occurred on 12 January 2010 (with a magnitude of 7.0 and depth of 10 km are investigated on the basis of subionospheric propagation data from the NAA transmitter on the east coast of the USA to a VLF receiving station in Peru. The local nighttime VLF amplitude data are extensively investigated during the period from the beginning of October 2009 to the end of March 2010, in which the trend (nighttime average amplitude, dispersion and nighttime fluctuation are analysed. It is found that a clear precursory ionosphere perturbation is detected just around New Years day of 2010, about 12 days before the main shock, which is characterised by the simultaneous decrease in the trend and the increases in dispersion and nighttime fluctuation. An additional finding might be the presence of the effect of the Earth's tide one and two months before the main shock, which can only be seen for a huge EQ.
Study of Ionospheric Perturbations in D-Layer Using VLF Receiver at Tashkent IHY Station
Ahmedov, Bobomurat
2016-07-01
Tashkent International Heliophysical Year (IHY) station is a member of Atmospheric Weather Electromagnetic System for Observation, Modeling and Education (AWESOME) network being operated globally to study the ionosphere and the magnetosphere with the help of electromagnetic waves in Very Low Frequency (VLF) band. Regular monitoring of the D- and F-layers of ionosphere over Central Asia territory is being performed on the permanent basis starting year 2008 when one VLF receiver and two SuperSID receivers were provided to Uzbekistan IHY cite by Stanford University. The results obtained at Tashkent IHY station are applied to earthquake electromagnetic precursors, lightning, and Solar flares and to ionospheric disturbances originating from gamma ray flares of Soft Gamma-Ray Repeaters connected with evolution of strongly magnetized neutron stars believed as magnetars. Regular monitoring of the D-layer of ionosphere over Central Asia territory has been performed on the permanent basis. Several Solar events are observed and the analysis has shown that there is simultaneous correlation between the times of change of amplitude of the waves and the Solar flares. Features of the lightning discharge generated by radio atmospherics are studied and its effectiveness in D-region ionosphere diagnostics is examined.
Physicochemical Perturbations of Phase Equilibriums
Dobruskin, Vladimir Kh
2010-01-01
The alternative approach to the displacement of gas/liquid equilibrium is developed on the basis of the Clapeyron equation. The phase transition in the system with well-established properties is taken as a reference process to search for the parameters of phase transition in the perturbed equilibrium system. The main equation, derived in the framework of both classical thermodynamics and statistical mechanics, establishes a correlation between variations of enthalpies of evaporation, \\Delta (\\Delta H), which is induced by perturbations, and the equilibrium vapor pressures. The dissolution of a solute, changing the surface shape, and the effect of the external field of adsorbents are considered as the perturbing actions on the liquid phase. The model provides the unified method for studying (1) solutions, (2) membrane separations (3) surface phenomena, and (4) effect of the adsorption field; it leads to the useful relations between \\Delta (\\Delta H), on the one hand, and the osmotic pressures, the Donnan poten...
Directory of Open Access Journals (Sweden)
Maria Solovieva
2015-11-01
Full Text Available Data from the European network of very low/ low frequency (VLF/LF receivers has been used to study the response of the lower ionosphere to the earthquake of magnitude 5.5 in Vrancea area on November 22, 2014. Negative amplitude anomalies have been observed during 3 days before the earthquake and two days after, on the LF (45.9 kHz signal passed above the seismic area. No perturbations have been found for the same signal in control paths during this period. Other possible influences both from above and below which can produce perturbations in the ionosphere have been taken into consideration.
Directory of Open Access Journals (Sweden)
F. Muto
2009-07-01
Full Text Available As the target earthquake we have taken a huge earthquake (EQ named Miyagi-oki earthquake on 16 August 2005 (with magnitude of 7.2 and we have analyzed the 4 month period including the date of this EQ. In addition to our previous analysis on the nighttime average amplitude (trend and nighttime fluctuation, we have proposed the use of fluctuation power spectra in the frequency rage of atmospheric gravity waves (period=10 min to 100 min as a third parameter of subionospheric VLF/LF propagation characteristics. Then it is found that this third parameter would be of additional importance in confirming the presence of seismo-ionospheric perturbations. Finally, we have discovered an important role of lunar tidal effect in the VLF/LF data, which appears one and two months before this large EQ.
Cosmological perturbations from an inhomogeneous phase transition
Energy Technology Data Exchange (ETDEWEB)
Matsuda, Tomohiro, E-mail: matsuda@sit.ac.j [Laboratory of Physics, Saitama Institute of Technology, Fusaiji, Okabe-machi, Saitama 369-0293 (Japan)
2009-07-21
A mechanism for generating metric perturbations in inflationary models is considered. Long-wavelength inhomogeneities of light scalar fields in a decoupled sector may give rise to superhorizon fluctuations of couplings and masses in the low-energy effective action. Cosmological phase transitions may then occur that are not simultaneous in space, but occur with time lags in different Hubble patches that arise from the long-wavelength inhomogeneities. Here an interesting model in which cosmological perturbations may be created at the electroweak phase transition is considered. The results show that phase transitions may be a generic source of non-Gaussianity.
Barr, R.; Jones, D. L.; Rodger, C. J.
2000-11-01
This review covers developments in ELF and VLF radio-wave propagation research over the last 50 years of the Journal of Atmospheric and Solar-Terrestrial Physics. A review of such a large field, over such a long period, cannot be fully comprehensive and the authors have therefore covered important areas which have they themselves have found interesting. The survey begins with a review of work on natural and man made sources of ELF and VLF radiation. This is followed by sections on experimental and theoretical studies of unperturbed (ambient) ELF and VLF radio propagation. Schumann resonance research, which is currently undergoing a renaissance, is then reviewed. A review of research into transient perturbations of ELF and VLF propagation follows, extending from the early work on nuclear explosions up to the current work on sprites. The review concludes with a brief summary of the VLF navigation systems of the USSR and USA, (Alpha and Omega) whose development and life-span covered most of the last 50 years.
Study of the effect of solar flares on VLF signals during D-layer preparation or disappearance time
Ray, Suman; Chakrabarti, Sandip Kumar; Palit, Sourav
2016-07-01
"Very Low Frequency" (VLF) is one of the bands of the Radio waves having frequency 3-30 KHz, which propagates through the Earth-ionosphere wave-guide. In relation to propagation of radio waves through ionosphere, low mass and high mobility cause electrons to play a vital role. Electrons are not distributed uniformly in the ionosphere and depending on this factor, ionosphere has different layers namely D, E and F. Different ionospheric layers generally exist during day and night time. During day-time when the main source of the ionization of the ionosphere is Sun, the lower most layer of ionosphere is D-layer. But during the night-time when Sun is absent and cosmic ray is the main source of the ionization of the ionosphere, this D-layer disappears and E-layer becomes the lower most region of the ionosphere. Normally, patterns of VLF signal depend on regular solar flux variations. However, during solar flares extra energetic particles are released from Sun, which makes the changes in the ionization of the ionosphere and these changes can perturb VLF signal amplitude. Usually if a solar flare occurs during any time of day, it only affects the amplitude and phase of the VLF signals. But in the present work, we found the if the flare occurs during D-layer preparation / disappearance time, then it will not only affect to amplitude and phase of the VLF signals but also to terminator times of VLF signals. We have observed that the sun set terminator time of the VLF signals shifted towards night time due to the effect of a M-class solar flare which occurred during the D-layer disappearance time. The shift is so high that it crossed 5σ level. We are now trying to a make model using the ion-chemistry and LWPC code to explain this observed effect.
Directory of Open Access Journals (Sweden)
Ammar Ahmed
2016-12-01
Full Text Available Ionosphere undergoes permanently solar flares that quickly change its properties inducing sometime unwanted effects. These changes, or events, are known as Sudden Ionospheric Disturbances (SIDs and the knowledge of their magnitude may be of great interest to anticipate probable damages. Currently, there does not exist any classification of these ionospheric changes based on their amplitude due to the wide variability of its responses. The only way to surmise their importance is to study them indirectly, throughout the classification of the X-ray flux intensity recorded by satellites. An attempt of classification based on their duration was proposed by the American Association of Variable Star Observers (AAVSO but it is not very accurate because SID’s duration is measured directly from the raw signal of the Very Low Frequency (VLF signal and/or the Low Frequency (LF signal. The aim of this work is to investigate, through a set of simple mathematical techniques applied to VLF/LF signals recorded by ground based receivers, the best method to estimate SIDs durations and then propose a new classification based on these durations.
Comparative Analysis of VLF Signal Variation along Trajectory Induced by X-ray Solar Flares
Indian Academy of Sciences (India)
A. Kolarski; D. Grubor
2015-12-01
Comparative qualitative analysis of amplitude and phase delay variations was carried out along the trajectory of GQD/22.1 kHz and NAA/24.0 kHz VLF signal traces, propagating from Skelton (UK) and Maine (USA) toward Belgrade, induced by four isolated solar X-ray flare events occurred during the period from September 2005 to December 2006. For monitoring, recording and for storage of VLF data at the Institute of Physics in Belgrade, Serbia, the AbsPAL system was used. For modeling purposes of propagating conditions along GQD and NAA signal propagation paths, LWPCv21 program code was used. Occurred solar flare events induced lower ionosphere electron density height profile changes, causing perturbations in VLF wave propagation within Earth-ionosphere waveguides. As analyzed VLF signals characterize by different propagation parameters along trajectories from their transmitters to the Belgrade receiver site, their propagation is affected in different ways for different solar flare events and also for the same solar flare events.
Comparative Analysis of VLF Signal Variation along Trajectory Induced by X-ray Solar Flares
Kolarski, A.; Grubor, D.
2015-12-01
Comparative qualitative analysis of amplitude and phase delay variations was carried out along the trajectory of GQD/22.1 kHz and NAA/24.0 kHz VLF signal traces, propagating from Skelton (UK) and Maine (USA) toward Belgrade, induced by four isolated solar X-ray flare events occurred during the period from September 2005 to December 2006. For monitoring, recording and for storage of VLF data at the Institute of Physics in Belgrade, Serbia, the AbsPAL system was used. For modeling purposes of propagating conditions along GQD and NAA signal propagation paths, LWPCv21 program code was used. Occurred solar flare events induced lower ionosphere electron density height profile changes, causing perturbations in VLF wave propagation within Earth-ionosphere waveguides. As analyzed VLF signals characterize by different propagation parameters along trajectories from their transmitters to the Belgrade receiver site, their propagation is affected in different ways for different solar flare events and also for the same solar flare events.
Stability of the Spin Glass Phase under Perturbations
Contucci, Pierluigi; Giberti, Claudio
2011-01-01
We introduce and prove a new stability property of the quenched equilibrium state for the spin glass phase and show that it implies the whole set of Ghirlanda-Guerra identities. The new stability deals with perturbations which reproduces both thermal and disorder fluctuations, thus generalizing the standard stochastic stability of disordered systems.
The impact of PMSE and NLC particles on VLF propagation
Directory of Open Access Journals (Sweden)
D. Nunn
2004-04-01
Full Text Available PMSE or Polar Mesosphere Summer Echoes are a well-known phenomenon in the summer northern polar regions, in which anomalous VHF/UHF radar echoes are returned from heights ~85km. Noctilucent clouds and electron density biteouts are two phenomena that sometimes occur together with PMSE. Electron density biteouts are electron density depletion layers of up to 90%, which may be several kms thick. Using the NOSC Modefndr code based on Wait's modal theory for subionospheric propagation, we calculate the shifts in received VLF amplitude and phase that occur as a result of electron density biteouts. The code assumes a homogeneous background ionosphere and a homogeneous biteout layer along the Great Circle Path (GCP corridor, for transmitter receiver path lengths in the range of 500–6000km.
For profiles during the 10h about midnight and under quiet geomagnetic conditions, where the electron density at 85km would normally be less than 500el/cc, it was found that received signal perturbations were significant, of the order of 1–4dB and 5–40° of phase. Perturbation amplitudes increase roughly as the square root of frequency. At short range perturbations are rather erratic, but more consistent at large ranges, readily interpretable in terms of the shifts in excitation factor, attenuation factor and v/c ratios for Wait's modes. Under these conditions such shifts should be detectable by a well constituted experiment involving multiple paths and multiple frequencies in the north polar region in summer. It is anticipated that VLF propagation could be a valuable diagnostic for biteout/PMSE when electron density at 85km is under 500el/cc, under which circumstances PMSE are not directly detectable by VHF/UHF radars.
Key words. Electromagnetism (wave propagation – Ionosphere (polar ionosphere – Radioscience (ionospheric propagation
DEFF Research Database (Denmark)
NaitAmor, S.; AlAbdoadaim, M. A.; Cohen, M. B.
2010-01-01
Two Very Low Frequency (VLF) AWESOME remote sensing systems located at Algiers, Algeria (36.45°N, 3.28°E) and Sebha, Libya (27.02°N, 14.26°E) monitor VLF signal perturbations for evidence of ionospheric disturbances. During the EuroSprite-2007 campaign a number of Transient Luminous Events (TLEs...
Phase Wrapping of Epicyclic Perturbations in the Wobbly Galaxy
de la Vega, Alexander; Carlin, Jeffrey L; Chakrabarti, Sukanya; D'Onghia, Elena
2015-01-01
We use test-particle integrations to show that epicyclic motions excited by a pericentre passage of a dwarf galaxy could account for bulk vertical velocity streaming motions recently observed in the Galactic stellar disc near the Sun. We use fixed potential test-particle integrations to isolate the role of phase wrapping of epicyclic perturbations from bending and breathing waves or modes, which require self-gravity to oscillate. Perturbations from a fairly massive Sagittarius dwarf galaxy, $M_d \\sim 2.5 \\times 10^{10} M_\\odot$, are required to account for the sizescale of the observed streaming motions from its orbital pericentre approximately a Gyr ago. A previous passage of the dwarf through the Galactic disc approximately 2.2 Gyr ago (with a then more massive dwarf galaxy) is less effective. If phase wrapping of epicyclic perturbations is responsible for stellar streaming motions in the Galactic disc, then there should be variations in velocity gradients on sizescales of a few kpc in the vicinity of the S...
Eichelberger, Hans; Schwingenschuh, Konrad; Besser, B. P.; Prattes, Gustav; Aydogar; Wolbang, Daniel; Rozhnoi, Alexander; Solovieva, Maria; Biagi, Pier Francesco; Boudjada, Mohammed
2016-07-01
We focus on natural disturbances of the sub-ionospheric VLF waveguide in the time span 2009 to 2015 (sunspot cycle 24), i.e. variations in amplitude and phase measurements of the radio paths are considered. In particular we're investigating numerous solar flares (up to X-class), geomagnetic storms and substorms, therefore discuss how to discriminate natural from artificial variations between different transmitters and receivers. Meteorological effects could be important [1] and we estimate the possibility to detect the influence of lithospheric sources in the VLF radio links. As part of the VLF multistation network we're using the single receiver mid-latitude station in Graz, Austria. This facility receives up to 12 transmitter simultaneously (frequency range 10-50 kHz), has 20 sec temporal resolution, and is running continuously since 2009 [2]. We obtain the statistics relating VLF amplitude and phase fluctuations with C/M/X-class solar flares, and characterise night time fluctuations in connection with enhanced particle precipitation in the northern latitude path (Iceland transmitter). The statistics is important to improve the quality of seismo-electromagnetic studies. We conclude that for ionospheric perturbations (D-layer), e.g. solar flares, a reliable real time monitoring service can be established. Atmospheric and lithospheric variations are generally difficult to characterise, it's harder to distinguish between natural and man made signals, therefore - as a future outlook - complementary ground and satellite based measurements can deliver valuable additional information for environmental monitoring. References: [1] A. Rozhnoi et al.: Meteorological effects in the lower ionosphere as based on VLF/LF signal observations, Nat. Hazards Earth Syst. Sci., 14, 2671-2679, 2014. [2] K. Schwingenschuh et al.: The Graz seismo-electromagnetic VLF facility, Nat. Hazards Earth Syst. Sci., 11, 1121-1127, 2011.
VLF Science at Indian Centre for Space Physics
Chakrabarti, Sandip Kumar
2016-07-01
Indian Centre for Space Physics has been monitoring VLF signals from stations around the world at its laboratories at Kolkata and Sitapur (Ionospheric and Earthquake Research Centre) as well as at several places throughout India when in a campaign mode. We have been interested to study high energy events from space, such as solar flares and gamma ray bursts. We have made studies during multiple solar eclipses and most importantly made substantial progress in the problem of lithosphere-ionosphere coupling while understanding various types of anomalies prior to major earthquakes. Other effects such as AGWs and LEPs are being studied. We have experience of two antarctic expedition and obtained VLF data from both Maitri and Bharati stations of India, which revealed, among other things, how the signal attenuation can indicate the extent of ice mass in Antarctica. We have been able to reproduce various VLF perturbation events using Atmospheric Chemical evolution model coupled with LWPC code. For instance we have reproduced solar flare induced VLF amplitude perturbation pattern by completely ab initio calculation. We also targeted the inverse problem, namely, deduction of the injected radiation spectra from space from the VLF signal alone, thereby establishing that the Earth can be used as a gigantic detector. These interesting results would be presented in my review talk.
Directory of Open Access Journals (Sweden)
Govinda Sharma
2015-08-01
Full Text Available Seismo-ionospheric changes often affect the VLF waves resulting in possible changes in the terminator times and often lead to night time fluctuations. The Bardarbunga volcano which started on 2014 ended on the last days of February of 2015. In this paper we present the results of the VLF analysis of the first three months of 2015 using a signal of 37.50 KHz where an analysis on the sunset terminator time D-layer dissipation time daytime fluctuation and night time fluctuation of the VLF amplitude was done. We contrasted the values of these parameters for the first two months of 2015 where the volcano was active with third month of 2015 when the volcano had completely subsided. The Sunset terminator time and the daytime fluctuations in the VLF amplitude for the first two months showed no major anomalies. The anomaly in the D-layer disappearance time and night time fluctuation count reached its peak values for the volcanically active months.
Institute of Scientific and Technical Information of China (English)
ZHANG Ming-Jiang; FANG Jian-Hui; LU Kai
2009-01-01
Based on the concept of adiabatic invariant, the perturbation to Noether-Mei symmetry and adiabatic invariants for nonholonomic mechanical systems in phase space are studied. The definition of the perturbation to Noether-Mei symmetry for the system is presented, and the criterion of the perturbation to Noether-Mei symmetry is given. Meanwhile, the Noether adiabatic invariants and the Mei adiabatic invariants for the perturbed system are obtained.
VLF signal anomalies dues to TS and Hurricanes
Nait Amor, Samir
2017-04-01
VLF signal propagates by multiples reflection in the Earth-Ionosphere wave guide. It constitutes a powerful tool to study the lower region of the ionosphere, the D region. This technique was applied to study perturbations related to the solar flares effect, TGF, the connection between TLEs and Early events.... In this contribution I will present a new results on the evidence of signal perturbations associated with TS and Hurricanes. A wavelet spectral analysis is applied to the signal amplitude to search for eventual Atmospheric Gravity wave which may be the origin of the signal perturbations.
A perturbative approach to the confinement-deconfinement phase transition
Reinosa, Urko
2016-11-01
We summarize recent progress in describing the confinement-deconfinement transition from a novel perturbative approach. Based on various works in collaboration with Julien Serreau, Matthieu Tissier and Nicolás Wschebor.
Seismo-electromagnetic VLF link calibration in Europe
Eichelberger, Hans; Schwingenschuh, Konrad; Wolbang, Daniel; Besser, Bruno P.; Rozhnoi, Alexander; Solovieva, Maria; Biagi, Pier Francesco; Stachel, Manfred; Prattes, Gustav; Boudjada, Mohammed Y.; Aydogar, Özer; Zehetleitner, Sigrid; Grill, Claudia; Jernej, Irmgard
2015-04-01
The general background is the investigation of seismic activity with electromagnetic signals, i.e. to disentangle amplitude and phase modifications from a variety of sources. This work focus on characterisation of very low frequency (VLF) radio links between several transmitters and the Graz receiver in the current active solar cycle. Particular emphasis is on solar flares related disturbances in the Earth-ionosphere waveguide, an important dayside non-seismic influence on the VLF paths. These variations can serve as a calibration tool of the facility even for nighttime periods when different seismo-electromagnetic (SEM) methods are applied, e.g. terminator time or nighttime amplitude. Supporting data are the GOES X-ray flux measurements. As immediate objective we study individual C/M/X-class solar flare events in the sub-ionospheric VLF waveguide (amplitude fluctuations) and calculate statistical parameters with the C-class population. The used system, which is part of a broader network of receiving stations, is primarily dedicated to investigate earthquake related phenomena and associated lithospheric atmospheric ionospheric coupling mechanisms. We receive simultaneously 12 VLF transmitters (amplitude and phase measurements) from the northern hemisphere with a selected temporal resolution of 20 seconds. We conclude that the numerous C/M/X-class solar flare events, together with the the high signal-to-noise ratio of the facility, are a valuable combination for short-term VLF path characterisation in a robust manner. As outlook, due to the steady VLF measurements, a monitoring service for certain lower atmospheric variations can be envisaged.
Eichelberger, Hans; Schwingenschuh, Konrad; Boudjada, Mohammed Y.; Besser, Bruno P.; Wolbang, Daniel; Rozhnoi, Alexander; Solovieva, Maria; Biagi, Pier F.; Stachel, Manfred; Prattes, Gustav; Aydogar, Özer; Muck, Cosima; Grill, Claudia; Jernej, Irmgard; Stachel, Thomas; Moro, Florian
2017-04-01
In this study we present a catalogue of solar flare induced very low frequency (VLF) variations along sub-ionospheric paths between several transmitters and the Graz seismo-electromagnetic UltraMSK receiving station. These measurements of non-seismic disturbances are important in order to carefully characterise the Earth-ionosphere VLF waveguide and disentangle possible earthquake related phenomena from natural and man-made ambient VLF amplitude and phase modifications. The period of investigation is from Jan. 2010 to April 2016, i.e. largely covers the sunspot cycle 24. In total we've 373 VLF amplitude and phase fluctuations related with C/M/X-class solar flare events (the data are from NOAA GOES x-ray flux measurements). We obtain the statistics (dependence on VLF signal vs. x-ray flux variations) for high signal-to-noise ratio VLF links under consideration of the zenith angle. We conclude, that with the mid-latitude Graz VLF knot, a part of the European receiver network, a reliable service for solar flare induced variations of the VLF waveguide can be established. In addition to complementary region-wide network multi-parameter observations this could be a crucial step towards a full characterisation of the behaviour of sub-ionospheric VLF paths including modifications related to seismic activity.
Inflationary perturbation theory is geometrical optics in phase space
Seery, David; Frazer, Jonathan; Ribeiro, Raquel H
2012-01-01
A pressing problem in comparing inflationary models with observation is the accurate calculation of correlation functions. One approach is to evolve them using ordinary differential equations ("transport equations"), analogous to the Schwinger-Dyson hierarchy of in-out quantum field theory. We extend this approach to the complete set of momentum space correlation functions. A formal solution can be obtained using raytracing techniques adapted from geometrical optics. We reformulate inflationary perturbation theory in this language, and show that raytracing reproduces the familiar "delta N" Taylor expansion. Our method produces ordinary differential equations which allow the Taylor coefficients to be computed efficiently. We use raytracing methods to express the gauge transformation between field fluctuations and the curvature perturbation, zeta, in geometrical terms. Using these results we give a compact expression for the nonlinear gauge-transform part of fNL in terms of the principal curvatures of uniform e...
NaitAmor, S.; Ghalila, H.; Cohen, M. B.
2017-01-01
Early very low frequency (VLF) events are perturbations to subionospherically propagating VLF radio transmitters which sometimes occur when lightning activity is near the transmitter-receiver path. They are often correlated to Transient Luminous Events (TLEs). Recent analysis have focused on a new type of early events whose recovery time persists for many minutes, called LOng Recovery Events (LOREs). The underlying cause of these events is still unclear. Curiously, LOREs sometimes appear on only one path, while the same event observed on a different transmitter-receiver path does not indicate a LORE. In this paper we observe and simulate two cases of early signal perturbations: The first is a typical early VLF event, and the second is a LORE. Both were recorded by two AWESOME VLF receivers in North Africa on 12 December 2009, during the EuroSprite campaign. We combine observations with theoretical modeling to infer the electron density change that most closely reproduces the observed perturbation. Our results explain the cases where LOREs are detected on only one path as resulting from transmitter-receiver geometry significantly which impacts the modal content and therefore the observed VLF recovery time.
Santosa, H.; Hobara, Y.
2017-01-01
The electric field amplitude of very low frequency (VLF) transmitter from Hawaii (NPM) has been continuously recorded at Chofu (CHF), Tokyo, Japan. The VLF amplitude variability indicates lower ionospheric perturbation in the D region (60-90 km altitude range) around the NPM-CHF propagation path. We carried out the prediction of daily nighttime mean VLF amplitude by using Nonlinear Autoregressive with Exogenous Input Neural Network (NARX NN). The NARX NN model, which was built based on the daily input variables of various physical parameters such as stratospheric temperature, total column ozone, cosmic rays, Dst, and Kp indices possess good accuracy during the model building. The fitted model was constructed within the training period from 1 January 2011 to 4 February 2013 by using three algorithms, namely, Bayesian Neural Network (BRANN), Levenberg Marquardt Neural Network (LMANN), and Scaled Conjugate Gradient (SCG). The LMANN has the largest Pearson correlation coefficient (r) of 0.94 and smallest root-mean-square error (RMSE) of 1.19 dB. The constructed models by using LMANN were applied to predict the VLF amplitude from 5 February 2013 to 31 December 2013. As a result the one step (1 day) ahead predicted nighttime VLF amplitude has the r of 0.93 and RMSE of 2.25 dB. We conclude that the model built according to the proposed methodology provides good predictions of the electric field amplitude of VLF waves for NPM-CHF (midlatitude) propagation path.
Ionospheric disturbances in D-layer recorded by VLF receiver at Tashkent IHY station
Ahmedov, Bobomurat
Tashkent International Heliophysical Year (IHY) station is a member of Atmospheric Weather Electromagnetic System for Observation, Modeling and Education (AWESOME) network being operated globally to study the ionosphere and the magnetosphere with the help of electromagnetic waves in Very Low Frequency (VLF) band. Regular monitoring of the D- and F-layers of ionosphere over Central Asia territory is being performed on the permanent basis starting year 2008. Solar flare events are permanently observed and the analysis showed that there is simultaneous correlation between the times of change of amplitude of the waves and the Solar flares. Features of the lightning discharge generated by radio atmospherics are studied and its effectiveness in D-region ionosphere diagnostics is explained. We have studied VLF amplitude anomalies related to the earthquakes (EQs) occurred in the recent years with magnitude more than 5 on the path way from the VLF transmitters to the Tashkent station assuming that propagation of VLF ground-based transmitters signals can be perturbed by EQ preparation can be detectable from the ground-based measurements in the VLF bands. For analyzing narrowband data we have used the Nighttime Fluctuation (NF) method paying attention to the data obtained during the local nighttime (20:00 LT-04:00 LT). The mean nighttime amplitude (or trend) and nighttime fluctuation are found to increase significantly before the EQ occurred on the path way from the transmitters to the receiver. The obtained results have revealed an agreement with VLF amplitude anomalies observed in Tashkent VLF station during the strong EQs occurred on the path way from the transmitters to the receiver. Some results are presented to show the probing potentiality of VLF waves to predict short term EQs with high magnitude.
Producing a scale-invariant spectrum of perturbations in a Hagedorn phase of string cosmology.
Nayeri, Ali; Brandenberger, Robert H; Vafa, Cumrun
2006-07-14
We study the generation of cosmological perturbations during the Hagedorn phase of string gas cosmology. Using tools of string thermodynamics we provide indications that it may be possible to obtain a nearly scale-invariant spectrum of cosmological fluctuations on scales which are of cosmological interest today. In our cosmological scenario, the early Hagedorn phase of string gas cosmology goes over smoothly into the radiation-dominated phase of standard cosmology, without having a period of cosmological inflation.
Subionospheric VLF signatures and their association with sprites observed during EuroSprite 2003
DEFF Research Database (Denmark)
Mika, A.; Haldoupis, C.; Marshall, R.A.
2005-01-01
to sprites. Bandpass filtering of the broadband VLF signal revealed that only about 5% of the sprites were escorted by early VLF perturbations, possibly due to backscatter. Finally, by using all 131 sprites captured during EuroSprite-2003, the time lags of the sprites to the preceding +/- CG discharges were...... computed and analyzed. The time-lag distribution had a well defined tail suggesting that at least one third of the sprites observed were lagging the +/- CG discharges by more than 30 up to 300 ms. In addition these "long-delayed" sprites were not accompanied by any radio-sferics during the sprite...
Directory of Open Access Journals (Sweden)
Marianne Rooman
Full Text Available Available DNA microarray time series that record gene expression along the developmental stages of multicellular eukaryotes, or in unicellular organisms subject to external perturbations such as stress and diauxie, are analyzed. By pairwise comparison of the gene expression profiles on the basis of a translation-invariant and scale-invariant distance measure corresponding to least-rectangle regression, it is shown that peaks in the average distance values are noticeable and are localized around specific time points. These points systematically coincide with the transition points between developmental phases or just follow the external perturbations. This approach can thus be used to identify automatically, from microarray time series alone, the presence of external perturbations or the succession of developmental stages in arbitrary cell systems. Moreover, our results show that there is a striking similarity between the gene expression responses to these a priori very different phenomena. In contrast, the cell cycle does not involve a perturbation-like phase, but rather continuous gene expression remodeling. Similar analyses were conducted using three other standard distance measures, showing that the one we introduced was superior. Based on these findings, we set up an adapted clustering method that uses this distance measure and classifies the genes on the basis of their expression profiles within each developmental stage or between perturbation phases.
Influence of perturbative phase noise on active coherent polarization beam combining system.
Ma, Pengfei; Zhou, Pu; Wang, Xiaolin; Ma, Yanxing; Su, Rongtao; Liu, Zejin
2013-12-02
In this manuscript, the influence of perturbative phase noise on active coherent polarization beam combining (CPBC) system is studied theoretically and experimentally. By employing a photo-detector to obtain phase error signal for feedback loop, actively coherent polarization beam combining of two 20 W-level single mode polarization-maintained (PM) fiber amplifiers are demonstrated with more than 94% combining efficiency. Then the influence of perturbative phase noise on active CPBC system is illustrated by incorporating a simulated phase noise signal in one of the two amplifiers. Experimental results show that the combining efficiency of the CPBC system is susceptible to the frequency or amplitude of the perturbative phase noise. In order to ensure the combining efficiency of the unit of CPBC system higher than 90%, the competence of our active phase control module for high power operation is discussed, which suggests that it could be worked at 100s W power level. The relationship between residual phase noise of the active controller and the normalized voltage signal of the photo-detector is developed and validated experimentally. Experimental results correspond exactly with the theoretically analyzed combining efficiency. Our method offers a useful approach to estimate the influence of phase noise on CPBC system.
Eichelberger, H. U.; Prattes, G.; Schwingenschuh, K.; Wolbang, D.; Boudjada, M. Y.; Rozhnoi, A.; Solovieva, M.; Biagi, P. F.; Maggipinto, T.; Stachel, M.; Jernej, I.; Aydogar, Ö.; Besser, B. P.
2012-04-01
In the frame of the European VLF/LF radio receiver network (International Network for Frontier Research on Earthquake Precursors - INFREP) we investigate radio paths between several transmitters and receivers, among them the Graz VLF facility. For this knot the data coverage spans more than two years of continuous samples from 11 transmitters with a network wide 20 seconds temporal resolution. The main scientific objective is the characterisation of VLF fluctuations in amplitude and phase related with artificial and natural sources, e.g. disturbances due to seismic phenomena. Examples of VLF disturbances due to seismic activity are given by Rozhnoi et al. (2009) and complementary investigations are carried out by Prattes et al. (2011). For VLF usually the (i) nighttime amplitude variations and (ii) terminator time methods are used. They have been regularly applied in data analysis of seismic events mainly in Asian area. Paths crossing the earthquake preparation zone and control links are used for earthquake events. Various VLF waveguide properties are important, e.g. the length of the individual paths, the lower lithospheric-surface boundary and the upper {day, night}-time ionospheric {D, E}-layer physics. Beside the nominal diurnal and seasonal behaviour we are measuring natural variations, e.g. solar flare effects and manmade noise, i.e. local disturbances related with the urban environment of the receiver location. Measurements indicate that above a threshold of magnitude M 5 the methods are successful applicable. We show for a time span of more than two years how VLF fluctuations and their seasonal variations relate with atmospheric parameters, e.g. temperatures, zonal wind, and heat- and momentum-fluxes and discuss the impact on seismic event detection via VLF methods. Complementary ground- and satellite-based investigations, e.g. in nearby ULF or LF frequency ranges, are useful.
Tönjes, Ralf; Blasius, Bernd
2009-01-01
The Kuramoto phase-diffusion equation is a nonlinear partial differential equation which describes the spatiotemporal evolution of a phase variable in an oscillatory reaction-diffusion system. Synchronization manifests itself in a stationary phase gradient where all phases throughout a system evolve with the same velocity, the synchronization frequency. The formation of concentric waves can be explained by local impurities of higher frequency which can entrain their surroundings. Concentric waves in synchronization also occur in heterogeneous systems, where the local frequencies are distributed randomly. We present a perturbation analysis of the synchronization frequency where the perturbation is given by the heterogeneity of natural frequencies in the system. The nonlinearity in the form of dispersion leads to an overall acceleration of the oscillation for which the expected value can be calculated from the second-order perturbation terms. We apply the theory to simple topologies, like a line or sphere, and deduce the dependence of the synchronization frequency on the size and the dimension of the oscillatory medium. We show that our theory can be extended to include rotating waves in a medium with periodic boundary conditions. By changing a system parameter, the synchronized state may become quasidegenerate. We demonstrate how perturbation theory fails at such a critical point.
Energy Technology Data Exchange (ETDEWEB)
Dowden, R.L.; Adams, C.D.D. (Univ. of Otago, Dunedin (New Zealand)); Rietveld, M.T. (EISCAT, Ramfjordbotn (Norway)); Stubbe, P.; Kopka, H. (Max-Panck-Institut fuer Aeronomie, Katlenburg-Lindau (Germany))
1991-01-01
The Ionospheric Heating Facility (1-MW HF transmitter and steerable array) at Ramfjordmoen, Norway, was used to generate a localized and steerable discontinuity in the Earth-ionosphere waveguide for scattering Omega signals. The phase of the scattered signal (echo) relative to the direct signal varied with position of the heated patch of ionosphere (the discontinuity) in proportion to the change in echo path length. Previous results by Barr et al. (1985), using the same technique, Omega signals and path, show very similar behavior when looked at in this way. In this respect, both experiments simulated the phase and amplitude perturbations (trimpis) produced by lightning-induced (via electron precipitation) changes in the waveguide and show that measurements of the varying echo phase of trimpis can be used to track lightning-induced perturbations. The steerable discontinuity can also be used as a waveguide probe to measure the phase velocity of the strongest waveguide mode received on the ground by such scattering.
Prastyani, Erina; Niasari, Sintia Windhi
2017-07-01
The goal of all geophysical survey techniques is to image the properties of the Earth's subsurface. Very Low Frequency (VLF) is one of the geophysical survey technique that has been commonly used for ore exploration and mapping faults or fracture zones. Faults or fracture zones are necessary components in providing the fluid pathway in geothermal systems. The Candi Umbul-Telomoyo is one of the geothermal prospect sites in Indonesia, which is located in Magelang, Central Java. Recent studies hypothesized that this site was an outflow area of Telomoyo volcano geothermal complex. We used the VLF-EM and VLF-R techniques to infer faults or fracture zones that might be a path for geothermal fluids in the Candi Umbul-Telomoyo. From the measurements, we got tilt angle, ellipticity, primary and secondary magnetic fieldfor VLF-EM data; and apparent resistivity, phase angle, electric and magnetic field for VLF-R data. To interpret the data, we used tipper and impedance analyses. The result of both analyses show similarities in the directions and positions of anomalous current concentrations. We conclude these anomalous current concentrations as faults. Our interpretation is agreeing with the Geologic Map of the Semarang and Magelang Quadrangles that shows the expected fault beneath the Mt. Telomoyo.
Physics based model of D-region variability related to VLF propagation effects
Chakravarty, S. C.
2012-07-01
D-region (~60-85 km) electron density profiles measured using large number of sounding rocket experiments carried out from two Indian low latitude stations show large variations with solar zenith angle, season and solar activity. Similarly the ground based multi frequency radio wave absorption technique has provided continuous data on the morphology of the hourly electron density variations. However suitable models of the D-region electron density profile variations both during quiet and disturbed solar conditions over the Indian region are lacking. The renewed interest in the study of the VLF/LF propagation anomalies taking place through perturbations in the D-region electron densities due to various geophysical phenomena requires the availability of a baseline D-region model over low latitudes. The purpose of this paper is to critically review the physical processes of D-region production and loss of free electrons, dynamical coupling due to variety of vertically propagating atmospheric waves, sudden changes brought about by the solar energetic events like CMEs and different categories of X-ray flares. Low latitude region is not likely to be affected by the PMSE or PCA type of events but the changes due to lightning induced mesospheric red sprites and LEPs need to be considered. Based on this analysis, a preliminary low latitude D-region electron density profile model development is proposed. Sample results would illustrate key requirements from such a model in terms of its effectiveness to simulate the low latitude observations of VLF/LF amplitude and phase variations using waveguide propagation models like LWPC.
Building and Testing a Portable VLF Receiver
McLaughlin, Robert; Krause, L.
2014-01-01
Unwanted emissions or signal noise is a major problem for VLF radio receivers. These can occur from man made sources such as power line hum, which can be prevalent for many harmonics after the fundamental 50 or 60 Hz AC source or from VLF radio transmissions such as LORAN, used for navigation and communications. Natural emissions can also be detrimental to the quality of recordings as some of the more interesting natural emissions such as whistlers or auroral chorus may be drowned out by the more common sferic emissions. VLF receivers must selectively filter out unwanted emissions and amplify the filtered signal to a record-able level without degrading the quality.
Phase reduction of weakly perturbed limit cycle oscillations in time-delay systems
Novičenko, V.; Pyragas, K.
2012-06-01
The phase reduction method is applied to a general class of weakly perturbed time-delay systems exhibiting periodic oscillations. The adjoint equation with an appropriate initial condition for the infinitesimal phase response curve of a time-delay system is derived. The method is demonstrated numerically for the Mackey-Glass equation as well as for a chaotic Rössler system subject to a delayed feedback control (DFC). We show that the profile of the phase response curve of a periodic orbit stabilized by the DFC algorithm does not depend on the control matrix. This property is universal and holds for any dynamical system subject to the DFC.
Revzen, Shai; Burden, Samuel A; Moore, Talia Y; Mongeau, Jean-Michel; Full, Robert J
2013-04-01
Instantaneous kinematic phase calculation allows the development of reduced-order oscillator models useful in generating hypotheses of neuromechanical control. When perturbed, changes in instantaneous kinematic phase and frequency of rhythmic movements can provide details of movement and evidence for neural feedback to a system-level neural oscillator with a time resolution not possible with traditional approaches. We elicited an escape response in cockroaches (Blaberus discoidalis) that ran onto a movable cart accelerated laterally with respect to the animals' motion causing a perturbation. The specific impulse imposed on animals (0.50 [Formula: see text] 0.04 m s[Formula: see text]; mean, SD) was nearly twice their forward speed (0.25 [Formula: see text] 0.06 m s[Formula: see text]. Instantaneous residual phase computed from kinematic phase remained constant for 110 ms after the onset of perturbation, but then decreased representing a decrease in stride frequency. Results from direct muscle action potential recordings supported kinematic phase results in showing that recovery begins with self-stabilizing mechanical feedback followed by neural feedback to an abstracted neural oscillator or central pattern generator. Trials fell into two classes of forward velocity changes, while exhibiting statistically indistinguishable frequency changes. Animals pulled away from the side with front and hind legs of the tripod in stance recovered heading within 300 ms, whereas animals that only had a middle leg of the tripod resisting the pull did not recover within this period. Animals with eight or more legs might be more robust to lateral perturbations than hexapods.
Modal analysis of untransposed bilateral three-phase lines -- a perturbation approach
Energy Technology Data Exchange (ETDEWEB)
Faria, J.A.B. [Inst. Superior Tecnico, Lisboa (Portugal). Centro de Electrotecnia Teorica e Medidas Electricas; Mendes, J.H.B. [Univ. de Los Andes, Merida (Venezuela). Escuela de Ingenieria Electrica
1997-01-01
Model analysis of three-phase power lines exhibiting bilateral symmetry leads to modal transformation matrices that closely resemble Clarke`s transformation. The authors develop a perturbation theory approach to justify, interpret, and gain understanding of this well known fact. Further, the authors show how to find new frequency dependent correction terms that once added to Clarke`s transformation lead to improved accuracy.
Terrestrial VLF transmitter injection into the magnetosphere
2012-01-01
Terrestrial VLF transmitter injection into the magnetosphere M. B. Cohen1 and U. S. Inan1,2 Received 1 June 2012; revised 15 June 2012; accepted 18 June 2012; published 9 August 2012. [1] Very Low Frequency (VLF, 3–30 kHz) radio waves emitted from ground sources (transmitters and lightning) strongly impact the radiation belts, driving electron precipitation via whistler-electron gyroresonance, and contributing to the formation of the slot region. However, calculations of the...
Lapa, Matthew F.; Hughes, Taylor L.
2017-09-01
We study perturbative and global anomalies at the boundaries of bosonic analogs of integer quantum Hall (BIQH) and topological insulator (BTI) phases using a description of the boundaries of these phases in terms of a nonlinear sigma model (NLSM) with Wess-Zumino term. One of the main results of the paper is that these anomalies are robust against arbitrary smooth deformations of the target space of the NLSM which describes the phase, provided that the deformations also respect the symmetry of the phase. In the first part of the paper, we discuss the perturbative U(1 ) anomaly at the boundary of BIQH states in all odd (space-time) dimensions. In the second part, we study global anomalies at the boundary of BTI states in even dimensions. In a previous work [Lapa et al., Phys. Rev. B 95, 035149 (2017), 10.1103/PhysRevB.95.035149] we argued that the boundary of the BTI phase exhibits a global anomaly which is an analog of the parity anomaly of Dirac fermions in three dimensions. Here, we elevate this argument to a proof for the boundary of the two-dimensional BTI state by explicitly computing the partition function of the gauged NLSM describing the boundary. We then use the powerful equivariant localization technique to show that this global anomaly is robust against all smooth deformations of the target space of the NLSM which preserve the U(1 ) ⋊Z2 symmetry of the BTI state. We also comment on the difficulties of generalizing this latter proof to higher dimensions. Finally, we discuss the expected low-energy behavior of the boundary theories studied in this paper when the coupling constants are allowed to flow under the renormalization group.
Directory of Open Access Journals (Sweden)
M. Saifur Rahman
2012-12-01
Full Text Available Recently, a unified Krylov-Bogoliubov-Mitropolskii method has been presented (by Shamsul \\cite{1} for solving an $n$-th, $n=2$ or $n>2$, order nonlinear differential equation. Instead of amplitude(s and phase(s, a set of variables is used in \\cite{1} to obtain a general formula in which the nonlinear differential equations can be solved. By a simple variables transformation the usual form solutions (i.e., in terms of amplitude(s and phase(s have been found. In this paper a perturbation technique is developed to calculate the initial values of the variables used in \\cite{1}. By the noted transformation the initial amplitude(s and phase(s can be calculated quickly. Usually the conditional equations are nonlinear algebraic or transcendental equations; so that a numerical method is used to solve them. Rink \\cite{7} earlier employed an asymptotic method for solving the conditional equations of a second-order differential equation; but his derived results were not so good. The new results agree with their exact values (or numerical results nicely. The method can be applied whether the eigen-values of the unperturbed equation are purely imaginary, complex conjugate or real. Thus the derived solution is a general one and covers the three cases, i.e., un-damped, under-damped and over-damped.
Cook, William R; Coalson, Rob D; Evans, Deborah G
2009-08-20
A description of electron transfer in condensed-phase media requires models that adequately describe the coupling of the electronic degrees of freedom to the surrounding nuclear coordinates. The spin-boson model has been the canonical model used to understand quantum dynamic processes in condensed-phase media over the last 25 years. Inherent in the standard model of a two-state quantum system coupled to a bosonic bath is the assumption that the Condon approximation is valid. In this context, the Condon approximation assumes that the bath configurations (coordinates) have no effect on the nonadiabatic coupling matrix element. While this is a useful model for electron transfer in small molecular systems, the validity of this approximation is less likely when large-scale motions of solvent molecules are strongly coupled to the electron transfer event, e.g., in molecular clamps and long-range electron transfer in biopolymers. In the present paper a general model for two-state electron transfer which allows for system-bath coupling in both the diagonal and off-diagonal (nonadiabatic) terms is studied. Time-dependent perturbation theory for this Hamiltonian is developed using a small polaron transformation. As noted in several recent studies, in a certain regime of parameter space, the relevant Hamiltonian admits an exact solution, termed the exactly solvable non-Condon Hamiltonian (or NCE). This limit, for which exact solutions are available, is used to benchmark the short- and long-time accuracy of various perturbative approaches. The validated perturbation equations are subsequently used to explore the role of non-Condon effects on electron transfer by systematically increasing the strength of the non-Condon coupling term from zero (i.e., the canonical spin-boson model) to the value that pertains to the exactly solvable non-Condon model (where non-Condon effects are significant).
Perturbative aspects of the phase diagram of QCD with heavy quarks
Serreau, Julien; Reinosa, Urko
2017-03-01
We report on recent progress in the description of the phase diagram of QCD with heavy quarks at nonzero temperature and chemical potential in the context of a modified perturbative approach. The latter is based on a simple massive extension of the QCD Lagrangian in the Landau-DeWitt gauge, the background field generalization of the Landau gauge. Here, the background field plays the role of an order parameter for the center symmetry, relevant for confinement-deconfinement transition. One-loop results in this approach give a fairly accurate description of the phase diagram both at real and imaginary chemical potential. We comment on issues related to the sign problem in continuum approaches. Based on works in collaboration with Matthieu Tissier and Nicolás Wschebor.
Thermodynamic Perturbation Theory for Solid-Liquid Phase Transition of Lennard-Jones Model
Institute of Scientific and Technical Information of China (English)
ZHOUShi-Qi; ZHANGXiao-Qi
2004-01-01
Both a free volume approach for Helmholtz free energy and a theoretically-based fitted formula for radial distribution function (rdf) of hard sphere solid are employed to describe the Helmholtz free energy of Lennard-Jones solid in the framework of the first order thermodynamic perturbation theory, which also is employed for the uniform Lennard Jones fluid. The dividing of the Lennard-Jones potential follows from the INCA prescription, but the specification of the equivalent hard sphere diameter is determined by a simple iteration procedure devised originally for liquid state, but extended to solid state in the present study. Two hundred shells are used in the rdf to get an accurate perturbation term.The present approach is very accurate for the description of excess Helmholtz free energy of LJ solid, but shows some deviation from the simulation for excess Helmholtz free energy of uniform LJ fluid when the reduced temperature kT/ε is higher then 5. The present approach is satisfactory for description of solid-liquid phase transition of the Lennard-Jones model.
Thermodynamic Perturbation Theory for Solid-Liquid Phase Transition of Lennard-Jones Model
Institute of Scientific and Technical Information of China (English)
ZHOU Shi-Qi; ZHANG Xiao-Qi
2004-01-01
Both a free volume approach for Helmholtz free energy and a theoretically-based fitted formula for radial distribution function (rdf) of hard sphere solid are employed to describe the Helmholtz free energy of Lennard-Jones solid in the framework of the first order thermodynamic perturbation theory, which also is employed for the uniform LennardJones fluid. The dividing of the Lennard-Jones potential follows from the WCA prescription, but the specification of the equivalent hard sphere diameter is determined by a simple iteration procedure devised originally for liquid state, but extended to solid state in the present study. Two hundred sheiks are used in the rdf to get an accurate perturbation term.The present approach is very accurate for the description of excess Helmholtz free energy of LJ solid, but shows some deviation from the simulation for excess Helmholtz free energy of uniform LJ fluid when the reduced temperature kT/ε is higher then 5. The present approach is satisfactory for description of solid-liquid phase transition of the Lennard-Jones model.
On multiple alternating steady states induced by periodic spin phase perturbation waveforms.
Buračas, Giedrius T; Jung, Youngkyoo; Lee, Jongho; Buxton, Richard B; Wong, Eric C; Liu, Thomas T
2012-05-01
Direct measurement of neural currents by means of MRI can potentially open a high temporal resolution (10-100 ms) window applicable for monitoring dynamics of neuronal activity without loss of the high spatial resolution afforded by MRI. Previously, we have shown that the alternating balanced steady state imaging affords high sensitivity to weak periodic currents owing to its amplification of periodic spin phase perturbations. This technique, however, requires precise synchronization of such perturbations to the radiofrequency pulses. Herein, we extend alternating balanced steady state imaging to multiple balanced alternating steady states for estimation of neural current waveforms. Simulations and phantom experiments show that the off-resonance profile of the multiple alternating steady state signal carries information about the frequency content of driving waveforms. In addition, the method is less sensitive than alternating balanced steady state to precise waveform timing relative to radiofrequency pulses. Thus, multiple alternating steady state technique is potentially applicable to MR imaging of the waveforms of periodic neuronal activity.
Santosa, H.; Hobara, Y.; Balikhin, M. A.
2015-12-01
Very Low Frequency (VLF) waves have been proposed as an approach to study and monitor the lower ionospheric conditions. The ionospheric perturbations are identified in relation with thunderstorm activity, geomagnetic storm and other factors. The temporal dependence of VLF amplitude has a complicated and large daily variabilities in general due to combinations of both effects from above (space weather effect) and below (atmospheric and crustal processes) of the ionosphere. Quantitative contributions from different external sources are not known well yet. Thus the modelling and prediction of VLF wave amplitude are important issues to study the lower ionospheric responses from various external parameters and to also detect the anomalies of the ionosphere. The purpose of the study is to model and predict nighttime average amplitude of VLF wave propagation from the VLF transmitter in Hawaii (NPM) to receiver in Chofu (CHO) Tokyo, Japan path using NARX neural network. The constructed model was trained for the target parameter of nighttime average amplitude of NPM-CHO path. The NARX model, which was built based on daily input variables of various physical parameters such as stratosphere temperature, cosmic rays and total column ozone, possessed good accuracies. As a result, the constructed models are capable of performing accurate multistep ahead predictions, while maintaining acceptable one step ahead prediction accuracy. The results of the predicted daily VLF amplitude are in good agreement with observed (true) value for one step ahead prediction (r = 0.92, RMSE = 1.99), multi-step ahead 5 days prediction (r = 0.91, RMSE = 1.14) and multi-step ahead 10 days prediction (r = 0.75, RMSE = 1.74). The developed model indicates the feasibility and reliability of predicting lower ionospheric properties by the NARX neural network approach, and provides physical insights on the responses of lower ionosphere due to various external forcing.
Energy Technology Data Exchange (ETDEWEB)
Jakowski, N.; Jungstand, A. (Deutsche Forschungsanstalt fuer Luft- and Raumfahrt, Neustrelitz (Germany)); Schlegel, K.; Kohl, H.; Rinnert, K. (Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau (Germany))
1992-07-01
The generation and propagation of ionospheric storms are studied by analyzing EISCAT radar, and vertical sounding and total electron content data obtained under different geophysical conditions. Both case studies as well as the average storm pattern of percentage deviations of different ionospheric parameters from their corresponding reference values such as total electron content, F2-layer critical frequency, F2 layer critical height, and slab thickness indicate the action of a perturbation electric field during the first few hours of the onset of geomagnetic storms. Considering the onset phase of the storm on July 28-29, 1987 evidence has been found that high latitude electric fields may penetrate to lower latitudes before the ring current has developed. Different mechanisms are assumed to be responsible for daytime and nightime behaviour, respectively. The negative phase propagates equatorward with velocities in the order of 70-350 m/s following a strong heating of the thermosphere and ionosphere due to the auroral electrojet. 24 refs., 10 figs.
Singh, A. K.; Singh, R.; Singh, A. K.
2011-12-01
Response of the D-region of the ionosphere to the total solar eclipse of 22 July 2009 at low latitude, Varanasi (geomagnetic lat = 140 55'N, longitude = 1540 E, dip. angle = 37.30) was investigated using ELF/VLF radio signal. The solar eclipse started at 05:30:04.4 hrs IST and lasted up to 07:27 hrs IST with totally from 6.25 IST to 6.27 IST.The changes in D-region ionospheric VLF reflection heights and electron density during eclipse have been estimated from tweek analysis. The reflection height increased from ~90 km from the first occurrence of tweek to about 93-94 km at the totality and then decreased to ~89 km at the end of the eclipse. The reflection heights are lower by 2-3 km as compared to the usual nighttime tweek reflection heights. The electron density is found to vary between 25-27 cm-3 at the reflection heights. The significant increase in tweek reflection height of about 15 km during the eclipse as compared to the daytime (morning) reflection heights of ~ 78 km is observed. Observations suggest that about 30-40% obscuration of solar disc can lead to the tweeks occurrence which otherwise occur only in the nighttime. A significant increase of 3dB in the strength of the amplitude of VLF signal is observed around the time of TSE as compared to a control day. These low latitude ionospheric perturbations on the eclipse day are discussed and compared with other normal days. During a solar eclipse, the decrease in solar flux due to moon's shadow causes sudden change in the D-region physical and chemical processes. During the totality due to blocking of Lyman-α 1215Å (major D-region ionizing radiation) by moon's umbral shadow, the electron density decreases drastically towards the nighttime values [Smith, 1972]. During the TSE, there was no production of ionization in the ionosphere and the ions and electrons in the lowest part of it recombined at a rapid rate resulting a depletion in the electron density in the 'D' region of the Ionosphere and hence an
The, Hao Chung; Florez de Sessions, Paola; Jie, Song; Pham Thanh, Duy; Thompson, Corinne N; Nguyen Ngoc Minh, Chau; Chu, Collins Wenhan; Tran, Tuan-Anh; Thomson, Nicholas R; Thwaites, Guy E; Rabaa, Maia A; Hibberd, Martin; Baker, Stephen
2017-08-02
Diarrheal diseases remain the second most common cause of mortality in young children in developing countries. Efforts have been made to explore the impact of diarrhea on bacterial communities in the human gut, but a thorough understanding has been impeded by inadequate resolution in bacterial identification and the examination of only few etiological agents. Here, by profiling an extended region of the 16S rRNA gene in the fecal microbiome, we aimed to elucidate the nature of gut microbiome perturbations during the early phase of infectious diarrhea caused by various etiological agents in Vietnamese children. Fecal samples from 145 diarrheal cases with a confirmed infectious etiology before antimicrobial therapy and 54 control subjects were analyzed. We found that the diarrheal fecal microbiota could be robustly categorized into 4 microbial configurations that either generally resembled or were highly divergent from a healthy state. Factors such as age, nutritional status, breastfeeding, and the etiology of the infection were significantly associated with these microbial community structures. We observed a consistent elevation of Fusobacterium mortiferum, Escherichia, and oral microorganisms in all diarrheal fecal microbiome configurations, proposing similar mechanistic interactions, even in the absence of global dysbiosis. We additionally found that Bifidobacterium pseudocatenulatum was significantly depleted during dysenteric diarrhea regardless of the etiological agent, suggesting that further investigations into the use of this species as a dysentery-orientated probiotic therapy are warranted. Our findings contribute to the understanding of the complex influence of infectious diarrhea on gut microbiome and identify new opportunities for therapeutic interventions.
Transionospheric Propagation of VLF Transmitter Signals
Cohen, M.; Inan, U. S.; Lehtinen, N. G.
2012-12-01
Ground based Very Low Frequency (VLF, 3-30 kHz) radio transmitters may play a significant role in precipitation of inner belt (L<2.5) energetic Van Allen electrons. Initial analyses of the total contribution of VLF transmitters utilized models of transionospheric propagation, but some recent studies have suggested that those models may overestimate (by 20-100 dB) the VLF energy reaching the magnetosphere. One possible cause of this discrepancy was suggested to be conversion of wave energy into electrostatic modes in the D, E, and F regions, from ionospheric density irregularities, either natural or generated by the transmitter heating itself. The DEMETER satellite built a six year history of continuous and global survey mode data which, when combined, yields detailed pictures of the radiation pattern from many transmitters into space at 680 km, with 25 km resolution, and clear features like the interference pattern on the ground mapped upwards. With both E and B survey mode data, we can also directly approximate the total power injected into the magnetosphere from each transmitter, separately for day and night, as well as the power arriving at the conjugate region. We find no detectable variation of signal intensity with geomagnetic conditions. We find evidence of transmitter heating affecting the transionospheric propagation of other transmitters. We find that the power reaching the conjugate region is a large fraction of the power injected above the transmitter. We then employ a full wave model to simulate VLF transmitter transionospheric propagation, calculating the electromagnetic fields and power flux injected into the magnetosphere. Although the model does not include ionospheric irregularities, the radiation pattern largely matches the observed one, and the total power calculated is within 6 dB of observations for every transmitter, both day and night, and across a range of low to middle latitudes and transmitter powers. We thus conclude that the effect of
Institute of Scientific and Technical Information of China (English)
FAN JianXing; YANG HuaZhong; WANG Hui; YAN XiaoLang; HOU ChaoHuan
2007-01-01
Phase noise analysis of an oscillator is implemented with its periodic time-varying small signal state equations by perturbing the autonomous large signal state equations of the oscillator. In this paper, the time domain steady solutions of oscillators are perturbed with traditional regular method; the periodic time-varying Jocobian modulus matrices are decomposed with Sylvester theorem, and on the resulting space spanned by periodic vectors, the conditions under which the oscillator holds periodic steady states with any perturbations are analyzed. In this paper, stochastic calculus is applied to disclose the generation process of phase noise and calculate the phase jitter of the oscillator by injecting a pseudo sinusoidal signal in frequency domain, representing the white noise, and a δ correlation signal in time domain into the oscillator. Applying the principle of frequency modulation, we learned how the power-law and the Lorentzian spectrums are formed. Their relations and the Lorentzian spectrums of harmonics are also worked out. Based on the periodic Jacobian modulus matrix, the simple algorithms for Floquet exponents and phase noise are constructed, as well as a simple case is demonstrated. The analysis difficulties and the future directions for the phase noise of oscillators are also pointed out at the end.
Liang, Xiaojun; Kumar, Shiva; Shao, Jing; Malekiha, Mahdi; Plant, David V
2014-08-25
A digital compensation scheme based on a perturbation theory for mitigation of cross-phase modulation (XPM) distortions is developed for dispersion-managed fiber-optic communication systems. It is a receiver-side scheme that uses a hard-decision unit to estimate data for the calculation of XPM fields using the perturbation technique. The intra-channel nonlinear distortions are removed by intra-channel digital backward propagation (DBP) based on split-step Fourier scheme before the hard-decision unit. The perturbation technique is shown to be effective in mitigating XPM distortions. However, wrong estimations in the hard-decision unit result in performance degradation. A hard-decision correction method is proposed to correct the wrong estimations. Numerical simulations show that the hybrid compensation scheme with DBP for dispersion and intra-channel nonlinear impairments compensation and the perturbation technique for XPM compensation brings up to 3.7 dBQ and 1.7 dBQ improvements as compared with the schemes of linear compensation only and intra-channel DBP, respectively. The perturbation technique for XPM compensation requires only one-stage (or two-stage when hard-decision correction is applied) compensation and symbol-rate signal processing.
Institute of Scientific and Technical Information of China (English)
HSUChaohsing; CHENTsongyi; PanJengshyang
2005-01-01
In this paper, a phase-amplitude perturbation method of an adaptive array factor based on the genetic algorithm is proposed. The design for an optimal beam pattern of an adaptive antenna is able to not only suppress interference by placing nulls at the directions of the interfering sources but also provide a maximized main lobe in the direction of the desired signal, i.e., to maximizethe Signal interference ratio (SIR). In order to achieve this goal, a kind of new convergent skill called the two-way convergent method for genetic algorithms is proposed. The phase-amplitude perturbation method is applied to realize the optimal beam pattern of an adaptively linear array antenna. The Genetic algorithms are applied to find the optimal phase-amplitude weighting vector of adaptive array factor. An optimal beam pattern of linear array is derived by phase-amplitude perturbations using a genetic algorithm. Computer simulation result is given to demonstrate the effectiveness of the proposed method.
Chakravarty, Subhas
Since IGY period (1957-58), natural and artificially produced Very Low Frequency (VLF) elec-tromagnetic radiations are being recorded at large number of ground stations all over the world and on-board satellites to study various radio wave-thermal/energetic plasma interactive pro-cesses related to earth's ionosphere-plasmasphere-magnetosphere environment. The terrestrial propagation of these VLF radio waves are primarily enabled through the earth ionosphere wave guide (EIWG) mode to long horizontal distances around the globe and ducted along the ge-omagnetic field lines into the conjugate hemisphere through the plasmasphere-magnetosphere regions. The time frequency spectra of the received signals indicate presence of dispersion (wave/group velocities changing with frequency) and various cut-off frequencies based on the width of the EIWG, electron gyro and plasma frequencies etc., providing several types of received signals like whistlers, chorus, tweeks, hiss and hisslers which can be heard on loud-speakers/earphones with distinguishing audio structures. While the VLF technique has been a very effective tool for studying middle and high latitude phenomena, the importance of the similar and anomalous observations over the Indian low latitude stations provide potentially new challenges for their scientific interpretation and modelling. The ducted and non-ducted magnetospheric propagation, pro-longitudinal (PL) mode, low latitude TRIMPI/TLE (Tran-sient Luminous Emissions) or other effects of wave-particle/wave-wave interactions, effects due to ionospheric irregularities and electric fields, full wave solutions to D-region ionisation per-turbations due to solar and stellar energetic X-and γ ray emissions during normal and flaring conditions are a few problems which have been addressed in these low latitude studies over India. Since the conjugate points of Indian stations lie over the Indian oceanic region, the VLF propagation effects would be relatively free from
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Interactions between very/extremely low frequency (VLF/ELF) waves and energetic electrons play a fundamental role in dynamics occurring in the inner magnetosphere. Here, we briefly discuss global properties of VLF/ELF waves, along with the variability of the electron radiation belts associated with wave-particle interactions and radial diffusion. We provide cases of electron loss and acceleration as a result of wave-particle interactions primarily due to such waves, and particularly some preliminary results of 3D evolution of phase space density from our currently developing 3D code. We comment on the existing mechanisms responsible for acceleration and loss, and identify several critical issues that need to be addressed. We review latest progress and suggest open questions for future investigation.
VLF emissions from ionospheric/magnetospheric plasma
Indian Academy of Sciences (India)
R P Patel; R P Singh
2001-05-01
VLF emissions such as hiss, chorus, oscillating tones, hiss-triggered chorus and whistler triggered emissions have been observed at low latitude Indian stations. In this paper we present dynamic spectra of these emissions and discuss their various observed features. It is argued that most of the emissions are generated during Doppler shifted cyclotron resonance interaction between the whistler mode wave and counter streaming energetic electrons. Resonance energy of the participating electron and interaction length are evaluated to explain the generation mechanism of some of these emissions observed at Indian stations.
Energy Technology Data Exchange (ETDEWEB)
NONE
1998-12-01
Using VLF frequencies, transmitted by the Navy`s network, for airborne remote sensing of the earth`s electrical, magnetic characteristics was first considered by the United States Geological Survey (USGS) around the mid 1970s. The first VLF system was designed and developed by the USGS for installation and operation on a single engine, fixed wing aircraft used by the Branch of Geophysics for geophysical surveying. The system consisted of five channels. Two E-field channels with sensors consisting of a fixed vertical loaded dipole antenna with pre-amp mounted on top of the fuselage and a gyro stabilized horizontal loaded dipole antenna with pre-amp mounted on a tail boom. The three channel magnetic sensor consisted of three orthogonal coils mounted on the same gyro stabilized platform as the horizontal E-field antenna. The main features of the VLF receiver were: narrow band-width frequency selection using crystal filters, phase shifters for zeroing out system phase variances, phase-lock loops for generating real and quadrature gates, and synchronous detectors for generating real and quadrature outputs. In the mid 1990s the Branch of Geophysics designed and developed a two-channel E-field ground portable VLF system. The system was built using state-of-the-art circuit components and new concepts in circuit architecture. Small size, light weight, low power, durability, and reliability were key considerations in the design of the instrument. The primary purpose of the instrument was for collecting VLF data during ground surveys over small grid areas. Later the system was modified for installation on a Unmanned Airborne Vehicle (UAV). A series of three field trips were made to Easton, Maryland for testing and evaluating the system performance.
Sulic, D M; Mihajlov, A A
2016-01-01
In this paper we confine our attention to the analysis of amplitude and phase data acquired by monitoring VLF/LF radio signals emitted by four European transmitters during a seven-year period (2008-2014). All the data were recorded at a Belgrade site (44.85$^{0}$ N, 20.38$^{0}$ E) by the Stanford University ELF/VLF receiver AWESOME. Propagation of VLF/LF radio signal takes place in the Earth-ionosphere waveguide and strongly depends on ionization level of the D-region, which means that it is mainly controlled by solar conditions. Some results of amplitude and phase variations on GQD/22.10 kHz, DHO/23.40 kHz, ICV/20.27 kHz and NSC/45.90 kHz radio signals measurements at short distances ($D < 2$ Mm) over Central Europe and their interpretation are summarized in this paper. Attention is restricted to regular diurnal, seasonal and solar variations including sunrise and sunset effects on propagation characteristics of four VLF/LF radio signals. We study VLF/LF propagation over short path as a superposition of d...
Wolbang, Daniel; Biernat, Helfried K.; Friedrich, Martin; Schwingenschuh, Konrad; Besser, B. P.; Eichelberger, Hans; Prattes, Gustav; Rozhnoi, Alexander; Solovieva, Maria; Biagi, Pier Francesco; Boudjada, Mohammed Y.
In this study we analyze low seismicity earthquakes (EQs) with magnitudes M earthquake precursor phenomena generated in the lithosphere and then propagating in the atmosphere / ionosphere [1]. The major challenge of this seismo-electromagnetic (SEM) method is to differentiate parameter variations and disentangle seismic from non-seismic sources. In the course of the European radio receiver network (International Network for Frontier Research on Earthquake Precursors, INFREP) radio signals in the VLF/LF frequency range are continuously recorded by dedicated, distributed transmitters. The major VLF receiving station for this study (10-50 kHz, Graz, Austria) operates continuously throughout the year, the selected network-wide temporal resolution is 20 sec, 12 transmitters, located mainly in Europe, are received (amplitude and phase). The facility has a proven high reliability and availability. The VLF links from the transmitters to the receivers are sometimes more, sometimes less influenced by various disturbances. In case the signal is crossing an EQ preparation zone, we are in principle able to detect seismic activity if the signal to noise ratio is high enough [2]. Generally we distinguish between ionospheric or atmospheric disturbances, influences which depend on the EQ properties, and transmitter variations itself. Ionospheric / Atmospheric variations can be generated, e.g. by geomagnetic storms, solar flares or waves in the troposphere. The properties of the sub-ionospheric VLF waveguide are affected by the length of the radio path, the distance to the EQ preparation zone, the parameters of the earthquake (magnitude, depth, type), and daytime / nighttime disturbances. In order to minimize ionospheric influences on the radio path we are considering mainly nighttime periods. Beside the terminator time method, where only the VLF sunrise and sunset period is analyzed, we are using the residual method (2 hours before and after local midnight), where the difference
Chakraborty, Suman; Palit, Sourav; Ray, Suman; Chakrabarti, Sandip K.
2016-02-01
The variation in the solar Extreme Ultraviolet (EUV) radiation flux by any measure is the most dominant natural source to produce perturbations or modulations in the ionospheric chemical and plasma properties. A solar eclipse, though a very rare phenomenon, is similarly bound to produce a significant short time effect on the local ionospheric properties. The influence of the ionizing solar flux reduction during a solar eclipse on the lower ionosphere or, more precisely, the D-region, can be studied with the observation of Very Low Frequency (VLF) radio wave signal modulation. The interpretation of such an effect on VLF signals requires a knowledge of the D-region ion chemistry, which is not well studied till date. Dominant parameters which govern the ion chemistry, such as the recombination coefficients, are poorly known. The occurrence of events such as a solar eclipse provides us with an excellent opportunity to investigate the accuracy of our knowledge of the chemical condition in this part of Earth's atmosphere and the properties which control the ionospheric stability under such disturbances. In this paper, using existing knowledge of the lower ionospheric chemical and physical properties we carry out an interpretation of the effects obtained during the total solar eclipse of 22 of July 2009 on the VLF signal. Data obtained from a week long campaign conducted by the Indian Centre for Space Physics (ICSP) over the Indian subcontinent has been used for this purpose. Both positive and negative amplitude changes during the eclipse were observed along various receiver locations. In this paper, data for a propagation path between a Indian Navy VLF transmitter named VTX3 and a pair of receivers in India are used. We start from the observed solar flux during the eclipse and calculate the ionization during the whole time span over most of the influenced region in a range of height. We incorporate a D-region ion-chemistry model to find the equilibrium ion density over
Van Pelt, A.
1992-01-01
I. INTRODUCTION AND THEORY This PhD research is mainly concerned with the global phase behaviour, that is calculated from the Simplified-Perturbed-Hard-Chain equation. This equation distinguishes itself from many other equations of state by a sound theoretical background. We enter the field of the t
Solovyeva, Alisa
2016-01-01
We assess the predictive power of alchemical perturbations for estimating fundamental properties in ionic crystals. Using density functional theory we have calculated formation energies, lattice constants, and bulk moduli for all sixteen iso-valence-electronic combinations of pure pristine alkali halides involving elements $A \\in \\{$Na, K, Rb, Cs$\\}$ and $X \\in \\{$F, Cl, Br, I$\\}$. For rock salt, zincblende and cesium chloride symmetry, alchemical Hellmann-Feynman derivatives, evaluated along lattice scans of sixteen reference crystals, have been obtained for all respective 16$\\times$15 combinations of reference and predicted target crystals. Mean absolute errors (MAE) are on par with density functional theory level of accuracy for energies and bulk modulus. Predicted lattice constants are less accurate. NaCl is the best reference salt for alchemical estimates of relative energies (MAE $<$ 40 meV/atom) while alkali fluorides are the worst. By contrast, lattice constants are predicted best using NaF as a re...
Directory of Open Access Journals (Sweden)
Zhangxin Chen
1999-12-01
Full Text Available This is the third paper of a three-part series where we develop and analyze a finite element approximation for a degenerate elliptic-parabolic partial differential system which describes the flow of two incompressible, immiscible fluids in porous media. The approximation uses a mixed finite element method for the pressure equation and a Galerkin finite element method for the saturation equation. It is based on a regularization of the saturation equation. In the first paper cite{RckA} we analyzed the regularized differential system and presented numerical results. In the second paper cite{RckB} we obtained error estimates. In the present paper we describe a perturbation analysis for the saturation equation and numerical experiments for complementing this analysis.
In connection with identification of VLF emissions before L'Aquila earthquake
Directory of Open Access Journals (Sweden)
M. K. Kachakhidze
2012-04-01
Full Text Available The present paper deals with an attempt to check the theoretical model of self-generated seismo-electromagnetic oscillations of LAI system on the basis of retrospective data.
Application of the offered simple model enables one to explain qualitatively the mechanism of VLF electromagnetic emission initiated in the process of an earthquake preparation. Besides, the model enables us to associate telluric character geoelectric and geomagnetic perturbations incited by rock polarization and self-generated electromagnetic oscillations of lithosphere-atmosphere system.
L'Aquila earthquake taken as an example to isolate reliably the Earth VLF emission from the magnetospheric electromagnetic emission of the same frequency range, MHD criterion is offered together with geomagnetic activity indexes.
On the basis of the considered three earthquakes, according to the opinion of authors the model of self-generated seismo-electromagnetic oscillations of the LAI system will enable us to approach the problem of resolution of earthquake prediction with certain accuracy.
Possibility of Earthquake-prediction by analyzing VLF signals
Ray, Suman; Chakrabarti, Sandip Kumar; Sasmal, Sudipta
2016-07-01
Prediction of seismic events is one of the most challenging jobs for the scientific community. Conventional ways for prediction of earthquakes are to monitor crustal structure movements, though this method has not yet yield satisfactory results. Furthermore, this method fails to give any short-term prediction. Recently, it is noticed that prior to any seismic event a huge amount of energy is released which may create disturbances in the lower part of D-layer/E-layer of the ionosphere. This ionospheric disturbance may be used as a precursor of earthquakes. Since VLF radio waves propagate inside the wave-guide formed by lower ionosphere and Earth's surface, this signal may be used to identify ionospheric disturbances due to seismic activity. We have analyzed VLF signals to find out the correlations, if any, between the VLF signal anomalies and seismic activities. We have done both the case by case study and also the statistical analysis using a whole year data. In both the methods we found that the night time amplitude of VLF signals fluctuated anomalously three days before the seismic events. Also we found that the terminator time of the VLF signals shifted anomalously towards night time before few days of any major seismic events. We calculate the D-layer preparation time and D-layer disappearance time from the VLF signals. We have observed that this D-layer preparation time and D-layer disappearance time become anomalously high 1-2 days before seismic events. Also we found some strong evidences which indicate that it may possible to predict the location of epicenters of earthquakes in future by analyzing VLF signals for multiple propagation paths.
Nwankwo, Victor U. J.; Chakrabarti, Sandip Kumar
Very low frequency (VLF) radio waves has been employed for the detection and study of various terrestrial and extra-terrestrial high energy phenomena such as solar flares, solar eclipse, gamma ray burst, lightning induced electron precipitation etc., and the subsequent variations in the lower ionosphere driven by these events. In this study, we exploit the propagation characteristics of VLF signal through the Earth-ionosphere waveguide, to probe changes in ionospheric signatures, induced by solar driven variations in magnetospheric conditions. Our study is based on the VLF signal (amplitude and phase) received at the Ionospheric and Earthquake Research Centre (IERC), Sitapur, under Indian Centre for Space Physics (ICSP), which is transmitted by the Australian NWC station at about 19.8kHz.
Energy Technology Data Exchange (ETDEWEB)
Boure, J. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires
1963-07-01
A small disturbance is, shown to give rise to two waves: a pressure (sonic) wave and a continuity wave. Their propagation velocities are calculated. These velocities are independent of the disturbance amplitude. The sonic velocity is primarily a function of that one corresponding to the same medium with no flow and of the liquid phase velocity. It is also a function of the physical properties of the phases on the saturation line, of the slip laws and of the void fraction. The continuity wave velocity is only a function of the slip laws, of the void fraction and of the velocity of either phase. It appears two kinds of critical flow rates which are calculated. The void fraction and the liquid and gas velocities variations are calculated. These results are extended to the case of a real loop and an approximative method is given for the treatment of this case. (author) [French] On montre qu'une petite perturbation donne naissance a deux ondes: une onde de pression (onde sonique) et une onde de continuite. On calcule leurs vitesses de propagation qui sont independantes de l'amplitude de la perturbation. La vitesse du son depend des proprietes physiques des phases le long de la courbe de saturation, des lois du glissement, de la fraction volumique de vapeur. Elle depend surtout de la vitesse qu'il aurait dans le milieu immobile de meme fraction volumique de vapeur, et de la vitesse de la phase liquide. La vitesse de l'onde de continuite depend des lois du glissement, de la fraction volumique de vapeur et de la vitesse d'une des phases. Il apparait deux types de debits critiques que l'on calcule. On calcule egalement les variations de la fraction volumique de vapeur et des vitesses des phases dans la perturbation. On generalise des resultats precedents dans le cas d'un circuit reel et on propose une methode approchee pour traiter le probleme dans ce cas. (auteur)
Scherrer, Arne; Vuilleumier, Rodolphe; Sebastiani, Daniel
2016-08-28
We report the first fully ab initio calculation of dynamical vibrational circular dichroism spectra in the liquid phase using nuclear velocity perturbation theory (NVPT) derived electronic currents. Our approach is rigorous and general and thus capable of treating weak interactions of chiral molecules as, e.g., chirality transfer from a chiral molecule to an achiral solvent. We use an implementation of the NVPT that is projected along the dynamics to obtain the current and magnetic dipole moments required for accurate intensities. The gauge problem in the liquid phase is resolved in a twofold approach. The electronic expectation values are evaluated in a distributed origin gauge, employing maximally localized Wannier orbitals. In a second step, the gauge invariant spectrum is obtained in terms of a scaled molecular moments, which allows to systematically include solvent effects while keeping a significant signal-to-noise ratio. We give a thorough analysis and discussion of this choice of gauge for the liquid phase. At low temperatures, we recover the established double harmonic approximation. The methodology is applied to chiral molecules ((S)-d2-oxirane and (R)-propylene-oxide) in the gas phase and in solution. We find an excellent agreement with the theoretical and experimental references, including the emergence of signals due to chirality transfer from the solute to the (achiral) solvent.
Scherrer, Arne; Vuilleumier, Rodolphe; Sebastiani, Daniel
2016-08-01
We report the first fully ab initio calculation of dynamical vibrational circular dichroism spectra in the liquid phase using nuclear velocity perturbation theory (NVPT) derived electronic currents. Our approach is rigorous and general and thus capable of treating weak interactions of chiral molecules as, e.g., chirality transfer from a chiral molecule to an achiral solvent. We use an implementation of the NVPT that is projected along the dynamics to obtain the current and magnetic dipole moments required for accurate intensities. The gauge problem in the liquid phase is resolved in a twofold approach. The electronic expectation values are evaluated in a distributed origin gauge, employing maximally localized Wannier orbitals. In a second step, the gauge invariant spectrum is obtained in terms of a scaled molecular moments, which allows to systematically include solvent effects while keeping a significant signal-to-noise ratio. We give a thorough analysis and discussion of this choice of gauge for the liquid phase. At low temperatures, we recover the established double harmonic approximation. The methodology is applied to chiral molecules ((S)-d2-oxirane and (R)-propylene-oxide) in the gas phase and in solution. We find an excellent agreement with the theoretical and experimental references, including the emergence of signals due to chirality transfer from the solute to the (achiral) solvent.
Effect of the total solar eclipse of March 20, 2015, on VLF/LF propagation
Solovieva, M. S.; Rozhnoi, A. A.; Fedun, V.; Schwingenschuh, K.
2016-05-01
The analyzed amplitude and phase variations in electromagnetic VLF and LF signals at 20-45 kHz, received in Moscow, Graz (Austria), and Sheffield (UK) during the total solar eclipse of March 20, 2015, are considered. The 22 analyzed paths have lengths of 200—6100 km, are differently oriented, and cross 40-100% occultation regions. Fifteen paths crossed the region where the occultation varied from 40 to 90%. Solar eclipse effects were found only on one of these paths in the signal phase (-50°). Four long paths crossed the 90-100% occultation region, and signal amplitude and phase anomalies were detected for all four paths. Negative phase anomalies varied from-75° to-90°, and the amplitude anomalies were both positive and negative and were not larger than 5 dB. It was shown that the effective height of the ionosphere varied from 6.5 to 11 km during the eclipse.
On the numerical modelling of VLF chorus dynamical spectra
Directory of Open Access Journals (Sweden)
D. Nunn
2009-06-01
Full Text Available This paper presents a study of the use of a one-dimensional Vlasov Hybrid Simulation (VHS computer code to simulate the dynamical spectra (i.e. frequency versus time spectrograms of ELF/VLF chorus signals (from ~a fraction to ~10 kHz. Recently excellent measurements of chorus have been made in the source region close to the geomagnetic equator aboard the four spacecraft Cluster mission. Using Cluster data for wave amplitude, which is up to 300 pT, local gyrofrequency, cold plasma density, and L-shell, observed chorus signals are reproduced with remarkable fidelity and, in particular, sweep rates in the range 1–10 kHz result as observed. Further, we find that the sweep rate is a falling function of increasing cold plasma density, again in accord with observations. Finally, we have satisfactorily simulated the rather rare falling frequency elements of chorus which are sometimes observed aboard Cluster in the generation region. For both rising and falling chorus we have presented detailed structural analyses of the generation regions. The main contributor to the frequency sweep rate is primarily the establishment of wave number/frequency gradients across the generation region by the out of phase component of the resonant particle current. The secondary contributor is the shortening of the wavelength of resonant particle current relative to that of the wave field. In view of the close agreement between observation and simulation, we conclude that nonlinear electron cyclotron resonance is indeed the mechanism underlying the generation of chorus signals just outside the plasmasphere.
Models of ionospheric VLF absorption of powerful ground based transmitters
Cohen, M. B.; Lehtinen, N. G.; Inan, U. S.
2012-12-01
Ground based Very Low Frequency (VLF, 3-30 kHz) radio transmitters play a role in precipitation of energetic Van Allen electrons. Initial analyses of the contribution of VLF transmitters to radiation belt losses were based on early models of trans-ionospheric propagation known as the Helliwell absorption curves, but some recent studies have found that the model overestimates (by 20-100 dB) the VLF energy reaching the magnetosphere. It was subsequently suggested that conversion of wave energy into electrostatic modes may be responsible for the error. We utilize a newly available extensive record of VLF transmitter energy reaching the magnetosphere, taken from the DEMETER satellite, and perform a direct comparison with a sophisticated full wave model of trans-ionospheric propagation. Although the model does not include the effect of ionospheric irregularities, it correctly predicts the average total power injected into the magnetosphere within several dB. The results, particularly at nighttime, appear to be robust against the variability of the ionospheric electron density. We conclude that the global effect of irregularity scattering on whistler mode conversion to quasi-electrostatic may be no larger than 6 dB.
An aerostat-supported ELF/VLF transmitter
Field, E. C., Jr.; Kies, L. R.; Bannister, P. R.; Ingram, R. F.; Hopkins, W. D.; Roberts, M. A.
1989-03-01
A demonstration of an aerostat-supported extremely low frequency/very low frequency (ELF/VLF) transmitting antenna was performed. At ELF the vertical electric dipole (VED) antenna radiated at least 100,000 times more power than would a horizontal electric dipole having the same moment. That efficiency was achieved with an altitude of 12,500 feet (3810 m). Calculations show that the radiated power will increase as the fourth power of aerostat altitude. The tether antenna exhibited a corona onset voltage of 180 kV and was resistant to the degrading effects of ELF corona. Prolonged in-corona operation is therefore possible. The antenna was continuously tuned, despite changes in height and capacitance caused by the aerostat flight dynamics. The huge 300-H ELF tuning inductor posed no problem. Enhanced VED moments were achieved at ELF by operation at voltages up to 260 kV, 40% above the corona onset voltage. At VLF the antenna emulated a monopole that had a radiation efficiency greater than 90%. The measured bandwidths were large: 1.5 kHz at 23 kHz and 3.5 kHz at 34 kHz. The antenna height exceeded one-quarter wavelength at VLF, so the antenna could be tuned capacitively and required relatively low base voltages. At both VLF and ELF the measured fields agreed closely with predictions.
The European VLF/LF radio network: current status
Biagi, Pier Francesco; Maggipinto, Tommaso; Ermini, A.
2014-11-01
For several years researches about correlation between seismicity and disturbances in radio broadcasting are being carried out: in particular, the Japanese Pacific VLF radio network and the European VLF-LF radio network have been developed during the last years. The European network has been developed starting from two LF receivers located in central Italy in 1996. Up to now, 11 receivers of a new type, able to sample the VLF and LF intensity of ten radio signals, are being into operation in different European countries. The daily updating of data is effective and the data bank is located at the Department of Physics of the University of Bari (Italy) which is the central node of the network. In order to discover anomalies, the software able to carry out automatically a daily data analysis by the Wavelet spectra method has been planned and realized. At the moment, the software operates on four signals (two LF and two VLF) collected by one of the receiver located in Italy. If the anomaly is particularly strong a warning system gives an advise on the work station into operation in the central node of the Network. In any case, before assuming an anomaly as a seismic anomaly, geomagnetic and meteorological data must be checked as well as any possible instrumental malfunction. At present these controls are carried out only discontinuously by the researchers of the Bari Team.
INSPIRE: A VLF Radio Project for High School Students
Marshall, Jill A.; Pine, Bill; Taylor, William W. L.
2007-01-01
Since 1988 the Interactive NASA Space Physics Ionospheric Radio Experiment, or INSPIRE, has given students the opportunity to build research-quality VLF radio receivers and make observations of both natural and stimulated radio waves in the atmosphere. Any high school science class is eligible to join the INSPIRE volunteer observing network and…
Pandian, Arun; Stellingwerf, Robert F.; Abarzhi, Snezhana I.
2017-07-01
While it is a common wisdom that initial conditions influence the evolution of the Richtmyer-Meshkov instability (RMI), the research in this area is focused primarily on the effects of the wavelength and amplitude of the interface perturbation. The information has hitherto largely ignored the influences on RMI dynamics of the relative phase of waves constituting a multiwave initial perturbation and the interference of the perturbation waves. In this work we systematically study the influence of the relative phase and the interference of waves constituting a multiwave initial perturbation on a strong-shock-driven Richtmyer-Meshkov unstable interface separating ideal fluids with contrast densities. We apply group theory analysis and smoothed particle hydrodynamics numerical simulations. For verification and validation of the simulations, qualitative and quantitative comparisons are performed with rigorous zeroth-order, linear, and nonlinear theories as well as with gas dynamics experiments achieving good agreement. For a sample case of a two-wave (two-mode) initial perturbation we select the first-wave amplitude enabling the maximum initial growth rate of the RMI and we vary the second-wave amplitude from 1% to 100% of the first-wave amplitude. We also vary the relative phase of the first and second waves and consider the in-phase, the antiphase and the random-phase cases. We find that the relative phase and the interference of waves are important factors of RMI dynamics influencing qualitatively and quantitatively the symmetry, morphology, and growth rate of the Richtmyer-Meshkov unstable interface, as well as the order and disorder in strong-shock-driven RMI.
Short-Term Perturbations Within the D-Region Detected Above the Mediterranean
Price, Colin; Silber, Israel
2016-07-01
The ionospheric D-region lies in the altitude range of ~60-95 km. This part of the atmosphere is highly sensitive to waves propagating upwards from the troposphere, either as pressure perturbations (gravity and acoustic waves) or electromagnetic (EM) perturbations from lightning discharges (resulting in EMPs, sprites, elves, etc.). These perturbations can affect the temperature, wind, species concentration, conductivity, and ionization in the upper atmosphere. Very low frequencies (VLF) radio signals, generated by man-made communication transmitters, have been recorded using ground-based VLF receivers in Israel. These radio waves propagate over long distances within the Earth-ionosphere waveguide, reflected off the Earth's surface and the D-region. The characteristics of the received signals depend on several parameters along the path, but are fairly constant over short periods of time. In this study we present analysis of VLF narrowband data transmitted from Sicily, Italy, spanning one year, and detected in Tel Aviv, Israel. We show observations of the interaction between both pressure and EM perturbations from thunderstorms with the narrowband VLF signals aloft. We clearly observe short period (~2-4 minutes) acoustic waves, longer period gravity waves (~5-7 minutes periods), while also many transient events related to heating and ionization of the D-region. Comparisons with WWLLN lightning data show the potential link between tropospheric thunderstorms and D-region variability.
An Artificial Particle Precipitation Technique Using HAARP-Generated VLF Waves
2006-11-02
AFRL-VS-HA-TR-2007-1021 An Artificial Particle Precipitation Technique Using HAARP -Generated VLF Waves O o o r- Q M. J. Kosch T. Pedersen J...Artificial Particle Precipitation Technique Using HAARP Generated VLF Waves. 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62101F...model. The frequency-time modulated VLF wave patterns have been successfully implemented at the HAARP ionospheric modification facility in Alaska
VLF wave injection experiments from Siple Station, Antarctica
R.A., Helliwell
1987-01-01
The background of VLF wave-particle experiments from Siple Station, Antarctica, including wave-induced precipitation is briefly reviewed. Single frequency ducted signals that exceed a certain 'threshold' intensity are observed at the conjugate point (Roberval, Quebec) to be amplified 30-50dB, with temporal growth rates of 30-200dB/s. Following saturation, variable frequency emissions are triggered. When a second signal is added to the first, with a frequency spacing Df
A Global Survey of ELF/VLF Radio Noise
2002-09-30
Smith, 2002]. Finally, our participation in one of the HAARP experimental programs, during which we made much use of the ELF/VLF radio noise data...Porrat, Teague, and Fraser-Smith, 1999]. Our objective was to make the first long-distance detection of ELF signals generated by the HAARP ...ionospheric heater; we did not succeed, but the continuing improve- ments to the HAARP heating facility in Alaska will ultimately lead to the routine
VLF Tan Delta Measurement for Used XLPE Power Cables
Energy Technology Data Exchange (ETDEWEB)
Lim, Woo Sang; Ha, Che Wung; Joo, Kwang Ho [Korea Hydro and Nuclear Power Co., Daejeon (Korea, Republic of)
2011-05-15
Medium voltage power cables in nuclear power plants are currently managed through the visual inspection or by monitoring environmental factors such as the temperature and radiation levels. However, these methods are insufficient to monitor aging degradation of power cables. The NRC requires an additional monitoring program to detect the aged degradation, especially for safety-related power cables which are inaccessible or installed underground. EPRI suggested that very low frequency (VLF) tan {delta} test be included in MV power cable diagnostic programs. In addition, the VLF tan {delta} test was recently adopted for domestic submarine distribution cable diagnostics. KEPRI suggested that the impacts of leakage current should be controlled in VLF tan {delta} test for the submarine cables. As a pre-process to develop such a program, tan {delta} tests have been performed for 4.16 kV cables which were removed from the domestic nuclear power plant after approximate 30 years of service to analyze the degradation of long time serviced cables and the effect of leakage current from the both ends of cables
Friedman, B.; Brophy, P.; Brune, W. H.; Farmer, D.
2015-12-01
The evolution of biogenic volatile organic compounds (BVOCs) in the atmosphere is impacted by concurrent emissions of anthropogenic pollutants, such as sulfur dioxide (SO2) and nitrogen oxides (NOx), which can impact air quality and SOA formation in regions of biogenic and anthropogenic influence. We present the impacts of anthropogenic perturbations in the form of sulfur dioxide on the oxidation systems of α- and β-pinene. An oxidative flow reactor simulated atmospheric aging by OH oxidation on the order of days, and high-resolution time-of-flight mass spectrometry (HR-TOF-CIMS) was utilized to identify gas-phase oxidation products and changes to the ensemble system as a function of the SO2 perturbation. Results show that the SO2 perturbation impacted the oxidation systems of α- and β-pinene, and that these perturbations affected the oxidation systems of α- and β-pinene differently. Bulk analysis comparing the perturbed system to the unperturbed system indicated a change in oxidation pathway or mechanism leading to an ensemble of products with a lesser degree of oxygenation, on the order of a 30% decrease in the bulk oxidation state and a 10% decrease in the bulk O:C ratio for both BVOC systems. Increasing the relative humidity in the oxidative flow reactor was found to dampen the impact of the perturbation. Experiments involving other anthropogenic emissions, such as NOx, as well as other pairs of BVOC structural isomers, were conducted to investigate if changes in the oxidation system were due to the BVOC structure or the specific anthropogenic pollutant.
Kozma, Gady
2012-01-01
We proved earlier that every measurable function on the circle, after a uniformly small perturbation, can be written as a power series (i.e. a series of exponentials with positive frequencies), which converges almost everywhere. Here we show that this result is basically sharp: the perturbation cannot be made smooth or even H\\"older. We discuss also a similar problem for perturbations with lacunary spectrum.
DEFF Research Database (Denmark)
Karakatsani, Eirini; Kontogeorgis, Georgios; Economou, Ioannis
2006-01-01
Perturbed chain-statistical associating fluid theory (PC-SAFT) was extended rigorously to polar fluids based on the theory of Stell and co-workers [Mol. Phys. 1977, 33, 987]. The new PC-PSAFT was simplified to truncated PC-PSAFT (tPC-PSAFT) so that it can be practical for real polar fluid thermod...
Maxworth, Ashanthi; Golkowski, Mark; University of Colorado Denver Team
2013-10-01
ELF/VLF wave generation via HF modulated ionospheric heating has been practiced for many years as a unique way to generate waves in the ELF/VLF band (3 Hz - 30 kHz). This paper presents experimental results and associated theoretical modeling from work performed at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska, USA. An experiment was designed to investigate the modulation frequency dependence of the generated ELF/VLF signal amplitudes and polarization at multiple sites at distances of 37 km, 50 km and 99 km from the facility. While no difference is observed for X mode versus O mode modulation of the heating wave, it is found that ELF/VLF amplitude and polarization as a function of modulated ELF/VLF frequency is different for each site. An ionospheric heating code is used to determine the primary current sources leading to the observations.
Aeed, Paul A; Sperry, Andrea E; Young, Casey L; Nagiec, Marek M; Elhammer, Ake P
2004-07-06
The effect of 26 different membrane-perturbing agents on the activity and phase distribution of inositol phosphorylceramide synthase (IPC synthase) activity in crude Candida albicans membranes was investigated. The nonionic detergents Triton X-100, Nonidet P-40, Brij, Tween, and octylglucoside all inactivated the enzyme. However, at moderate concentrations, the activity of the Triton X-100- and octylglucoside-solubilized material could be partially restored by inclusion of 5 mM phosphatidylinositol (PI) in the solubilization buffer. The apparent molecular mass of IPC synthase activity solubilized in 2% Triton X-100 was between 1.5 x 10(6) and 20 x 10(6) Da, while under identical conditions, octylglucoside-solubilized activity remained associated with large presumably membrane-like structures. Increased detergent concentrations produced more drastic losses of enzymatic activity. The zwitterionic detergents Empigen BB, N-dodecyl-N,N-(dimethylammonio)butyrate (DDMAB), Zwittergent 3-10, and amidosulfobetaine (ASB)-16 all appeared capable of solubilizing IPC synthase. However, these agents also inactivated the enzyme essentially irreversibly. Solubilization with lysophospholipids again resulted in drastic losses of enzymatic activity that were not restored by the inclusion of PI. Lysophosphatidylinositol also appeared to compete, to some extent, with the donor substrate phosphatidylinositol. The sterol-containing agent digitonin completely inactivated IPC synthase. By contrast, sterol-based detergents such as 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate (CHAPSO), and taurodeoxycholate (tDOC) had little or no effect on the enzyme activity. The IPC synthase activity in C. albicans membranes remained largely intact and sedimentable at CHAPS concentrations (4%) where >90% of the phospholipids and 60% of the total proteins were extracted from the membranes. At 2.5% CHAPS, a
Remenets, G. F.; Astafiev, A. M.
2016-09-01
Here we present the results of a case study of the rare, abnormal, qualitatively specific behavior of Aldra (northern Norway) and GBR (UK) VLF transmitter signals (10-16 kHz) received at Kola Peninsula. The abnormal amplitude and the phase disturbances of signals were used as a proxy for ultra-energetic relativistic (solar?) electron precipitation (URE, ∼100 MeV) into the middle polar atmosphere. The disturbances have been observed under quiet or moderately disturbed geomagnetic activity. Based on bearing results, it was established that the abnormal variations of the electric conductivity of ionized middle atmosphere (of a sporadic Ds layer under the regular ionosphere D layer) were characterized by the following: (i) the time function of height h(t) of an effective spherical waveguide between the Earth surface and the sporadic Ds layer shows a minimum value equal to ∼30 km and (ii) the reflection coefficient R(t) of radio wave with a grazing angle of incidence from a virtual boundary with height h(t) has a minimum value equal to ∼0.4. The southern boundaries of the ultra-energetic relativistic electron precipitations have been found as well. They turned out to be not southerly than 61 degree of magnetic latitude and similar to the ones obtained in our previous study of the events for other dates under the similar geophysical conditions although we do not know anything definite about the rigidity and density of the electron fluxes. A used calculation method of analysis is based on a necessary condition that a number n of input data should be greater than a number m of output parameter-functions. We have stated by numerical testing that a decrease of n from 6 to 4 generates a lack of uniqueness of an inverse VLF problem solution for m = 2. It is important for future VLF ground-based monitoring of the URE precipitation events.
Directory of Open Access Journals (Sweden)
Yu.V. Kalyuzhnyi
2012-06-01
Full Text Available The liquid-gas phase diagram for polydisperse dipolar hard-sphere fluid with polydispersity in the hard-sphere size and dipolar moment is calculated using extension of the recently proposed thermodynamic perturbation theory for central force (TPT-CF associating potential. To establish the connection with the phase behavior of ferrocolloidal dispersions it is assumed that the dipole moment is proportional to the cube of the hard-sphere diameter. We present and discuss the full phase diagram, which includes cloud and shadow curves, binodals and distribution functions of the coexisting daughter phases at different degrees of the system polydispersity. In all cases studied polydispersity increases the region of the phase instability and shifts the critical point to the higher values of the temperature and density. The larger size particles always fractionate to the liquid phase and the smaller size particles tend to move to the gas phase. At relatively high values of the system polydispersity three-phase coexistence is observed.
Theoretical Predictions for VLF Radio Propagation
1983-08-22
field strength is calculated as follows: E =(( Ezl cos OEzl + Ez2 cos OEz2 + Ez3 cos OEz3 )2 zi Ezi Ez z32 E1/2 E zl sin OEzl + Ez 2 sin OEz2 + Ez 3...NADC-83062-40 and the corresponding phase is calculated from 0 ta- 1 Ez sin 0 Ezl + Ez 2 sin Ez2 + Ez3 sin 0Ez3 0 tan ",__ _ _ _ _ _ _ _ _ E
Chakraborty, Suman; Chakrabarti, Sandip Kumar; Palit, Sourav; Ray, Suman
2016-07-01
One of the major sources of ionospheric perturbations is variations in solar Extreme Ultraviolet (EUV) radiation flux. Solar eclipse is a phenomenon which is capable of producing significant effects on the physical and chemical properties of the ionospheric plasma. During a solar eclipse, the solar radiation flux reduces considerably for a limited period of time over specific locations on the Earth. This induces certain changes within the ionosphere or more precisely, in the D-region which can be studied with the observation of Very Low Frequency (VLF) radio signal modulations. The parameters which mainly govern the ion-chemistry, such as the recombination coefficients are poorly known till date. Solar eclipse provides us with an excellent opportunity to study these parameters as its time of occurrence is known beforehand and thus we can equip ourselves accordingly. In the present study we considered the Total Solar Eclipse (TSE) that occurred on 22nd July, 2009 within the Indian subcontinent. Indian Centre for Space Physics (ICSP) conducted a week long campaign during the eclipse and data were recorded from dozens of places within India and abroad. Both positive and negative changes in VLF signal amplitude were observed. In this paper, data for a propagation path between Indian Navy VLF transmitter named VTX3 and a pair of receivers in India, namely Malda and Kolkata are used. We start with calculating the obscuration function for these two places to find the variations in ionization flux within the period of the eclipse. After this, we incorporated the D region ion chemistry model to find the equilibrium ion density over the region and employ the LWPC code to find the VLF signal amplitude. We varied the values of recombination coefficients to achieve desired accuracy in our results. In doing so, we achieved two goals: First, we have been able to reproduce the trend of variation in VLF signal amplitude (both positive and negative) at both the receiving locations
ELF/VLF wave generation from the beating of two HF ionospheric heating sources
Cohen, M. B.; Moore, R. C.; Golkowski, M.; Lehtinen, N. G.
2012-12-01
It is well established that Extremely Low Frequency (ELF, 0.3-3 kHz) and Very Low Frequency (VLF, 3-30 kHz) radio waves can be generated via modulated High Frequency (HF, 3-10 MHz) heating of the lower ionosphere (60-100 km). The ionospheric absorption of HF power modifies the conductivity of the lower ionosphere, which in the presence of natural currents such as the auroral electrojet, creates an `antenna in the sky.' We utilize a theoretical model of the HF to ELF/VLF conversion and the ELF/VLF propagation, and calculate the amplitudes of the generated ELF/VLF waves when two HF heating waves, separated by the ELF/VLF frequency, are transmitted from two adjacent locations. The resulting ELF/VLF radiation pattern exhibits a strong directional dependence (as much as 15 dB) that depends on the physical spacing of the two HF sources. This beat wave source can produce signals 10-20 dB stronger than those generated using amplitude modulation, particularly for frequencies greater than 5-10 kHz. We evaluate recent suggestions that beating two HF waves generates ELF/VLF waves in the F-region (>150 km), and conclude that those experimental results may have misinterpreted, and can be explained strictly by the much more well established D region mechanism.
Electric and VLF-MT survey of Tegatayama tunnel; Tegatayama tunnel no denki tansa oyobi VLF tansa
Energy Technology Data Exchange (ETDEWEB)
Nishitani, T. [Akita University, Akita (Japan). Mining College
1997-05-27
To survey the structure at the depth between 20 and 30 m, field tests were conducted by means of vertical electric and VFL-MT (magnetotelluric) survey. Tegatayama tunnel has a total length of 276 m, width of 7.5 m, and height of 4.7 m, and the depth from the surface is about 28 m near the top of mountain. Near the tunnel, the thickness of surface soil is about 60 cm, which consists of clay soil including soft mudstone gravel. It was found that terrace deposit is distributed up to the depth of 8 m, and that mudstone is distributed below the depth of 8 m. Weighted four-electrode method was adopted for the vertical electrical survey. Measurements were conducted at the immediately above the tunnel, 10 m apart from the center of tunnel in the right and left, and 20 m apart from the center in the east. For the VLF-MT method, component of frequency 22.2 kHz was used. As a result of the tests, it was difficult to illustrate the existence of tunnel from the vertical electrical survey only at one point. Feature of the tunnel could be well illustrated by means of the VLF-MT method. 3 refs., 9 figs.
Zetzer, J. I.; Lyakhov, A.; Yakymenko, K.
2012-12-01
The results of comprehensive analysis of long-term records of VLF-LF European transmitters by means of Mikhnevo geophysical observatory (Institute of Geospheres Dynamics), SID station A118 (France) and a number of AWESOM receivers are presented. In the previous study (A.A.Egoshin et al., Izvestiya, Physics of the Solid Earth, 2012, Vol. 48, No. 3, pp. 275-286) the results obtained under the minimum solar activity were presented that have shown the link between the lower ionosphere parameters and meteorological fields of the middle atmosphere. The current study expands the evidence to the increased solar activity level as well as the number of receivers, thus allowing more dense coverage of the Europe by the radio paths. Middle atmosphere data under study were provided by the EOS Aura Microwave Limb Sounder. These asynoptic data, in turn, were processed by the space-time spectral analysis on various pressure levels for various window lengths. The results are presented for the spatial structure of wave-like perturbations in the VLF-LF signal strength, which result from the lower ionosphere disturbances on various radio paths. Special short-windowed space-time study was evaluated for the periods of anomalous temporal behavior of the VLF-LF signals and the results of the altitude-latitude mode structures of the geopotential height, neutral temperature, water and ozone constituents are presented. It is shown that the spatial properties of the lower ionosphere can vary significantly at relatively small scale. Moreover, the altitude-latitude mode structures do not coincide in space as well as in time, thus, complicating the lower ionosphere response to the meteorological variations of the middle atmosphere. The analysis of all assembled data proves two main points. At first, it is possible to evaluate synoptic long-term monitoring of the middle atmosphere via the lower ionosphere perturbations as seen by VLF-LF receivers. At second, the theoretical models of the lower
Decrease of VLF transmitter signal and Chorus-whistler waves before l'Aquila earthquake occurrence
Directory of Open Access Journals (Sweden)
M. Y. Boudjada
2010-07-01
Full Text Available We investigate the VLF emissions observed by the Instrument Champ Electrique (ICE experiment onboard the DEMETER micro-satellite. We analyze intensity level variation 10 days before and after the occurrence of l'Aquila earthquake (EQ. We found a clear decrease of the VLF received signal related to ionospheric whistler mode (mainly Chorus emission and to signal transmitted by the DFY VLF station in Germany, few days (more than one week before the earthquake. The VLF power spectral density decreases of more than two orders of magnitude until the EQ, and it recovers to normal levels just after the EQ occurrence. The geomagnetic activity is principally weak four days before EQ and increases again one day before l'Aquila seismic event. Our results are discussed in the frame of short- and long-terms earthquakes prediction focusing on the crucial role of the magnetic field of the Earth.
DEFF Research Database (Denmark)
jora, Renata; Schechter, Joseph; Naeem Shahid, M.
2009-01-01
We study the effects of the perturbation which violates the permutation symmetry of three Majorana neutrinos but preserves the well known (23) interchange symmetry. This is done in the presenceof an arbitrary Majorana phase which serves to insure the degeneracy of the three neutrinos at the unper...
Lightning Location With Single-Station Observation of VLF Spherics
Nagano, I.; Yagitani, S.; Komonmae, H.; Takezono, N.
2001-12-01
Most of the lightning location systems recently available require the simultaneous reception of lightning-generated radio pulses (spherics) at multiple stations. In this work, we develop a lightning location system to determine both the direction and range of a lightning stroke with a single-station observation of VLF spherics. The technique used here is a rather classical one, but we try to improve the ranging accuracy by applying sophisticated signal processing techniques, and our final goal is to develop a portable lightning locator. We observe wave forms of two horizontal magnetic fields and one vertical electric field of VLF spherics, each of which usually consists of a couple of sequential pulses. The first pulse comes directly from a lightning return stroke, and is used for the direction finding of the stroke. On the other hand, the second and later pulses are the multiple reflections of the first pulse inside the Earth-ionosphere waveguide. Since the time-of-arrival (ToA) of each pulse is determined by its propagation path length in the waveguide, by using the observed difference in ToA of two or more pulses, we can inversely estimate not only the reflection height at the ionosphere but also the range of the lightning stroke. By installing the developed system at Kanazawa University, we have been observing lightning-generated spherics since April, 2000. Compared with the lightning location data provided by a local power company, preliminary analysis shows that this system can locate each lightning stroke within several hundred km with a sufficient accuracy.
Shendi, El-Arabi Hendi [العربيى هندي شندي
1997-01-01
The VLF-EM method is proved to be an effective, fast and inexpensive tool for ground water prospecting in the basement terrains of Southern Sinai. The resistive shallow alluvial deposits increase the penetration depth of the received VLF waves to as deep as 40 meters which is very reasonable to detect the water bearing alluvium in the studied areas. The measured horizontal and vertical components of the resultant VLF-EM field were used to calculate the apparent resistivities of the conductive...
Di Troia, Claudio
2016-01-01
The non perturbative guiding center transformation [Di Troia C., Phys. Plasmas 22, 042103 (2015)] is extended to the relativistic regime. The single particle dynamic is described in the Minkowski flat space-time. The main solutions are obtained in covariant form: the gyrating particle solutions and the guiding particle solution, both in gyro-kinetic as in MHD orderings. It is shown the relevance of the ideal Ohm's law in the context of the guiding center transformation. Moreover, it is also considered the presence of a gravitational field. The way to introduce the gravitational field is original and based on the Einstein conjecture on the feasibility to extend the general relativity theory to include electromagnetism. In gyro-kinetic theory, some interesting novelties appear in a natural way, such as the exactness of the conservation of magnetic moment, or the fact that the gyro-phase is treated as the non observable fifth dimension of the Kaluza-Klein model.
Henderson, R. L.
1974-01-01
The partial structure factors of classical simple liquid mixtures near phase separation are dicussed. The theory is developed for particles interacting through pair potentials, and is thus appropriate both to insulating fluids, and also to metallic systems if these may be described by an effective ion-ion pair interaction. The motivation arose from consideration of metallic liquid mixtures, in which resistive anomalies have been observed near phase separation. A mean field theory correction appropriate to 3 pair potential for the effects of correlated motions in the reference fluid is studied. The work is cast in terms of functions which are closely related to the direct correlation functions of Ornstein and Zernike. The results are qualitatively in accord with physical expectations. Quantitative agreement with experiment seems to turn on the selection of the hard core reference potential in terms of the metallic effective pair potential. It is suggested that the present effective pair potentials are perhaps not properly used to calculate the metallic structure factors at long wavelength.
On the ionospheric perturbation for the 1995 Kobe earthquake: revisited
Directory of Open Access Journals (Sweden)
Masashi Hayakawa
2016-01-01
Full Text Available The presence of seismo-lower ionospheric perturbation for the Kobe earthquake (EQ has been revisited with a relatively new phenomenon of ULF (ultra-low-frequency magnetic field depression effect. By using the ULF data in Japan only at Kakioka belonging to Japan Meteorological Agency (because data from Memambetsu and Kanoya were not available, we have found that a very clear ULF depression was observed at Kakioka on 14 January 1995. A comparison with our former result on subionospheric VLF (very low frequency propagation anomaly indicates that the occurrence of ULF depression exhibits a temporal coincidence (synchronization with that of subionospheric VLF anomaly. This may be acceptable because the ULF depression can be explained in terms of enhanced absorption of magnetospheric ULF waves through the disturbed lower ionosphere prior to an EQ. The result of ULF magnetic field depression in this paper is likely to provide a further support to the presence of the lower ionospheric perturbation before the Kobe EQ.
100 Days of ELF/VLF Generation via HF Heating with HAARP (Invited)
Cohen, M.; Golkowski, M.
2013-12-01
ELF/VLF radio waves are difficult to generate with conventional antennas. Ionospheric HF heating facilities generate ELF/VLF waves via modulated heating of the lower ionosphere. HF heating of the ionosphere changes the lower ionospheric conductivity, which in the presence of natural currents such as the auroral electrojet, creates an antenna in the sky when heating is modulated at ELF/VLF frequencies. We present a summary of nearly 100 days of ELF/VLF wave generation experiments at the 3.6 MW HAARP facility near Gakona, Alaska, and provide a baseline reference of ELF/VLF generation capabilities with HF heating. Between February 2007 and August 2008, HAARP was operated on close to 100 days for ELF/VLF wave generation experiments, at a variety of ELF/VLF frequencies, seasons and times of day. We present comprehensive statistics of generated ELF/VLF magnetic fields observed at a nearby site, in the 500-3500 Hz band. Transmissions with a specific HF beam configuration (3.25 MHz, vertical beam, amplitude modulation) are isolated so the data comparison is self-consistent, across nearly 5 million individual measurements of either a tone or a piece of a frequency-time ramp. There is a minimum in the average generation close to local midnight. It is found that generation during local nighttime is on average weaker, but more highly variable, with a small number of very strong generation periods. Signal amplitudes from day to day may vary by as much as 20-30 dB. Generation strengthens by ~5 dB during the first ~30 minutes of transmission, which may be a signature of slow electron density changes from sustained HF heating. Theoretical calculations are made to relate the amplitude observed to the power injected into the waveguide and reaching 250 km. The median power generated by HAARP and injected into the waveguide is ~0.05-0.1 W in this base-line configuration (vertical beam, 3.25 MHz, amplitude modulation), but may have generated hundreds of Watts for brief durations
Mushtak, V.; Price, C.; Williams, E.
Single -station electromagnetic methods for global lightning location are based on specific features of ELF wave propagation. First, ELF waves propagate with an extremely low attenuation not exceeding 1.5 dB/Mm up to 100 Hz. For this reason, the propagation has a resonant character (the Schumann resonance phenomena) imparting a unique pattern to the spectrum of a lightning waveform depending on the parent lightning's location relative to the given observer. The wave impedance technique realized by Kemp and Jones (1971) and widely adopted afterwards eliminates any need for the frequency dependence of the spectral density of the source's current moment for the location purpose. At the same time, an adequate single-mode propagation model can be applied for recovering this dependence and providing additional information about the source. As the only shortcoming of ELF location procedure, considerable error in estimates of the arrival directions of lightning waveforms was revealed by means of the satellite (OTD) identification of parent lightning events. These azimuthal deviations result in global location accuracies of 1-2 Mm (Boccippio et al, 1998) hardly acceptable in many geophysical problems. Price et al. (2002) found similar azimuthal errors in the ELF technique by means of the ground-truth (NLDN) identification of sprite-producing thunderstorms in Colorado when observing atmospherics in the Negev Desert, Israel. The location accuracy had been essentially improved - to better than 0.2 Mm on this 11 Mm path - by combining ELF distance estimates with VLF direction finding. Theoretical considerations show that this improvement is to be explained by a distinction between the ELF and VLF refraction effects at the day-night boundary of the Earth- ionosphere waveguide. While the difference between the day-time and night-time values of the phase velocity in the ELF range reaches 15%, it does not exceed 1% in the VLF range, with a corresponding diminishment of azimuthal
The European VLF/LF Radio Network: the current status
Biagi, Pier Francesco; Maggipinto, Tommaso; Schiavulli, Luigi; Ligonzo, Teresa; Colella, Roberto; Ermini, Anita; Martinelli, Giovanni; Palangio, Paolo; Moldovan, Iren; Silva, Hugo; Contadakis, Michael; Frantzis, Xenophon; Katzis, Konstantinos; Buyuksarac, Aydin; D'Amico, Sebastiano
2014-05-01
Since 2009 a network of VLF (20-60 kHz) and LF (150-300 kHz) radio receivers has been put into operation in Europe in order to study earthquakes precursors. At the moment the network consists of eleven receivers four of which are located in Italy, two in Greece and one in Portugal, Romania, Malta, Cyprus and Turkey. The data (sampling rate of 1min) are downloaded automatically at the end of each day and they are stored in the server located at the Department of Physics of the University of Bari (Italy), that is the central node of the network. Still, in some case, problems of connection exist. The different trends are open and visible on the web site: http://beta.fisica.uniba.it/infrep/Hom.aspx. The data files can be downloaded by the same web site but they are protected by username and password. Among the different methods of data analysis the Wavelet spectra appear to be the most sensitive ones. The software able to apply this technique on the radio data automatically at the end of each day has been planned and realized. At the moment it operates on four signals collected by one of the Italian receivers; if an anomaly stands up and it is over a fixed threshold a warning advise appears. In the web site, this activity is protected by a specific username and password.
Foster, J. C.; Erickson, P. J.; Baker, D. N.; Jaynes, A. N.; Mishin, E. V.; Fennel, J. F.; Li, X.; Henderson, M. G.; Kanekal, S. G.
2016-06-01
Van Allen Probes observations during the 17 March 2015 major geomagnetic storm strongly suggest that VLF transmitter-induced waves play an important role in sculpting the earthward extent of outer zone MeV electrons. A magnetically confined bubble of very low frequency (VLF) wave emissions of terrestrial, human-produced origin surrounds the Earth. The outer limit of the VLF bubble closely matches the position of an apparent barrier to the inward extent of multi-MeV radiation belt electrons near 2.8 Earth radii. When the VLF transmitter signals extend beyond the eroded plasmapause, electron loss processes set up near the outer extent of the VLF bubble create an earthward limit to the region of local acceleration near L = 2.8 as MeV electrons are scattered into the atmospheric loss cone.
Liu, Ningyu; Dwyer, Joseph; Rassoul, Hamid
2013-04-01
The fact that lightning/thunderstorm activities can directly modify the lower ionosphere has long been established by observations of the perturbations of very low frequency (VLF) signals propagating in the earth-ionosphere waveguide. These perturbations are known as early VLF events [Inan et al., 2010, JGR, 115, A00E36, 2010]. More recently discovered transient luminous events caused by the lightning/thunderstorm activities only last ~1-100 ms, but studies of the early VLF events show that the lightning ionospheric effects can persist much longer, >10s min [Cotts and Inan, GRL, 34, L14809, 2007; Haldoupis et al., JGR, 39, L16801, 2012; Salut et al., JGR, 117, A08311, 2012]. It has been suggested that the long recovery is caused by long-lasting conductivity perturbations in the lower ionosphere, which can be created by sprites/sprite halos which in turn are triggered by cloud-to-ground (CG) lightning [Moore et al., JGR, 108, 1363, 2003; Haldoupis et al., 2012]. We recently developed a two-dimensional fluid model with simplified ionospheric chemistry for studying the quasi-electrostatic effects of lightning in the lower ionosphere [Liu, JGR, 117, A03308, 2012]. The model chemistry captures major ion species and reactions in the lower ionosphere. Additional important features of the model include self-consistent background ion density profiles and full description of electron and ion transport. In this talk, we present the simulation results on the dynamics of sprite halos caused by negative CG lightning. The modeling results indicate that electron density around 60 km altitude can be enhanced in a region as wide as 80 km. The enhancement reaches its full extent in ~1 s and recovers in 1-10 s, which are on the same orders as the durations of slow onset and post-onset peaks of some VLF events, respectively. In addition, long-lasting electron and ion density perturbations can occur around 80 km altitude due to negative halos as well as positive halos, which can explain
A new type of daytime high-frequency VLF emissions at auroral latitudes ("bird emissions")
Manninen, J.; Turunen, T.; Kleimenova, N. G.; Gromova, L. I.; Kozlovskii, A. E.
2017-01-01
This paper is concerned with a new, previously unknown type of high-frequency (above 4 kHz) VLF emissions that were detected during winter VLF campaigns in Kannuslehto ( L 5.5), Finland. These previously unknown emissions have been discovered as a result of the application of special digital filtering: it clears the VLF records from pulse signals of intensive atmospherics, which prevent other kinds of VLF emissions in the same frequency range from being seen on spectrograms. As it appears, aside from wellknown bursts of auroral hisses and discrete quasiperiodic emissions, a previously unknown type of daytime right-hand polarized VLF waves is also present at frequencies above 4 kHz. These emissions can persist for several hours as series of separate short discrete wideband (from 4 to 10 kHz and higher) signals, each with a duration between one and several minutes. It has been found that such signals can be observed almost daily in winter. These emissions sound like bird's chirping to a human ear; for that reason, they were called "bird emissions." The dynamic spectra of individual signals often resemble flying birds. The signals are observed during daytime, more often in magnetically quiet conditions preceded by geomagnetic disturbances. As a rule, the occurrence of these bird emissions is accompanied by a slight increase in electron density in the lower ionosphere, which is evidence of the precipitation of energetic (>30 keV) electrons. This raises a number of questions as to where and how the VLF bird emissions are generated and how such emissions, at frequencies greatly exceeding half the electron equatorial gyrofrequency at L 5.5, can reach the Earth's surface.
ELF/VLF wave disturbances detected by the DEMETER satellite over the HAARP transmitter
Titova, Elena; Demekhov, Andrei; Parrot, Michel; Mogilevsky, Mikhail; Mochalov, Alexey; Pashin, Anatoly
We report observations of electromagnetic the ELF/VLF wave disturbances by the DEMETER satellite (670 km altitude) overflying the HAARP heating facility (62.39(°) N, 145.15(°) W, L = 4.9). The HAARP HF transmitter operated at the maximum available power of 3.6 MW, O-mode polarization, and the beam directed towards the magnetic zenith. ELF/VLF waves caused by the HAARP heating are detected by the DEMETER satellite when the HF radio wave frequency was close to the critical frequency (foF2) of the ionospheric F2 layer but below it. ELF/VLF wave disturbances observed above the HAARP transmitter were detected by electrical antennas in an area with characteristic size 10 (2) km. We analyze amplitude and polarization spectra of the ELF disturbances and compare them with the characteristics of natural ELF hiss above HAARP. The VLF wave disturbances in the topside ionosphere above the HAARP transmitter were detected in the frequency ranges 8-17 kHz and 15-18 kHz which are close to the lower hybrid resonance frequency f _LHR in the heating region and its second harmonic (2f _LHR), respectively. In the case where the HAARP HF power was modulated, the detected VLF waves were also modulated with the same frequency whereas in the ELF frequency range the modulation period of the HAARP power was not observed. Possible mechanisms of generation of the ELF/VLF disturbances produced by the HAARP transmitter in the topside ionosphere are discussed.
Combined ULF and VLF observations of seismo-electro-magnetic phenomena in Europe
Schwingenschuh, Konrad; Eichelberger, Hans; Wolbang, Daniel; Prattes, Gustav; Besser, Bruno; Boudjada, Mohammed Y.; Stangl, Günter; Magnes, Werner; Berghofer, Gerhard; Aydogar, Özer; Rozhnoi, Alexander; Solovieva, Maria; Vellante, Massimo; Villante, Umberto; Biagi, Pier F.
2014-05-01
A combined analysis of magnetic ultra-low-frequency (ULF) and electromagnetic very-low-frequency (VLF) fluctuations before, during and after earthquakes in south and south-east Europe is presented. The magnetic fluctuations are studied in the frame of the South European Geomagnetic Array (SEGMA) network. The fluxgate and searchcoil magnetometers, located in Italy, Bulgaria and Hungary perform measurements of fluctuations in the pico-Tesla and nano-Tesla range from milli-Hertz to 100 Hz. The properties of VLF radio links (10 kHz - 50 kHz) are studied in the frame of the European VLF/LF radio receiver network (INFREP). Single parameter studies of ULF and VLF variations in the vicinity of earthquakes in Europe have been performed in the last decade (Villante et al. 2010, Rozhnoi et al. 2009). We present the first results of a dual parameter study based on single parameter ULF and VLF observations. The proposed method provides the opportunity to decrease the number of false alerts. A dual parameter seismo-electro-magnetic reliability number is developed and compared with single parameter quality numbers. References: Rozhnoi, A., Solovieva, M., Molchanov, O., Schwingenschuh, K., Boudjada, M., Biagi, P. F., Maggipinto, T., Castellana, L., Ermini, A., and Hayakawa, M.: Anomalies in VLF radio signals prior the Abruzzo earthquake (M=6.3) on 6 April 2009, Nat. Hazards Earth Syst. Sci., 9, 1727-1732, doi:10.5194/nhess-9-1727-2009, 2009. Villante, U., De Lauretis, M., De Paulis, C., Francia, P., Piancatelli, A., Pietropaolo, E., Vellante, M., Meloni, A., Palangio, P., Schwingenschuh, K., Prattes, G., Magnes, W., and Nenovski, P.: The 6 April 2009 earthquake at L'Aquila: a preliminary analysis of magnetic field measurements, Nat. Hazards Earth Syst. Sci., 10, 203-214, doi:10.5194/nhess-10-203-2010, 2010.
Extended lateral heating of the nighttime ionosphere by ground-based VLF transmitters
İnan, Umran Savaş; Graf, K. L.; Spasojevic, M.; Marshall, R. A.; Lehtinen, N. G.; Foust, F. R.
2013-01-01
JOURNAL OF GEOPHYSICAL RESEARCH: SPACE PHYSICS, VOL. 118, 7783–7797, doi:10.1002/2013JA019337, 2013 Extended lateral heating of the nighttime ionosphere by ground-based VLF transmitters K. L. Graf,1 M. Spasojevic,1 R. A. Marshall,2 N. G. Lehtinen,1 F. R. Foust,1 and U. S. Inan1,3 Received 16 August 2013; revised 9 October 2013; accepted 11 November 2013; published 3 December 2013. [1] The effects of ground-based very low frequency (VLF) transmitters on the lower ionospher...
Quasi-periodic VLF emissions observed during daytime at a low latitude Indian ground station Jammu
Indian Academy of Sciences (India)
K K Singh; J Singh; R P Patel; A K Singh; R P Singh; Rejesh Singh; P A Ganai
2009-06-01
This paper reports quasi-periodic pulsing hiss emissions recorded during daytime in the frequency range of 50 Hz –15 kHz at low latitude station Jammu (geomag.lat.=22° 26′N; =1.17). It is noted that pulsing VLF emissions are a rare phenomena at low latitudes.The various spectrograms of pulsing VLF hiss emissions presented in this paper clearly show band limited spectrums regularly pulsing with almost equal period of the order of few seconds in the frequency range of ∼3-8 kHz. Generation and propagation mechanism of these emissions are brieﬂy discussed.
Similar Data Retrieval from Enormous Datasets on ELF/VLF Wave Spectrum Observed by Akebono
Directory of Open Access Journals (Sweden)
Y Kasahara
2010-02-01
Full Text Available As the total amount of data measured by scientific spacecraft is drastically increasing, it is necessary for researchers to develop new computation methods for efficient analysis of these enormous datasets. In the present study, we propose a new algorithm for similar data retrieval. We first discuss key descriptors that represent characteristics of the VLF/ELF waves observed by the Akebono spacecraft. Second, an algorithm for similar data retrieval is introduced. Finally, we demonstrate that the developed algorithm works well for the retrieval of the VLF spectrum with a small amount of CPU load.
Sanfui, Minu; Haldar, D. K.; Biswas, Debasish
2016-10-01
The space between the two spherical conducting shells, Earth surface and the lower boundary of the ionosphere, behaves as a spherical cavity in which some electromagnetic signals can propagate a long distance and is called Earth-ionosphere waveguide. Through this waveguide ultra low frequency (ULF), extremely low frequency (ELF) and very low frequency (VLF) signals can propagate efficiently with low attenuation. Resonances which occur for ELF waves due to round-the-world propagation interfering with 2n π phase difference are called Schumann resonances. Lightnings are the main sources of energy continuously producing these electromagnetic radiations from the troposphere. Some fixed frequency signals are also transmitted through the waveguide from different stations for navigation purposes. The intensity and phase of these signals at a particular position depend on the waveguide characteristics which are highly influenced by different natural events. Thus the signatures of different geophysical and extra-terrestrial events may be investigated by studying these signals through proper monitoring of the time series data using suitable techniques. In this article, we provide a review on ULF, ELF and VLF signals within the waveguide in terms of different geophysical and extra-terrestrial events like lightning, earthquakes, Leonid meteor shower, solar flares, solar eclipse, geomagnetic storms, and TLEs etc.
Directory of Open Access Journals (Sweden)
M. Platino
2004-07-01
Full Text Available It is now well known that amplitude modulated HF transmissions into the ionosphere can be used to generate ELF/VLF signals using the so-called "electrojet antenna". Although most observations of the generated ELF/VLF signals have been made on the ground, several low and high-altitude satellite observations have also been reported (James et al., 1990. One of the important unknowns in the physics of ELF/VLF wave generation by ionospheric heating is the volume of the magnetosphere illuminated by the ELF/VLF waves. In an attempt to investigate this question further, ground-satellite conjunction experiments have recently been conducted using the four Cluster satellites and the HF heater of the High-Frequency Active Auroral Research Program (HAARP facility in Gakona, Alaska. Being located on largely closed field lines at L≈4.9, HAARP is currently also being used for ground-to-ground type of ELF/VLF wave-injection experiments, and will be increasingly used for this purpose as it is now being upgraded for higher power operation. In this paper, we describe the HAARP installation and present recent results of the HAARP-Cluster experiments. We give an overview of the detected ELF/VLF signals at Cluster, and a possible explanation of the spectral signature detected, as well as the determination of the location of the point of injection of the HAARP ELF/VLF signals into the magnetosphere using ray tracing.
Modulation of auroral electrojet currents using dual HF beams with ELF phase offset
Golkowski, M.; Cohen, M.; Moore, R. C.
2012-12-01
The modulation of naturally occuring ionospheric currents with high power radio waves in the high frequency (HF, 3-10 MHz) band is a well known technique for generation of extremely low frequency (ELF, 3-3000 Hz) and very low frequency (VLF, 3-30 kHz) waves. We use the heating facility of the High Frequency Active Auroral Research Program (HAARP) to investigate the effect of using dual HF beams with an ELF/VLF phase offset between the modulation waveforms. Experiments with offset HF beams confirm the model of independent ELF/VLF sources. Experiments with co-located HF beams exhibit interaction between the first and second harmonics of the modulated tones when square and sine wave modulation waveforms are employed. Using ELF/VLF phase offsets for co-loacted beams is also shown to be a potential diagnostic for the D-region ionospheric profile.
Energy Technology Data Exchange (ETDEWEB)
Ghobadi, Ahmadreza F.; Elliott, J. Richard, E-mail: elliot1@uakron.edu [Department of Chemical and Biomolecular Engineering, The University of Akron, Akron Ohio 44325 (United States)
2014-09-07
In Paper I [A. F. Ghobadi and J. R. Elliott, J. Chem. Phys. 139(23), 234104 (2013)], we showed that how a third-order Weeks–Chandler–Anderson (WCA) Thermodynamic Perturbation Theory and molecular simulation can be integrated to characterize the repulsive and dispersive contributions to the Helmholtz free energy for realistic molecular conformations. To this end, we focused on n-alkanes to develop a theory for fused and soft chains. In Paper II [A. F. Ghobadi and J. R. Elliott, J. Chem. Phys. 141(2), 024708 (2014)], we adapted the classical Density Functional Theory and studied the microstructure of the realistic molecular fluids in confined geometries and vapor-liquid interfaces. We demonstrated that a detailed consistency between molecular simulation and theory can be achieved for both bulk and inhomogeneous phases. In this paper, we extend the methodology to molecules with partial charges such as carbon dioxide, water, 1-alkanols, nitriles, and ethers. We show that the electrostatic interactions can be captured via an effective association potential in the framework of Statistical Associating Fluid Theory (SAFT). Implementation of the resulting association contribution in assessing the properties of these molecules at confined geometries and interfaces presents satisfactory agreement with molecular simulation and experimental data. For example, the predicted surface tension deviates less than 4% comparing to full potential simulations. Also, the theory, referred to as SAFT-γ WCA, is able to reproduce the specific orientation of hydrophilic head and hydrophobic tail of 1-alkanols at the vapor-liquid interface of water.
Del Ben, Mauro; Hutter, Jürg; VandeVondele, Joost
2015-09-01
The forces acting on the atoms as well as the stress tensor are crucial ingredients for calculating the structural and dynamical properties of systems in the condensed phase. Here, these derivatives of the total energy are evaluated for the second-order Møller-Plesset perturbation energy (MP2) in the framework of the resolution of identity Gaussian and plane waves method, in a way that is fully consistent with how the total energy is computed. This consistency is non-trivial, given the different ways employed to compute Coulomb, exchange, and canonical four center integrals, and allows, for example, for energy conserving dynamics in various ensembles. Based on this formalism, a massively parallel algorithm has been developed for finite and extended system. The designed parallel algorithm displays, with respect to the system size, cubic, quartic, and quintic requirements, respectively, for the memory, communication, and computation. All these requirements are reduced with an increasing number of processes, and the measured performance shows excellent parallel scalability and efficiency up to thousands of nodes. Additionally, the computationally more demanding quintic scaling steps can be accelerated by employing graphics processing units (GPU's) showing, for large systems, a gain of almost a factor two compared to the standard central processing unit-only case. In this way, the evaluation of the derivatives of the RI-MP2 energy can be performed within a few minutes for systems containing hundreds of atoms and thousands of basis functions. With good time to solution, the implementation thus opens the possibility to perform molecular dynamics (MD) simulations in various ensembles (microcanonical ensemble and isobaric-isothermal ensemble) at the MP2 level of theory. Geometry optimization, full cell relaxation, and energy conserving MD simulations have been performed for a variety of molecular crystals including NH3, CO2, formic acid, and benzene.
Energy Technology Data Exchange (ETDEWEB)
Del Ben, Mauro, E-mail: mauro.delben@chem.uzh.ch; Hutter, Jürg, E-mail: hutter@chem.uzh.ch [Department of Chemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich (Switzerland); VandeVondele, Joost, E-mail: Joost.VandeVondele@mat.ethz.ch [Department of Materials, ETH Zürich, Wolfgang-Pauli-Strasse 27, CH-8093 Zürich (Switzerland)
2015-09-14
The forces acting on the atoms as well as the stress tensor are crucial ingredients for calculating the structural and dynamical properties of systems in the condensed phase. Here, these derivatives of the total energy are evaluated for the second-order Møller-Plesset perturbation energy (MP2) in the framework of the resolution of identity Gaussian and plane waves method, in a way that is fully consistent with how the total energy is computed. This consistency is non-trivial, given the different ways employed to compute Coulomb, exchange, and canonical four center integrals, and allows, for example, for energy conserving dynamics in various ensembles. Based on this formalism, a massively parallel algorithm has been developed for finite and extended system. The designed parallel algorithm displays, with respect to the system size, cubic, quartic, and quintic requirements, respectively, for the memory, communication, and computation. All these requirements are reduced with an increasing number of processes, and the measured performance shows excellent parallel scalability and efficiency up to thousands of nodes. Additionally, the computationally more demanding quintic scaling steps can be accelerated by employing graphics processing units (GPU’s) showing, for large systems, a gain of almost a factor two compared to the standard central processing unit-only case. In this way, the evaluation of the derivatives of the RI-MP2 energy can be performed within a few minutes for systems containing hundreds of atoms and thousands of basis functions. With good time to solution, the implementation thus opens the possibility to perform molecular dynamics (MD) simulations in various ensembles (microcanonical ensemble and isobaric-isothermal ensemble) at the MP2 level of theory. Geometry optimization, full cell relaxation, and energy conserving MD simulations have been performed for a variety of molecular crystals including NH{sub 3}, CO{sub 2}, formic acid, and benzene.
Del Ben, Mauro; Hutter, Jürg; VandeVondele, Joost
2015-09-14
The forces acting on the atoms as well as the stress tensor are crucial ingredients for calculating the structural and dynamical properties of systems in the condensed phase. Here, these derivatives of the total energy are evaluated for the second-order Møller-Plesset perturbation energy (MP2) in the framework of the resolution of identity Gaussian and plane waves method, in a way that is fully consistent with how the total energy is computed. This consistency is non-trivial, given the different ways employed to compute Coulomb, exchange, and canonical four center integrals, and allows, for example, for energy conserving dynamics in various ensembles. Based on this formalism, a massively parallel algorithm has been developed for finite and extended system. The designed parallel algorithm displays, with respect to the system size, cubic, quartic, and quintic requirements, respectively, for the memory, communication, and computation. All these requirements are reduced with an increasing number of processes, and the measured performance shows excellent parallel scalability and efficiency up to thousands of nodes. Additionally, the computationally more demanding quintic scaling steps can be accelerated by employing graphics processing units (GPU's) showing, for large systems, a gain of almost a factor two compared to the standard central processing unit-only case. In this way, the evaluation of the derivatives of the RI-MP2 energy can be performed within a few minutes for systems containing hundreds of atoms and thousands of basis functions. With good time to solution, the implementation thus opens the possibility to perform molecular dynamics (MD) simulations in various ensembles (microcanonical ensemble and isobaric-isothermal ensemble) at the MP2 level of theory. Geometry optimization, full cell relaxation, and energy conserving MD simulations have been performed for a variety of molecular crystals including NH3, CO2, formic acid, and benzene.
Development of ground-based ELF/VLF receiver system in Wuhan and its first results
Chen, Yanping; Yang, Guobin; Ni, Binbin; Zhao, Zhengyu; Gu, Xudong; Zhou, Chen; Wang, Feng
2016-05-01
A new digital low-frequency receiver system has been developed at Wuhan University for sensitive reception of low-latitude broadband Extremely Low Frequency (ELF) and Very Low Frequency (VLF) radio waves originating from either natural or artificial sources. These low-frequency radio waves are useful for ionospheric remote sensing, geospace environment monitoring, and submarine communications. This paper presents the principle and architecture of the system framework, including magnetic loop antenna design, low-noise analog front-end and digital receiver with data sampling and transmission. A new structure is adopted in the analog front end to provide high common-mode rejection and to reduce interference. On basis of field programmable gate array (FPGA) device and Universal Serial Bus (USB) architecture, the digital receiver is developed along with time keeping and synchronization module. The validity and feasibility of the self-developed ground-based ELF/VLF receiver system is evaluated by first results of experimental data that show the temporal variation of broadband ELF/VLF wave spectral intensity in Wuhan (30.54 °N, 114.37 °E). In addition to the acquisition of VLF transmitter signals at various frequencies, tweek atmospherics are also clearly captured to occur at multiple modes up to n = 6.
Investigation of TEC and VLF space measurements associated to L'Aquila (Italy earthquakes
Directory of Open Access Journals (Sweden)
G. Stangl
2011-04-01
Full Text Available In this study, we report on Total Electron Content (TEC and Very Low Frequency (VLF space measurements derived from Global Positioning System (GPS and DEMETER satellites, respectively. These measurements are associated with the earthquake (EQ of a magnitude of 6.3, which occurred on 6 April 2009, in L'Aquila (Italy. Anomaly features are derived from the analysis of TEC and VLF observations recorded two weeks before and after the seismic event occurrence. A TEC map with an interpolated regional pixel resolution of 1° × 1° × 15 min in latitude, longitude and time was generated, allowing for the checking of a possible presence of disturbances over the L'Aquila region. This analysis is combined with the study of the time profile associated to the VLF flux density variations recorded by the Instrument Champ Electrique (ICE experiment on-board DEMETER satellite. We discuss, on the one hand, the combination efficiency of the electronic density and the VLF electromagnetic measurements and, on the other hand, the difficulty to distinguish between global effects and regional ones related to the earthquake.
Study of latitudinal effects on VLF transmitter signals recorded by DEMETER/ICE experiment
Boudjada, M. Y.; Schwingenschuh, K.; Berthelier, J. J.; Döller, R.; Galopeau, P. H. M.; Parrot, M.; Stangl, G.; Biernat, H.; Voller, W.; Besser, B.
2010-05-01
We report on VLF transmitter signals observed by the ‘Instrument Capteur Electrique' (ICE) experiment onboard the DEMETER micro-satellite. The DEMETER polar and circular sun-synchronous orbits lead to cover an invariant latitude range between -65° and +65° where up- and down-going half-orbits correspond to night-time (22:00 LT) and day-time (10:00 LT), respectively. The DEMETER orbit features permit to record signals emitted by some VLF ground-stations and detected by ICE experiment. We consider three transmitter signals emitted by stations in Europe (Germany, DFY, 16.58 kHz), in Asia (Japan, JP, 17.8 kHz) and in Australia (Australia, NWC, 19.8 kHz). We study the variation of these VLF signals taking into consideration the DEMETER satellite latitudes .We emphasis on latitudes where the satellite is close to the Earth's sub-auroral regions. We discuss particularly the presence, or not, of auroral magnetic activity effect on the VLF transmitter signals.
Platino, M.; Inan, U.S.; Bell, T. F.; Pickett, J; Kennedy, E J; Trotignon, J. G.; Rauch, J. L.; Canu, P.
2004-01-01
It is now well known that amplitude modulated HF transmissions into the ionosphere can be used to generate ELF/VLF signals using the so-called "electrojet antenna". Although most observations of the generated ELF/VLF signals have been made on the ground, several low and high-altitude satellite observations have also been reported (James et al., 1990). One of the important unknowns in the physics of ELF/VLF wave generation by ionospheric heating is the volume of the magnetosphere ill...
Platino, M.; U. S. Inan; Bell, T.F.; Pickett, J.; Kennedy, E.J.; J. G. Trotignon; Rauch, J.L.; P. Canu
2004-01-01
It is now well known that amplitude modulated HF transmissions into the ionosphere can be used to generate ELF/VLF signals using the so-called "electrojet antenna". Although most observations of the generated ELF/VLF signals have been made on the ground, several low and high-altitude satellite observations have also been reported (James et al., 1990). One of the important unknowns in the physics of ELF/VLF wave generation by ionospheric heating is the volume of the magnetosphere ill...
100 days of ELF/VLF generation via HF heating with HAARP
Cohen, M. B.; Gołkowski, M.
2013-10-01
Extremely low frequency/very low frequency (ELF/VLF) radio waves are difficult to generate with conventional antennas. Ionospheric high frequency (HF) heating facilities generate ELF/VLF waves via modulated heating of the lower ionosphere. HF heating of the ionosphere changes the lower ionospheric conductivity, which in the presence of natural currents such as the auroral electrojet creates an antenna in the sky when heating is modulated at ELF/VLF frequencies. We present a summary of nearly 100 days of ELF/VLF wave generation experiments at the 3.6 MW High Frequency Active Auroral Research Program (HAARP) facility near Gakona, Alaska, at a variety of ELF/VLF frequencies, seasons, and times of day. We present comprehensive statistics of generated ELF/VLF magnetic fields observed at a nearby site, in the 500-3500 Hz band. Transmissions with a specific HF beam configuration (3.25 MHz, vertical beam, amplitude modulation) are isolated so the data comparison is self-consistent, across nearly 5 million individual measurements of either a tone or a piece of a frequency-time ramp. There is a minimum in the average generation close to local midnight. It is found that generation during local nighttime is on average weaker but more highly variable, with a small number of very strong generation periods. Signal amplitudes from day to day may vary by as much as 20-30 dB. Generation strengthens by ˜5 dB during the first ˜30 min of transmission, which may be a signature of slow electron density changes from sustained HF heating. Theoretical calculations are made to relate the amplitude observed to the power injected into the waveguide and reaching 250 km. The median power generated by HAARP and injected into the waveguide is ˜0.05-0.1 W in this baseline configuration (vertical beam, 3.25 MHz, amplitude modulation) but may have generated hundreds of watts for brief durations. Several efficiency improvements have improved the ELF/VLF wave generation efficiency further.
Cosmological density perturbations from perturbed couplings
Tsujikawa, S
2003-01-01
The density perturbations generated when the inflaton decay rate is perturbed by a light scalar field $\\chi$ are studied. By explicitly solving the perturbation equations for the system of two scalar fields and radiation, we show that even in low energy-scale inflation nearly scale-invariant spectra of scalar perturbations with an amplitude set by observations are obtained through the conversion of $\\chi$ fluctuations into adiabatic density perturbations. We demonstrate that the spectra depend on the average decay rate of the inflaton & on the inflaton fluctuations. We then apply this new mechanism to string cosmologies & generalized Einstein theories and discuss the conditions under which scale-invariant spectra are possible.
Sondhiya, Deepak Kumar; Gwal, Ashok Kumar; Kasde, Satish Kumar
2016-07-01
Symmetric sidebands are observed in the ionosphere by the DEMETER (Detection of Electromagnetic Radiation Transmitted through Earthquake Region) satellite, when it passes above the Indian VLF transmitter, named VTX (18.2 kHz), located near Kanyakumari, India. The spectral boarding phenomena may be divided into two types: (1) spectrally broadened components occurring without any association with ELF/VLF emissions under disturbed ionospheric condition, (2) Spectrally broadened components with predominant side band structure in association with ELF emission. Generally spectral analysis at second order (Power spectrum) is used to analyze the frequency component of signal, but it losses the phase information among the different Fourier components. To retain this information the bispectrum (third order) and/or the bicoherence (normalized bispectrum) are used. Results suggest a non-linear mode coupling between the transmitter signal and ELF emission which produces sidebands that are quasi-electrostatic in nature. However, faint spectral broadened components in both types 1 and 2 may be connected with Doppler shift of quasi-electrostatic, whistler mode waves with a broad spectrum near resonance cone, due to scattering of the transmitter signals from ionospheric irregularities in the F-region. Keywords: spectral boarding, wave-wave Interaction, whistler mode waves and Doppler shift
Poulsen, William L.; Inan, Umran S.; Bell, Timothy F.
1993-01-01
Transient localized D region disturbances, such as those associated with lightning discharges, affect the characteristics of VLF waves propagating in the Earth-ionosphere waveguide. In particular, both phase and amplitude changes in the subionospheric signal can be observed at receiving sites as a result of the wave scattering that takes place in the disturbed region. In the present paper we present a multiple-mode three-dimensional model of VLF propagation in the Earth-ionosphere waveguide in the presence of localized D region disturbances. The model takes into account great circle (GC) propagation paths with realistic ground and ionospheric conductivity changes that result in mode conversion along the path. It is assumed that conductivity changes transverse to the GC paths are negligible except in the vicinity of the D region disturbance and that mode coupling is negligible within the disturbed region. This new model is applied to experimental observations and is found to be in general agreement. The diagnostics potential of the model for characterizing energetic particle precipitation events is discussed.
Cosmological perturbations through a simple bounce
Allen, L E
2004-01-01
We present a detailed study of a simple scalar field model that yields non-singular cosmological solutions. We study both the qualitative dynamics of the homogeneous and isotropic background and the evolution of inhomogeneous linear perturbations. We calculate the spectrum of perturbations generated on super-Hubble scales during the collapse phase from initial vacuum fluctuations on small scales and then evolve these numerically through the bounce. We show there is a gauge that remains well-defined throughout the bounce, even though other commonly used gauges break down. We show that the comoving curvature perturbation calculated during the collapse phase provides a good estimate of the resulting large scale adiabatic perturbation in the expanding phase while the Bardeen metric potential is dominated by what becomes a decaying mode after the bounce. We show that a power-law collapse phase with scale factor proportional $(-t)^{2/3}$ can yield a scale-invariant spectrum of adiabatic scalar perturbations in the ...
Lauben, D.; Cohen, M.; Inan, U.
2012-12-01
We deduce the 3d intra-plasmaspheric distribution of VLF wave power between conjugate regions of strong VLF wave amplitudes as measured by DEMETER for high-power terrestrial VLF transmitters during its ~6-yr lifetime. We employ a mixed WKB/full-wave technique to solve for the primary and secondary electromagnetic and electrostatic waves which are transmitted and reflected from strong cold-plasma density gradients and posited irregularities, in order to match the respective end-point measured amplitude distributions. Energy arriving in the conjugate region and also escaping to other regions of the magnetosphere is note. The resulting 3d distribution allows improved estimates for the long-term average particle scattering induced by terrestrial VLF transmitters.
Kabirzadeh, Rasoul
The GEODESIC sounding rocket encountered hundreds of localized, VLF-wave-filled density depletions in an auroral return current region at altitudes between 900--1000 km. While these are similar to well-studied lower-hybrid "spikelets", which are electrostatic, many of the GEODESIC events exhibited strong VLF magnetic field enhancements as well. In the present study we show that these magnetic field fluctuations can be interpreted as the result of geomagnetic field-aligned electron currents driven by fluctuating electric fields parallel to the geomagnetic field lines. This observation suggests that the electromagnetic wave-filled cavities are signatures of unstable filaments of return current fluctuating at VLF frequencies. We argue that the cavities' spatial dimensions, their location inside the return current region and their total radiated power are consistent with the properties of VLF saucer source regions inferred from earlier satellite observations taken at higher altitudes.
Foster, J. C.; Erickson, P. J.; Omura, Y.; Baker, D. N.; Kletzing, C. A.; Claudepierre, S. G.
2017-01-01
Prompt recovery of MeV (millions of electron Volts) electron populations in the poststorm core of the outer terrestrial radiation belt involves local acceleration of a seed population of energetic electrons in interactions with VLF chorus waves. Electron interactions during the generation of VLF rising tones are strongly nonlinear, such that a fraction of the relativistic electrons at resonant energies are trapped by waves, leading to significant nonadiabatic energy exchange. Through detailed examination of VLF chorus and electron fluxes observed by Van Allen Probes, we investigate the efficiency of nonlinear processes for acceleration of electrons to MeV energies. We find through subpacket analysis of chorus waveforms that electrons with initial energy of hundreds of keV to 3 MeV can be accelerated by 50 keV-200 keV in resonant interactions with a single VLF rising tone on a time scale of 10-100 ms.
1993-05-01
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Excitation of VLF quasi-electrostatic oscillations in the ionospheric plasma
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B. Lundin
Full Text Available A numerical solution of the dispersion equation for electromagnetic waves in a hot magnetized collisionless plasma has shown that, in a current-free ionospheric plasma, the distortion of the electron distribution function reproducing the downward flow of a thermal electron component and the compensating upward flow of the suprathermal electrons, which are responsible for the resulting heat flux, can destabilize quasi-electrostatic ion sound waves. The numerical analysis, performed with ion densities and electron temperature taken from the data recorded by the Interkosmos-24 (IK-24, Aktivny satellite, is compared with a VLF spectrum registered at the same time on board. This spectrum shows a wide frequency band emission below the local ion plasma frequency. The direction of the electron heat flux inherent to the assumed model of VLF emission generation is discussed
Prediction Capabilities of VLF/LF Emission as the Main Precursor of Earthquake
Kachakhidze, Manana
2013-01-01
Recent satellite and ground-based observations proved that in earthquake preparation period in the seismogenic area we have VLF/LF and ULF electromagnetic emissions. According to the opinion of the authors of the present paper this phenomenon is more universal and reliable than other earthquake indicators. Hypothetically, in case of availability of adequate methodological grounds, in the nearest future, earth VLF/LF electromagnetic emission might be declared as the main precursor of earthquake. In particular, permanent monitoring of frequency spectrum of earth electromagnetic emission generated in the earthquake preparation period might turn out very useful with the view of prediction of large (M 5) inland earthquakes. The present paper offers a scheme of the methodology according to which the reality of the above given hypothesis can be checked up. To prove the prediction capabilities of earth electromagnetic emission we have used avalanche-like unstable model of fault formation and an analogous model of ele...
Electron dispersion events in the morningside auroral zone and their relationship with VLF emissions
Hardy, David A.; Burke, William J.; Villalon, Elena
1990-05-01
This paper reports on observations of electron precipitation bursts observed in the morningside auroral zone with the J sensor, an electron detector aboard the Hilat satellite. The characteristics of these precipitation events are documented, and a theoretical explanation that could account for the observed properties is presented. According to this model, the dispersion events result from impulsive interactions of the electrons with intense asymmetric packets of VLF waves via the nonlinear ponderomotive force.
Unusually high frequency natural VLF radio emissions observed during daytime in Northern Finland
Manninen, Jyrki; Turunen, Tauno; Kleimenova, Natalia; Rycroft, Michael; Gromova, Liudmila; Sirviö, Iina
2016-12-01
Geomagnetic field variations and electromagnetic waves of different frequencies are ever present in the Earth’s environment in which the Earth’s fauna and flora have evolved and live. These waves are a very useful tool for studying and exploring the physics of plasma processes occurring in the magnetosphere and ionosphere. Here we present ground-based observations of natural electromagnetic emissions of magnetospheric origin at very low frequency (VLF, 3-30 kHz), which are neither heard nor seen in their spectrograms because they are hidden by strong impulsive signals (sferics) originating in lightning discharges. After filtering out the sferics, peculiar emissions are revealed in these digital recordings, made in Northern Finland, at unusually high frequencies in the VLF band. These recently revealed emissions, which are observed for several hours almost every day in winter, contain short (˜1-3 min) burst-like structures at frequencies above 4-6 kHz, even up to 15 kHz; fine structure on the 1 s time scale is also prevalent. It seems that these whistler mode emissions are generated deep inside the magnetosphere, but the detailed nature, generation region and propagation behaviour of these newly discovered high latitude VLF emissions remain unknown; however, further research on them may shed new light on wave-particle interactions occurring in the Earth’s radiation belts.
Sasmal, Sudipta; Pal, Sujay; Chakrabarti, Sandip K.
2014-10-01
To examine the quality and propagation characteristics of the Very Low Frequency (VLF) radio waves in a very long propagation path, Indian Centre for Space Physics, Kolkata, participated in the 27th Indian scientific expedition to Antarctica during 2007-2008. One Stanford University made AWESOME VLF receiving system was installed at the Indian Antarctic station Maitri and about five weeks of data were recorded successfully from the Indian transmitter VTX and several other transmitting stations worldwide. The quality of the signal from the VTX transmitter was found to be very good, consistent and highly stable in day and night. The signal shows the evidences of the presence of the 24 h solar radiation in the Antarctic region during local summer. Here we report the both narrow band and broadband VLF observations from this site. The diurnal variations of VTX signal (18.2 kHz) are presented systematically for Antarctica path and also compared the same with the variations for a short propagation path (VTX-Kolkata). We compute the spatial distribution of the VTX signal along the VTX-Antarctica path using the most well-known LWPC model for an all-day and all-night propagation conditions. The calculated signal amplitudes corresponding to those conditions relatively corroborate the observations. We also present the attenuation rate of the dominant waveguide modes corresponding to those propagation conditions where the effects of the Antarctic polar ice on the attenuation of different propagating waveguide modes are visible.
Initial Results from SQUID Sensor: Analysis and Modeling for the ELF/VLF Atmospheric Noise
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Huan Hao
2017-02-01
Full Text Available In this paper, the amplitude probability density (APD of the wideband extremely low frequency (ELF and very low frequency (VLF atmospheric noise is studied. The electromagnetic signals from the atmosphere, referred to herein as atmospheric noise, was recorded by a mobile low-temperature superconducting quantum interference device (SQUID receiver under magnetically unshielded conditions. In order to eliminate the adverse effect brought by the geomagnetic activities and powerline, the measured field data was preprocessed to suppress the baseline wandering and harmonics by symmetric wavelet transform and least square methods firstly. Then statistical analysis was performed for the atmospheric noise on different time and frequency scales. Finally, the wideband ELF/VLF atmospheric noise was analyzed and modeled separately. Experimental results show that, Gaussian model is appropriate to depict preprocessed ELF atmospheric noise by a hole puncher operator. While for VLF atmospheric noise, symmetric α-stable (SαS distribution is more accurate to fit the heavy-tail of the envelope probability density function (pdf.
On adiabatic perturbations in the ekpyrotic scenario
Linde, A.; Mukhanov, V.; Vikman, A.
2010-02-01
In a recent paper, Khoury and Steinhardt proposed a way to generate adiabatic cosmological perturbations with a nearly flat spectrum in a contracting Universe. To produce these perturbations they used a regime in which the equation of state exponentially rapidly changed during a short time interval. Leaving aside the singularity problem and the difficult question about the possibility to transmit these perturbations from a contracting Universe to the expanding phase, we will show that the methods used in Khoury are inapplicable for the description of the cosmological evolution and of the process of generation of perturbations in this scenario.
On adiabatic perturbations in the ekpyrotic scenario
Linde, A; Vikman, A
2009-01-01
In a recent paper arXiv:0910.2230, Khoury and Steinhardt proposed a way to generate adiabatic cosmological perturbations with a nearly flat spectrum in a contracting Universe. To produce these perturbations they used a regime in which the equation of state exponentially rapidly changed during a short time interval. Leaving aside the singularity problem and the difficult question about the possibility to transmit these perturbations from a contracting Universe to the expanding phase, we will show that the methods used in arXiv:0910.2230 are inapplicable for the description of the cosmological evolution and of the process of generation of perturbations in this scenario.
Perturbation growth in accreting filaments
Clarke, Seamus D; Hubber, David A
2016-01-01
We use smoothed particle hydrodynamic simulations to investigate the growth of perturbations in infinitely long, initially sub-critical but accreting filaments. The growth of these perturbations leads to filament fragmentation and the formation of cores. Most previous work on this subject has been confined to the growth and fragmentation of equilibrium filaments and has found that there exists a preferential fragmentation length scale which is roughly 4 times the filament's diameter. Our results show a more complicated dispersion relation with a series of peaks linking perturbation wavelength and growth rate. These are due to gravo-acoustic oscillations along the longitudinal axis during the sub-critical phase of growth. The positions of the peaks in growth rate have a strong dependence on both the mass accretion rate onto the filament and the temperature of the gas. When seeded with a multi-wavelength density power spectrum there exists a clear preferred core separation equal to the largest peak in the dispe...
Chang, Shanshan; Zhu, Zhengping; Ni, Binbin; Cao, Xing; Luo, Weihua
2016-10-01
Several extremely low-frequency (ELF)/very low-frequency (VLF) wave generation experiments have been performed successfully at High-Frequency Active Auroral Research Program (HAARP) heating facility and the artificial ELF/VLF signals can leak into the outer radiation belt and contribute to resonant interactions with energetic electrons. Based on the artificial wave properties revealed by many of in situ observations, we implement test particle simulations to evaluate the effects of energetic electron resonant scattering driven by the HAARP-induced ELF/VLF waves. The results indicate that for both single-frequency/monotonic wave and multi-frequency/broadband waves, the behavior of each electron is stochastic while the averaged diffusion effect exhibits temporal linearity in the wave-particle interaction process. The computed local diffusion coefficients show that, the local pitch-angle scattering due to HARRP-induced single-frequency ELF/VLF whistlers with an amplitude of ∼10 pT can be intense near the loss cone with a rate of ∼10-2 rad2 s-1, suggesting the feasibility of HAARP-induced ELF/VLF waves for removal of outer radiation belt energetic electrons. In contrast, the energy diffusion of energetic electrons is relatively weak, which confirms that pitch-angle scattering by artificial ELF/VLF waves can dominantly lead to the precipitation of energetic electrons. Moreover, diffusion rates of the discrete, broadband waves, with the same amplitude of each discrete frequency as the monotonic waves, can be much larger, which suggests that it is feasible to trigger a reasonable broadband wave instead of the monotonic wave to achieve better performance of controlled precipitation of energetic electrons. Moreover, our test particle scattering simulation show good agreement with the predictions of the quasi-linear theory, confirming that both methods are applied to evaluate the effects of resonant interactions between radiation belt electrons and artificially generated
Picturing perturbative parton cascades in QCD matter
Directory of Open Access Journals (Sweden)
Aleksi Kurkela
2015-01-01
Full Text Available Based on parametric reasoning, we provide a simple dynamical picture of how a perturbative parton cascade, in interaction with a QCD medium, fills phase space as a function of time.
Directory of Open Access Journals (Sweden)
Pier Francesco Biagi
2012-04-01
Full Text Available
Signals from very low frequency (VLF/ low frequency (LF transmitters recorded on the ground station at Petropavlovsk-Kamchatsky and on board the French DEMETER satellite were analyzed for the Simushir earthquake (M 8.3; November 15, 2006. The period of analysis was from October 1, 2006, to January 31, 2007. The ground and satellite data were processed by a method based on the difference between the real signal at night-time and the model signal. The model for the ground observations was the monthly averaged signal amplitudes and phases, as calculated for the quiet days of every month. For the satellite data, a two-dimensional model of the signal distribution over the selected area was constructed. Preseismic effects were found several days before the earthquake, in both the ground and satellite observations.
New Generation of ELF/VLF Wave Injection Experiments for HAARP
Sonwalkar, V. S.; Reddy, A.; Watkins, B. J.
2016-12-01
We present a ray tracing study to investigate the feasibility of a new generation of wave injection experiments from HAARP transmitter (L 4.9). Highly successful whistler mode wave injection experiments from SIPLE station, Antarctica, have established the importance of such experiments to study magnetospheric wave-particle interactions, and for cold and hot plasma diagnostics [Helliwell and Katsufrakis, 1974; Carpenter and Miller, 1976; Sonwalkar et al., 1997]. Modulated heating experiments from HAARP have shown that it is possible to launch ELF/VLF waves into the magnetosphere that can be observed on the ground after one-, two-, and multi-hop ducted propagation [Inan et al., 2004]. Recent research has also shown that ionospheric heating experiments using HAARP can lead to the formation of magnetospheric ducts [e.g. Milikh et al., 2010; Fallen et al., 2011]. Collectively, these results indicate that the HAARP (or similar) transmitter can be used first to form ducts on nearby L shells, and then to inject and trap transmitter generated ELF/VLF waves in those ducts. Ray tracing studies using a model magnetosphere shows that ELF/VLF waves in a few kilohertz range can be trapped in ducts with L shells near the HAARP transmitter. For example, 1.5 kHz waves injected from L shell = 4.9 and altitude = 200 km can be trapped in ducts located within 0.3 L of the transmitter L-shell. The duct parameters needed for ray-trapping are typically duct width dL 0.1-0.3 and duct enhancement factor dNe/Ne 10-20% or more. The location of plasmapause with respect to transmitter plays a role in the nature of trapping. The duct locations and parameters required for trapping ELF/VLF waves inside the ducts are consistent with past observations of ducts generated by the HAARP transmitter. Ray tracing calculations provide trapped wave normal angles, time delays, resonant energetic electron energy, estimates of wave intensity inside the duct, on the ground, and on satellites such DEMETER, Van
Brane World Cosmological Perturbations
Casali, A G; Wang, B; Casali, Adenauer G.; Abdalla, Elcio; Wang, Bin
2004-01-01
We consider a brane world and its gravitational linear perturbations. We present a general solution of the perturbations in the bulk and find the complete perturbed junction conditions for generic brane dynamics. We also prove that (spin 2) gravitational waves in the great majority of cases can only arise in connection with a non-vanishing anisotropic stress. This has far reaching consequences for inflation in the brane world. Moreover, contrary to the case of the radion, perturbations are stable.
New Methods in Non-Perturbative QCD
Energy Technology Data Exchange (ETDEWEB)
Unsal, Mithat [North Carolina State Univ., Raleigh, NC (United States)
2017-01-31
In this work, we investigate the properties of quantum chromodynamics (QCD), by using newly developing mathematics and physics formalisms. Almost all of the mass in the visible universe emerges from a quantum chromodynamics (QCD), which has a completely negligible microscopic mass content. An intimately related issue in QCD is the quark confinement problem. Answers to non-perturbative questions in QCD remained largely elusive despite much effort over the years. It is also believed that the usual perturbation theory is inadequate to address these kinds of problems. Perturbation theory gives a divergent asymptotic series (even when the theory is properly renormalized), and there are non-perturbative phenomena which never appear at any order in perturbation theory. Recently, a fascinating bridge between perturbation theory and non-perturbative effects has been found: a formalism called resurgence theory in mathematics tells us that perturbative data and non-perturbative data are intimately related. Translating this to the language of quantum field theory, it turns out that non-perturbative information is present in a coded form in perturbation theory and it can be decoded. We take advantage of this feature, which is particularly useful to understand some unresolved mysteries of QCD from first principles. In particular, we use: a) Circle compactifications which provide a semi-classical window to study confinement and mass gap problems, and calculable prototypes of the deconfinement phase transition; b) Resurgence theory and transseries which provide a unified framework for perturbative and non-perturbative expansion; c) Analytic continuation of path integrals and Lefschetz thimbles which may be useful to address sign problem in QCD at finite density.
Anomalous propagation of Omega VLF waves near the geomagnetic equator
Ohtani, A.; Kikuchi, T.; Nozaki, K.; Kurihara, N.; Kuratani, Y.; Ohse, M.
1983-09-01
Omega HAIKU, REUNION, and LIBERIA signals were received and anomalous propagation characteristics were obtained near the geomagnetic equator. Short-period fluctuations were found in the phase of the HAIKU 10.2 kHz signal in November 1979 and in the phase and amplitude of the HAIKU 13.6 kHz signal in November 1981. These cyclic fluctuations are in close correlation with the phase cycle slippings, which occur most frequently when the receiver is located at 6 S geomagnetic latitude. On the basis of anisotropic waveguide mode theory indicating much less attenuation in WE propagation than in EW propagation at the geomagnetic equator, it is concluded that the short-period fluctuations in the phase and amplitude are due to interference between the short-path and the long-path signals.
Indian Academy of Sciences (India)
R Singh; A K Singh; D Siingh; R P Singh
2007-12-01
During the analysis of archived VLF data from Indian low latitude ground stations, some discrete VLF emissions recorded at the low latitude ground station Gulmarg (geomagnetic latitude 24°26′N; geomagnetic longitude 147° 09′E, L = 1.28) during moderate magnetic storm activity ( $K^{−}_{P}$} = 32, index varies from 4 to 6 during the observation period) on 6/7 March, 1986 are presented in this paper. The dynamic spectra of these discrete VLF emissions were observed along with tweeks and its harmonics, which is interesting and complex to explain. In most of the events the harmonic frequency of tweeks correlates with the starting frequency of harmonics of discrete emissions. In order to explain the observed features of discrete VLF emissions, we propose cyclotron resonance interaction between whistler mode wave and energetic electrons of inner radiation belt as possible generation mechanism. An attempt is also made to determine parallel energy, anisotropy and wave growth relevant to the generation process of VLF emissions.
Dipolar fluids under external perturbations
Energy Technology Data Exchange (ETDEWEB)
Klapp, Sabine H L [Stranski-Laboratorium fuer Physikalische und Theoretische Chemie Sekretariat TC7, Technische Universitaet Berlin, Strasse des 17. Juni 124, D-10623 Berlin (Germany)
2005-04-20
We discuss recent developments and present new findings on the structural and phase properties of dipolar model fluids influenced by various external perturbations. We concentrate on systems of spherical particles with permanent (point) dipole moments. Starting from what is known about the three-dimensional systems, particular emphasis is given to dipolar fluids in different confining situations involving both simple and complex (disordered) pore geometries. Further topics concern the effect of quenched positional disorder, the influence of external (electric or magnetic) fields, and the fluid-fluid phase behaviour of various dipolar mixtures. It is demonstrated that due to the translational-orientational coupling and due to the long range of dipolar interactions even simple perturbations such as hard walls can have a profound impact on the systems. (topical review)
GołKowski, M.; Cohen, M. B.; Moore, R. C.
2013-05-01
Experiments at the ionospheric heating facility of the High Frequency Active Auroral Research Program (HAARP) are performed employing dual HF beams amplitude modulated at ELF/VLF with a phase offset between the two modulation waveforms. The amplitude of the observed ELF/VLF waves is strongly dependent on the imposed ELF/VLF phase offset, the modulation waveform, and the orientation of the HF beams. Data from two ground stations are interpreted using simulations of modulated heating power envelopes as well as a comprehensive model of ionospheric ELF/VLF generation. It is found that two colocated vertical beams HF beams excite a single ionospheric ELF/VLF source, but independent ELF/VLF sources can be induced in the ionospheric region above the heater if the HF beams are offset from zenith to intersect at their 3 dB points. Furthermore, the use of two vertical HF beams with ELF phase offset is found to be a potential diagnostic method for the ionospheric D region.
Energy Technology Data Exchange (ETDEWEB)
Schaefer, B.; Lambert, S.M.; Song, Y.; Prausnitz, J.M.
1994-10-01
Goal of this work is the extension of a Perturbed-Hard-Sphere-Chain equation of state (PHSC EOS) to systems containing strong polar components. Three different types of association models (ten Brinke/Karasz, SAFI, modified Veytsman) were used to calculate the contribution of specific interactions like hydrogen bonding to thermodynamic quantities. Pure component parameters obtained from regression of temperature dependent density and vapor pressure data allow the prediction of VLE and LLE data. The results of simple fluids and polymer solutions were compared with experimental data. The SAFT and the modified Veytsman extension give similar results for pure fluids and mixtures with components of similar segment size. Differences increase with increasing difference of segment size.
Directory of Open Access Journals (Sweden)
Ibrahim Gaafar
2015-12-01
Full Text Available This study is an attempt to use the gamma ray spectrometric measurements and VLF-EM data to identify the subsurface structure and map uranium mineralization along El Sela shear zone, South Eastern Desert of Egypt. Many injections more or less mineralized with uranium and associated with alteration processes were recorded in El Sela shear zone. As results from previous works, the emplacement of these injections is structurally controlled and well defined by large shear zones striking in an ENE–WSW direction and crosscut by NW–SE to NNW–SSE fault sets. VLF method has been applied to map the structure and the presence of radioactive minerals that have been delineated by the detection of high uranium mineralization. The electromagnetic survey was carried out to detect the presence of shallow and deep conductive zones that cross the granites along ENE–WSW fracturing directions and to map its spatial distribution. The survey comprised seventy N–S spectrometry and VLF-EM profiles with 20 m separation. The resulted data were displayed as composite maps for K, eU and eTh as well as VLF-Fraser map. Twelve profiles with 100 m separation were selected for detailed description. The VLF-EM data were interpreted qualitatively as well as quantitatively using the Fraser and the Karous–Hjelt filters. Fraser filtered data and relative current density pseudo-sections indicate the presence of shallow and deep conductive zones that cross the granites along ENE–WSW shearing directions. High uranium concentrations found just above the higher apparent current-density zones that coincide with El-Sela shear zone indicate a positive relation between conductivity and uranium minerals occurrence. This enables to infer that the anomalies detected by VLF-EM data are due to the highly conductive shear zone enriched with uranium mineralization extending for more than 80 m.
Al-Tarazi, E.; Abu Rajab, J.; Al-Naqa, A.; El-Waheidi, M.
2008-09-01
A Very Low Frequency-Electromagnetic (VLF-EM) survey was carried out in two sites of domestic waste of old and recent landfills. The landfill structures lie on a major highly fractured limestone aquifer of shallow groundwater less than 30 m, which is considered as the main source of fresh water in Amman-Zarqa region. A total of 18 VLF-EM profiles were conducted with length ranges between 250 and 1500 m. Hydrochemical and biochemical analysis of water samples, taken from wells in the region, has also been conducted. The integrated results of previous DC resistivity method of the same study area and the outcomes of the 2-D tipper inversion of VLF-EM data proved the efficiency of this method in locating shallow and deep leachate plume with resistivity less than 20 Ω m, and enabling the mapping of anomalous bodies and their extensions down to 40 m depth. The sign of groundwater contamination was noticed in many surrounding wells resulting in the high number of fecal coliform bacteria and total coliform bacteria and the increase in inorganic parameters such as chloride (Cl). The pollution of groundwater wells in the landfill area is attributed to the leachate bodies which flow through the upper part of Wadi Es Sir (A7) or Amman-Wadi Es Sir Aquifer (B2/A7). Furthermore, several structural features were detected and the direction of local groundwater movement has been determined. The structural features have been found to have critical effects on the flowing of leachate plume towards north-northeast and west-southwest of the potable aquifer in the area.
Institute of Scientific and Technical Information of China (English)
M.; Parrot
2009-01-01
Here we used the VLF signal data received by the DEMETER satellite, transmitted from various ground VLF transmitters which are located around China, to study the changes in the signal to noise ratio (SNR) before and after the Wenchuan earthquake, which had a magnitude of 8.0. We also found that the SNRs of different frequency signals decreased significantly over the epicenter region before the earthquake, and reverted to their original levels after the earthquake. This phenomenon may be related to the earthquake.
Automated Lattice Perturbation Theory
Energy Technology Data Exchange (ETDEWEB)
Monahan, Christopher
2014-11-01
I review recent developments in automated lattice perturbation theory. Starting with an overview of lattice perturbation theory, I focus on the three automation packages currently "on the market": HiPPy/HPsrc, Pastor and PhySyCAl. I highlight some recent applications of these methods, particularly in B physics. In the final section I briefly discuss the related, but distinct, approach of numerical stochastic perturbation theory.
Numerical simulation of whistler-triggered VLF emissions observed in Antartica
Energy Technology Data Exchange (ETDEWEB)
Nunn, D. [Southhampton Univ., Southhampton (United Kingdom); Smith, A.J. [British Antarctic Survey, Cambridge (United Kingdom)
1996-03-01
The authors have extracted from VLF databases from British Antarctica Survey data taken at Halley and Faraday stations, examples of whistler-triggered emissions (WTE). The WTE are relatively narrow band emissions triggered by natural background whistlers undergoing nonlinear wave particle interactions generally in the equatorial regions. They occur with either rising or falling frequency relative to the triggering waves. Using a Vlasov type code the authors are able to simulate the types of emissions which are observed. 24 refs., 8 figs., 3 tabs.
Circuit Methods for VLF Antenna Couplers. [for use in Loran or Omega receiver systems
Burhans, R. W.
1977-01-01
The limitations of different E-field antenna coupler or preamplifier circuits are presented. All circuits were evaluated using actual Loran or Omega signals. Electric field whip or wire antennas are the simplest types which can be used for reception of VLF signals in the 10 to 100 kHz range. JFET or MOSFET transistors provide impedance transformation and some voltage gain in simple circuits where the power for operating the preamplifier uses the same coaxial cable that feeds the signal back to the receiver. The circuit techniques provide useful alternative methods for Loran-Omega receiver system designers.
LINFOMA RELACIONADO AO VÍRUS DA LEUCEMIA FELINA (VLF) – RELATO DE CASO
Eleutério, Daniela Aparecida Sampaio; Faculdade Dr. Francisco Maeda - FAFRAM
2014-01-01
O presente trabalho tem como objetivo relatar um caso de linfoma relacionado ao vírus da leucemia felina (VLF) ocorrido na cidade de Uberlândia-MG. Um felino, macho, de três anos de idade, foi encaminhado ao Hospital Veterinário da Universidade Federal de Uberlândia, apresentando-se apático, dispneico, com alterações oculares, mucosas hipocoradas e linfonodos reativos. O hemograma do animal indicou anemia normocítica. No exame radiográfico observou deslocamento da traquéia dorsalmente e não f...
Full-wave model of D-region upward VLF coupling to whistlers in the plasmasphere
Jacobson, A. R.; Shao, X.; Lay, E. H.
2012-12-01
Atmospheric-lightning-to-plasmasphere VLF coupling via whistlers is key to understanding the problem of radiation-belt losses and the slot region. In the lowermost ionosphere, the "D-region" (roughly 60 - 100 km altitude), the coupling occurs between the VLF incident from the "vacuum" below, to the electron whistler capable of transiting upward through the E- and F-regions above. We have modified our successful and data-validated D-region VLF downward-reflection model to predict upward-coupled whistler waveforms recorded on topside satellites. The model has been run in production mode for predicting downward-reflected waveforms recorded at ground stations, but the model's internal calculation also fully describes the "penetrating" solution that merges into the oblique electron whistler. We have begun to test the model against VLF, three-dimensional electric-field recordings from the Vector Electric Field Instrument (VEFI) [Pfaff et al., 2010] on the C/NOFS satellite. VEFI's broadband recording and large on-board memory serendipitously provide an excellent platform for studying lightning whistlers in the plasmasphere. We have already demonstrated [Jacobson et al., 2011] that VEFI is superbly suited for testing transionospheric propagation, in conjunction with the World Wide Lightning Location Network (WWLLN; see www.wwlln.net) to provide groundtruth location/time of the lightning strokes. This poster will describe latest results. Jacobson, A. R., R. H. Holzworth, R. F. Pfaff, and M. P. McCarthy (2011), Study of oblique whistlers in the low-latitude ionosphere, jointly with the C/NOFS satellite and the World-Wide Lightning Location Network, Annales Geophysicae, 29, 851-863. Pfaff, R., D. Rowland, H. Freudenreich, K. Bromund, K. Le, M. Acuna, J. Klenzing, C. Liebrecht, S. Martin, W. J. Burke, N. C. Maynard, D. E. Hunton, P. A. Roddy, J. O. Ballenthin, and G. R. Wilson (2010), Observations of DC electric fields in the low-latitude ionosphere and their variations with
Perturbative tests of non-perturbative counting
Dabholkar, Atish; Gomes, João
2010-03-01
We observe that a class of quarter-BPS dyons in mathcal{N} = 4 theories with charge vector ( Q, P) and with nontrivial values of the arithmetic duality invariant I := gcd( Q∧ P) are nonperturbative in one frame but perturbative in another frame. This observation suggests a test of the recently computed nonperturbative partition functions for dyons with nontrivial values of the arithmetic invariant. For all values of I, we show that the nonperturbative counting yields vanishing indexed degeneracy for this class of states everywhere in the moduli space in precise agreement with the perturbative result.
Generalized Supersymmetric Perturbation Theory
Institute of Scientific and Technical Information of China (English)
B. G(o)n(ǖ)l
2004-01-01
@@ Using the basic ingredient of supersymmetry, a simple alternative approach is developed to perturbation theory in one-dimensional non-relativistic quantum mechanics. The formulae for the energy shifts and wavefunctions do not involve tedious calculations which appear in the available perturbation theories. The model applicable in the same form to both the ground state and excited bound states, unlike the recently introduced supersymmetric perturbation technique which, together with other approaches based on logarithmic perturbation theory, are involved within the more general framework of the present formalism.
Density matrix perturbation theory.
Niklasson, Anders M N; Challacombe, Matt
2004-05-14
An orbital-free quantum perturbation theory is proposed. It gives the response of the density matrix upon variation of the Hamiltonian by quadratically convergent recursions based on perturbed projections. The technique allows treatment of embedded quantum subsystems with a computational cost scaling linearly with the size of the perturbed region, O(N(pert.)), and as O(1) with the total system size. The method allows efficient high order perturbation expansions, as demonstrated with an example involving a 10th order expansion. Density matrix analogs of Wigner's 2n+1 rule are also presented.
Geometric singular perturbation theory in biological practice
Hek, G.
2010-01-01
Geometric singular perturbation theory is a useful tool in the analysis of problems with a clear separation in time scales. It uses invariant manifolds in phase space in order to understand the global structure of the phase space or to construct orbits with desired properties. This paper explains an
Perturbative Topological Field Theory
Dijkgraaf, Robbert
We give a review of the application of perturbative techniques to topological quantum field theories, in particular three-dimensional Chern-Simons-Witten theory and its various generalizations. To this end we give an introduction to graph homology and homotopy algebras and the work of Vassiliev and Kontsevich on perturbative knot invariants.
Perturbing supersymmetric black hole
Onozawa, H; Mishima, T; Ishihara, H; Onozawa, Hisashi; Okamura, Takashi; Mishima, Takashi; Ishihara, Hideki
1996-01-01
An investigation of the perturbations of the Reissner-Nordstr\\"{o}m black hole in the N=2 supergravity is presented. In the extreme case, the black hole responds to the perturbation of each field in the same manner. This is possibly because we can match the modes of the graviton, gravitino, and photon using supersymmetry transformations.
Perturbation analysis of Poisson processes
Last, Günter
2012-01-01
We consider a Poisson process $\\Phi$ on a general phase space. The expectation of a function of $\\Phi$ can be considered as a functional of the intensity measure $\\lambda$ of $\\Phi$. Extending ealier results of Molchanov and Zuyev (2000) on finite Poisson processes, we study the behaviour of this functional under signed (possibly infinite) perturbations of $\\lambda$. In particular we obtain general Margulis--Russo type formulas for the derivative with respect to non-linear transformations of the intensity measure depending on some parameter. As an application we study the behaviour of expectations of functions of multivariate pure jump L\\'evy processes under perturbations of the L\\'evy measure. A key ingredient of our approach is the explicit Fock space representation obtained in Last and Penrose (2011).
Perturbations in electromagnetic dark energy
Energy Technology Data Exchange (ETDEWEB)
Jiménez, Jose Beltrán; Maroto, Antonio L. [Departamento de Física Teórica, Universidad Complutense de Madrid, 28040 Madrid (Spain); Koivisto, Tomi S. [Institute for Theoretical Physics, University of Heidelberg, 69120 Heidelberg (Germany); Mota, David F., E-mail: jobeltra@fis.ucm.es, E-mail: T.Koivisto@thphys.uni-heidelberg.de, E-mail: maroto@fis.ucm.es, E-mail: d.f.mota@astro.uio.no [Institute of Theoretical Astrophysics, University of Oslo, 0315 Oslo (Norway)
2009-10-01
It has been recently proposed that the presence of a temporal electromagnetic field on cosmological scales could explain the phase of accelerated expansion that the universe is currently undergoing. The field contributes as a cosmological constant and therefore, the homogeneous cosmology produced by such a model is exactly the same as that of ΛCDM. However, unlike a cosmological constant term, electromagnetic fields can acquire perturbations which in principle could affect CMB anisotropies and structure formation. In this work, we study the evolution of inhomogeneous scalar perturbations in this model. We show that provided the initial electromagnetic fluctuations generated during inflation are small, the model is perfectly compatible with both CMB and large scale structure observations at the same level of accuracy as ΛCDM.
Frame independent cosmological perturbations
Energy Technology Data Exchange (ETDEWEB)
Prokopec, Tomislav; Weenink, Jan, E-mail: t.prokopec@uu.nl, E-mail: j.g.weenink@uu.nl [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, Leuvenlaan 4, 3585 CE Utrecht (Netherlands)
2013-09-01
We compute the third order gauge invariant action for scalar-graviton interactions in the Jordan frame. We demonstrate that the gauge invariant action for scalar and tensor perturbations on one physical hypersurface only differs from that on another physical hypersurface via terms proportional to the equation of motion and boundary terms, such that the evolution of non-Gaussianity may be called unique. Moreover, we demonstrate that the gauge invariant curvature perturbation and graviton on uniform field hypersurfaces in the Jordan frame are equal to their counterparts in the Einstein frame. These frame independent perturbations are therefore particularly useful in relating results in different frames at the perturbative level. On the other hand, the field perturbation and graviton on uniform curvature hypersurfaces in the Jordan and Einstein frame are non-linearly related, as are their corresponding actions and n-point functions.
Characteristics of VLF/LF Sferics from Elve-producing Lightning Discharges
Blaes, P.; Zoghzoghy, F. G.; Marshall, R. A.
2013-12-01
Lightning return strokes radiate an electromagnetic pulse (EMP) which interacts with the D-region ionosphere; the largest EMPs produce new ionization, heating, and optical emissions known as elves. Elves are at least six times more common than sprites and other transient luminous events. Though the probability that a lightning return stroke will produce an elve is correlated with the return stroke peak current, many large peak current strokes do not produce visible elves. Apart from the lightning peak current, elve production may depend on the return stroke speed, lightning altitude, and ionospheric conditions. In this work we investigate the detailed structure of lightning that gives rise to elves by analyzing the characteristics of VLF/LF lightning sferics in conjunction with optical elve observations. Lightning sferics were observed using an array of six VLF/LF receivers (1 MHz sample-rate) in Oklahoma, and elves were observed using two high-speed photometers pointed over the Oklahoma region: one located at Langmuir Laboratory, NM and the other at McDonald Observatory, TX. Hundreds of elves with coincident LF sferics were observed during the summer months of 2013. We present data comparing the characteristics of elve-producing and non-elve producing lightning as measured by LF sferics. In addition, we compare these sferic and elve observations with FDTD simulations to determine key properties of elve-producing lightning.
Some unusual discrete VLF emissions observed at a low-latitude ground station at Agra
Directory of Open Access Journals (Sweden)
B. Singh
Full Text Available A detailed analysis of the VLF emissions data obtained during occasional whistler campaigns at the low-latitude ground station Agra (geomagnetic latitude 17°1' N, L = 1.15 has yielded some unusual discrete VLF emissions of the rising type. These include (1 emissions occurring at time intervals increasing in ge ommetrical progression, (2 emissions occuring simulta neously in different frequency ranges and (3 emissions observed during daytime. In the present study, the observed characteristics of these emissions are described and interpreted. It is shown that the increasing time delay between different components of the emissions match closely with the propagation time delays between different hops of a whistler of dispersion 19 s^{1/2}, the unusual occurrence of the emissions in two different frequency ranges approximately at the same time may possibly be linked with their generation at two different locations, and the occurrence of emissions during daytime may be due to propagation under the influence of equatorial anomaly.
Characteristic of Tweek Atmospherics Observed in Mid-latitude using AWESOME VLF Receiver
Directory of Open Access Journals (Sweden)
Norbayah Yusop
2014-03-01
Full Text Available This study presents the analysis of tweek atmospherics received by AWESOME VLF receiver at station of Gakona (62.71°N, 143.99°W during four months observation from January to April 2011. Tweek which originates from lightning discharge are used to monitor the nighttime D-region ionosphere using the fundamental cut-off frequency to measure the variations of the lower ionosphere’s reflection height, the equivalent electron density at the reflection height and the propagation distance travel by tweeks. In this study, a total of 1316 tweeks are analyzed and from the analysis, it shows that equinox’s season has the highest tweek occurrence compared to winter season in March and April. The maximum harmonic (m of t weeks is found to be up to fourth ( m = 4 and tweeks with mode number one (m = 1 are more dominantly occurred. Our observations indicate that the equivalent electron densities for tweeks varies from 22-27 eL/cm3 in the altitude ranged of 75 to 91 km and demonstrate that these ELF/VLF signals travel considerable distances up to 6700 km from the causative lightning discharges. The ionospheric parameters for three locations (high, middle and low latitude respectively were compared and the results show that they are almost consistent for all the locations.
In connection with identification of VLF emissions before L'Aquila earthquake
Kachakhidze, M; Kachakhidze, N
2012-01-01
The present paper deals with an attempt to check up the theoretical model of self-generated seismo-electromagnetic oscillations of LAI system on the basis of retrospective data. Application of the offered simple model enables one to explain qualitatively the mechanism of VLF electromagnetic emission initiated in the process of an earthquake preparation. It is worth to pay attention to the fact that frequency changes from MHz to kHz in electromagnetic emission spectrum comes to a good agreement with avalanche-like unstable model of fault formation. L'Aquila earthquake taken as an example to isolate reliably the Earth VLF emission from the magnetospheric electromagnetic emission of the same frequency range, MHD criterion is offered together with geomagnetic activity indexes. On the basis of the considered three earthquakes, according to the opinion of authors the model of self-generated seismo-electromagnetic oscillations of the LAI system will enable us to approach the problem of resolution of earthquake predi...
Orbiting transmitter and antenna for spaceborne communications at ELF/VLF to submerged submarines
Bannister, P. R.; Harrison, J. K.; Rupp, C. C.; King, R. W. P.; Cosmo, M. L.; Lorenzini, E. C.; Dyer, C. J.; Grossi, M. D.
1993-01-01
An orbital emplacement for the transmitter and the antenna of a communications link at ELF (30 to 300 Hz) and VLF (3 kHz to 30 kHz) to submerged submarines has been considered since the very inception of the space age. However, only recently has space technology reached a sufficient level of maturity for system designers to undertake serious studies of this link configuration. The optimistic outlook stems from recent space technology developments, such as the design and construction by NASA of long orbiting tethers, and the testing, onboard Shuttle Orbiter ATLANTIS, of the first spaceborne 20 km metal wire. This is known as the Tethered Satellite System-1 (TSS-1), a space mission that might be possibly followed by other flights, with tether lengths that could reach 100 km. Once deployed at a height of, say, 300 km, from a Shuttle Orbiter, or from another suitable platform, a long, thin tether aligns itself along the local vertical by virtue of the gradient of the Earth gravity field. If made of metal, the tether can function as a VED (Vertical Electric Dipole) transmitting antenna at ELF and VLF.
DEFF Research Database (Denmark)
Greenberg, E.; Price, C.; Yair, Y.
2009-01-01
During the summer of 2005, transient luminous events were optically imaged from the French Pyrénées as part of the EuroSprite campaign. Simultaneously, extremely low frequency (ELF: 3–3000 Hz) and broadband very low frequency (VLF: 3–30 kHz) data were recorded continuously at two separate receive...
Directory of Open Access Journals (Sweden)
A. Rozhnoi
2008-10-01
Full Text Available In our earlier papers we have found the effect of VLF transmitter signal depression over epicenters of the large earthquakes from observation on the French DEMETER satellite that can be considered as new method of global diagnostics of seismic influence on the ionosphere. At present paper we investigate a possibility VLF signal-ionospheric turbulence interaction using additional characteristic of VLF signal-spectrum broadening. This characteristic is important for estimation of the interaction type: linear or nonlinear scattering. Our main results are the following:
– There are two zones of increased spectrum broadening, which are centered near magnetic latitudes Φ=±10° and Φ=±40°. Basing on the previous case study research and ground ionosonde registrations, probably it is evidence of nonlinear (active scattering of VLF signal on the ionospheric turbulence. However occurrence rate of spectrum broadening in the middle-latitude area is higher than in the near-equatorial zone (~15–20% in comparison with ~100% in former area that is probably coincides with the rate of ionospheric turbulence.
– From two years statistics of observation in the selected 3 low-latitude regions and 1 middle-latitude region inside reception area of VLF signal from NWC transmitter we find a correlation of spectrum broadening neither with ion-cyclotron noise (f=150–500 Hz, which possibly means poor representation of the turbulence by the noise due to its mixture with natural ELF emission (which correlates with whistler, nor with magnetic storm activity.
– We find rather evident correlation of ion-cyclotron frequency noise, VLF signal depression and weak correlation of spectrum broadening with seismicity in the middle-latitude region over Japan. But in the low-latitude regions we do not find such a correlation. Statistical decrease of VLF signal supports our previous case study results. However rather weak spectrum broadening
Pasmanik, Dmitry; Demekhov, Andrei
We study the propagation of VLF waves in the Earth's ionosphere and magnetosphere in the presence of large-scale artificial plasma inhomogeneities which can be created by HF heating facilities like HAARP and ``Sura''. A region with enhanced cold plasma density can be formed due to the action of HF heating. This region is extended along geomagnetic field (up to altitudes of several thousand km) and has rather small size across magnetic field (about 1 degree). The geometric-optical approximation is used to study wave propagation. The plasma density and ion composition are calculated with the use of SAMI2 model, which was modified to take the effect of HF heating into account. We calculate ray trajectories of waves with different initial frequency and wave-normal angles and originating at altitudes of about 100 km in the region near the heating area. The source of such waves could be the lightning discharges, modulated HF heating of the ionosphere, or VLF transmitters. Variation of the wave amplitude along the ray trajectories due to refraction is considered and spatial distribution of wave intensity in the magnetosphere is analyzed. We show that the presence of such a density disturbances can lead to significant changes of wave propagation trajectories, in particular, to efficient guiding of VLF waves in this region. This can result in a drastic increase of the VLF-wave intensity in the density duct. The dependence of wave propagation properties on parameters of heating facility operation regime is considered. We study the variation of the spatial distribution of VLF wave intensity related to the slow evolution of the artificial inhomogeneity during the heating.
Rong, Shu-Jun; Liu, Qiu-Yu
2012-04-01
The puma model on the basis of the Lorentz and CPT violation may bring an economical interpretation to the conventional neutrinos oscillation and part of the anomalous oscillations. We study the effect of the perturbation to the puma model. In the case of the first-order perturbation which keeps the (23) interchange symmetry, the mixing matrix element Ue3 is always zero. The nonzero mixing matrix element Ue3 is obtained in the second-order perturbation that breaks the (23) interchange symmetry.
Converting entropy to curvature perturbations after a cosmic bounce
Energy Technology Data Exchange (ETDEWEB)
Fertig, Angelika; Lehners, Jean-Luc; Mallwitz, Enno; Wilson-Ewing, Edward [Max Planck Institute for Gravitational Physics, Albert Einstein Institute,14476 Potsdam-Golm (Germany)
2016-10-04
We study two-field bouncing cosmologies in which primordial perturbations are created in either an ekpyrotic or a matter-dominated contraction phase. We use a non-singular ghost condensate bounce model to follow the perturbations through the bounce into the expanding phase of the universe. In contrast to the adiabatic perturbations, which on large scales are conserved across the bounce, entropy perturbations can grow significantly during the bounce phase. If they are converted into adiabatic/curvature perturbations after the bounce, they typically form the dominant contribution to the observed temperature fluctuations in the microwave background, which can have several beneficial implications. For ekpyrotic models, this mechanism loosens the constraints on the amplitude of the ekpyrotic potential while naturally suppressing the intrinsic amount of non-Gaussianity. For matter bounce models, the mechanism amplifies the scalar perturbations compared to the associated primordial gravitational waves.
Converting entropy to curvature perturbations after a cosmic bounce
Fertig, Angelika; Mallwitz, Enno; Wilson-Ewing, Edward
2016-01-01
We study two-field bouncing cosmologies in which primordial perturbations are created in either an ekpyrotic or a matter-dominated contraction phase. We use a non-singular ghost condensate bounce model to follow the perturbations through the bounce into the expanding phase of the universe. In contrast to the adiabatic perturbations, which on large scales are conserved across the bounce, entropy perturbations can grow significantly during the bounce phase. If they are converted into adiabatic/curvature perturbations after the bounce, they typically form the dominant contribution to the observed temperature fluctuations in the microwave background, which can have several beneficial implications. For ekpyrotic models, this mechanism loosens the constraints on the amplitude of the ekpyrotic potential while naturally suppressing the intrinsic amount of non-Gaussianity. For matter bounce models, the mechanism amplifies the scalar perturbations compared to the associated primordial gravitational waves.
Perturbation growth in accreting filaments
Clarke, S. D.; Whitworth, A. P.; Hubber, D. A.
2016-05-01
We use smoothed particle hydrodynamic simulations to investigate the growth of perturbations in infinitely long filaments as they form and grow by accretion. The growth of these perturbations leads to filament fragmentation and the formation of cores. Most previous work on this subject has been confined to the growth and fragmentation of equilibrium filaments and has found that there exists a preferential fragmentation length-scale which is roughly four times the filament's diameter. Our results show a more complicated dispersion relation with a series of peaks linking perturbation wavelength and growth rate. These are due to gravo-acoustic oscillations along the longitudinal axis during the sub-critical phase of growth. The positions of the peaks in growth rate have a strong dependence on both the mass accretion rate onto the filament and the temperature of the gas. When seeded with a multiwavelength density power spectrum, there exists a clear preferred core separation equal to the largest peak in the dispersion relation. Our results allow one to estimate a minimum age for a filament which is breaking up into regularly spaced fragments, as well as an average accretion rate. We apply the model to observations of filaments in Taurus by Tafalla & Hacar and find accretion rates consistent with those estimated by Palmeirim et al.
Perturbations of planar algebras
Das, Paramita; Gupta, Ved Prakash
2010-01-01
We introduce the concept of {\\em weight} of a planar algebra $P$ and construct a new planar algebra referred as the {\\em perturbation of $P$} by the weight. We establish a one-to-one correspondence between pivotal structures on 2-categories and perturbations of planar algebras by weights. To each bifinite bimodule over $II_1$-factors, we associate a {\\em bimodule planar algebra} bimodule corresponds naturally with sphericality of the bimodule planar algebra. As a consequence of this, we reproduce an extension of Jones' theorem (of associating 'subfactor planar algebras' to extremal subfactors). Conversely, given a bimodule planar algebra, we construct a bifinite bimodule whose associated bimodule planar algebra is the one which we start with using perturbations and Jones-Walker-Shlyakhtenko-Kodiyalam-Sunder method of reconstructing an extremal subfactor from a subfactor planar algebra. We show that the perturbation class of a bimodule planar algebra contains a unique spherical unimodular bimodule planar algeb...
Introduction to perturbation techniques
Nayfeh, Ali H
2011-01-01
Similarities, differences, advantages and limitations of perturbation techniques are pointed out concisely. The techniques are described by means of examples that consist mainly of algebraic and ordinary differential equations. Each chapter contains a number of exercises.
Perturbations around black holes
Wang, B
2005-01-01
Perturbations around black holes have been an intriguing topic in the last few decades. They are particularly important today, since they relate to the gravitational wave observations which may provide the unique fingerprint of black holes' existence. Besides the astrophysical interest, theoretically perturbations around black holes can be used as testing grounds to examine the proposed AdS/CFT and dS/CFT correspondence.
Perturbations and quantum relaxation
Kandhadai, Adithya
2016-01-01
We investigate whether small perturbations can cause relaxation to quantum equilibrium over very long timescales. We consider in particular a two-dimensional harmonic oscillator, which can serve as a model of a field mode on expanding space. We assume an initial wave function with small perturbations to the ground state. We present evidence that the trajectories are highly confined so as to preclude relaxation to equilibrium even over very long timescales. Cosmological implications are briefly discussed.
Institute of Scientific and Technical Information of China (English)
RONG Shu-Jun; LIU Qiu-Yu
2012-01-01
The puma model on the basis of the Lorentz and CPT violation may bring an economical interpretation to the conventional neutrinos oscillation and part of the anomalous oscillations.We study the effect of the perturbation to the puma model.In the case of the first-order perturbation which keeps the (23) interchange symmetry,the mixing matrix element Ue3 is always zero.The nonzero mixing matrix element Ue3 is obtained in the second-order perturbation that breaks the (23) interchange symmetry.%The puma model on the basis of the Lorentz and CPT violation may bring an economical interpretation to the conventional neutrinos oscillation and part of the anomalous oscillations. We study the effect of the perturbation to the puma model. In the case of the first-order perturbation which keeps the (23) interchange symmetry, the mixing matrix element Ue3 is always zero. The nonzero mixing matrix element Ue3 is obtained in the second-order perturbation that breaks the (23) interchange symmetry.
Sondhiya, Deepak Kumar; Gwal, Ashok Kumar; Verma, Shivali; Kasde, Satish Kumar; Sonakia, Anjana
In this work Wavelet Transform Modulus Maxima (WTMM) based multifractal analysis method is used to extracts the earthquake precursory signatures from scaling characteristics of subionospheric Very Low Frequency (VLF) signals. We found specific dynamics of their fractal characteristics before the earthquake, appearance of the spike in the signal and increase of the fractal dimension. We analyze VLF signals of famous Turkey Bafa transmitter (N 370 24’, E 27019’) recorded by sudden Ionospheric Disturbance (SID) monitoring station located at South of France during the Earthquake occurred at Greece during the year 2011-2012. The analysis of VLF signal during some days before and after the occurrence of earthquake has been done. Keywords: Multifractal analysis, VLF signal, Sudden Ionospheric disturbances
Electron dispersion events in the morningside auroral zone and their relationship with VLF emissions
Energy Technology Data Exchange (ETDEWEB)
Hardy, D.A.; Burke, W.J. (Hanscom Air Force Base, MA (United States)); Villalon, E. (Northeastern Univ., Boston, MA (United States))
1990-05-01
Energy/time dispersion events have been observed in the precipitating electron data in the energy range from 630 eV to 20 keV recorded by the J sensor on the low-altitude, polar-orbiting HILAT satellite. The dispersions are such that the higher-energy electrons are observed earlier in time than the lower-energy electrons The time interval for single dispersion event is from 1 to 2 s. Within an auroral pass in which such energy/time dispersion events are observed, there are typically several such events, and they can be spaced within the pass in either a periodic or aperiodic manner. The events are typically observed within and toward the equatorward edge of the region of diffuse auroral electron precipitation. During a given pass the events can be observed over a wide range of L shells. The occurrence of these events maximizes in the interval 0600-1,200 hours MLT. The energy/time dispersion is generally consistent with the electrons originating from a common source. The events are seen at L shells from 3.7 to greater than 15. The source distance for the electrons is inferred to be generally beyond the equator for events at L shells less than approximately 8 and before the equator for events at higher L shells. Because of the low energies at which the dispersions are observed, it is unlikely that their occurrence can be explained by resonant interaction with VLF waves. Based on circumstantial evidence from other reported observations common to the morning sector, and alternative theoretical explanation is presented. According to this model the dispersion events result from impulsive interactions of the electrons with intense, asymmetric packets of VLF waves via the nonlinear, ponderomotive force.
Cone structure and focusing of VLF and LF electromagnetic waves at high altitudes in the ionosphere
Alpert, Ya. L.; Green, J. L.
1994-01-01
The frequency and angle dependencies of the electric field radiated by an electric dipole E = E(sub 0) cos omega(t) are studied through numerical calculations of absolute value of E in the VLF and LF frequency bands where F is less than or equal 0.02 to 0.05 f(sub b) in a model ionosphere over an altitude region of 800-6000 km where the wave frequency and electron gyrofrequency varies between F approximately 4-500 kHz and f(sub b) is approximately equal (1.1 to 0.2) MHz respectively. It is found that the amplitudes of the electric field have large maxima in four regions: close to the direction of the Earth magnetic field line B(sub 0) (it is called the axis field E(sub 0), in the Storey E(sub St), reversed Storey E(sub RevSt), and resonance E(sub Res) cones. The maximal values of E(sub 0), E(sub Res), and E(sub RevSt) are the most pronounced close to the lower hybrid frequency, F approximately F(sub L). The flux of the electric field is concentrated in very narrow regions, with the apex angles of the cones Delta-B is approximately (0.1-1) deg. The enhancement and focusing of the electric field increases with altitude starting at Z greater than 800 km. At Z greater than or equal to 1000 up to 6000 km, the relative value of absolute value of E, in comparison with its value at Z = 800 km is about (10(exp 2) to 10(exp 4)) times larger. Thus the flux of VLF and LF electromagnetic waves generated at high altitudes in the Earth's ionosphere are trapped into very narrow conical beams similar to laser beams.
Cone structure and focusing of VLF and LF electromagnetic waves at high altitudes in the ionosphere
Alpert, Ya. L.; Green, J. L.
1994-01-01
The frequency and angle dependencies of the electric field radiated by an electric dipole E = E(sub 0) cos omega(t) are studied through numerical calculations of absolute value of E in the VLF and LF frequency bands where F is less than or equal 0.02 to 0.05 f(sub b) in a model ionosphere over an altitude region of 800-6000 km where the wave frequency and electron gyrofrequency varies between F approximately 4-500 kHz and f(sub b) is approximately equal (1.1 to 0.2) MHz respectively. It is found that the amplitudes of the electric field have large maxima in four regions: close to the direction of the Earth magnetic field line B(sub 0) (it is called the axis field E(sub 0), in the Storey E(sub St), reversed Storey E(sub RevSt), and resonance E(sub Res) cones. The maximal values of E(sub 0), E(sub Res), and E(sub RevSt) are the most pronounced close to the lower hybrid frequency, F approximately F(sub L). The flux of the electric field is concentrated in very narrow regions, with the apex angles of the cones Delta-B is approximately (0.1-1) deg. The enhancement and focusing of the electric field increases with altitude starting at Z greater than 800 km. At Z greater than or equal to 1000 up to 6000 km, the relative value of absolute value of E, in comparison with its value at Z = 800 km is about (10(exp 2) to 10(exp 4)) times larger. Thus the flux of VLF and LF electromagnetic waves generated at high altitudes in the Earth's ionosphere are trapped into very narrow conical beams similar to laser beams.
Jacobson, A. R.; Holzworth, R.; Pfaff, R. F., Jr.; Heelis, R. A.
2016-12-01
The C/NOFS satellite had a low-inclination (13 deg) orbit and provided multi-year observations (2008 - 2015) of the innermost plasmasphere within 26 deg of the magnetic equator. We report on VEFI (Vector Electric Field Instrument) recordings of zero-hop whistler-wave electric fields in this low-latitude region. We describe evidence regarding the VLF coupling variabilities, in particular versus magnetic latitude. We rely critically on data provided by the CINDI (C/NOFS Ion and Neutral Drift Investigation) measurements of the ion-composition, and by WWLLN (World-Wide Lightning-Location Network) groundtruthing of lightning-VLF source location, energy, and time. This low-latitude region has been predicted to permit only reduced VLF coupling, due essentially to a Snell's Law total reflection from the underside of the ionosphere. Nonetheless various studies of VLF coupling at discrete frequencies (from naval VLF transmitters) indicate that there is some intermittent, anomalous coupling not predicted by a simple Snell's Law. We address this problem using broadband illumination by lightning-generated VLF.
Clustering under Perturbation Resilience
Balcan, Maria Florina
2011-01-01
Recently, Bilu and Linial \\cite{BL} formalized an implicit assumption often made when choosing a clustering objective: that the optimum clustering to the objective should be preserved under small multiplicative perturbations to distances between points. They showed that for max-cut clustering it is possible to circumvent NP-hardness and obtain polynomial-time algorithms for instances resilient to large (factor $O(\\sqrt{n})$) perturbations, and subsequently Awasthi et al. \\cite{ABS10} considered center-based objectives, giving algorithms for instances resilient to O(1) factor perturbations. In this paper, we greatly advance this line of work. For the $k$-median objective, we present an algorithm that can optimally cluster instances resilient to $(1 + \\sqrt{2})$-factor perturbations, solving an open problem of Awasthi et al.\\cite{ABS10}. We additionally give algorithms for a more relaxed assumption in which we allow the optimal solution to change in a small $\\epsilon$ fraction of the points after perturbation. ...
Cosmic Perturbations Through the Cyclic Ages
Erickson, J K; Steinhardt, P J; Turok, N G; Erickson, Joel K.; Gratton, Steven; Steinhardt, Paul J.; Turok, Neil
2006-01-01
We analyze the evolution of cosmological perturbations in the cyclic model, paying particular attention to their behavior and interplay over multiple cycles. Our key results are: (1) galaxies and large scale structure present in one cycle are generated by the quantum fluctuations in the preceding cycle without interference from perturbations or structure generated in earlier cycles and without interfering with structure generated in later cycles; (2) the ekpyrotic phase, an epoch of gentle contraction with equation of state $w\\gg 1$ preceding the hot big bang, makes the universe homogeneous, isotropic and flat within any given observer's horizon; and, (3) although the universe is uniform within each observer's horizon, the global structure of the cyclic universe is more complex, owing to the effects of superhorizon length perturbations, and cannot be described in a uniform Friedmann-Robertson-Walker picture. In particular, we show that the ekpyrotic phase is so effective in smoothing, flattening and isotropiz...
Renormalized Cosmological Perturbation Theory
Crocce, M
2006-01-01
We develop a new formalism to study nonlinear evolution in the growth of large-scale structure, by following the dynamics of gravitational clustering as it builds up in time. This approach is conveniently represented by Feynman diagrams constructed in terms of three objects: the initial conditions (e.g. perturbation spectrum), the vertex (describing non-linearities) and the propagator (describing linear evolution). We show that loop corrections to the linear power spectrum organize themselves into two classes of diagrams: one corresponding to mode-coupling effects, the other to a renormalization of the propagator. Resummation of the latter gives rise to a quantity that measures the memory of perturbations to initial conditions as a function of scale. As a result of this, we show that a well-defined (renormalized) perturbation theory follows, in the sense that each term in the remaining mode-coupling series dominates at some characteristic scale and is subdominant otherwise. This is unlike standard perturbatio...
Perturbations in Symmetric Lee-Wick Bouncing Universe
Cho, Inyong
2012-01-01
We investigate the tensor and the scalar perturbations in the symmetric bouncing universe driven by one ordinary field and its Lee-Wick partner field which is a ghost. We obtain the even- and the odd-mode functions of the tensor perturbation in the matter-dominated regime. The tensor perturbation grows in time during the contracting phase of the Universe, and decays during the expanding phase. The power spectrum for the tensor perturbation is evaluated and the spectral index is given by $n_{\\rm T} =6$. We add the analysis on the scalar perturbation by inspecting the even- and the odd-mode functions in the matter-dominated regime, which was studied numerically in our previous work. We conclude that the comoving curvature by the scalar perturbation is constant in the super-horizon scale and starts to decay in the far sub-horizon scale while the Universe expands.
Evolutions of perturbations with special frequencies in lossless optical fibers
Institute of Scientific and Technical Information of China (English)
Xianqiong Zhong(钟先琼); Jianguo Chen(陈建国); Guoying Feng(冯国英); Dayi Li(李大义); Song Gao(高松)
2004-01-01
Expressing the perturbation optical field in terms of module and phase, using the linearized nonlinear Schrodinger equation governing the evolution of perturbations, we have deduced the analytical expressions of the modules, phases, and gain coefficients of the perturbations with zero or cut-off frequency, and studied the evolutions of the two perturbations travelling along lossless optical fibers in the negative dispersion regime. The results indicate that the phase of the perturbation with zero (or cut-off) frequency increases (or decreases) with the propagation distance monotonously and tends to its asymptotic value nπ + π/2 (or nπ) eventually. The evolution rates of the phases are closely related to the initial phase values. Although the asymptotic values of the field gain coefficients of the above mentioned two perturbations are equal to zero, and the increasing fashion of the modules is different from the familiar exponential type, it still suggests that the perturbations have a divergent nature when the propagation distance goes to infinity,indicating that the two kinds of perturbations can both lead to instability.
Directory of Open Access Journals (Sweden)
Saurabh Mittal
2014-01-01
Full Text Available This study is an attempt to correlate VLF-EM data with the radiometric measurements to decipher the subsurface structure and to locate uranium mineralization in the shear zone. The study area is around Beldih mine which is an open cast apatite mine located on the South Purulia Shear Zone. VLF method has been applied to map the structure and the presence of radioactive minerals has been delineated by the detection of high α and γ counts with respect to the background radiations. High radiation counts and high surface γ activity are found just above the higher apparent current-density zones in all the profiles studied, at various locations, indicating uranium and/or thorium mineralization as well as good correlation between these techniques.
Ionospheric Perturbations Possibly Caused by Preseismic Electromagnetic Emissions
Sgrigna, V.; Conti, L.; Corsi, M.; Galper, A. M.; Malvezzi, V.; Picozza, P.; Scrimaglio, R.; Stagni, L.; Zilpimiani, D.
2001-05-01
The seismicity is one of the main manifestations of the dynamical processes into the lithosphere. Electromagnetic emissions (EME) in the ULF/ELF/VLF/LF/HF range, that are related to the seismic activity, are known since a long time, but their generation mechanisms are not well understood. Two types of emissions can be considered. First, precursory emissions observed in a large frequency range, from some fraction of Hz up to several MHz, which occur a few hours before earthquakes and related to the rock microfracturing in the preparation focal area. Second, emissions observed after a shock and generally attributed to the propagation of acoustic-gravity waves. Several mechanisms have been proposed for the ionospheric perturbations caused by EME: ionospheric motion; Joule heating; plasma instabilities; precipitations of high energy charged particles (particle bursts) from the radiation belt. The explanation of the last phenomenon is connected with a disturbance of the particle flux in the lower radiation belt caused by the ULF EME waves generated in the forthcoming earthquake hypocenter and propagated upwards into the near Earth space. ULF EME interact with charged particles trapped by the Geomagnetic field modifying their pitch angle and provoking the precipitation of such particles from the radiation belt. The precipitated particle bursts (PB) drift around the Earth along the L-shell which corresponds to the earthquake epicenter. The results of correlations between PBs and earthquakes will be reported.
İnan, Umran Savaş; Golkowski, M.; Cohen, M. B.; Carpenter, D. L.
2011-01-01
The ionospheric heating facility of the High Frequency Active Auroral Research Program (HAARP) has been used extensively in the last 3 years for injection of ELF/VLF waves into the magnetosphere via modulated heating of the overhead auroral electrojet currents. Of particular interest are waves that are observed to be nonlinearly amplified after interaction with hot plasma electrons in the Earth's radiation belts. Past results have shown HAARP to be an effective platform for controlled studies...
Cosmological perturbations in antigravity
Oltean, Marius; Brandenberger, Robert
2014-10-01
We compute the evolution of cosmological perturbations in a recently proposed Weyl-symmetric theory of two scalar fields with oppositely signed conformal couplings to Einstein gravity. It is motivated from the minimal conformal extension of the standard model, such that one of these scalar fields is the Higgs while the other is a new particle, the dilaton, introduced to make the Higgs mass conformally symmetric. At the background level, the theory admits novel geodesically complete cyclic cosmological solutions characterized by a brief period of repulsive gravity, or "antigravity," during each successive transition from a big crunch to a big bang. For simplicity, we consider scalar perturbations in the absence of anisotropies, with potential set to zero and without any radiation. We show that despite the necessarily wrong-signed kinetic term of the dilaton in the full action, these perturbations are neither ghostlike nor tachyonic in the limit of strongly repulsive gravity. On this basis, we argue—pending a future analysis of vector and tensor perturbations—that, with respect to perturbative stability, the cosmological solutions of this theory are viable.
Instantaneous stochastic perturbation theory
Lüscher, Martin
2015-01-01
A form of stochastic perturbation theory is described, where the representative stochastic fields are generated instantaneously rather than through a Markov process. The correctness of the procedure is established to all orders of the expansion and for a wide class of field theories that includes all common formulations of lattice QCD.
Perturbation Monte Carlo methods for tissue structure alterations.
Nguyen, Jennifer; Hayakawa, Carole K; Mourant, Judith R; Spanier, Jerome
2013-01-01
This paper describes an extension of the perturbation Monte Carlo method to model light transport when the phase function is arbitrarily perturbed. Current perturbation Monte Carlo methods allow perturbation of both the scattering and absorption coefficients, however, the phase function can not be varied. The more complex method we develop and test here is not limited in this way. We derive a rigorous perturbation Monte Carlo extension that can be applied to a large family of important biomedical light transport problems and demonstrate its greater computational efficiency compared with using conventional Monte Carlo simulations to produce forward transport problem solutions. The gains of the perturbation method occur because only a single baseline Monte Carlo simulation is needed to obtain forward solutions to other closely related problems whose input is described by perturbing one or more parameters from the input of the baseline problem. The new perturbation Monte Carlo methods are tested using tissue light scattering parameters relevant to epithelia where many tumors originate. The tissue model has parameters for the number density and average size of three classes of scatterers; whole nuclei, organelles such as lysosomes and mitochondria, and small particles such as ribosomes or large protein complexes. When these parameters or the wavelength is varied the scattering coefficient and the phase function vary. Perturbation calculations give accurate results over variations of ∼15-25% of the scattering parameters.
New type of ensemble of quasi-periodic, long-lasting VLF emissions at the auroral zone
Directory of Open Access Journals (Sweden)
J. Manninen
2012-12-01
Full Text Available A new type of the series of quasi-periodic (QP very low frequency (VLF emissions in frequency range of 1–5 kHz, and not associated with geomagnetic pulsations, has been discovered at auroral latitudes (L = 5.3 during the Finnish VLF campaign (held in December 2011. At least five unusually spectacular events, each with a duration of several hours, have been observed during the night under conditions of quiet geomagnetic activity (Kp = 0–1, although QPs usually occur during the daytime. Contrary to the QP emissions typically occurring during the day, the spectral structure of these QP events represented an extended, complicated sequence of repeated discrete rising VLF signals. Their duration was about 2–3 min each, with the repetition periods ranging from ~1 min to ~10 min. Two such nighttime non-typical events are reported in this paper. The fine structure of the separated QP elements may represent a mixture of the different frequency band signals, which seem to have independent origins. It was found that the periodic signals with lower frequency appear to trigger the strong dispersive upper frequency signals. The temporal dynamics of the spectral structure of the QPs studied were significantly controlled by some disturbances in the solar wind and interplanetary magnetic field (IMF. This finding is very important for future theoretical investigations because the generation mechanism of this new type of QP emissions is not yet understood.
Pal, Sujay
2015-01-01
In this thesis, we theoretically predict the normal characteristics of Very Low Frequency (3~30 kHz) radio wave propagation through Earth-ionosphere waveguide corresponding to normal behavior of the D-region ionosphere. We took the VLF narrow band data from the receivers of Indian Centre for Space Physics (ICSP) to validate our models. Detection of sudden ionospheric disturbances (SIDs) are common to all the measurements. We apply our theoretical models to infer the D-region characteristics and to reproduce the observed VLF signal behavior corresponding to such SIDs. We develop a code based on ray theory to simulate the diurnal behavior of VLF signals over short propagation paths (2000~3000 km). The diurnal variation from this code are comparable to the variation obtained from a more general Long Wave Propagation Capability (LWPC) code which is based on mode theory approach. We simulate the observational results obtained during the Total Solar Eclipse of July 22, 2009 in India. We also report and simulate a h...
High order multiplication perturbation method for singular perturbation problems
Institute of Scientific and Technical Information of China (English)
张文志; 黄培彦
2013-01-01
This paper presents a high order multiplication perturbation method for sin-gularly perturbed two-point boundary value problems with the boundary layer at one end. By the theory of singular perturbations, the singularly perturbed two-point boundary value problems are first transformed into the singularly perturbed initial value problems. With the variable coeﬃcient dimensional expanding, the non-homogeneous ordinary dif-ferential equations (ODEs) are transformed into the homogeneous ODEs, which are then solved by the high order multiplication perturbation method. Some linear and nonlinear numerical examples show that the proposed method has high precision.
Perturbations can enhance qauntum search
Bae, J; Bae, Joonwoo; Kwon, Younghun
2003-01-01
In general, a quantum algorithm wants to avoid decoherence or perturbation, since such factors may cause errors in the algorithm. In this letter, we will supply the answer to the interesting question: can the factors seemingly harmful to a quantum algorithm(for example, perturbations) enhance the algorithm? We show that some perturbations to the generalized quantum search Hamiltonian can reduce the running time and enhance the success probability. We also provide the narrow bound to the perturbation which can be beneficial to quantum search. In addition, we show that the error induced by a perturbation on the Farhi and Gutmann Hamiltonian can be corrected by another perturbation.
Lightning and ionospheric remote sensing using VLF/ELF radio atmospherics
Cummer, Steven Andrew
Lightning discharges radiate the bulk of their electromagnetic energy in the Very Low Frequency (VLF, 3- 30 kHz) and Extremely Low Frequency (ELF, 3-3000 Hz) frequency ranges. This energy, contained in impulse-like signals called radio atmospherics or sferics, is guided for long distances by multiple reflections from the ground and lower ionosphere. These two facts suggest that observed sferic waveforms radiated from lightning contain a great deal of information about both the state of the ionosphere along the propagation path and the dynamics of the current in the lightning return stroke. The aim of this dissertation is to develop and implement the necessary techniques to use sferic observations to determine the characteristics of the ionosphere and lightning. In this work, a quantitative model of sferic propagation is developed, and with it the spectral characteristics of VLF (> 1.5 kHz) sferics are shown to depend primarily on the propagation-path-averaged ionospheric D region electron density profile. Using this propagation model, a parameterized ionosphere is iteratively varied to find the theoretical sferic spectrum that agrees best with an observed sferic spectrum composed of the average of many individual sferic spectra. In most nighttime cases, the quality of the agreement allows the height of an exponentially-varying electron density profile to be inferred with a precision of 0.2 km. Since the general sferic waveform depends on the source current-moment waveform as well as the ionospherically- controlled propagation, the former quantity can be measured for individual discharges from observed sferics. Of particular interest are those lightning discharges associated with mesospheric optical emissions known as sprites. By using a robust deconvolution technique, source current-moment waveforms are extracted from individual observed ELF (< 1.5 kHz) sferics. The cases studied in detail show that optical emissions are sometimes produced with a smaller vertical
Perturbations of vortex ring pairs
Gubser, Steven S; Parikh, Sarthak
2015-01-01
We study pairs of co-axial vortex rings starting from the action for a classical bosonic string in a three-form background. We complete earlier work on the phase diagram of classical orbits by explicitly considering the case where the circulations of the two vortex rings are equal and opposite. We then go on to study perturbations, focusing on cases where the relevant four-dimensional transfer matrix splits into two-dimensional blocks. When the circulations of the rings have the same sign, instabilities are mostly limited to wavelengths smaller than a dynamically generated length scale at which single-ring instabilities occur. When the circulations have the opposite sign, larger wavelength instabilities can occur.
Aspects of perturbative unitarity
Anselmi, Damiano
2016-07-01
We reconsider perturbative unitarity in quantum field theory and upgrade several arguments and results. The minimum assumptions that lead to the largest time equation, the cutting equations and the unitarity equation are identified. Using this knowledge and a special gauge, we give a new, simpler proof of perturbative unitarity in gauge theories and generalize it to quantum gravity, in four and higher dimensions. The special gauge interpolates between the Feynman gauge and the Coulomb gauge without double poles. When the Coulomb limit is approached, the unphysical particles drop out of the cuts and the cutting equations are consistently projected onto the physical subspace. The proof does not extend to nonlocal quantum field theories of gauge fields and gravity, whose unitarity remains uncertain.
Aspects of perturbative unitarity
Anselmi, Damiano
2016-01-01
We reconsider perturbative unitarity in quantum field theory and upgrade several arguments and results. The minimum assumptions that lead to the largest time equation, the cutting equations and the unitarity equation are identified. Using this knowledge and a special gauge, we give a new, simpler proof of perturbative unitarity in gauge theories and generalize it to quantum gravity, in four and higher dimensions. The special gauge interpolates between the Feynman gauge and the Coulomb gauge without double poles. When the Coulomb limit is approached, the unphysical particles drop out of the cuts and the cutting equations are consistently projected onto the physical subspace. The proof does not extend to nonlocal quantum field theories of gauge fields and gravity, whose unitarity remains uncertain.
Degenerate Density Perturbation Theory
Palenik, Mark C
2016-01-01
Fractional occupation numbers can be used in density functional theory to create a symmetric Kohn-Sham potential, resulting in orbitals with degenerate eigenvalues. We develop the corresponding perturbation theory and apply it to a system of $N_d$ degenerate electrons in a harmonic oscillator potential. The order-by-order expansions of both the fractional occupation numbers and unitary transformations within the degenerate subspace are determined by the requirement that a differentiable map exists connecting the initial and perturbed states. Using the X$\\alpha$ exchange-correlation (XC) functional, we find an analytic solution for the first-order density and first through third-order energies as a function of $\\alpha$, with and without a self-interaction correction. The fact that the XC Hessian is not positive definite plays an important role in the behavior of the occupation numbers.
Large Spin Perturbation Theory
Alday, Luis F
2016-01-01
We consider conformal field theories around points of large twist degeneracy. Examples of this are theories with weakly broken higher spin symmetry and perturbations around generalised free fields. At the degenerate point we introduce twist conformal blocks. These are eigenfunctions of certain quartic operators and encode the contribution, to a given four-point correlator, of the whole tower of intermediate operators with a given twist. As we perturb around the degenerate point, the twist degeneracy is lifted. In many situations this breaking is controlled by inverse powers of the spin. In such cases the twist conformal blocks can be decomposed into a sequence of functions which we systematically construct. Decomposing the four-point correlator in this basis turns crossing symmetry into an algebraic problem. Our method can be applied to a wide spectrum of conformal field theories in any number of dimensions and at any order in the breaking parameter. As an example, we compute the spectrum of various theories ...
Cosmological Perturbations in Antigravity
Oltean, Marius
2014-01-01
We compute the evolution of cosmological perturbations in a recently proposed Weyl-symmetric theory of two scalar fields with oppositely-signed conformal couplings to Einstein gravity. It is motivated from the minimal conformal extension of the Standard Model, such that one of these scalar fields is the Higgs while the other is a new particle, the dilaton, introduced to make the Higgs mass conformally symmetric. At the background level, the theory admits novel geodesically-complete cyclic cosmological solutions characterized by a brief period of repulsive gravity, or "antigravity", during each successive transition from a Big Crunch to a Big Bang. We show that despite the necessarily wrong-signed kinetic term of the dilaton in the full action, its cosmological solutions are stable at the perturbative level.
Perturbatively charged holographic disorder
O'Keeffe, Daniel K
2015-01-01
Within the framework of holography applied to condensed matter physics, we study a model of perturbatively charged disorder in D=4 dimensions. Starting from initially uncharged AdS_4, a randomly fluctuating boundary chemical potential is introduced by turning on a bulk gauge field parameterized by a disorder strength and a characteristic scale k_0. Accounting for gravitational backreaction, we construct an asymptotically AdS solution perturbatively in the disorder strength. The disorder averaged geometry displays unphysical divergences in the deep interior. We explain how to remove these divergences and arrive at a well behaved solution. The disorder averaged DC conductivity is calculated and is found to contain a correction to the AdS result. The correction appears at second order in the disorder strength and scales inversely with k_0. We discuss the extension to a system with a finite initial charge density. The disorder averaged DC conductivity may be calculated by adopting a technique developed for hologr...
Degenerate density perturbation theory
Palenik, Mark C.; Dunlap, Brett I.
2016-09-01
Fractional occupation numbers can be used in density functional theory to create a symmetric Kohn-Sham potential, resulting in orbitals with degenerate eigenvalues. We develop the corresponding perturbation theory and apply it to a system of Nd degenerate electrons in a harmonic oscillator potential. The order-by-order expansions of both the fractional occupation numbers and unitary transformations within the degenerate subspace are determined by the requirement that a differentiable map exists connecting the initial and perturbed states. Using the X α exchange-correlation (XC) functional, we find an analytic solution for the first-order density and first- through third-order energies as a function of α , with and without a self-interaction correction. The fact that the XC Hessian is not positive definite plays an important role in the behavior of the occupation numbers.
Ooguri, H; Ooguri, Hirosi; Yin, Zheng
1996-01-01
These lecture notes are based on a course on string theories given by Hirosi Ooguri in the first week of TASI 96 Summer School at Boulder, Colorado. It is an introductory course designed to provide students with minimum knowledge before they attend more advanced courses on non-perturbative aspects of string theories in the School. The course consists of five lectures: 1. Bosonic String, 2. Toroidal Compactifications, 3. Superstrings, 4. Heterotic Strings, and 5. Orbifold Compactifications.
Covariant Bardeen perturbation formalism
Vitenti, S. D. P.; Falciano, F. T.; Pinto-Neto, N.
2014-05-01
In a previous work we obtained a set of necessary conditions for the linear approximation in cosmology. Here we discuss the relations of this approach with the so-called covariant perturbations. It is often argued in the literature that one of the main advantages of the covariant approach to describe cosmological perturbations is that the Bardeen formalism is coordinate dependent. In this paper we will reformulate the Bardeen approach in a completely covariant manner. For that, we introduce the notion of pure and mixed tensors, which yields an adequate language to treat both perturbative approaches in a common framework. We then stress that in the referred covariant approach, one necessarily introduces an additional hypersurface choice to the problem. Using our mixed and pure tensors approach, we are able to construct a one-to-one map relating the usual gauge dependence of the Bardeen formalism with the hypersurface dependence inherent to the covariant approach. Finally, through the use of this map, we define full nonlinear tensors that at first order correspond to the three known gauge invariant variables Φ, Ψ and Ξ, which are simultaneously foliation and gauge invariant. We then stress that the use of the proposed mixed tensors allows one to construct simultaneously gauge and hypersurface invariant variables at any order.
Perturbation semigroup of matrix algebras
Neumann, N.; Suijlekom, W.D. van
2016-01-01
In this article we analyze the structure of the semigroup of inner perturbations in noncommutative geometry. This perturbation semigroup is associated to a unital associative *-algebra and extends the group of unitary elements of this *-algebra. We compute the perturbation semigroup for all matrix algebras.
Perturbative quantum chromodynamics
1989-01-01
This book will be of great interest to advanced students and researchers in the area of high energy theoretical physics. Being the most complete and updated review volume on Perturbative QCD, it serves as an extremely useful textbook or reference book. Some of the reviews in this volume are the best that have been written on the subject anywhere. Contents: Factorization of Hard Processes in QCD (J C Collins, D E Soper & G Sterman); Exclusive Processes in Quantum Chromodynamics (S J Brodsky & G P Lepage); Coherence and Physics of QCD Jets (Yu L Dokshitzer, V A Khoze & S I Troyan); Pomeron in Qu
Beane, Silas R; Vuorinen, Aleksi
2009-01-01
We present a new formulation of effective field theory for nucleon-nucleon (NN) interactions which treats pion interactions perturbatively, and we offer evidence that the expansion converges satisfactorily to third order in the expansion, which we have computed analytically for s and d wave NN scattering. Starting with the Kaplan-Savage-Wise (KSW) expansion about the nontrivial fixed point corresponding to infinite NN scattering length, we cure the convergence problems with that theory by summing to all orders the singular short distance part of the pion tensor interaction. This method makes possible a host of high precision analytic few-body calculations in nuclear physics.
Non-Perturbative Renormalization
Mastropietro, Vieri
2008-01-01
The notion of renormalization is at the core of several spectacular achievements of contemporary physics, and in the last years powerful techniques have been developed allowing to put renormalization on a firm mathematical basis. This book provides a self-consistent and accessible introduction to the sophisticated tools used in the modern theory of non-perturbative renormalization, allowing an unified and rigorous treatment of Quantum Field Theory, Statistical Physics and Condensed Matter models. In particular the first part of this book is devoted to Constructive Quantum Field Theory, providi
Gauge Invariant Cosmological Perturbation Theory
Durrer, R
1993-01-01
After an introduction to the problem of cosmological structure formation, we develop gauge invariant cosmological perturbation theory. We derive the first order perturbation equations of Einstein's equations and energy momentum ``conservation''. Furthermore, the perturbations of Liouville's equation for collisionless particles and Boltzmann's equation for Compton scattering are worked out. We fully discuss the propagation of photons in a perturbed Friedmann universe, calculating the Sachs--Wolfe effect and light deflection. The perturbation equations are extended to accommodate also perturbations induced by seeds. With these general results we discuss some of the main aspects of the texture model for the formation of large scale structure in the Universe (galaxies, clusters, sheets, voids). In this model, perturbations in the dark matter are induced by texture seeds. The gravitational effects of a spherically symmetric collapsing texture on dark matter, baryonic matter and photons are calculated in first orde...
Higher representations on the lattice: perturbative studies
Del Debbio, Luigi; Panagopoulos, Haralambos; Sannino, Francesco
2008-01-01
We present analytical results to guide numerical simulations with Wilson fermions in higher representations of the colour group. The ratio of $\\Lambda$ parameters, the additive renormalization of the fermion mass, and the renormalization of fermion bilinears are computed in perturbation theory, including cactus resummation. We recall the chiral Lagrangian for the different patterns of symmetry breaking that can take place with fermions in higher representations, and discuss the possibility of an Aoki phase as the fermion mass is reduced at finite lattice spacing.
Irwandi, Marwan, Muksin, Fashbir
2017-07-01
Aceh is an area which is located at volcanically active region and at the meeting point of the Eurasian and the Indo-Australian plates. Many mountain formations and folds are formed as a result of the meeting of these plates. One of the mountains in Aceh is The Gunung Leuser, the highest mountain in the province with altitude of 3,404 m. The active geodynamic conditions could lead to the formation of potentially active faults which produce earthquakes. Due to safety reason, there are few researches done to identify active faults in the LE (Leuser Ecosystem). Therefore, we propose a preliminary study to identify morphological patterns of the fault system from the topography data of SRTM (Shuttle Radar Topography Mission). Having obtained the approximate location of fault, then a Very Low Frequency method is applied to determine the detail characteristic of the fault. This method can determine the subsurface structure to a depth of 50 m without digging or drilling. In this study, we measure three profiles with length of each profile of 12-16 km. Along profile 1, the VLF data fluctuated due to relatively high iron deposition along the line. For profile 2, the results are very consistent with the adjacent to the fault Blangkejeren which is the main part of the Sumatran Fault. Profile 3 Lokop - Kutacane fault also shows the correction of the topography. In general, VLF method is relatively influenced by noise as the consequences of the passive electromagnetic measurement. Thus, it is important to develop an analysis method of VLF data that includes the topographical correction so that better lateral anomaly map can be created.
Ammar, A. I.; Kruse, S. E.
2016-04-01
Seasonal shortages of groundwater are common in parts of the Arabian Shield, where complex basement hydrogeology can make siting of water wells difficult. To identify optimal production well locations, six 200-400 m-long Very Low Frequency (VLF) electromagnetic traverses and ten Vertical Electrical Soundings (VESes) were run at the western edge of the Arabian Shield near At-Taif town, Saudi Arabia. Here wadi sediments overlie fractured Precambrian basement, which in turn overlies unfractured basement. The fractured basement forms the water supply aquifer. Both VLF and VES data indicate significant lateral heterogeneity in the electrical conductivity of both wadi and basement deposits over lengths scales as small as ∼100 m. VES results correlate closely with data from two wells in the study area. The change in resistivity at the wadi-to-fractured basement contact is relatively subtle, but the transition from low resistivity fractured basement to high resistivity unfractured basement is well resolved. Inferred wadi thicknesses range from 0 to 14 m; the electrically conductive fractured basement extends from wadi down to 12-32 m depth. VES data indicate the fractured basement aquifer thickens progressively to the south in this area. A production well, sited on the basis of the VES analysis, successfully yielded 70m3/day. The relationship between VLF and VES data is complex, suggesting that the terrain is heterogeneous on the scale of the different effective sampling volumes of the two methods, and/or that fracture azimuth is locally heterogeneous. Overall resistivities in this study are similar to those observed at other locations in Saudi Arabia, suggesting these methods may be widely applicable for siting of groundwater wells in the complex basement of the Arabian Shield.
Bitzer, Phillip M.; Christian, Hugh J.; Stewart, Mike; Burchfield, Jeff; Podgorny, Scott; Corredor, David; Hall, John; Kuznetsov, Evgeny; Franklin, Veronica
2013-04-01
Arrays that detect and locate the four-dimensional spacetime positions of radiation sources from lightning have largely utilized sensors sensitive to the very high frequency (VHF) regime with ˜ 15 km baselines or very low frequency/low frequency (VLF/LF) regime with ˜ 100 km baselines. This paper details initial results from the newly developed Huntsville Alabama Marx Meter Array (HAMMA), consisting of Marx meters (electric field change meters) sensitive to a frequency band ˜ 1 Hz to 400 kHz. The arrival time of HAMMA waveforms due to radiation sources from lightning are used to determine the spacetime position of these sources. The locations are compared with two well-documented and operational arrays, the National Lightning Detection Network (NLDN) and the North Alabama Lightning Mapping Array (NALMA). The standard deviation of the difference between HAMMA and NLDN locations of return strokes is 305 and 266 m in x and y, respectively, while the standard deviation of the difference between HAMMA and NALMA sources is 237, 226, and 688 m in x, y and z, respectively. We further show that NLDN intracloud locations differ in horizontal distance from the corresponding HAMMA locations by a median value of 479 m. In addition, we use HAMMA source locations to map several lightning flashes in the VLF/LF and show HAMMA sources largely map out the same electrical extent as VHF sources and provide unique insights to the properties of the discharges occurring. Finally, we show that VLF/LF sources can determine the leader polarity in several example flashes but not necessarily whether a flash comes to ground. Copyright 2013 American Geophysical Union. All rights reserved.
Building and the analysis of two radio antennas (SSRT) in vlf zone
Marbouti, Marjan; Khakian Ghomi, Mehdi; Salmanpour Paeen Afrakati, Mohammad Reza; Riahi, Jahad; Ghanbari, Keyvan; Moradi Khanghahi, Abolfazl; Nahavandi, Behzad
This design is a joint project between telecommunication and astrophysics subjects carried out for the first time in Iran. In this article, we engage in building of two looped antennas (SSRT) that the first type of it is a SSRT (octagonal looped antenna) with an outer filter system of 80 cm diameter, cable thickness of 0.55 mm, inductance 38.24 MH and capacitor’s capacitance of 919 pf. The software of Spectrum lab and SSRT Robot2 were used for software section and to store the related information. While second antenna type is a SSRT (two interconnected square type loop antennas) with inner filter system in the form of two interconnected squares with beveled corners such that the number of windings for outer square are (larger) 60 rounds, while for inner square (smaller) 95 rounds. The CATIA software was used to design the antenna structure and “Protel Dxp’’ software has been used to design its circuit. A program has been designed with C# language for receiving section and processing of data. Considering the closeness of Turkey transmitter to the city of Tehran (test location), the designed SSRTs are responsible for receiving the frequency of 26.7 kHz while TBB (Bafa, Turkey) is considered the frequency producing source for it. In the continuation of project, we started to store our receiving data from SSRTs following the calibration, average taking as well as noise elimination that was produced due to different factors such as the noises caused by electrical equipment and the everyday activities of telecommunication devices. In this stage, we were observing our receiving coincidences with all SSRTs as well as the Goes satellite. Afterwards, we dealt with the analysis of solar flares, sunrise-sunset effects and electrical disturbances. Then, in a separate project, the received data secured from 8 different VLF receivers were studied and examined, by means of Mr. Loudet receiver located in France, for the years of 2010, 2011 and 2012 and we attained the
VLF/ELF wave activity in the vicinity of the polar cusp: Cluster observations
Directory of Open Access Journals (Sweden)
N. Lin
2006-08-01
Full Text Available Observations by the Cluster spacecraft of VLF/ELF wave activity show distinct signatures for different regions in the vicinity of high altitude polar cusps, which are identified by using magnetic field and plasma data along spacecraft trajectories. These waves include: (1 Broad band magnetic noise observed in the polar cusp at frequencies from several Hz to ~100 Hz, below the local electron cyclotron frequency, f_{ce}. Similar magnetic noise is also observed in the high latitude magnetosheath and the magnetopause boundary layer. (2 Strong broad band electrostatic emissions observed in the cusp, in the magnetosheath, and in the high latitude magnetopause boundary layer, at frequencies extending from several Hz to tens of kHz, with maximum intensities below ~100 Hz. (3 Narrow-band electromagnetic whistler waves at frequencies ~0.2–0.6 f_{ce}, frequently observed in the closed boundary layer (CBL adjacent to the polar cusp. These waves are for the first time observed in this region to be accompanied by counter-streaming electron beams of ~100 eV, which suggests that the waves are excited by these electrons through wave-particle interaction. (4 Narrow-band electrostatic waves observed slightly above the local f_{ce} in the CBL. (5 Lion roars, observed in the high latitude magnetosheath, often in magnetic troughs of mirror mode oscillations. The above wave signatures can serve as indicators of the regions in the vicinity of the magnetospheric cusp.
Direct perturbation method for perturbed complex Burgers equation
Institute of Scientific and Technical Information of China (English)
Cheng Xue-Ping; Lin Ji; Yao Jian-Ming
2009-01-01
So far, Lou's direct perturbation method has been applied successfully to solve the nonlinear Schrōdinger equa-tion(NLSE) hierarchy, such as the NLSE, the coupled NLSE, the critical NLSE, and the derivative NLSE. But to our knowledge, this method for other types of perturbed nonlinear evolution equations has still been lacking. In this paper, Lou's direct perturbation method is applied to the study of perturbed complex Burgers equation. By this method, we calculate not only the zero-order adiabatic solution, but also the first order modification.
Introduction to perturbation methods
Holmes, M
1995-01-01
This book is an introductory graduate text dealing with many of the perturbation methods currently used by applied mathematicians, scientists, and engineers. The author has based his book on a graduate course he has taught several times over the last ten years to students in applied mathematics, engineering sciences, and physics. The only prerequisite for the course is a background in differential equations. Each chapter begins with an introductory development involving ordinary differential equations. The book covers traditional topics, such as boundary layers and multiple scales. However, it also contains material arising from current research interest. This includes homogenization, slender body theory, symbolic computing, and discrete equations. One of the more important features of this book is contained in the exercises. Many are derived from problems of up- to-date research and are from a wide range of application areas.
Applications of Cosmological Perturbation Theory
Christopherson, Adam J
2011-01-01
Cosmological perturbation theory is crucial for our understanding of the universe. The linear theory has been well understood for some time, however developing and applying the theory beyond linear order is currently at the forefront of research in theoretical cosmology. This thesis studies the applications of perturbation theory to cosmology and, specifically, to the early universe. Starting with some background material introducing the well-tested 'standard model' of cosmology, we move on to develop the formalism for perturbation theory up to second order giving evolution equations for all types of scalar, vector and tensor perturbations, both in gauge dependent and gauge invariant form. We then move on to the main result of the thesis, showing that, at second order in perturbation theory, vorticity is sourced by a coupling term quadratic in energy density and entropy perturbations. This source term implies a qualitative difference to linear order. Thus, while at linear order vorticity decays with the expan...
Applications Of Chiral Perturbation Theory
Mohta, V
2005-01-01
Effective field theory techniques are used to describe the spectrum and interactions of hadrons. The mathematics of classical field theory and perturbative quantum field theory are reviewed. The physics of effective field theory and, in particular, of chiral perturbation theory and heavy baryon chiral perturbation theory are also reviewed. The geometry underlying heavy baryon chiral perturbation theory is described in detail. Results by Coleman et. al. in the physics literature are stated precisely and proven. A chiral perturbation theory is developed for a multiplet containing the recently- observed exotic baryons. A small coupling expansion is identified that allows the calculation of self-energy corrections to the exotic baryon masses. Opportunities in lattice calculations are discussed. Chiral perturbation theory is used to study the possibility of two multiplets of exotic baryons mixed by quark masses. A new symmetry constraint on reduced partial widths is identified. Predictions in the literature based ...
Cosmological perturbations in massive bigravity
Energy Technology Data Exchange (ETDEWEB)
Lagos, Macarena; Ferreira, Pedro G., E-mail: m.lagos13@imperial.ac.uk, E-mail: p.ferreira1@physics.ox.ac.uk [Astrophysics, University of Oxford, DWB, Keble road, Oxford OX1 3RH (United Kingdom)
2014-12-01
We present a comprehensive analysis of classical scalar, vector and tensor cosmological perturbations in ghost-free massive bigravity. In particular, we find the full evolution equations and analytical solutions in a wide range of regimes. We show that there are viable cosmological backgrounds but, as has been found in the literature, these models generally have exponential instabilities in linear perturbation theory. However, it is possible to find stable scalar cosmological perturbations for a very particular choice of parameters. For this stable subclass of models we find that vector and tensor perturbations have growing solutions. We argue that special initial conditions are needed for tensor modes in order to have a viable model.
Generating Ekpyrotic Curvature Perturbations Before the Big Bang
Lehners, J L; Steinhardt, P J; Turok, N G; Fadden, Paul Mc; Lehners, Jean-Luc; Steinhardt, Paul J.; Turok, Neil
2007-01-01
We analyze a general mechanism for producing a nearly scale-invariant spectrum of cosmological curvature perturbations during a contracting phase preceding a big bang, that can be entirely described using 4d effective field theory. The mechanism, based on first producing entropic perturbations and then converting them to curvature perturbations, can be naturally incorporated in cyclic and ekpyrotic models in which the big bang is modelled as a brane collision, as well as other types of cosmological models with a pre-big bang phase. We show that the correct perturbation amplitude can be obtained and that the scalar spectral tilt n tends to range from slightly blue to red, with 0.97 < n < 1.02 for the simplest models, a range compatible with current observations but shifted by a few per cent towards the blue compared to the prediction of the simplest, large-field inflationary models.
Non-Perturbative Asymptotic Improvement of Perturbation Theory and Mellin-Barnes Representation
Directory of Open Access Journals (Sweden)
Samuel Friot
2010-10-01
Full Text Available Using a method mixing Mellin-Barnes representation and Borel resummation we show how to obtain hyperasymptotic expansions from the (divergent formal power series which follow from the perturbative evaluation of arbitrary ''N-point'' functions for the simple case of zero-dimensional φ4 field theory. This hyperasymptotic improvement appears from an iterative procedure, based on inverse factorial expansions, and gives birth to interwoven non-perturbative partial sums whose coefficients are related to the perturbative ones by an interesting resurgence phenomenon. It is a non-perturbative improvement in the sense that, for some optimal truncations of the partial sums, the remainder at a given hyperasymptotic level is exponentially suppressed compared to the remainder at the preceding hyperasymptotic level. The Mellin-Barnes representation allows our results to be automatically valid for a wide range of the phase of the complex coupling constant, including Stokes lines. A numerical analysis is performed to emphasize the improved accuracy that this method allows to reach compared to the usual perturbative approach, and the importance of hyperasymptotic optimal truncation schemes.
Directory of Open Access Journals (Sweden)
S. Palit
2013-09-01
Full Text Available X-ray photons emitted during solar flares cause ionization in the lower ionosphere (~60 to 100 km in excess of what is expected to occur due to a quiet sun. Very low frequency (VLF radio wave signals reflected from the D-region of the ionosphere are affected by this excess ionization. In this paper, we reproduce the deviation in VLF signal strength during solar flares by numerical modeling. We use GEANT4 Monte Carlo simulation code to compute the rate of ionization due to a M-class flare and a X-class flare. The output of the simulation is then used in a simplified ionospheric chemistry model to calculate the time variation of electron density at different altitudes in the D-region of the ionosphere. The resulting electron density variation profile is then self-consistently used in the LWPC code to obtain the time variation of the change in VLF signal. We did the modeling of the VLF signal along the NWC (Australia to IERC/ICSP (India propagation path and compared the results with observations. The agreement is found to be very satisfactory.
Inversion of the perturbation series
Energy Technology Data Exchange (ETDEWEB)
Amore, Paolo [Facultad de Ciencias, Universidad de Colima, Bernal DIaz del Castillo 340, Colima, Colima (Mexico); Fernandez, Francisco M [INIFTA (Conicet, UNLP), Division Quimica Teorica, Diag 113 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)
2008-01-18
We investigate the inversion of the perturbation series and its resummation, and prove that it is related to a recently developed parametric perturbation theory. Results for some illustrative examples show that in some cases series reversion may improve the accuracy of the results.
Propagation of Ion Acoustic Perturbations
DEFF Research Database (Denmark)
Pécseli, Hans
1975-01-01
Equations describing the propagation of ion acoustic perturbations are considered, using the assumption that the electrons are Boltzman distributed and isothermal at all times. Quasi-neutrality is also considered.......Equations describing the propagation of ion acoustic perturbations are considered, using the assumption that the electrons are Boltzman distributed and isothermal at all times. Quasi-neutrality is also considered....
Path integral for inflationary perturbations
Prokopec, T.; Rigopoulos, G.
2010-01-01
The quantum theory of cosmological perturbations in single-field inflation is formulated in terms of a path integral. Starting from a canonical formulation, we show how the free propagators can be obtained from the well-known gauge-invariant quadratic action for scalar and tensor perturbations, and
Directory of Open Access Journals (Sweden)
F. Muto
2008-02-01
Full Text Available There have been recently reported a lot of electromagnetic phenomena associated with earthquakes (EQs. Among these, the ground-based reception of subionospheric waves from VLF/LF transmitters, is recognized as a promising tool to investigate the ionospheric perturbations associated with EQs. This paper deals with the corresponding whistler-mode signals in the upper ionosphere from those VLF/LF transmitters, which is the counterpart of subionospheric signals. The whistler-mode VLF/LF transmitter signals are detected on board the French satellite, DEMETER launched on 29 June 2004. We have chosen several large Japanese EQs including the Miyagi-oki EQ (16 August 2005; M=7.2, depth=36 km, and the target transmitter is a Japanese LF transmitter (JJY whose transmitter frequency is 40 kHz. Due to large longitudinal separation of each satellite orbit (2500 km, we have to adopt a statistical analysis over a rather long period (such as 3 weeks or one month to have reliable data set. By analyzing the spatial distribution of JJY signal intensity (in the form of signal to noise ratio SNR during a period of 4 months including the Miyagi-oki EQ, we have found significant changes in the intensity; generally the SNR is significantly depleted before the EQ, which is considered to be a precursory ionospheric signature of the EQ. This abnormal effect is reasonably explained in terms of either (1 enhanced absorption of whistler-mode LF signals in the lower ionosphere due to the lowering of the lower ionosphere, or (2 nonlinear wave-wave scattering. Finally, this analysis suggests an important role of satellite observation in the study of lithosphere-atmosphere-ionosphere coupling.
Non-Perturbative Flat Direction Decay
Basboll, A; Riva, F; West, S M; Basboll, Anders; Maybury, David; Riva, Francesco; West, Stephen M.
2007-01-01
We argue that supersymmetric flat direction vevs can decay non-perturbatively via preheating. Considering the case of a single flat direction, we explicitly calculate the scalar potential in the unitary gauge for a U(1) theory and show that the mass matrix for excitations around the flat direction has non-diagonal entries which vary with the phase of the flat direction vev. Furthermore, this mass matrix has 2 zero eigenvalues (associated with the excitations along the flat direction) whose eigenstates change with time. We show that these 2 light degrees of freedom are produced copiously in the non-perturbative decay of the flat direction vev. We also comment on the application of these results to the MSSM flat direction H_uL.
Nucleophilicity index from perturbed electrostatic potentials.
Cedillo, A; Contreras, R; Galván, M; Aizman, A; Andrés, J; Safont, V S
2007-03-29
We introduce and test a nucleophilicity index as a new descriptor of chemical reactivity. The index is derived from a perturbation model for the interaction between the nucleophile and a positive test charge. The computational implementation of the model uses an isoelectronic process involving the minimum values of the electronic part of the perturbed molecular electrostatic potential. The working expression defining the nucleophilicity index encompasses both the electrostatic contributions and the second-order polarization effects in a form which is consistent with the empirical scales previously proposed. The index is validated for a series of neutral nucleophiles in the gas phase for which the nucleophilicity pattern has been experimentally established within a spectroscopic scale.
Junction conditions of cosmological perturbations
Tomita, K
2004-01-01
The behavior of perturbations is studied in cosmological models which consist of two different homogeneous regions connected in a spherical shell boundary. The junction conditions for the metric perturbations and the displacements of the shell boundary are analyzed and the surface densities of the perturbed energy and momentum in the shell are derived, using Mukohyama's gauge-invariant formalism and the Israel discontinuity condition. In both homogeneous regions the perturbations of scalar, vector and tensor types are expanded using the 3-dimensional harmonic functions, but the model coupling among them is caused in the shell by the inhomogeneity. By treating the perturbations with odd and even parities separately, it is found, however, that we can have consistent displacements and surface densities for given metric parturbations
Perturbations in Massive Gravity Cosmology
Crisostomi, Marco; Pilo, Luigi
2012-01-01
We study cosmological perturbations for a ghost free massive gravity theory formulated with a dynamical extra metric that is needed to massive deform GR. In this formulation FRW background solutions fall in two branches. In the dynamics of perturbations around the first branch solutions, no extra degree of freedom with respect to GR ispresent at linearized level, likewise what is found in the Stuckelberg formulation of massive gravity where the extra metric isflat and non dynamical. In the first branch, perturbations are probably strongly coupled. On the contrary, for perturbations around the second branch solutions all expected degrees of freedom propagate. While tensor and vector perturbations of the physical metric that couples with matter follow closely the ones of GR, scalars develop an exponential Jeans-like instability on sub-horizon scales. On the other hand, around a de Sitter background there is no instability. We argue that one could get rid of the instabilities by introducing a mirror dark matter ...
Multiplicative perturbations of local -semigroups
Indian Academy of Sciences (India)
Chung-Cheng Kuo
2015-02-01
In this paper, we establish some left and right multiplicative perturbation theorems concerning local -semigroups when the generator of a perturbed local -semigroup $S(\\cdot)$ may not be densely defined and the perturbation operator is a bounded linear operator from $\\overline{D(A)}$ into () such that = on $\\overline{D(A)}$, which can be applied to obtain some additive perturbation theorems for local -semigroups in which is a bounded linear operator from $[D(A)]$ into () such that = on $\\overline{D(A)}$. We also show that the perturbations of a (local) -semigroup $S(\\cdot)$ are exponentially bounded (resp., norm continuous, locally Lipschitz continuous, or exponentially Lipschitz continuous) if $S(\\cdot)$ is.
Disformal transformation of cosmological perturbations
Directory of Open Access Journals (Sweden)
Masato Minamitsuji
2014-10-01
Full Text Available We investigate the gauge-invariant cosmological perturbations in the gravity and matter frames in the general scalar–tensor theory where two frames are related by the disformal transformation. The gravity and matter frames are the extensions of the Einstein and Jordan frames in the scalar–tensor theory where two frames are related by the conformal transformation, respectively. First, it is shown that the curvature perturbation in the comoving gauge to the scalar field is disformally invariant as well as conformally invariant, which gives the predictions from the cosmological model where the scalar field is responsible both for inflation and cosmological perturbations. Second, in case that the disformally coupled matter sector also contributes to curvature perturbations, we derive the evolution equations of the curvature perturbation in the uniform matter energy density gauge from the energy (nonconservation in the matter sector, which are independent of the choice of the gravity sector. While in the matter frame the curvature perturbation in the uniform matter energy density gauge is conserved on superhorizon scales for the vanishing nonadiabatic pressure, in the gravity frame it is not conserved even if the nonadiabatic pressure vanishes. The formula relating two frames gives the amplitude of the curvature perturbation in the matter frame, once it is evaluated in the gravity frame.
Cosmological perturbations beyond linear order
CERN. Geneva
2013-01-01
Cosmological perturbation theory is the standard tool to understand the formation of the large scale structure in the Universe. However, its degree of applicability is limited by the growth of the amplitude of the matter perturbations with time. This problem can be tackled with by using N-body simulations or analytical techniques that go beyond the linear calculation. In my talk, I'll summarise some recent efforts in the latter that ameliorate the bad convergence of the standard perturbative expansion. The new techniques allow better analytical control on observables (as the matter power spectrum) over scales very relevant to understand the expansion history and formation of structure in the Universe.
The theory of singular perturbations
De Jager, E M
1996-01-01
The subject of this textbook is the mathematical theory of singular perturbations, which despite its respectable history is still in a state of vigorous development. Singular perturbations of cumulative and of boundary layer type are presented. Attention has been given to composite expansions of solutions of initial and boundary value problems for ordinary and partial differential equations, linear as well as quasilinear; also turning points are discussed. The main emphasis lies on several methods of approximation for solutions of singularly perturbed differential equations and on the mathemat
Density perturbations with relativistic thermodynamics
Maartens, R
1997-01-01
We investigate cosmological density perturbations in a covariant and gauge- invariant formalism, incorporating relativistic causal thermodynamics to give a self-consistent description. The gradient of density inhomogeneities splits covariantly into a scalar part, a rotational vector part that is determined by the vorticity, and a tensor part that describes the shape. We give the evolution equations for these parts in the general dissipative case. Causal thermodynamics gives evolution equations for viswcous stress and heat flux, which are coupled to the density perturbation equation and to the entropy and temperature perturbation equations. We give the full coupled system in the general dissipative case, and simplify the system in certain cases.
Instabilities in mimetic matter perturbations
Firouzjahi, Hassan; Gorji, Mohammad Ali; Mansoori, Seyed Ali Hosseini
2017-07-01
We study cosmological perturbations in mimetic matter scenario with a general higher derivative function. We calculate the quadratic action and show that both the kinetic term and the gradient term have the wrong sings. We perform the analysis in both comoving and Newtonian gauges and confirm that the Hamiltonians and the associated instabilities are consistent with each other in both gauges. The existence of instabilities is independent of the specific form of higher derivative function which generates gradients for mimetic field perturbations. It is verified that the ghost instability in mimetic perturbations is not associated with the higher derivative instabilities such as the Ostrogradsky ghost.
Perturbation Theory of Embedded Eigenvalues
DEFF Research Database (Denmark)
Engelmann, Matthias
We study problems connected to perturbation theory of embedded eigenvalues in two different setups. The first part deals with second order perturbation theory of mass shells in massive translation invariant Nelson type models. To this end an expansion of the eigenvalues w.r.t. fiber parameter up...... project gives a general and systematic approach to analytic perturbation theory of embedded eigenvalues. The spectral deformation technique originally developed in the theory of dilation analytic potentials in the context of Schrödinger operators is systematized by the use of Mourre theory. The group...
Causal compensated perturbations in cosmology
Energy Technology Data Exchange (ETDEWEB)
Veeraraghavan, S.; Stebbins, A. (Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (USA) California Univ., Berkeley (USA) Canadian Institute for Theoretical Astrophysics, Toronto (Canada))
1990-12-01
A theoretical framework is developed to calculate linear perturbations in the gravitational and matter fields which arise causally in response to the presence of stiff matter sources in a FRW cosmology. It is shown that, in order to satisfy energy and momentum conservation, the gravitational fields of the source must be compensated by perturbations in the matter and gravitational fields, and the role of such compensation in containing the initial inhomogeneities in their subsequent evolution is discussed. A complete formal solution is derived in terms of Green functions for the perturbations produced by an arbitrary source in a flat universe containing cold dark matter. Approximate Green function solutions are derived for the late-time density perturbations and late-time gravitational waves in a universe containing a radiation fluid. A cosmological energy-momentum pseudotensor is defined to clarify the nature of energy and momentum conservation in the expanding universe. 55 refs.
Dynamical Friction on extended perturbers
Esquivel, O
2008-01-01
Following a wave-mechanical treatment we calculate the drag force exerted by an infinite homogeneous background of stars on a perturber as this makes its way through the system. We recover Chandrasekhar's classical dynamical friction (DF) law with a modified Coulomb logarithm. We take into account a range of models that encompasses all plausible density distributions for satellite galaxies by considering the DF exerted on a Plummer sphere and a perturber having a Hernquist profile. It is shown that the shape of the perturber affects only the exact form of the Coulomb logarithm. The latter converges on small scales, because encounters of the test and field stars with impact parameters less than the size of the massive perturber become inefficient. We confirm this way earlier results based on the impulse approximation of small angle scatterings.
Review of chiral perturbation theory
Indian Academy of Sciences (India)
B Ananthanarayan
2003-11-01
A review of chiral perturbation theory and recent developments on the comparison of its predictions with experiment is presented. Some interesting topics with scope for further elaboration are touched upon.
Sondhiya, Deepak Kumar; Gwal, Ashok Kumar; Verma, Shivali; Kasde, Satish Kumar
Abstract: In this paper, a wavelet-based neural network system for the detection and identification of four types of VLF whistler’s transients (i.e. dispersive, diffuse, spiky and multipath) is implemented and tested. The discrete wavelet transform (DWT) technique is integrated with the feed forward neural network (FFNN) model to construct the identifier. First, the multi-resolution analysis (MRA) technique of DWT and the Parseval’s theorem are employed to extract the characteristics features of the transients at different resolution levels. Second, the FFNN identifies these extracted features to identify the transients according to the features extracted. The proposed methodology can reduce a great quantity of the features of transients without losing its original property; less memory space and computing time are required. Various transient events are tested; the results show that the identifier can detect whistler transients efficiently. Keywords: Discrete wavelets transform, Multi-resolution analysis, Parseval’s theorem and Feed forward neural network
Energy Technology Data Exchange (ETDEWEB)
Meloni, A.; Di Mauro, D.; Mele, G.; Palangio, P. [Istituto Nazionale di Geofisica e Vulcanologia, Rome (Italy); Ernst, T.; Teisseyre, R. [Institute of Geophysics, Warszawa (Poland)
2001-04-01
Magnetotelluric data were collected at Collemeluccio (41.72{sup 0}N, 14.37{sup 0}E) in Central Italy from summer 1991 to spring 1998. Analyzed by means of tensor decomposition on the geoelectric potential and robust estimation on the geomagnetic field, this set of data allowed the investigation of the electromagnetic induction, is presented here in its time evolution and compared to local and regional seismic activity. Tecto magnetic field observations from absolute magnetic field level in Central Italy were also made on data simultaneously recorded at four magnetometer stations, using L'Aquila Geomagnetic Observatory as a reference for differentiation. Recent results gathered from a system of two VLF search coil wide-band antennas, installed in the L'Aquila Observatory, are also discussed in relation to local seismic activity.
Survey of ELF-VLF plasma waves in outer radiation belt observed by Cluster STAFF-SA experiment
Directory of Open Access Journals (Sweden)
D. Pokhotelov
2008-10-01
Full Text Available Various types of plasma waves have profound effects on acceleration and scattering of radiation belt particles. For the purposes of radiation belt modeling it is necessary to know statistical distributions of plasma wave parameters. This paper analyzes four years of plasma wave observations in the Earth's outer radiation belt obtained by the STAFF-SA experiment on board Cluster spacecraft. Statistical distributions of spectral density of different plasma waves observed in ELF-VLF range (chorus, plasmaspheric hiss, magnetosonic waves are presented as a function of magnetospheric coordinates and geomagnetic activity indices. Comparison with other spacecraft studies supports some earlier conclusions about the distribution of chorus and hiss waves and helps to remove the long-term controversy regarding the distribution of equatorial magnetosonic waves. This study represents a step towards the development of multi-spacecraft database of plasma wave activity in radiation belts.
Snakes and perturbed random walks
Basak, Gopal
2011-01-01
In this paper we study some properties of random walks perturbed at extrema, which are generalizations of the walks considered e.g., in Davis (1999). This process can also be viewed as a version of {\\em excited random walk}, studied recently by many authors. We obtain a few properties related to the range of the process with infinite memory. We also prove the Strong law, Central Limit Theorem, and the criterion for the recurrence of the perturbed walk with finite memory.
Perturbed Einstein field equations using Maple
De Campos, M
2003-01-01
We obtain the perturbed components of affine connection and Ricci tensor using algebraic computation. Naturally, the perturbed Einstein field equations for the vacuum can written. The method can be used to obtain perturbed equations of the superior order.
Perturbation of Initial Stability of an FSAPDS Projectile
Directory of Open Access Journals (Sweden)
R. S. Acharya
2006-11-01
Full Text Available For a spinning projectile, the initial stability condition is 2 = 1+ (4 K3 / K22 > 0. In the presentstudy, this condition has been modified for the malalignments arising due to pressure gradientand damping moment for an FSAPDS projectile. The equations of motion are established for thefirst phase of motion. A mathematical model for the first phase of motion has been developed.The effect of perturbation on the trajectory and stability of motion are discussed. It is provedthat if 3 K(a parameter appearing due to perturbation(-K22 2 /4 , the initial stability ofmotion will breakdown.
Maxworth, A. S.; Golkowski, M.; Cohen, M.; Moore, R. C.
2014-12-01
Generation of Extremely Low Frequency (ELF) and Very Low Frequency (VLF) signals through ionospheric modification has been practiced for many years. Heating the lower ionosphere with high power HF waves allows for modulation of natural current systems. Our experiments were carried out at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska, USA. In this experiment, the ionosphere was heated with a vertical amplitude modulating signal and the modulation frequency was changed sequentially within an array of 40 frequencies followed by a frequency ramp. The observed magnetic field amplitude and polarization of the generated ELF/VLF signals were analyzed for multiple sites and as a function of modulation frequency. Our three observation sites: Chistochina, Paxson and Paradise are located within 36km (azimuth 47.7°), 50.2km (azimuth -20°) and 99km (azimuth 80.3°) respectively. We show that the peak amplitudes observed as a function of frequency result from vertical resonance in the Earth-ionosphere waveguide and can be used to diagnose the D-region profile. Polarization analysis showed that out of the three sites Paxson shows the highest circularity in the magnetic field polarization, compared to Chistochina and Paradise which show highly linear polarizations. The experimental results were compared with a theoretical simulation model results and it was clear that in both cases, the modulated Hall current dominates the observed signals at Chistochina and Paradise sites and at Paxson there is an equal contribution from Hall and Pedersen currents. The Chistochina site shows the highest magnetic field amplitudes in both experimental and simulation environments. Depending upon the experimental and simulation observations at the three sites, a radiation pattern for the HAARP ionospheric heater can be mapped
Duque, J.
The use of geophysics prospection in hydrogeology is widely used as a way to find groundwater under difficult hydrogeologic potential rocks. The porphyric rocks lay- ered in the northern part of Beja city, are the most unproductive regional aquifer. Usu- ally this aquifer has an upper layer of 5 to 15 meters deep of weathered rock and a second layer build by fractures rock till 30 metres deep. Above this deep the probabil- ity to find groundwater is extremely low. For instance it is a very superficial aquifer that usually accomplish the topographic surface. The water use is essential for human purposes and here are used mainly for human and cattle supply. In order verify the goodness of a geophysic method and at the same time to supply a large farm called Herdade da Apariça, it was performed the geophysical method of Very Low Frequency (VLF-EM) with ABEM (WADI) equipment, in three areas previously defined by inter- pretation of aerial photography, as zones that have relative hydrogeological potential. It was performed a total of 5 profiles with 1970 m. The geophysic prospecting and hydrogeologic research allowed to drill 5 boreholes, being 4 extraction wells and 1 piezometric well. The productivity of the abstraction wells are between 2,000 L/h and 10,000 L/h, which is a very good yield when compared with the other yield values get from wells inside this aquifer. VLF proved in this conditions to be an essential tool to increment the tax success of drilling wells.
Geometric perturbation theory and plasma physics
Energy Technology Data Exchange (ETDEWEB)
Omohundro, S.M.
1985-04-04
Modern differential geometric techniques are used to unify the physical asymptotics underlying mechanics, wave theory and statistical mechanics. The approach gives new insights into the structure of physical theories and is suited to the needs of modern large-scale computer simulation and symbol manipulation systems. A coordinate-free formulation of non-singular perturbation theory is given, from which a new Hamiltonian perturbation structure is derived and related to the unperturbed structure. The theory of perturbations in the presence of symmetry is developed, and the method of averaging is related to reduction by a circle group action. The pseudo-forces and magnetic Poisson bracket terms due to reduction are given a natural asymptotic interpretation. Similar terms due to changing reference frames are related to the method of variation of parameters, which is also given a Hamiltonian formulation. These methods are used to answer a question about nearly periodic systems. The answer leads to a new secular perturbation theory that contains no ad hoc elements. Eikonal wave theory is given a Hamiltonian formulation that generalizes Whitham's Lagrangian approach. The evolution of wave action density on ray phase space is given a Hamiltonian structure using a Lie-Poisson bracket. The relationship between dissipative and Hamiltonian systems is discussed. A new type of attractor is defined which attracts both forward and backward in time and is shown to occur in infinite-dimensional Hamiltonian systems with dissipative behavior. The theory of Smale horseshoes is applied to gyromotion in the neighborhood of a magnetic field reversal and the phenomenon of reinsertion in area-preserving horseshoes is introduced. The central limit theorem is proved by renormalization group techniques. A natural symplectic structure for thermodynamics is shown to arise asymptotically from the maximum entropy formalism.
Inan, U. S.; Cohen, M.; Scherrer, P.; Scherrer, D.
2006-11-01
Stanford University Very Low Frequency (VLF) radio receivers have been used extensively for remote sensing of the ionosphere and the magnetosphere. Among the phenomena that can be uniquely measured via VLF receivers are radio atmospherics, whistlers, electron precipitation, solar flares, sudden ionospheric disturbances, gravity waves, sprites, and cosmic gamma-ray flares. With the use of simple square air-core magnetic loop antennas of a couple of meters in size, the sensitivity of these instruments allows the measurement of magnetic fields as low as several tens of femtoTesla per root Hz, in the frequency range of ~300 Hz to 50 kHz. This sensitivity well exceeds that required to detect any event above the ambient atmospheric noise floor, determined by the totality of lightning activity on this planet. In recent years, as cost of production, timing accuracy (due to low cost GPS cards), and data handling flexibility of the systems has improved, it has become possible to distribute many of these instruments in the form of arrays, to perform interferometric and holographic imaging of the lower ionosphere. These goals can be achieved using the newest version of the Stanford VLF receiver, known as AWESOME: Atmospheric Weather Educational System for Observation and Modeling of Electromagnetics. In the context of the IHY/UNBSS program for 2007, the AWESOME receivers can be used extensively as part of the United Nations initiative to place scientific instruments in developing countries. Drawing on the Stanford experiences from setting up arrays of VLF receivers, including an interferometer in Alaska, the Holographic Array for Ionospheric and Lightning research (HAIL) consisting of instruments at 13 different high schools in mid-western United States, a broader set of ELF/VLF receivers in Alaska, and various receivers abroad, including in France, Japan, Greece, Turkey, and India, a global network of ELF/VLF receivers offer possibilities for a wide range of scientific topics
Institute of Scientific and Technical Information of China (English)
张扬; 查晓明; 刘雅琦; 张鲲; 熊一; 樊友平
2012-01-01
This paper deals with the issue of modeling method by perturbation solution to the single-phase AC-DC converter. A continuous circuit that includes a single-phase AC-DC converter is inducted first. And then a differential equation is presented with two parameters, which are controlling parameter and small perturbation parameter. A strict proof indicates that this equation can be solved by the regular perturbation. The compareison between the result and the simulation figures of PSCAD/EMTDC, shows that the result is correct and simple, thus avoiding the requirements for large computation capacity. Finally, the physical significance of the two parameters is analyzed, showing that they may incur the period-doubling chaos. This method not only fits the single-phase AC-DC converter circuit, but also meets the need of two-phase or N-phase circuits.%针对单相交直流全桥变流电路，推导出其在脉宽调制下的连续等效摄动解析模型．首先通过研究非线性振荡过程得到其连续微分方程，该方程含有控制参数和摄动参数．随后通过数学理论证明正则摄动方法能够求出其近似解，求解后对比PSCAD／EMTDC的仿真结果从而验证了解析的正确性．该方法在大规模计算中具有优势．最后分析了控制参数和摄动参数的物理意义，指出这两个参数能够影响变流器的工作状态，甚至引发倍周期混沌．该摄动建模方法不仅适用于单相变流电路，也适用于三相变流电路甚至多相变流电路．
Nonlinearly perturbed semi-Markov processes
Silvestrov, Dmitrii
2017-01-01
The book presents new methods of asymptotic analysis for nonlinearly perturbed semi-Markov processes with a finite phase space. These methods are based on special time-space screening procedures for sequential phase space reduction of semi-Markov processes combined with the systematical use of operational calculus for Laurent asymptotic expansions. Effective recurrent algorithms are composed for getting asymptotic expansions, without and with explicit upper bounds for remainders, for power moments of hitting times, stationary and conditional quasi-stationary distributions for nonlinearly perturbed semi-Markov processes. These results are illustrated by asymptotic expansions for birth-death-type semi-Markov processes, which play an important role in various applications. The book will be a useful contribution to the continuing intensive studies in the area. It is an essential reference for theoretical and applied researchers in the field of stochastic processes and their applications that will cont...
Cohen, M.; Kosovichev, P.; Marshall, R. A.; Droscoll, A.; Scherrer, D. K.
2013-12-01
It has been proposed that Very Low Frequency (VLF, 3-30 kHz) radio remote sensing may be used to detect ionospheric changes which may precede major earthquakes by hours or days. We report the results of a search for VLF precursors to the M9.0 Tohoku earthquake of 11-Mar-2011, the fifth most powerful earthquake in recorded history. Broadband and narrowband radio recordings were made at a site in Onagawa, Japan located ~102 km from the epicenter. The receiver operated for about two minutes after the start of the earthquake, after which the receiver lost power. Examination of the VLF data shows no radio emissions preceding or coincident with the onset of the earthquake. However, once the secondary seismic waves reached the receiver, a number of impulses and diffuse noise bands arose which may result from the entire power grid shaking or from radio emissions from compressing or fracturing rocks. Examination of the ELF data (0.2-1 kHz) shows no precursor effect in the hours preceding the seismic activity. We also examine the amplitudes of VLF subionospherically propagating transmitter signals going back months before the earthquake. We apply previously proposed techniques to extract properties of the diurnal amplitude profile that have been thought to correlate with earthquake precursors, but find no anomalous effect despite the remarkable intensity of the earthquake and proximity of the receiver to the epicenter. In general there are anomalous deviations but they cannot be reliably correlated with seismic activity. We also report the results of a global search for a lightning precursor effect on lightning flash rates, using the GLD360 network.
Gravitational waves from perturbed stars
Ferrari, Valeria
2011-01-01
Non radial oscillations of neutron stars are associated with the emission of gravitational waves. The characteristic frequencies of these oscillations can be computed using the theory of stellar perturbations, and they are shown to carry detailed information on the internal structure of the emitting source. Moreover, they appear to be encoded in various radiative processes, as for instance in the tail of the giant flares of Soft Gamma Repeaters. Thus, their determination is central to the theory of stellar perturbation. A viable approach to the problem consists in formulating this theory as a problem of resonant scattering of gravitational waves incident on the potential barrier generated by the spacetime curvature. This approach discloses some unexpected correspondences between the theory of stellar perturbations and the theory of quantum mechanics, and allows us to predict new relativistic effects.
Walking is not like reaching: evidence from periodic mechanical perturbations.
Directory of Open Access Journals (Sweden)
Jooeun Ahn
Full Text Available The control architecture underlying human reaching has been established, at least in broad outline. However, despite extensive research, the control architecture underlying human locomotion remains unclear. Some studies show evidence of high-level control focused on lower-limb trajectories; others suggest that nonlinear oscillators such as lower-level rhythmic central pattern generators (CPGs play a significant role. To resolve this ambiguity, we reasoned that if a nonlinear oscillator contributes to locomotor control, human walking should exhibit dynamic entrainment to periodic mechanical perturbation; entrainment is a distinctive behavior of nonlinear oscillators. Here we present the first behavioral evidence that nonlinear neuro-mechanical oscillators contribute to the production of human walking, albeit weakly. As unimpaired human subjects walked at constant speed, we applied periodic torque pulses to the ankle at periods different from their preferred cadence. The gait period of 18 out of 19 subjects entrained to this mechanical perturbation, converging to match that of the perturbation. Significantly, entrainment occurred only if the perturbation period was close to subjects' preferred walking cadence: it exhibited a narrow basin of entrainment. Further, regardless of the phase within the walking cycle at which perturbation was initiated, subjects' gait synchronized or phase-locked with the mechanical perturbation at a phase of gait where it assisted propulsion. These results were affected neither by auditory feedback nor by a distractor task. However, the convergence to phase-locking was slow. These characteristics indicate that nonlinear neuro-mechanical oscillators make at most a modest contribution to human walking. Our results suggest that human locomotor control is not organized as in reaching to meet a predominantly kinematic specification, but is hierarchically organized with a semi-autonomous peripheral oscillator operating under
Multi-field inflation and cosmological perturbations
Gong, Jinn-Ouk
2016-01-01
We provide a concise review on multi-field inflation and cosmological perturbations. We discuss convenient and physically meaningful bases in terms of which perturbations can be systematically studied. We give formal accounts on the gauge fixing conditions and present the perturbation action in two gauges. We also briefly review non-linear perturbations.
A Perturbative Window into Non-Perturbative Physics
Dijkgraaf, R; Dijkgraaf, Robbert; Vafa, Cumrun
2002-01-01
We argue that for a large class of N=1 supersymmetric gauge theories the effective superpotential as a function of the glueball chiral superfield is exactly given by a summation of planar diagrams of the same gauge theory. This perturbative computation reduces to a matrix model whose action is the tree-level superpotential. For all models that can be embedded in string theory we give a proof of this result, and we sketch an argument how to derive this more generally directly in field theory. These results are obtained without assuming any conjectured dualities and can be used as a systematic method to compute instanton effects: the perturbative corrections up to n-th loop can be used to compute up to n-instanton corrections. These techniques allow us to see many non-perturbative effects, such as the Seiberg-Witten solutions of N=2 theories, the consequences of Montonen-Olive S-duality in N=1* and Seiberg-like dualities for N=1 theories from a completely perturbative planar point of view in the same gauge theo...
Doppler peaks from active perturbations
Magueijo, J; Coulson, D; Ferreira, P; Magueijo, Joao; Albrecht, Andreas; Coulson, David; Ferreira, Pedro
1995-01-01
We examine how the qualitative structure of the Doppler peaks in the angular power spectrum of the cosmic microwave anisotropy depends on the fundamental nature of the perturbations which produced them. The formalism of Hu and Sugiyama is extended to treat models with cosmic defects. We discuss how perturbations can be ``active'' or ``passive'' and ``incoherent'' or ``coherent'', and show how causality and scale invariance play rather different roles in these various cases. We find that the existence of secondary Doppler peaks and the rough placing of the primary peak unambiguously reflect these basic properties.
Directory of Open Access Journals (Sweden)
Damien H. Chua
2009-01-01
Full Text Available We investigate the spatial variability of electron densities in the nightside ionosphere and its effects on very-low frequency (VLF wave propagation using a suite of instruments from the FORMOSAT-3/Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC spacecraft.We use observations from the Tiny Ionospheric Photometer (TIP instruments to infer the horizontal electron density gradients along each satellite track. We demonstrate that the OI 1356 _ radiance measured by the TIP instruments tracks the horizontal electron density structure well with high spatial resolution and unprecedented sensitivity. Accurate measurements of the horizontal electron density gradients are important for improving retrieved electron density profiles from GPS occultation and other tomographic remote sensing techniques. The processes underlying the variability in the large-scale, nightside electron density gradients are the main drivers of ionospheric weather. TIP observations reveal significant variability in both the small and large scale structure of the nightside ionosphere. The relative intensities, relative widths, and latitudinal separation of the northern and southern ionization crests of the Appleton anomalies show a high degree of longitudinal variation.We demonstrate how the TIP observations can be used to measure the horizontal gradient of the refractive index of whistler-mode VLF waves propagating in a cold, collisionless plasma. These measurements are critical for understanding how gradients in electron density associated with ionospheric structure such as depletions and the Appleton anomalies affect VLF wave propagation through the equatorial and mid-latitude ionosphere.
Dalgarno-Lewis perturbation theory for scattering states
Energy Technology Data Exchange (ETDEWEB)
Amore, Paolo [Facultad de Ciencias, Universidad de Colima, Bernal Diaz del Castillo 340, Colima, Colima Mexico (Mexico)]. E-mail: paolo@ucol.mx; Fernandez, Francisco M. [INIFTA (Conicet, UNLP), Division Quimica Teorica, Diag. 113 y 64 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)]. E-mail: fernande@quimica.unlp.edu.ar
2007-07-23
We apply the method of Dalgarno and Lewis to scattering states and discuss the choice of the unperturbed model in order to have a convergent perturbation series for the phase shift. We show that a recently proposed approach is a particular case of the method of Dalgarno and Lewis.
Gauge invariant cosmological perturbations for the nonminimally coupled inflaton field
Weenink, J.; Prokopec, T.
2010-01-01
We construct the gauge invariant free action for cosmological perturbations for the nonminimally coupled inflaton field in the Jordan frame. For this the phase space formalism is used, which keeps track of all the dynamical and constraint fields. We perform explicit conformal transformations to demo
Inducing chaos by resonant perturbations: theory and experiment.
Lai, Ying-Cheng; Kandangath, Anil; Krishnamoorthy, Satish; Gaudet, John A; de Moura, Alessandro P S
2005-06-03
We propose a scheme to induce chaos in nonlinear oscillators that either are by themselves incapable of exhibiting chaos or are far away from parameter regions of chaotic behaviors. Our idea is to make use of small, judiciously chosen perturbations in the form of weak periodic signals with time-varying frequency and phase, and to drive the system into a hierarchy of nonlinear resonant states and eventually into chaos. We demonstrate this method by using numerical examples and a laboratory experiment with a Duffing type of electronic circuit driven by a phase-locked loop. The phase-locked loop can track the instantaneous frequency and phase of the Duffing circuit and deliver resonant perturbations to generate robust chaos.
Perturbation theory calculations of model pair potential systems
Energy Technology Data Exchange (ETDEWEB)
Gong, Jianwu [Iowa State Univ., Ames, IA (United States)
2016-01-01
Helmholtz free energy is one of the most important thermodynamic properties for condensed matter systems. It is closely related to other thermodynamic properties such as chemical potential and compressibility. It is also the starting point for studies of interfacial properties and phase coexistence if free energies of different phases can be obtained. In this thesis, we will use an approach based on the Weeks-Chandler-Anderson (WCA) perturbation theory to calculate the free energy of both solid and liquid phases of Lennard-Jones pair potential systems and the free energy of liquid states of Yukawa pair potentials. Our results indicate that the perturbation theory provides an accurate approach to the free energy calculations of liquid and solid phases based upon comparisons with results from molecular dynamics (MD) and Monte Carlo (MC) simulations.
Intersegmental coupling and recovery from perturbations in freely running cockroaches.
Couzin-Fuchs, Einat; Kiemel, Tim; Gal, Omer; Ayali, Amir; Holmes, Philip
2015-01-15
Cockroaches are remarkably stable runners, exhibiting rapid recovery from external perturbations. To uncover the mechanisms behind this important behavioral trait, we recorded leg kinematics of freely running animals in both undisturbed and perturbed trials. Functional coupling underlying inter-leg coordination was monitored before and during localized perturbations, which were applied to single legs via magnetic impulses. The resulting transient effects on all legs and the recovery times to normal pre-perturbation kinematics were studied. We estimated coupling architecture and strength by fitting experimental data to a six-leg-unit phase oscillator model. Using maximum-likelihood techniques, we found that a network with nearest-neighbor inter-leg coupling best fitted the data and that, although coupling strengths vary among preparations, the overall inputs entering each leg are approximately balanced and consistent. Simulations of models with different coupling strengths encountering perturbations suggest that the coupling schemes estimated from our experiments allow animals relatively fast and uniform recoveries from perturbations. © 2015. Published by The Company of Biologists Ltd.
Cosmological perturbation theory and quantum gravity
Brunetti, Romeo; Hack, Thomas-Paul; Pinamonti, Nicola; Rejzner, Katarzyna
2016-01-01
It is shown how cosmological perturbation theory arises from a fully quantized perturbative theory of quantum gravity. Central for the derivation is a non-perturbative concept of gauge-invariant local observables by means of which perturbative invariant expressions of arbitrary order are generated. In particular, in the linearised theory, first order gauge-invariant observables familiar from cosmological perturbation theory are recovered. Explicit expressions of second order quantities are presented as well.
Cosmological perturbation theory and quantum gravity
Energy Technology Data Exchange (ETDEWEB)
Brunetti, Romeo [Dipartimento di Matematica, Università di Trento,Via Sommarive 14, 38123 Povo TN (Italy); Fredenhagen, Klaus [II Institute für Theoretische Physik, Universität Hamburg,Luruper Chaussee 149, 22761 Hamburg (Germany); Hack, Thomas-Paul [Institute für Theoretische Physik, Universität Leipzig,Brüderstr. 16, 04103 Leipzig (Germany); Pinamonti, Nicola [Dipartimento di Matematica, Università di Genova,Via Dodecaneso 35, 16146 Genova (Italy); INFN, Sezione di Genova,Via Dodecaneso 33, 16146 Genova (Italy); Rejzner, Katarzyna [Department of Mathematics, University of York,Heslington, York YO10 5DD (United Kingdom)
2016-08-04
It is shown how cosmological perturbation theory arises from a fully quantized perturbative theory of quantum gravity. Central for the derivation is a non-perturbative concept of gauge-invariant local observables by means of which perturbative invariant expressions of arbitrary order are generated. In particular, in the linearised theory, first order gauge-invariant observables familiar from cosmological perturbation theory are recovered. Explicit expressions of second order quantities are presented as well.
Adaptation Strategies in Perturbed /s/
Brunner, Jana; Hoole, Phil; Perrier, Pascal
2011-01-01
The purpose of this work is to investigate the role of three articulatory parameters (tongue position, jaw position and tongue grooving) in the production of /s/. Six normal speakers' speech was perturbed by a palatal prosthesis. The fricative was recorded acoustically and through electromagnetic articulography in four conditions: (1) unperturbed,…
Basics of QCD perturbation theory
Energy Technology Data Exchange (ETDEWEB)
Soper, D.E. [Univ. of Oregon, Eugene, OR (United States). Inst. of Theoretical Science
1997-06-01
This is an introduction to the use of QCD perturbation theory, emphasizing generic features of the theory that enable one to separate short-time and long-time effects. The author also covers some important classes of applications: electron-positron annihilation to hadrons, deeply inelastic scattering, and hard processes in hadron-hadron collisions. 31 refs., 38 figs.
Seven topics in perturbative QCD
Energy Technology Data Exchange (ETDEWEB)
Buras, A.J.
1980-09-01
The following topics of perturbative QCD are discussed: (1) deep inelastic scattering; (2) higher order corrections to e/sup +/e/sup -/ annihilation, to photon structure functions and to quarkonia decays; (3) higher order corrections to fragmentation functions and to various semi-inclusive processes; (4) higher twist contributions; (5) exclusive processes; (6) transverse momentum effects; (7) jet and photon physics.
Chiral Perturbation Theory and Unitarization
Ruiz-Arriola, E; Nieves, J; Peláez, J R
2000-01-01
We review our recent work on unitarization and chiral perturbation theory both in the $\\pi\\pi$ and the $\\pi N$ sectors. We pay particular attention to the Bethe-Salpeter and Inverse Amplitude unitarization methods and their recent applications to $\\pi\\pi$ and $\\pi N$ scattering.
Transport studies using perturbative experiments
Hogeweij, G. M. D.
2000-01-01
By inducing a small electron temperature perturbation in a plasma in steady state one can in principle determine the conductive and convective components of the electron heat flux, and the associated thermal diffusivity and convection velocity. The same can be done for other plasma parameters, like
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
Using qualitative analysis, we study perturbed Hamiltonian systems with different n-th order polynomial as perturbation terms. By numerical simulation, we show that these perturbed systems have the same distribution of limit cycles. Our results imply that these perturbed systems are equivalent in the sense of distribution of limit cycles. This is useful for studying limit cycles of perturbed systems.
Phase Behavior and Implications for Travel time Observables (PHASE 2)
2015-09-30
Phase behavior and implications for travel - time observables (PHASE-2) Emmanuel Skarsoulis Foundation for Research and Technology Hellas...perturbation behavior of travel time observables due to sound-speed perturbations. OBJECTIVES The objective is to study the behavior of the wave-theoretic...for this work came from the results of previous studies, supported by ONR, suggesting that the perturbation behavior of different travel - time
Cataldi, Daniele; Cataldi, Gabriele; Straser, Valentino
2017-04-01
On August 24, 2016 at 01:36:32 UTC a destructive earthquake hit Central Italy with a magnitude of M6.2. The authors of this study have recorded some electromagnetic signals that have preceded this strong earthquake. These signals were recorded through two electromagnetic monitoring stations realized by Gabriele Cataldi and Daniele Cataldi, located near the town of Albano Laziale (Rome, Italy) and near the city of Lariano (Rome, Italy) and can monitor the radio spectrum 24h7 between 0.001 Hz and 96 kHz (SELF-LF band). The electromagnetic monitoring allowed to identify two interesting types of electromagnetic anomalies: the first electromagnetic anomaly was recorded on August 18, 2016 between 02:47 UTC and 06:21 UTC, in the VLF band prevalently between 18kHz and 26kHz; the second electromagnetic anomaly was registered between 08:00 UTC on August 23, 2016 and 05:00 UTC on August 24, 2016, prevalently between 0.01 and 0.7Hz: the most intense signals were recorded at 08:50 UTC on August 23, 2016 and approximately 1 hour before the strong earthquake. The Earth's electromagnetic background monitoring in the SELF-VLF band (0Hztechnological) have allowed us to understand that there are actually two families of pre-seismic radio emissions: 1) radio emissions identified as Earth's geomagnetic field disturbances related to "near Earth" solar wind proton density increase variations, and for this reason it can be seen from any point on the Earth (this is "no local" type emissions); 2) radio signals are not connected directly to the solar and geomagnetic activity: these radio signals are probably generated by piezoelectricity phenomena occurring near the focal area of the earthquake and are detectable near earthquake epicenter (this is a "local" type emissions). It is therefore clear that the monitoring of solar activity and Earth's geomagnetic activity is an activity of fundamental importance to be able to have a general understanding of pre-seismic radio signals nature. In fact
Energy Technology Data Exchange (ETDEWEB)
Kimura, I.; Hashimoto, K.; Matsumoto, H.; Mukai, T.; Bell, T.F.; Inan, U.S.; Helliwell, R.A.; Katsufrakis, J.P.
1983-01-01
In situ measurements of both energetic particles and VLF waves have been carried out in a joint program involving the Japanese satellite EXOS-B and the Siple Station VLF transmitter. A general description of the experiment is given as well as some results concerning wave-particle correlations. Detailed analysis of the observed wave characteristics is given in a companion paper. Correlations of electron flux and pitch angle anisotropy in the energy range from 85 eV to 6.9 keV with waves in a range from 300 Hz to 9 kHz are examined. These electrons sometimes have a pitch angle distributions with a peak flux at 90/sup 0/ pitch angle (so-called pancake distribution). On five passes out of a total of 50 during the summer campaign in 1979, the energy of the electrons that showed a high pitch angle anisotropy shifted upward as the satellite moved into the plasmasphere, crossing the plasmapause in the equatorial region. In two cases out of five, strong Siple signals were observed in the geomagnetic equatorial region just outside the plasmapause, in association with such a pancake pitch angle distribution of electrons. The Siple signals are most likely amplified by the cyclotron instability due to the high pitch angle anisotropy (HPAA), although the flux of resonant electrons was relatively small. For three other cases of HPAA, the satellite location was so far away from the Siple meridian that the signal level, even if amplified, was too weak to be detected by the satellite. Emissions associated with Siple signals were detected on five (two equatorial and three high latitude) passes, which were all confined on 6 days after a large magnetic storm. On the days when the Siple triggered emissions were observed, the pitch angle anisotropy was low, but the electron flux at resonant energies in the equatorial region was four or five times larger than that on other non-triggering days in all energy channels from 85 eV to 6.9 keV.
Ho, Keang-Po
2003-01-01
The characteristic function of soliton phase jitter is found analytically when the soliton is perturbed by amplifier noise. In additional to that from amplitude jitter, the nonlinear phase noise due to frequency and timing jitter is also analyzed. Because the nonlinear phase noise is not Gaussian distributed, the overall phase jitter is also non-Gaussian. For a fixed mean nonlinear phase shift, the contribution of nonlinear phase noise from frequency and timing jitter decreases with distance ...
Notes on Rank One Perturbed Resolvent. Perturbation of Isolated Eigenvalue.
Chorosavin, S A
2003-01-01
This paper is a didactic commentary (a transcription with variations) to the paper of S.R. Foguel {\\it Finite Dimensional Perturbations in Banach Spaces}. Addressed, mainly: postgraduates and related readers. Subject: Suppose we have two linear operators, A, B, so that B - A is rank one. Let \\lambda_o be an {\\it isolated} point of the spectrum of A. In addition, let \\lambda_o be an {\\it eigenvalue} of A: \\lambda_o \\in \\sigma_{pp}(A) . The question is: Is \\lambda_o an eigenvalue of B ? And, if so, is the multiplicity of \\lambda_o in \\sigma_{pp}(B) equal to the multiplicity of \\lambda_o in \\sigma_{pp}(A) ? -- or less? -- or greater? Keywords: M.G.Krein's Formula, Finite Rank Perturbation.
Tan, J. H.; Cohen, M.; Inan, U. S.; Scherrer, P. H.; Scherrer, D.
2005-12-01
Stanford University Very Low Frequency (VLF) and Extremely Low Frequency (ELF) radio receivers have been used extensively for remote sensing of the ionosphere and the magnetosphere. Among the phenomena that can be uniquely measured via ELF/VLF receivers are radio atmospherics, whistlers, electron precipitation, solar flares, sudden ionospheric disturbances, gravity waves, sprites, and cosmic gamma-ray flares. With the use of simple square air-core magnetic loop antennas of a couple of meters in size, the sensitivity of these instruments allows the measurement of magnetic fields as low as several tens of femtoTesla per root-Hz, in the frequency range of ~30 Hz to 50 kHz. This sensitivity well exceeds that required to detect any event above the ambient atmospheric noise floor, determined by the totality of lightning activity on the planet. In recent years, as cost of production, timing accuracy (due to low cost GPS clocks), and data handling flexibility of the systems has improved, it has become possible to distribute many of these instruments in the form of arrays, to perform interferometric and holographic imaging of the lower ionosphere. In the context of the IHY in 2007, the ELF/VLF receiver can used extensively as part of the United Nations initiative to place scientific instruments in developing countries. Stanford University's past experiences setting up arrays of ELF/VLF receivers include an interferometer in Alaska, the Holographic Array for Ionospheric and Lightning research (HAIL) consisting of instruments at 13 different high schools in mid-western United States, a broader set of ELF/VLF receivers in Alaska, and various receivers abroad, including in France, Japan, Greece, Turkey, Ireland, and India. A global network of ELF/VLF receivers offer possibilities for a wide range of scientific topics, as well as serving as a means for educational outreach. These goals will be achieved using the newest version of the Stanford VLF receiver, known as AWESOME
Perturbative QCD analysis of $B \\to \\phi K^* $ decays
Chen Chuan Hung; Li, H; Chen, Chuan-Hung; Keum, Yong-Yeon; Li, Hsiang-nan
2002-01-01
We study the first observed charmless $B\\to VV$ modes, the $B\\to\\phi K^*$ decays, in perturbative QCD formalism. The obtained branching ratios $B(B\\to\\phi K^*)\\sim 15 \\times 10^{-6}$ are larger than $\\sim 9\\times 10^{-6}$ from QCD factorization. The comparison of the predicted magnitudes and phases of the different helicity amplitudes, and branching ratios with experimental data can test the power counting rules, the evaluation of annihilation contributions, and the mechanism of dynamical penguin enhancement in perturbative QCD, respectively.
On high-order perturbative calculations at finite density
Ghisoiu, Ioan
2017-01-01
We discuss the prospects of performing high-order perturbative calculations in systems characterized by a vanishing temperature but finite density. In particular, we show that the determination of generic Feynman integrals containing fermionic chemical potentials can be reduced to the evaluation of three-dimensional phase space integrals over vacuum on-shell amplitudes. Applications of these rules will be discussed in the context of the thermodynamics of cold and dense QCD, where it is argued that they facilitate an extension of the Equation of State of cold quark matter to higher perturbative orders.
On high-order perturbative calculations at finite density
Ghişoiu, Ioan; Gorda, Tyler; Kurkela, Aleksi; Romatschke, Paul; Säppi, Matias; Vuorinen, Aleksi
2017-02-01
We discuss the prospects of performing high-order perturbative calculations in systems characterized by a vanishing temperature but finite density. In particular, we show that the determination of generic Feynman integrals containing fermionic chemical potentials can be reduced to the evaluation of three-dimensional phase space integrals over vacuum on-shell amplitudes - a result reminiscent of a previously proposed "naive real-time formalism" for vacuum diagrams. Applications of these rules are discussed in the context of the thermodynamics of cold and dense QCD, where it is argued that they facilitate an extension of the Equation of State of cold quark matter to higher perturbative orders.
Solitary magnetic perturbations at the ELM onset
Wenninger, RP; Boom, JE; Burckhart, A; Dunne, MG; Dux, R; Eich, T; Fischer, R; Fuchs, C; Garcia-Munoz, M; Igochine, V; Hoelzl, M; Luhmann, NC; Lunt, T; Maraschek, M; Mueller, HW; Park, HK; Schneider, PA; Sommer, F; Suttrop, W; Viezzer, E
2012-01-01
Edge localised modes (ELMs) allow maintaining sufficient purity of tokamak H-mode plasmas and thus enable stationary H-mode. On the other hand in a future device ELMs may cause divertor power flux densities far in excess of tolerable material limits. The size of the energy loss per ELM is determined by saturation effects in the non-linear phase of the ELM, which at present is hardly understood. Solitary magnetic perturbations (SMPs) are identified as dominant features in the radial magnetic fluctuations below 100kHz. They are typically observed close (+-0.1ms) to the onset of pedestal erosion. SMPs are field aligned structures rotating in the electron diamagnetic drift direction with perpendicular velocities of about 10km/s. A comparison of perpendicular velocities suggests that the perturbation evoking SMPs is located at or inside the separatrix. Analysis of very pronounced examples showed that the number of peaks per toroidal turn is 1 or 2, which is clearly lower than corresponding numbers in linear stabil...
Vector perturbations of galaxy number counts
Durrer, Ruth; Tansella, Vittorio
2016-07-01
We derive the contribution to relativistic galaxy number count fluctuations from vector and tensor perturbations within linear perturbation theory. Our result is consistent with the the relativistic corrections to number counts due to scalar perturbation, where the Bardeen potentials are replaced with line-of-sight projection of vector and tensor quantities. Since vector and tensor perturbations do not lead to density fluctuations the standard density term in the number counts is absent. We apply our results to vector perturbations which are induced from scalar perturbations at second order and give numerical estimates of their contributions to the power spectrum of relativistic galaxy number counts.
Vector perturbations of galaxy number counts
Durrer, Ruth
2016-01-01
We derive the contribution to relativistic galaxy number count fluctuations from vector and tensor perturbations within linear perturbation theory. Our result is consistent with the the relativistic corrections to number counts due to scalar perturbation, where the Bardeen potentials are replaced with line-of-sight projection of vector and tensor quantities. Since vector and tensor perturbations do not lead to density fluctuations the standard density term in the number counts is absent. We apply our results to vector perturbations which are induced from scalar perturbations at second order and give numerical estimates of their contributions to the power spectrum of relativistic galaxy number counts.
Effect of Magnetohydrodynamic Perturbations on the Orbit Loss of Alpha Particles in Tokamak Plasma
Institute of Scientific and Technical Information of China (English)
邬良能; 俞国扬
2002-01-01
We investigate the orbit loss of alpha particles under helical magnetic perturbation in a tokamak. The results show that low-frequency andlow-mode number magnetic perturbation can cause stochastic loss ofalpha particles.This effect is significant for those particles close to the boundary between the transit zone and the trapped zone.The particle loss is sensitive to the phase of the magnetic perturbation, indicating the modulation of the particle loss with respect to magnetic perturbation. It is also found that the precession of the particle banana orbit can even further enhance the particle loss.
Integrability and non-perturbative effects in the AdS/CFT correspondence
Gómez, C; Gómez, César; Hernández, Rafael
2007-01-01
We present a non-perturbative resummation of the asymptotic strong-coupling expansion for the dressing phase factor of the AdS_5xS^5 string S-matrix. The non-perturbative resummation provides a general form for the coefficients in the weak-coupling expansion, in agreement with crossing symmetry and transcendentality. The ambiguities of the non-perturbative prescription are discussed together with the similarities with the non-perturbative definition of the c=1 matrix model.
van Westen, Thijs; Gross, Joachim
2017-07-01
The Helmholtz energy of a fluid interacting by a Lennard-Jones pair potential is expanded in a perturbation series. Both the methods of Barker-Henderson (BH) and of Weeks-Chandler-Andersen (WCA) are evaluated for the division of the intermolecular potential into reference and perturbation parts. The first four perturbation terms are evaluated for various densities and temperatures (in the ranges ρ*=0 -1.5 and T*=0.5 -12 ) using Monte Carlo simulations in the canonical ensemble. The simulation results are used to test several approximate theoretical methods for describing perturbation terms or for developing an approximate infinite order perturbation series. Additionally, the simulations serve as a basis for developing fully analytical third order BH and WCA perturbation theories. The development of analytical theories allows (1) a careful comparison between the BH and WCA formalisms, and (2) a systematic examination of the effect of higher-order perturbation terms on calculated thermodynamic properties of fluids. Properties included in the comparison are supercritical thermodynamic properties (pressure, internal energy, and chemical potential), vapor-liquid phase equilibria, second virial coefficients, and heat capacities. For all properties studied, we find a systematically improved description upon using a higher-order perturbation theory. A result of particular relevance is that a third order perturbation theory is capable of providing a quantitative description of second virial coefficients to temperatures as low as the triple-point of the Lennard-Jones fluid. We find no reason to prefer the WCA formalism over the BH formalism.
Plasma Braking Due to External Magnetic Perturbations
Frassinetti, L.; Olofsson, Kejo; Brunsell, P. R.; Khan, M. W. M.; Drake, J. R.
2010-11-01
The RFP EXTRAP T2R is equipped with a comprehensive active feedback system (128 active saddle coils in the full-coverage array) and active control of both resonant and non-resonant MHD modes has been demonstrated. The feedback algorithms, based on modern control methodology such as reference mode tracking (both amplitude and phase), are a useful tool to improve the ``state of the art'' of the MHD mode control. But this tool can be used also to improve the understanding and the characterization of other phenomena such as the ELM mitigation with a resonant magnetic perturbation or the plasma viscosity. The present work studies plasma and mode braking due to static RMPs. Results show that a static RMP produces a global braking of the flow profile. The study of the effect of RMPs characterized by different helicities will also give information on the plasma viscosity profile. Experimental results are finally compared to theoretical models.
Inflationary perturbations in a closed FLRW universe
Yokomizo, Nelson; Bonga, Beatrice; Gupt, Brajesh
2016-03-01
We investigate the evolution of gauge invariant quantum perturbations in the closed FLRW model in the presence of an inflationary potential. We first find out initial conditions for the background geometry which lead to a desired slow-roll phase that is compatible with observation. Providing the initial conditions for the quantum field at the onset of slow-roll we study the influence of the spatial curvature on the scalar and tensor power spectra at the end of inflation. By comparing our results with the recent Planck data we discuss the role of spatial curvature on the estimation of various cosmological parameters. We highlight the main differences from the standard inflationary scenario in a flat FLRW model and potential implications for future observations. Finally, we comment on the quantum gravitational extension of this scenario to the Planck scale. Supported by CNPq-Brazil and NSF.
BRST quantization of cosmological perturbations
Energy Technology Data Exchange (ETDEWEB)
Armendariz-Picon, Cristian [Physics Department, St. Lawrence University,Canton, NY 13617 (United States); Şengör, Gizem [Department of Physics, Syracuse University,Syracuse, NY 13244 (United States)
2016-11-08
BRST quantization is an elegant and powerful method to quantize theories with local symmetries. In this article we study the Hamiltonian BRST quantization of cosmological perturbations in a universe dominated by a scalar field, along with the closely related quantization method of Dirac. We describe how both formalisms apply to perturbations in a time-dependent background, and how expectation values of gauge-invariant operators can be calculated in the in-in formalism. Our analysis focuses mostly on the free theory. By appropriate canonical transformations we simplify and diagonalize the free Hamiltonian. BRST quantization in derivative gauges allows us to dramatically simplify the structure of the propagators, whereas Dirac quantization, which amounts to quantization in synchronous gauge, dispenses with the need to introduce ghosts and preserves the locality of the gauge-fixed action.
Back Reaction of Cosmological Perturbations
Brandenberger, R H
2000-01-01
The presence of cosmological perturbations affects the background metric and matter configuration in which the perturbations propagate. This effect, studied a long time ago for gravitational waves, also is operational for scalar gravitational fluctuations, inhomogeneities which are believed to be more important in inflationary cosmology. The back-reaction of fluctuations can be described by an effective energy-momentum tensor. The issue of coordinate invariance makes the analysis more complicated for scalar fluctuations than for gravitational waves. We show that the back-reaction of fluctuations can be described in a diffeomorphism-invariant way. In an inflationary cosmology, the back-reaction is dominated by infrared modes. We show that these modes give a contribution to the effective energy-momentum tensor of the form of a negative cosmological constant whose absolute value grows in time. We speculate that this may lead to a self-regulating dynamical relaxation mechanism for the cosmological constant. This ...
BRST Quantization of Cosmological Perturbations
Armendariz-Picon, Cristian
2016-01-01
BRST quantization is an elegant and powerful method to quantize theories with local symmetries. In this article we study the Hamiltonian BRST quantization of cosmological perturbations in a universe dominated by a scalar field, along with the closely related quantization method of Dirac. We describe how both formalisms apply to the perturbations in a time-dependent background, and how expectation values of gauge-invariant operators can be calculated in the in-in formalism. Our analysis focuses mostly on the free theory. By appropriate canonical transformations we simplify and diagonalize the free Hamiltonian. BRST quantization in derivative gauges allows us to dramatically simplify the structure of the propagators, whereas quantization in synchronous gauge, which amounts to Dirac quantization, dispenses with the need to introduce ghosts and preserves the locality of the gauge-fixed action.
Perturbations of Dark Matter Gravity
Maia, M D; Müller, D; 10.1142/S0218271809015072
2009-01-01
Until recently the study of the gravitational field of dark matter was primarily concerned with its local effects on the motion of stars in galaxies and galaxy clusters. On the other hand, the WMAP experiment has shown that the gravitational field produced by dark matter amplifies the higher acoustic modes of the CMBR power spectrum, more intensely than the gravitational field of baryons. Such a wide range of experimental evidences from cosmology to local gravity suggests the necessity of a comprehensive analysis of the dark matter gravitational field per se, regardless of any other attributes that dark matter may eventually possess. In this paper we introduce and apply Nash's theory of perturbative geometry to the study of the dark matter gravitational field alone, in a higher-dimensional framework. It is shown that the dark matter gravitational perturbations in the early universe can be explained by the extrinsic curvature of the standard cosmology. Together with the estimated presence of massive neutrinos,...
Non-Hamiltonian perturbations of integrable systems and resonance trapping
Ghil, M.; Wolansky, G.
1992-01-01
This paper studies general, non-Hamiltonian perturbations of integrable systems with two degrees of freedom and derives conditions for temporary and permanent resonance trapping. The analysis involves a noncanonical transformation of variables near the resonant manifold and averaging with respect to the fast phase to investigate oscillatory behavior on the intermediate timescale. The resulting reduced system is Hamiltonian to leading order and permits, after averaging on the intermediate, or libration, timescale, a canonical transformation to action-angle variables in the oscillation zone. The final system so obtained reveals the possible existence of two- and three-dimensional invariant tori in the vicinity of the resonant manifold. An explicit divergence condition for general perturbations to be dissipative on the slow timescale follows from the analysis. An application of this approach to the problem of resonant trapping and escape is outlined for the restricted problem of three bodies subject to dissipative perturbations with a radial symmetry.
Perturbation Solutions for Thermal Process of Honeycomb Regenerator
Institute of Scientific and Technical Information of China (English)
AI Yuan-fang; MEI Chi; HUANG Guo-dong; JIANG Shao-jian
2007-01-01
A parameter perturbation for the unsteady-state heat-transfer characteristics of honeycomb regenerator is presented. It is limited to the cases where the storage matrix has a small wall thickness so that no temperature variation in the matrix perpendicular to the flow direction is considered. Starting from a two-phase transient thermal model for the gas and storage matrix, an approximate solution for regenerator heat transfer process is derived using the multiple-scale method for the limiting case where the longitudinal heat conduction of solid matrix is far less than the convective heat transfer between the gas and the solid. The regenerator temperature profiles are expressed as Taylor series of the coefficient of solid heat conduction item in the model. The analytical validity is shown by comparing the perturbation solution with the experiment and the numerical solution. The results show that it is possible for the perturbation to improve the effectiveness and economics of thermal research on regenerators.
Perturbative Computation of Glueball Superpotentials
Dijkgraaf, R; Lam, C S; Vafa, C; Zanon, D
2003-01-01
Using N=1 superspace techniques in four dimensions we show how to perturbatively compute the superpotential generated for the glueball superfield upon integrating out massive charged fields. The technique applies to arbitrary gauge groups and representations. Moreover we show that for U(N) gauge theories admitting a large N expansion the computation dramatically simplifies and we prove the validity of the recently proposed recipe for computation of this quantity in terms of planar diagrams of matrix integrals.
Perturbative computation of glueball superpotentials
Dijkgraaf, R.; Grisaru, M. T.; Lam, C. S.; Vafa, C.; Zanon, D.
2003-10-01
Using N=1 superspace techniques in four dimensions we show how to perturbatively compute the superpotential generated for the glueball superfield upon integrating out massive charged fields. The technique applies to arbitrary gauge groups and representations. Moreover, we show that for U(N) gauge theories admitting a large N expansion the computation dramatically simplifies and we prove the validity of the recently proposed recipe for computation of this quantity in terms of planar diagrams of matrix integrals.
Perturbative computation of glueball superpotentials
Energy Technology Data Exchange (ETDEWEB)
Dijkgraaf, R.; Grisaru, M.T.; Lam, C.S.; Vafa, C.; Zanon, D
2003-10-30
Using N=1 superspace techniques in four dimensions we show how to perturbatively compute the superpotential generated for the glueball superfield upon integrating out massive charged fields. The technique applies to arbitrary gauge groups and representations. Moreover, we show that for U(N) gauge theories admitting a large N expansion the computation dramatically simplifies and we prove the validity of the recently proposed recipe for computation of this quantity in terms of planar diagrams of matrix integrals.
Delocalization and Sensitivity of Quantum Wavepacket in Coherently Perturbed Kicked Anderson Model
Directory of Open Access Journals (Sweden)
Hiroaki Yamada
2004-03-01
Full Text Available Abstract: We consider quantum diffusion of the initially localized wavepacket in one-dimensional kicked disordered system with classical coherent perturbation. The wavepacket localizes in the unperturbed kicked Anderson model. However, the wavepacket get delocalized even by coupling with monochromatic perturbation. We call the state "dynamically delocalized state". It is numerically shown that the delocalized wavepacket spread obeying diffusion law, and the perturbation strength dependence of the diffusion rate is given. The sensitivity of the delocalized state is also shown by the time-reversal experiment after random change in phase of the wavepacket. Moreover, it is found that the diffusion strongly depend on the initial phase of the perturbation. We discuss a relation between the "classicalization" of the quantum wave packet and the time-dependence of the initial phase dependence. The complex structure of the initial phase dependence is related to the entropy production in the quantum system.
Evolution of cosmological perturbations in a stage dominated by an oscillatory scalar field
Kodama, H; Kodama, Hideo; Hamazaki, Takashi
1996-01-01
In the investigation of the evolution of cosmological perturbations in inflationary universe models the behavior of perturbations during the reheating stage is the most unclear point. In particular in the early reheating phase in which a rapidly oscillating scalar field dominates the energy density, the behavior of perturbations is not known well because their evolution equation expressed in terms of the curvature perturbation becomes singular. In this paper it is shown that in spite of this singular behavior of the evolution equation the Bardeen parameter stays constant in a good accuracy during this stage for superhorizon-scale perturbations except for a sequence of negligibly short intervals around the zero points of the time derivative of the scalar field. This justifies the conventional formula relating the amplitudes of quantum fluctuations during inflation and those of adiabatic perturbations at horizon crossing in the Friedmann stage, except for possible corrections produced by the energy transfer fro...
Cosmological Perturbations: Vorticity, Isocurvature and Magnetic Fields
Christopherson, Adam J
2014-01-01
In this paper I review some recent, interlinked, work undertaken using cosmological perturbation theory -- a powerful technique for modelling inhomogeneities in the Universe. The common theme which underpins these pieces of work is the presence of non-adiabatic pressure, or entropy, perturbations. After a brief introduction covering the standard techniques of describing inhomogeneities in both Newtonian and relativistic cosmology, I discuss the generation of vorticity. As in classical fluid mechanics, vorticity is not present in linearized perturbation theory (unless included as an initial condition). Allowing for entropy perturbations, and working to second order in perturbation theory, I show that vorticity is generated, even in the absence of vector perturbations, by purely scalar perturbations, the source term being quadratic in the gradients of first order energy density and isocurvature, or non-adiabatic pressure perturbations. This generalizes Crocco's theorem to a cosmological setting. I then introduc...
Perturbation theory and renormalisation group equations
Litim, Daniel F; Litim, Daniel F.; Pawlowski, Jan M.
2002-01-01
We discuss the perturbative expansion of several one-loop improved renormalisation group equations. It is shown that in general the integrated renormalisation group flows fail to reproduce perturbation theory beyond one loop.
Non-perturbative closure calculation for fluids and plasmas
Tang, Xianzhu; McDevitt, Chris; Guo, Zehua
2015-11-01
Closure calculation of the Chapman-Enskog type is based on a perturbative expansion in the small parameter of Knudsen number, which is defined as the ratio of the thermal particle mean-free-path and the system gradient length scale. The error in the analysis can be locally measured in phase space using the local Knudsen number, which for the energy squared dependence of the mean-free-path, is much larger for high energy particles. Such breakdown, if occurs at sufficiently high energy, has small impact on closure results, but in cases of strong spatial gradients, can have large effect and invalidate the perturbative calculation. Here we show a non-perturbative closure formulation and its application in calculating standard closure quantitities such as heat flux. This approach applies as long as the thermal bulk is close to a Maxwellian, where a perturbative analysis can be matched onto a non-perturbative treatment of the tail population. Work supported by DOE via LANL-LDRD.
Data perturbation analysis of a linear model
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The linear model features were carefully studied in the cases of data perturbation and mean shift perturbation.Some important features were also proved mathematically. The results show that the mean shift perturbation is equivalentto the data perturbation, that is, adding a parameter to an observation equation means that this set of data is deleted fromthe data set. The estimate of this parameter is its predicted residual in fact
Perturbative versus non-perturbative decoupling of heavy quarks
Energy Technology Data Exchange (ETDEWEB)
Knechtli, Francesco [Wuppertal Univ. (Germany). Dept. of Physics; Bruno, Mattia [Brookhaven National Laboratory, Upton, NY (United States); Finkenrath, Jacob [CaSToRC, Cyl Athalassa Campus, Nicosia (Cyprus); Leder, Bjoern [Humboldt Univ. Berlin (Germany). Inst. fuer Physik; Sommer, Rainer [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Collaboration: ALPHA Collaboration
2015-11-15
We simulate a theory with N{sub f}=2 heavy quarks of mass M. At energies much smaller than M the heavy quarks decouple and the theory can be described by an effective theory which is a pure gauge theory to leading order in 1/M. We present results for the mass dependence of ratios such as t{sub 0}(M)/t{sub 0}(0). We compute these ratios from simulations and compare them to the perturbative prediction. The latter relies on a factorisation formula for the ratios which is valid to leading order in 1/M.
Tensorial Perturbations in an Accelerating Universe
De Campos, M
2002-01-01
We study tensorial perturbations (gravitational waves) in a universe with particle production (OSC). The background of gravitational waves produces a perturbation in the redshift observed from distant sources. The modes for the perturbation in the redshift (induced redshift) are calculated in a universe with particle production.
FRW Cosmological Perturbations in Massive Bigravity
Comelli, D; Pilo, L
2014-01-01
Cosmological perturbations of FRW solutions in ghost free massive bigravity, including also a second matter sector, are studied in detail. At early time, we find that sub horizon exponential instabilities are unavoidable and they lead to a premature departure from the perturbative regime of cosmological perturbations.
Matrix perturbations: bounding and computing eigenvalues
Reis da Silva, R.J.
2011-01-01
Despite the somewhat negative connotation of the word, not every perturbation is a bad perturbation. In fact, while disturbing the matrix entries, many perturbations still preserve useful properties such as the orthonormality of the basis of eigenvectors or the Hermicity of the original matrix. In t
Geometric Hamiltonian structures and perturbation theory
Energy Technology Data Exchange (ETDEWEB)
Omohundro, S.
1984-08-01
We have been engaged in a program of investigating the Hamiltonian structure of the various perturbation theories used in practice. We describe the geometry of a Hamiltonian structure for non-singular perturbation theory applied to Hamiltonian systems on symplectic manifolds and the connection with singular perturbation techniques based on the method of averaging.
Perturbative Transport Studies in Fusion Plasmas
Cardozo, N. J. L.
1995-01-01
Studies of transport in fusion plasmas using perturbations of an equilibrium state reviewed. Essential differences between steady-state and perturbative transport studies are pointed out. Important transport issues that can be addressed with perturbative experiments are identified as: (i) Are the tr
Threshold Effects And Perturbative Unification
Bastero-Gil, M; Pérez-Mercader, J
1995-01-01
We discuss the effect of the renormalization procedure in the computation of the unification point for running coupling constants. We explore the effects of threshold--crossing on the $\\beta$--functions. We compute the running of the coupling constants of the Standard Model, between $m_Z$ and $M_P$, using a mass dependent subtraction procedure, and then compare the results with $\\bar{MS}$, and with the $\\theta$-- function approximation. We also do this for the Minimal Supersymmetric extension of the Standard Model. In the latter, the bounds on susy masses that one obtains by requiring perturbative unification are dependent, to some extent, on the procedure.
Perturbation analyses of intermolecular interactions
Koyama, Yohei M.; Kobayashi, Tetsuya J.; Ueda, Hiroki R.
2011-08-01
Conformational fluctuations of a protein molecule are important to its function, and it is known that environmental molecules, such as water molecules, ions, and ligand molecules, significantly affect the function by changing the conformational fluctuations. However, it is difficult to systematically understand the role of environmental molecules because intermolecular interactions related to the conformational fluctuations are complicated. To identify important intermolecular interactions with regard to the conformational fluctuations, we develop herein (i) distance-independent and (ii) distance-dependent perturbation analyses of the intermolecular interactions. We show that these perturbation analyses can be realized by performing (i) a principal component analysis using conditional expectations of truncated and shifted intermolecular potential energy terms and (ii) a functional principal component analysis using products of intermolecular forces and conditional cumulative densities. We refer to these analyses as intermolecular perturbation analysis (IPA) and distance-dependent intermolecular perturbation analysis (DIPA), respectively. For comparison of the IPA and the DIPA, we apply them to the alanine dipeptide isomerization in explicit water. Although the first IPA principal components discriminate two states (the α state and PPII (polyproline II) + β states) for larger cutoff length, the separation between the PPII state and the β state is unclear in the second IPA principal components. On the other hand, in the large cutoff value, DIPA eigenvalues converge faster than that for IPA and the top two DIPA principal components clearly identify the three states. By using the DIPA biplot, the contributions of the dipeptide-water interactions to each state are analyzed systematically. Since the DIPA improves the state identification and the convergence rate with retaining distance information, we conclude that the DIPA is a more practical method compared with the
Eikonal perturbation theory in photoionization
Cajiao Vélez, F.; Krajewska, K.; Kamiński, J. Z.
2016-02-01
The eikonal perturbation theory is formulated and applied to photoionization by strong laser pulses. A special emphasis is put on the first order approximation with respect to the binding potential, which is known as the generalized eikonal approximation [2015 Phys. Rev. A 91 053417]. The ordinary eikonal approximation and its domain of applicability is derived from the generalized eikonal approximation. While the former approach is singular for the electron trajectories which return to the potential center, the generalized eikonal avoids this problem. This property makes it a promising tool for further investigations of rescattering and high-order harmonic generation processes.
Sasmal, S.; Chakrabarti, S. K.
2009-01-01
VLF signals are long thought to give away important information about the lithosphere-ionosphere coupling. In order to establish co-relations, if any, between the ionospheric activities and the earthquakes, we need to understand what the reference signals are, throughout the year. The best opportunity to do this is during the period of solar minimum where the number of flares and sunspots are negligible and the data would be primarily affected by the sun and variation would be due to normal s...
Skeberis, Christos; Zaharis, Zaharias; Xenos, Thomas; Spatalas, Spyridon; Stratakis, Dimitrios; Maggipinto, Tommaso; Biagi, Pier francesco
2016-04-01
This study provides an evaluation of the application of high-order differential analysis on VLF signals on a multiple-receiver multiple-transmitter network. This application provides a method for near-real-time detection of disturbances that can be attributed to seismic-ionospheric precursor phenomena and can discriminate disturbances that could be classified as false positives and thus should be attributed to other geomagnetic influences. VLF data acquired in Thessaloniki, Greece (40.59N, 22,78E) Herakleion, Greece (35.31N, 25.10E), Nicosia, Cyprus (35.17N, 33.35E), Italy (42.42N, 13.08E) and transmitted by the VLF station in Tavolara, Italy (ICV station 40.923N, 9.731E) and the station in Keflavik, Iceland (ICE 64.02N, 22.57W) from January 2015 to January 2016 were used for the purpose of this paper. The receivers have been developed by Elettronika Srl and are part of the International Network for Frontier Research on Earthquake Precursors (INFREP). The process applied for this study has been further developed and is based on differential analysis. The signals undergo transformation using an enhanced version of the Hilbert Huang Transform, and relevant spectra are produced. On the product of this process, differential analysis is applied. Finally, the method produces the correlation coefficient of signals that are on the same path over an earthquake epicenter in order to highlight disturbances, and on the opposite can make comparisons with unrelated transmitted signals of different paths to eliminate disturbances that are not localized to the area of interest. This improvement provides a simple method of noise cancellation to signals that would otherwise be considered as false positives. A further evaluation of the method is provided with the presentation and discussion of sample results. The method seems to be a robust tool of analysis of VLF signals and also an automatic detection tool with built-in noise cancellation of outside disturbances.
The ambiguity in ray perturbation theory
Energy Technology Data Exchange (ETDEWEB)
Snieder, R.; Sambridge, M. [Utrecht Univ., Utrecht (Netherlands)]|[Cambridge Univ., Cambridge (United Kingdom)
1993-12-01
Ray perturbation theory is concerned with the change in ray paths and travel times due to changes in the slowness model or the end-point conditions of rays. Several different formulations of ray perturbation theory have been developed. Even for the same physical problem different perturbation equations have been derived. The reason for this is that ray perturbation theory contains a fundamental ambiguity. One can move a point along a curve without changing the shape of the curve. This means that the mapping from a reference curve to a perturbed curve is not uniquely defined, because on may associated a point on the reference curve with different points on the perturbed curve. The mapping that is used is usually defined implicitly by the choice of the coordinate system or the independent parameter. In this paper, a fomalism is developed where one can specify explicitly the mapping from the reference curve to the perturbed curve by choosing a stretch factor that relates increments in arc length along the reference curve and the perturbed curve. This is incorporated in a theory that is accurate to first order in the ray position and to second order in the travel time. The second order travel time perturbation describes the effect of changes in the position of the ray on the travel time. In the formulation of this paper, paraxial ray perturbations, slowness perturbations, and pure ray bending are treated in a uniform fashion. This may be very useful in nonlinear tomographic inversions which include earthquake relocation.
Testing gauge-invariant perturbation theory
Törek, Pascal
2016-01-01
Gauge-invariant perturbation theory for theories with a Brout-Englert-Higgs effect, as developed by Fr\\"ohlich, Morchio and Strocchi, starts out from physical, exactly gauge-invariant quantities as initial and final states. These are composite operators, and can thus be considered as bound states. In case of the standard model, this reduces almost entirely to conventional perturbation theory. This explains the success of conventional perturbation theory for the standard model. However, this is due to the special structure of the standard model, and it is not guaranteed to be the case for other theories. Here, we review gauge-invariant perturbation theory. Especially, we show how it can be applied and that it is little more complicated than conventional perturbation theory, and that it is often possible to utilize existing results of conventional perturbation theory. Finally, we present tests of the predictions of gauge-invariant perturbation theory, using lattice gauge theory, in three different settings. In ...
Kachakhidze, Manana; Kachakhidze, Nino
2016-04-01
Authors of abstract have created work which offers model of earth electromagnetic emissions generation detected in the process of earthquake preparation on the basis of electrodynamics. The model gives qualitative explanation of a mechanism of generation of electromagnetic waves emitted in the earthquake preparation period. Besides, scheme of the methodology of earthquake forecasting is created based on avalanche-like unstable model of fault formation and an analogous model of electromagnetic contour, synthesis of which, is rather harmonious. According to the authors of the work electromagnetic emissions in radiodiapason is more universal and reliable than other anomalous variations of various geophysical phenomena in earthquake preparation period; Besides, VLF/LF electromagnetic emissions might be declared as the main precursor of earthquake because it might turn out very useful with the view of prediction of large (M ≥5) inland earthquakes and to govern processes going on in lithosphere-atmosphere - ionosphere coupling (LAIC) system. Since the other geophysical phenomena, which may accompany earthquake preparation process and expose themselves several months, weeks or days prior to earthquakes are less informative with the view of earthquake forecasting, it is admissible to consider them as earthquake indicators. Physical mechanisms of mentioned phenomena are explained on the basis of the model of generation of electromagnetic emissions detected before earthquake, where a process of earthquake preparation and its realization are considered taking into account distributed and conservative systems properties. Up to these days electromagnetic emissions detection network did not exist in Georgia. European colleagues helped us (Prof. Dr. PF Biagi, Prof. Dr. Aydın BÜYÜKSARAÇ) and made possible the installation of a receiver. We are going to develop network and put our share in searching of earthquakes problem. Participation in conference is supported by financial
Feynman integral and perturbation theory in quantum tomography
Fedorov, Aleksey
2013-11-01
We present a definition for tomographic Feynman path integral as representation for quantum tomograms via Feynman path integral in the phase space. The proposed representation is the potential basis for investigation of Path Integral Monte Carlo numerical methods with quantum tomograms. Tomographic Feynman path integral is a representation of solution of initial problem for evolution equation for tomograms. The perturbation theory for quantum tomograms is constructed.
Control of a perturbed under-actuated mechanical system
Zayane, Chadia
2015-11-05
In this work, the trajectory tracking problem for an under-actuated mechanical system in presence of unknown input disturbances is addressed. The studied inertia wheel inverted pendulum falls in the class of non minimum phase systems. The proposed high order sliding mode control architecture including a controller and differentiator allows to track accurately the predefined trajectory and to stabilize the internal dynamics. The robustness of the proposed approach is illustrated through different perturbation and output noise configurations.
Inflationary Perturbations and Precision Cosmology
Habib, S; Heitmann, K; Jungman, G; Habib, Salman; Heinen, Andreas; Heitmann, Katrin; Jungman, Gerard
2005-01-01
Inflationary cosmology provides a natural mechanism for the generation of primordial perturbations which seed the formation of observed cosmic structure and lead to specific signals of anisotropy in the cosmic microwave background radiation. In order to test the broad inflationary paradigm as well as particular models against precision observations, it is crucial to be able to make accurate predictions for the power spectrum of both scalar and tensor fluctuations. We present detailed calculations of these quantities utilizing direct numerical approaches as well as error-controlled uniform approximations, comparing with the (uncontrolled) traditional slow-roll approach. A simple extension of the leading-order uniform approximation yields results for the power spectra amplitudes, the spectral indices, and the running of spectral indices, with accuracy of the order of 0.1% - approximately the same level at which the transfer functions are known. Several representative examples are used to demonstrate these resul...
World-line perturbation theory
van Holten, Jan-Willem
2016-01-01
The motion of a compact body in space and time is commonly described by the world line of a point representing the instantaneous position of the body. In General Relativity such a world-line formalism is not quite straightforward because of the strict impossibility to accommodate point masses and rigid bodies. In many situations of practical interest it can still be made to work using an effective hamiltonian or energy-momentum tensor for a finite number of collective degrees of freedom of the compact object. Even so exact solutions of the equations of motion are often not available. In such cases families of world lines of compact bodies in curved space-times can be constructed by a perturbative procedure based on generalized geodesic deviation equations. Examples for simple test masses and for spinning test bodies are presented.
Sudakov Safety in Perturbative QCD
Larkoski, Andrew J; Thaler, Jesse
2015-01-01
Traditional calculations in perturbative quantum chromodynamics (pQCD) are based on an order-by-order expansion in the strong coupling $\\alpha_s$. Observables that are calculable in this way are known as "safe". Recently, a class of unsafe observables was discovered that do not have a valid $\\alpha_s$ expansion but are nevertheless calculable in pQCD using all-orders resummation. These observables are called "Sudakov safe" since singularities at each $\\alpha_s$ order are regulated by an all-orders Sudakov form factor. In this letter, we give a concrete definition of Sudakov safety based on conditional probability distributions, and we study a one-parameter family of momentum sharing observables that interpolate between the safe and unsafe regimes. The boundary between these regimes is particularly interesting, as the resulting distribution can be understood as the ultraviolet fixed point of a generalized fragmentation function, yielding a leading behavior that is independent of $\\alpha_s$.
Perturbativity in the seesaw mechanism
Directory of Open Access Journals (Sweden)
Takehiko Asaka
2016-02-01
Full Text Available We consider the Standard Model extended by right-handed neutrinos to explain massive neutrinos through the seesaw mechanism. The new fermion can be observed when it has a sufficiently small mass and large mixings to left-handed neutrinos. If such a particle is the lightest right-handed neutrino, its contribution to the mass matrix of active neutrinos needs to be canceled by that of a heavier one. Yukawa couplings of the heavier one are then larger than those of the lightest one. We show that the perturbativity condition gives a severe upper bound on the mixing of the lightest right-handed neutrino, depending on the masses of heavier ones. Models of high energy phenomena, such as leptogenesis, can be constrained by low energy experiments.
Initial conditions for cosmological perturbations
Ashtekar, Abhay
2016-01-01
Penrose proposed that the big bang singularity should be constrained by requiring that the Weyl curvature vanishes there. The idea behind this past hypothesis is attractive because it constrains the initial conditions for the universe in geometric terms and is not confined to a specific early universe paradigm. However, the precise statement of Penrose's hypothesis is tied to classical space-times and furthermore restricts only the gravitational degrees of freedom. These are encapsulated only in the tensor modes of the commonly used cosmological perturbation theory. Drawing inspiration from the underlying idea, we propose a quantum generalization of Penrose's hypothesis using the Planck regime in place of the big bang, and simultaneously incorporating tensor as well as scalar modes. Initial conditions selected by this generalization constrain the universe to be as homogeneous and isotropic in the Planck regime \\emph{as permitted by the Heisenberg uncertainty relations}.
Noncommutative Fluid and Cosmological Perturbations
Das, Praloy
2016-01-01
In the present paper we have developed a Non-Commutative (NC) generalization of perfect fluid model from first principles, in a Hamiltonian framework. The noncommutativity is introduced at the Lagrangian (particle) coordinate space brackets and the induced NC fluid bracket algebra for the Eulerian (fluid) field variables is derived. Together with a Hamiltonian this NC algebra generates the generalized fluid dynamics that satisfies exact local conservation laws for mass and energy thereby maintaining mass and energy conservation. However, nontrivial NC correction terms appear in charge and energy fluxes. Other non-relativistic spacetime symmetries of the NC fluid are also discussed in detail. This constitutes the NC fluid dynamics and kinematics. In the second part we construct an extension of Friedmann-Robertson-Walker (FRW) cosmological model based on the NC fluid dynamics presented here. We outline the way in which NC effects generate cosmological perturbations bringing in anisotropy and inhomogeneity in th...
Shiraz, Farzin Amirkhani; Ardejani, Faramarz Doulati; Moradzadeh, Ali; Arab-Amiri, Ali Reza
2013-01-01
Coal washing factories may create serious environmental problems due to pyrite oxidation and acid mine drainage generation from coal waste piles on nearby land. Infiltration of pyrite oxidation products through the porous materials of the coal waste pile by rainwater cause changes in the conductivity of underground materials and groundwater downstream of the pile. Electromagnetic and electrical methods are effective for investigation and monitoring of the contaminated plumes caused by coal waste piles and tailings impoundments. In order to investigate the environmental impact from a coal waste pile at the Alborz Sharghi coal washing plant, an EM34 ground conductivity meter was used on seven parallel lines in an E-W direction, downstream of the waste pile. Two-dimensional resistivity models obtained by the inversion of EM34 conductivity data identified conductive leachate plumes. In addition, quasi-3D inversion of EM34 data has confirmed the decreasing resistivity at depth due to the contaminated plumes. Comparison between EM34, VLF and DC-resistivity datasets, which were acquired for similar survey lines, agree well in identifying changes in the resistivity trend. The EM34 and DC-resistivity sections have greater similarity and better smoothness rather than those of the VLF model. Two-dimensional inversion models of these methods have shown some contaminated plumes with low resistivity.
Directory of Open Access Journals (Sweden)
M. Parrot
2010-05-01
Full Text Available In Samoa Islands, a powerful earthquake took place at 17:48:10.99 UTC (06:48:10.99 LT on 29 September 2009 with a magnitude Mw=8.1. Using ICE (Instrument Champ Electrique and IMSC (Instrument Magnetic Search Coil experiments onboard the DEMETER (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions satellite we have surveyed possible variations in electromagnetic signals transmitted by the ground-based VLF transmitter NPM in Hawaii and in HF plasma waves close to the Samoa earthquake during the seismic activity. The indices Dst and Kp were used to distinguish pre-earthquake anomalies from the other anomalies related to the geomagnetic activities. In a previous study we have shown that anomalies in IAP (plasma analyzer and ISL (Langmuir probe experiments onboard the DEMETER and also TEC (Total Electron Content data appear 1 to 5 days before the Samoa earthquake. In this paper we show that the anomalies in the VLF transmitter signal and in the HF range appear with the same time scale. The lack of significant geomagnetic activities indicates that these anomalous behaviors could be regarded as seismo-ionospheric precursors. It is also shown that comparative analysis is more effective in seismo-ionospheric studies.
Entanglement dynamics in critical random quantum Ising chain with perturbations
Energy Technology Data Exchange (ETDEWEB)
Huang, Yichen, E-mail: ychuang@caltech.edu
2017-05-15
We simulate the entanglement dynamics in a critical random quantum Ising chain with generic perturbations using the time-evolving block decimation algorithm. Starting from a product state, we observe super-logarithmic growth of entanglement entropy with time. The numerical result is consistent with the analytical prediction of Vosk and Altman using a real-space renormalization group technique. - Highlights: • We study the dynamical quantum phase transition between many-body localized phases. • We simulate the dynamics of a very long random spin chain with matrix product states. • We observe numerically super-logarithmic growth of entanglement entropy with time.
Boosted perturbations at the end of inflation
Zaballa, Ignacio
2009-01-01
We study the effect on the primordial cosmological perturbations of a sharp transition from inflationary to a radiation and matter dominated epoch respectively. We assume that the perturbations are generated by the vacuum fluctuations of a scalar field slowly rolling down its potential, and that the transition into the subsequent epoch takes place much faster than a Hubble time. The behaviour of the superhorizon perturbations corresponding to cosmological scales in this case is well known. However, it is not clear how perturbations on scales of and smaller than the Hubble horizon scale at the end of inflation may evolve through such a transition. We derive the evolution equation for the gravitational potential $\\Psi$, which allows us to study the evolution of the perturbations on all scales under these circumstances. We show that for a certain range of scales inside the horizon at the end of inflation, the amplitude of the perturbations are enhanced relative to the superhorizon scales. This enhancement may le...
Transient dynamics of perturbations in astrophysical disks
Razdoburdin, Dmitry N
2015-01-01
This paper reviews some aspects of one of the major unsolved problems in understanding astrophysical (in particular, accretion) disks: whether the disk interiors may be effectively viscous in spite of the absence of marnetorotational instability? In this case a rotational homogeneous inviscid flow with a Keplerian angular velocity profile is spectrally stable, making the transient growth of perturbations a candidate mechanism for energy transfer from the regular motion to perturbations. Transient perturbations differ qualitatively from perturbation modes and can grow substantially in shear flows due to the nonnormality of their dynamical evolution operator. Since the eigenvectors of this operator, alias perturbation modes, are mutually nonorthogonal, they can mutually interfere, resulting in the transient growth of their linear combinations. Physically, a growing transient perturbation is a leading spiral whose branches are shrunk as a result of the differential rotation of the flow. This paper discusses in d...
Dynamics of Cosmological Perturbations in Position Space
Bashinsky, S V; Bashinsky, Sergei; Bertschinger, Edmund
2002-01-01
We show that the linear dynamics of cosmological perturbations can be described by coupled wave equations, allowing their efficient numerical and, in certain limits, analytical integration directly in position space. The linear evolution of any perturbation can then be analyzed with the Green's function method. Prior to hydrogen recombination, assuming tight coupling between photons and baryons, neglecting neutrino perturbations, and taking isentropic (adiabatic) initial conditions, the obtained Green's functions for all metric, density, and velocity perturbations vanish beyond the acoustic horizon. At the acoustic wavefronts, a positive gravitational potential perturbation produces narrow photon-baryon density spikes, which provide one of the major contributions to the observed cosmic microwave background radiation anisotropy on all scales. The gravitational interaction between cold dark matter and baryons causes a dip in the observed temperature of the radiation at the center of the initial perturbation. We...
Newtonian Limits of the Relativistic Cosmological Perturbations
Hwang, J
1997-01-01
Relativistic cosmological perturbation analyses can be made based on several different fundamental gauge conditions. In the pressureless limit the variables in certain gauge conditions show the correct Newtonian behaviors. We consider the general curvature and the cosmological constant in the background medium. The perturbed density in the comoving gauge, and the perturbed velocity and the perturbed potential in the zero-shear gauge show the same behavior as the Newtonian ones in a general scale. Far inside horizon, except for the uniform-density gauge, density perturbations in all the fundamental gauge conditions show the correct Newtonian behavior. In this paper we elaborate these Newtonian correspondences. We also present the relativistic results considering general pressures in the background and perturbation.
Unsafe but Calculable: Ratios of Angularities in Perturbative QCD
Larkoski, Andrew J
2013-01-01
Infrared- and collinear-safe (IRC-safe) observables have finite cross sections to each fixed-order in perturbative QCD. Generically, ratios of IRC-safe observables are themselves not IRC safe and do not have a valid fixed-order expansion. Nevertheless, in this paper we present an explicit method to calculate the cross section for a ratio observable in perturbative QCD with the help of resummation. We take the IRC-safe jet angularities as an example and consider the ratio formed from two angularities with different angular exponents. While the ratio observable is not IRC safe, it is "Sudakov safe", meaning that the perturbative Sudakov factor exponentially suppresses the singular region of phase space. At leading logarithmic (LL) order, the distribution is finite but has a peculiar expansion in the square root of the strong coupling constant, a consequence of IRC unsafety. The accuracy of the LL distribution can be further improved with higher-order resummation and fixed-order matching. Non-perturbative effect...
Contadakis, Michael E.; Arabelos, Demetrios N.; Vergos, George; Spatala, Spyrous; Skeberis, Christos; Xenos, Tomas D.; Biagi, Pierfrancesco; Scordilis, Emmanuel M.
2017-04-01
In this paper we investigate the ionospheric turbulence from TEC variations and VLF/LF transmitter signal observations before and during the disastrous seismic activity of August and October 2016 in Central Italy . The Total Electron Content (TEC) data of 8 Global Positioning System (GPS) stations of the EUREF network, which are being provided by IONOLAB (Turkey), were analysed using Discrete Fourier Analysis in order to investigate the TEC variations (Contadakis et al. 2009, Contadakis et al. 2012, Contadakis et al. 2015). The data acquired for VLF/LF signal observations are from the receiver of Thessaloniki(40.59N, 22,78E), Greece (Skeberis et al. 2015) which monitor the VLF/LF transmitters of the International Network for Frontier Research on Earthquake Precursors (INFREP). A method of normalization according to the distance between the receiver and the transmitter is applied on the above data and then they are processed by the Hilbert Huang Transform (HHT) to produce the corresponding spectra for visual analysis. The results of this investigation indicate that the High- Frequency limit fo, of the ionospheric turbulence content, increases as the site and the moment of the earthquake occurrence is approaching, pointing to the earthquake locus. In accordence ,the analyzed data from the receiver of INFREP network in Thessaloniki, Greece show that the signals from the two VLF European transmitters, Tavolara ( Italy) and Le Blanc (France), for wich the transmission path crosses the epicentral zones, indicate enhanced high frequency variations, the last ten days before the moment of the earthquake occurrence. We conclude that the LAIC mechanism through acoustic or gravity wave could explain this phenomenology. Reference Contadakis, M.E., Arabelos, D.N., Asteriadis, G., Spatalas, S.D., Pikridas, C. TEC variations over the Mediterranean during the seismic activity period of the last quarter of 2005 in the area of Greece, Nat. Hazards and Earth Syst. Sci., 8, 1267
Approximation of pressure perturbations by FEM
Bichir, Cătălin - Liviu
2011-01-01
In the mathematical problem of linear hydrodynamic stability for shear flows against Tollmien-Schlichting perturbations, the continuity equation for the perturbation of the velocity is replaced by a Poisson equation for the pressure perturbation. The resulting eigenvalue problem, an alternative form for the two - point eigenvalue problem for the Orr - Sommerfeld equation, is formulated in a variational form and this one is approximated by finite element method (FEM). Possible applications to concrete cases are revealed.
Cosmological perturbations in a noncommutative braneworld inflation
Institute of Scientific and Technical Information of China (English)
Kourosh Nozari; Siamak Akhshabi
2012-01-01
We use the smeared,coherent state picture of noncommutativity to study evolution of perturbations in a noncommutative braneworld scenario.Within the standard procedure of studying braneworld cosmological perturbations,we study the evolution of the Bardeen metric potential and curvature perturbations in this model.We show that in this setup,the early stage of the universe's evolution has a transient phantom evolution with imaginary effective sound speed.
Non-Perturbative Theory of Dispersion Interactions
Boström, M; Persson, C; Parsons, D F; Buhmann, S Y; Brevik, I; Sernelius, Bo E
2015-01-01
Some open questions exist with fluctuation-induced forces between extended dipoles. Conventional intuition derives from large-separation perturbative approximations to dispersion force theory. Here we present a full non-perturbative theory. In addition we discuss how one can take into account finite dipole size corrections. It is of fundamental value to investigate the limits of validity of the perturbative dispersion force theory.
Optical solitons in resonant and nonresonant nonlinear media in the presence of perturbations.
Piscureanu, M; Manaila-Maximean, D
2000-01-01
We studied the optical solitons in nonlinear resonant and nonresonant media in the presence of perturbations, assuming that the transient effects are stimulated by the light scanning beam. We treated a slight deviation from the exact necessary condition for the soliton existence (2betanu=1), as a small perturbation for the integrable system, studying its influence upon the soliton propagation conditions. The approximation is constructed by the help of an algebraic version of the soliton perturbation theory using a Riemann boundary problem in connection with the inverse scattering method. We have obtained the soliton equation and we have solved it in the presence of a small perturbation in the adiabatic approximation. In this case we have demonstrated that for a Lorentz profile line the amplitude of the soliton remains unchanged, the only effect of the perturbation results in a phase shift.
Kato expansion in quantum canonical perturbation theory
Nikolaev, A S
2015-01-01
This work establishes a connection between canonical perturbation series in quantum mechanics and a Kato expansion for the resolvent of the Liouville superoperator. Our approach leads to an explicit expression for a generator of a block-diagonalizing Dyson ordered exponential in arbitrary perturbation order. Unitary intertwining of perturbed and unperturbed averaging superprojectors allows for a description of ambiguities in the generator and block-diagonalized Hamiltonian. The corresponding computational algorithm is more efficient for high perturbative orders than the algorithms of Van Vleck and Magnus methods.
Superhorizon Perturbations and the Cosmic Microwave Background
Erickcek, Adrienne L; Kamionkowski, Marc
2008-01-01
Superhorizon perturbations induce large-scale temperature anisotropies in the cosmic microwave background (CMB) via the Grishchuk-Zel'dovich effect. We analyze the CMB temperature anisotropies generated by a single-mode adiabatic superhorizon perturbation. We show that an adiabatic superhorizon perturbation in a LCDM universe does not generate a CMB temperature dipole, and we derive constraints to the amplitude and wavelength of a superhorizon potential perturbation from measurements of the CMB quadrupole and octupole. We also consider constraints to a superhorizon fluctuation in the curvaton field, which was recently proposed as a source of the hemispherical power asymmetry in the CMB.
Perturbative spacetimes from Yang-Mills theory
Luna, Andrés; Nicholson, Isobel; Ochirov, Alexander; O'Connell, Donal; Westerberg, Niclas; White, Chris D.
2017-04-12
The double copy relates scattering amplitudes in gauge and gravity theories. In this paper, we expand the scope of the double copy to construct spacetime metrics through a systematic perturbative expansion. The perturbative procedure is based on direct calculation in Yang-Mills theory, followed by squaring the numerator of certain perturbative diagrams as specified by the double-copy algorithm. The simplest spherically symmetric, stationary spacetime from the point of view of this procedure is a particular member of the Janis-Newman-Winicour family of naked singularities. Our work paves the way for applications of the double copy to physically interesting problems such as perturbative black-hole scattering.
Kato expansion in quantum canonical perturbation theory
Nikolaev, Andrey
2016-06-01
This work establishes a connection between canonical perturbation series in quantum mechanics and a Kato expansion for the resolvent of the Liouville superoperator. Our approach leads to an explicit expression for a generator of a block-diagonalizing Dyson's ordered exponential in arbitrary perturbation order. Unitary intertwining of perturbed and unperturbed averaging superprojectors allows for a description of ambiguities in the generator and block-diagonalized Hamiltonian. We compare the efficiency of the corresponding computational algorithm with the efficiencies of the Van Vleck and Magnus methods for high perturbative orders.
Perturbative spacetimes from Yang-Mills theory
Luna, Andres; Nicholson, Isobel; Ochirov, Alexander; O'Connell, Donal; Westerberg, Niclas; White, Chris D.
2016-01-01
The double copy relates scattering amplitudes in gauge and gravity theories. In this paper, we expand the scope of the double copy to construct spacetime metrics through a systematic perturbative expansion. The perturbative procedure is based on direct calculation in Yang-Mills theory, followed by squaring the numerator of certain perturbative diagrams as specified by the double-copy algorithm. The simplest spherically symmetric, stationary spacetime from the point of view of this procedure is a particular member of the Janis-Newman-Winicour family of naked singularities. Our work paves the way for applications of the double copy to physically interesting problems such as perturbative black-hole scattering.
Controlling Disorder in Traffic Flow by Perturbation
Institute of Scientific and Technical Information of China (English)
LIKe-Ping; GAOZi-You; CHENTian-Lun
2004-01-01
We propose a new technique for controlling disorder in traffic system. A kind of control signal which can be considered as a perturbation has been designated at a given site (perturbation point) of the single-lane highway. When a vehicle passes the perturbation point at a time, the velocity of the vehicle will be changed at the next time by the perturbation. This technique is tested for the deterministic NaSch traffic model. The simulation results indicate that the traffic system can be transited from the disorder states to the order states, such as fixed-point, periodic motion, etc.
Yamashita, Kozo; Takahashi, Yukihiro; Ohya, Hiroyo; Tsuchiya, Fuminori; Sato, Mitsuteru; Matsumoto, Jun
2013-04-01
Data of lightning discharge has been focused on as an effective way for monitoring and nowcasting of thunderstorm activity which causes extreme weather. Spatial distribution of lightning discharge has been used as a proxy of the presence or absence of deep convection. Latest observation shows that there is extremely huge lightning whose scale is more than hundreds times bigger than that of averaged event. This result indicates that lightning observation should be carried out to estimate not only existence but also scale for quantitative evaluation of atmospheric convection. In this study, lightning observation network in the Maritime Continent is introduced. This network is consisted of the sensors which make possible to measure electromagnetic wave radiated from lightning discharges. Observation frequency is 0.1 - 40 kHz for the measurement of magnetic field and 1 - 40 kHz for that of electric field. Sampling frequency is 100 kHz. Waveform of electromagnetic wave is recorded by personal computer. We have already constructed observation stations at Tainan in Taiwan (23.1N, 121.1E), Saraburi in Thailand (14.5N, 101.0E), and Pontianak in Indonesia (0.0N, 109.4E). Furthermore, we plan to install the monitoring system at Los Banos in Philippines (14.18, 121.25E) and Hanoi in Viet Nam. Data obtained by multipoint observation is synchronized by GPS receiver installed at each station. By using data obtained by this network, location and scale of lightning discharge can be estimated. Location of lightning is determined based on time of arrival method. Accuracy of geolocation could be less than 10km. Furthermore, charge moment is evaluated as a scale of each lightning discharge. It is calculated from electromagnetic waveform in ELF range (3-30 kHz). At the presentation, we will show the initial result about geolocation for source of electromagnetic wave and derivation of charge moment value based on the measurement of ELF and VLF sferics.
Voter Model Perturbations and Reaction Diffusion Equations
Cox, J Theodore; Perkins, Edwin
2011-01-01
We consider particle systems that are perturbations of the voter model and show that when space and time are rescaled the system converges to a solution of a reaction diffusion equation in dimensions $d \\ge 3$. Combining this result with properties of the PDE, some methods arising from a low density super-Brownian limit theorem, and a block construction, we give general, and often asymptotically sharp, conditions for the existence of non-trivial stationary distributions, and for extinction of one type. As applications, we describe the phase diagrams of three systems when the parameters are close to the voter model: (i) a stochastic spatial Lotka-Volterra model of Neuhauser and Pacala, (ii) a model of the evolution of cooperation of Ohtsuki, Hauert, Lieberman, and Nowak, and (iii) a continuous time version of the non-linear voter model of Molofsky, Durrett, Dushoff, Griffeath, and Levin. The first application confirms a conjecture of Cox and Perkins and the second confirms a conjecture of Ohtsuki et al in the ...
Perturbation theory in light-cone quantization
Energy Technology Data Exchange (ETDEWEB)
Langnau, A.
1992-01-01
A thorough investigation of light-cone properties which are characteristic for higher dimensions is very important. The easiest way of addressing these issues is by analyzing the perturbative structure of light-cone field theories first. Perturbative studies cannot be substituted for an analysis of problems related to a nonperturbative approach. However, in order to lay down groundwork for upcoming nonperturbative studies, it is indispensable to validate the renormalization methods at the perturbative level, i.e., to gain control over the perturbative treatment first. A clear understanding of divergences in perturbation theory, as well as their numerical treatment, is a necessary first step towards formulating such a program. The first objective of this dissertation is to clarify this issue, at least in second and fourth-order in perturbation theory. The work in this dissertation can provide guidance for the choice of counterterms in Discrete Light-Cone Quantization or the Tamm-Dancoff approach. A second objective of this work is the study of light-cone perturbation theory as a competitive tool for conducting perturbative Feynman diagram calculations. Feynman perturbation theory has become the most practical tool for computing cross sections in high energy physics and other physical properties of field theory. Although this standard covariant method has been applied to a great range of problems, computations beyond one-loop corrections are very difficult. Because of the algebraic complexity of the Feynman calculations in higher-order perturbation theory, it is desirable to automatize Feynman diagram calculations so that algebraic manipulation programs can carry out almost the entire calculation. This thesis presents a step in this direction. The technique we are elaborating on here is known as light-cone perturbation theory.
Tweel, I. van der; Herbschleb, J.N.; Borst, C.; Meijler, F.L.
1986-01-01
The atrio-ventricular (AV) node may be regarded as a periodically perturbed, biologicaL oscillator. In that case the ventricular response to atrial excitation can be described by a latency-phase curve. The phase is approximated by the time between a QRS-complex and an atrial stimulus S (R-S interval
Can Treadmill Perturbations Evoke Stretch Reflexes in the Calf Muscles?
Directory of Open Access Journals (Sweden)
Lizeth H Sloot
Full Text Available Disinhibition of reflexes is a problem amongst spastic patients, for it limits a smooth and efficient execution of motor functions during gait. Treadmill belt accelerations may potentially be used to measure reflexes during walking, i.e. by dorsal flexing the ankle and stretching the calf muscles, while decelerations show the modulation of reflexes during a reduction of sensory feedback. The aim of the current study was to examine if belt accelerations and decelerations of different intensities applied during the stance phase of treadmill walking can evoke reflexes in the gastrocnemius, soleus and tibialis anterior in healthy subjects. Muscle electromyography and joint kinematics were measured in 10 subjects. To determine whether stretch reflexes occurred, we assessed modelled musculo-tendon length and stretch velocity, the amount of muscle activity, as well as the incidence of bursts or depressions in muscle activity with their time delays, and co-contraction between agonist and antagonist muscle. Although the effect on the ankle angle was small with 2.8±1.0°, the perturbations caused clear changes in muscle length and stretch velocity relative to unperturbed walking. Stretched muscles showed an increasing incidence of bursts in muscle activity, which occurred after a reasonable electrophysiological time delay (163-191 ms. Their amplitude was related to the muscle stretch velocity and not related to co-contraction of the antagonist muscle. These effects increased with perturbation intensity. Shortened muscles showed opposite effects, with a depression in muscle activity of the calf muscles. The perturbations only slightly affected the spatio-temporal parameters, indicating that normal walking was retained. Thus, our findings showed that treadmill perturbations can evoke reflexes in the calf muscles and tibialis anterior. This comprehensive study could form the basis for clinical implementation of treadmill perturbations to functionally
Perturbative Chern-Simons theory revisited
DEFF Research Database (Denmark)
McLellan, Brendan Donald Kenneth
2013-01-01
We reconsider perturbative Chern-Simons theory on a closed and oriented three-manifold with a choice of contact structure following C. Beasley and E. Witten. Closed three manifolds that admit a Sasakian structure are explicitly computed to first order in perturbation in terms of their Seifert dat...
Double soft theorem for perturbative gravity
Saha, Arnab Priya
2016-09-01
Following up on the recent work of Cachazo, He and Yuan [1], we derive the double soft graviton theorem in perturbative gravity. We show that the double soft theorem derived using CHY formula precisely matches with the perturbative computation involving Feynman diagrams. In particular, we find how certain delicate limits of Feynman diagrams play an important role in obtaining this equivalence.
Identifying influential multinomial observations by perturbation
Nyangoma, S.O.; Fung, W.-K.; Jansen, R.C.
2006-01-01
The assessment of the influence of individual observations on the outcome of the analysis by perturbation has received a lot of attention for situations in which the observations are independent and identically distributed. However, no methods based on minor perturbations for carrying out such asses
Tokamak Transport Studies Using Perturbation Analysis
Cardozo, N. J. L.; Dehaas, J. C. M.; Hogeweij, G. M. D.; Orourke, J.; Sips, A.C.C.; Tubbing, B. J. D.
1990-01-01
Studies of the transport properties of tokamak plasmas using perturbation analysis are discussed. The focus is on experiments with not too large perturbations, such as sawtooth induced heat and density pulse propagation, power modulation and oscillatory gas-puff experiments. The approximations made
ADDITIVE FUNCTIONALS AND PERTURBATION OF SEMIGROUP
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The perturbation of semigroup by a multiplicative functional with bounded variation is investigated in the frame of weak duality. The strong continuity and Schrodinger type equation of the perturbated semigroup are discussed. A few switching identities and formulae conerning dual additive functionals and Revuz measures are given.
ADDITIVE FUNCTIONALS AND PERTURBATION OF SEMIGROUP
Institute of Scientific and Technical Information of China (English)
JINMENGWEI; YINGJIANGANG
2001-01-01
The perturbation of semigroup by a multiplicative functional with bounded variation is investigated in the frame of weak duality. The strong continuity and SchrSdinger type equation of the perturbated semigroup are discussed. A few switching identities and formulae conerning dual additive functionais and Revuz measures are given.
Perturbation of eigenvalues embedded at a threshold
DEFF Research Database (Denmark)
Jensen, Arne; Melgaard, Michael
2002-01-01
Results are obtained on perturbation of eigenvalues and half-bound states (zero-resonances) embedded at a threshold. The results are obtained in a two-channel framework for small off-diagonal perturbations. The results are based on given asymptotic expansions of the component Hamiltonians....
Tokamak Transport Studies Using Perturbation Analysis
Cardozo, N. J. L.; Dehaas, J. C. M.; Hogeweij, G. M. D.; Orourke, J.; Sips, A.C.C.; Tubbing, B. J. D.
1990-01-01
Studies of the transport properties of tokamak plasmas using perturbation analysis are discussed. The focus is on experiments with not too large perturbations, such as sawtooth induced heat and density pulse propagation, power modulation and oscillatory gas-puff experiments. The approximations made
Perturbative expansion of Chern-Simons theory
SAWON, Justin
2005-01-01
An overview of the perturbative expansion of the Chern--Simons path integral is given. The main goal is to describe how trivalent graphs appear: as they already occur in the perturbative expansion of an analogous finite-dimensional integral, we discuss this case in detail.
An Analytical Study for Controlling Chaos in Duffing Oscillator with Weak Periodic Perturbation
Institute of Scientific and Technical Information of China (English)
FANG Jian-Shu; HAI Wen-Hua; ZHANG Xi-Li
2001-01-01
We obtain a general unstable periodic solution near the homoclinic orbit of the Duffing oscillator with weak periodic perturbation by using the direct perturbation technique. Theoretical analysis reveals that the stable periodic orbits are embedded in the Melnikov chaotic attractor. The corresponding numerical results show that fitting control parameters into the stability conditions can control chaos in the system, and the phase difference between the two sinusoidal forces added to the Duffing equation plays an important role in controlling chaos.
Perturbation to TBM mixing and its phenomenological implications
M., Sruthilaya
2016-01-01
To accommodate the recently observed non-zero reactor mixing angle $\\theta_{13}$, we consider the lepton mixing matrix as Tri-bimaximal mixing (TBM) form in the leading order along with a perturbation in neutrino sector. The perturbation is taken to be a rotation in 23 plane followed by a rotation in 13 plane, i.e., $R_{23}(\\theta_{23}')R_{13}(\\theta_{13}',\\phi)$. We obtain the allowed values of the parameters $\\theta_{23}'$, $\\theta_{13}'$ and $\\phi$, which can accommodate all the observed mixing angles consistently and calculate the phenomenological observables such as the Dirac CP violating phase ($\\delta_{CP}$), Jarlskog invariant ($J_{CP}$), effective majorana mass $M_{ee}^{\
Cosmological perturbation theory in the synchronous and conformal newtonian gauges
Ma Chung Pei; Ma, Chung Pei; Bertschinger, Edmund
1995-01-01
This paper presents a systematic treatment of the linear theory of scalar gravitational perturbations in the synchronous gauge and the conformal Newtonian (or longitudinal) gauge. It differs from others in the literature in that we give, in both gauges, a complete discussion of all particle species that are relevant to any flat cold dark matter (CDM), hot dark matter (HDM), or CDM+HDM models (including a possible cosmological constant). The particles considered include CDM, baryons, photons, massless neutrinos, and massive neutrinos (an HDM candidate), where the CDM and baryons are treated as fluids while a detailed phase-space description is given to the photons and neutrinos. Particular care is applied to the massive neutrino component, which has been either ignored or approximated crudely in previous works. Isentropic initial conditions on super-horizon scales are derived. The coupled, linearized Boltzmann, Einstein and fluid equations that govern the evolution of the metric and density perturbations are t...
VARIANCE OF NONLINEAR PHASE NOISE IN FIBER-OPTIC SYSTEM
RANJU KANWAR; SAMEKSHA BHASKAR
2013-01-01
In communication system, the noise process must be known, in order to compute the system performance. The nonlinear effects act as strong perturbation in long- haul system. This perturbation effects the signal, when interact with amplitude noise, and results in random motion of the phase of the signal. Based on the perturbation theory, the variance of nonlinear phase noise contaminated by both self- and cross-phase modulation, is derived analytically for phase-shift- keying system. Through th...
Relevant Perturbation of Entanglement Entropy and Stationarity
Nishioka, Tatsuma
2014-01-01
A relevant perturbation of the entanglement entropy of a sphere is examined holographically near the UV fixed point. Varying the conformal dimension of the relevant operator, we obtain three different sectors: 1) the entanglement entropy is stationary and the perturbative expansion is well-defined with respect to the relevant coupling, 2) the entropy is stationary, but the perturbation fails, 3) the entropy is neither stationary nor perturbative. We compare our holographic results with the numerical calculation for a free massive scalar field in three-dimensions, and find a qualitative agreement between them. We argue that these statements hold for any relevant perturbation in any quantum field theory invariant under the Poincare symmetry.
Perturbative stability of catenoidal soap films
Jana, Soumya
2013-01-01
The perturbative stability of catenoidal soap films formed between parallel, equal radii, coaxial rings is studied using analytical and semi-analytical methods. Using a theorem on the nature of eigenvalues for a class of Sturm--Liouville operators, we show that for the given boundary conditions, azimuthally asymmetric perturbations are stable, while symmetric perturbations lead to an instability--a result demonstrated in Ben Amar et. al [7] using numerics and experiment. Further, we show how to obtain the lowest real eigenvalue of perturbations, using the semi-analytical Asymptotic Iteration Method (AIM). Conclusions using AIM support the analytically obtained result as well as the results in [7]. Finally, we compute the eigenfunctions and show, pictorially, how the perturbed soap film evolves in time.
Metric perturbations in Einstein-Cartan Cosmology
Garcia de Andrade, L C
2002-01-01
Metric perturbations the stability of solution of Einstein-Cartan cosmology (ECC) are given. The first addresses the stability of solutions of Einstein-Cartan (EC) cosmological model against Einstein static universe background. In this solution we show that the metric is stable against first-order perturbations and correspond to acoustic oscillations. The second example deals with the stability of de Sitter metric also against first-order perturbations. Torsion and shear are also computed in these cases. The resultant perturbed anisotropic spacetime with torsion is only de Sitter along one direction or is unperturbed along one direction and perturbed against the other two. Cartan torsion contributes to the frequency of oscillations in the model. Therefore gravitational waves could be triggered by the spin-torsion scalar density .
Perturbative photon production in a dispersive medium
Belgiorno, Francesco; Piazza, Francesco Dalla
2014-01-01
We investigate photon pair-creation in a dispersive dielectric medium induced by the presence of a spacetime varying dielectric constant. Our aim is to examine the possibility to observe new phenomena of pair creation induced by travelling dielectric perturbations e.g. created by laser pulses by means of the Kerr effect. In this perspective, we adopt a semi-phenomenological version of the Hopfield model in which a space-time dependent dielectric susceptibility appears. We focus our attention on perturbation theory, and provide general formulas for the photon production induced by a local but arbitrarily spacetime dependent refractive index perturbation. As an example, we further explore the case of an uniformly travelling perturbation, and provide examples of purely time-dependent perturbations.
Adiabatic density-functional perturbation theory
Gonze, Xavier
1995-08-01
The treatment of adiabatic perturbations within density-functional theory is examined, at arbitrary order of the perturbation expansion. Due to the extremal property of the energy functional, standard variation-perturbation theorems can be used. The different methods (Sternheimer equation, extremal principle, Green's function, and sum over state) for obtaining the perturbation expansion of the wave functions are presented. The invariance of the Hilbert space of occupied wave functions with respect to a unitary transformation leads to the definition of a ``parallel-transport-gauge'' and a ``diagonal-gauge'' perturbation expansion. Then, the general expressions are specialized for the second, third, and fourth derivative of the energy, with an example of application of the method up to third order.
Accommodation of the spinal cat to a tripping perturbation
Directory of Open Access Journals (Sweden)
Hui eZhong
2012-05-01
Full Text Available Adult cats with a complete spinal cord transection at T12-T13 can relearn over a period of days-to-weeks how to generate full weight-bearing stepping on a treadmill or standing ability if trained specifically for that task. In the present study, we assessed short-term (msec-min adaptations by repetitively imposing a mechanical perturbation on the hindlimb of chronic spinal cats by placing a rod in the path of the leg during the swing phase to trigger a tripping response. The kinematics and EMG were recorded during control (10 steps, trip (1 to 60 steps with various patterns and then release (without any tripping stimulus, 10 to 20 steps sequences. Our data show that the activation patterns and kinematics of the hindlimb in the step cycle immediately following the initial trip (mechanosensory stimulation of the dorsal surface of the paw was modified in a way that increased the probability of avoiding the obstacle in the subsequent step. This indicates that the spinal sensorimotor circuitry reprogrammed the trajectory of the swing following a perturbation prior to the initiation of the swing phase of the subsequent step, in effect attempting to avoid the re-occurrence of the perturbation. The average height of the release steps was elevated compared to control regardless of the pattern and the length of the trip sequences. In addition, the average impact force on the tripping rod tended to be lower with repeated exposure to the tripping stimulus. EMG recordings suggest that the semitendinosus, a primary knee flexor, was a major contributor to the adaptive tripping response. These results demonstrate that the lumbosacral locomotor circuitry can modulate the activation patterns of the hindlimb motor pools within the time frame of single step in a manner that tends to minimize repeated perturbations. Furthermore, these adaptations remained evident for a number of steps after removal of the mechanosensory stimulation.
Skeberis, Christos; Xenos, Thomas; Contadakis, Michael; Arabelos, Dimitrios; Biagi, Pier Francesco; Maggipinto, Tommaso
2013-04-01
This paper studies the development and application of an automated system based on Predictive Modular Neural Networks (PREMONNs) and Self Organizing Maps (SOMs) along with the necessary backend development of database classification required to provide a fully integrated system for detecting disturbances that can be attributed to seismic-ionospheric precursor phenomena using VLF radio signals. The aforementioned system can analyze all the relevant data and bring forth and adaptively discriminate different characteristics in the received signals, in real time in order to provide data segments of interest that can be correlated to subsequent seismic phenomena and can be classified with respect to pre-recorded samples of previous points of interest (POIs). PREMONNs as it was demonstrated in previous studies can be used for time-series switching detection and can be applied to the detection of POIs , whereas SOMs have been extensively used in unsupervised pattern recognition and classification of datasets. For the purpose of this paper, data acquired in Thessaloniki (40.59N, 22,78E) from the VLF station in Tavolara, Italy (ICV station Lat 40.923, Lon. 9.731) for over two years (December 2010 - December 2012) are used. The receiver was developed by Elettronika Srl, and is part of the International Network for Frontier Research on Earthquake Precursors (INFREP). The received VLF signal is normalized and then processed using the Empirical Mode Decomposition Method (EMD). The resulting data are passed to an Artificial Neural Network (ANN) based on PREMONNs trained specifically for this purpose and the output from that stage is passed onto a classifier based on SOMs to compare and classify points of interest based on a current database of received signals and identifying and storing new ones for future reference. The efficacy of the detection and the results of the aforementioned process is then discussed and results are presented. Therefore, based on the results it may be
Building a non-perturbative quark-gluon vertex from a perturbative one
Bermudez, Rocio
2016-10-01
The quark-gluon vertex describes the electromagnetic and the strong interaction among these particles. The description of this interaction at high precision in both regimes, perturbative and non-perturbative, continues being a matter of interest in the context of QCD and Hadron Physics. There exist very helpful models in the literature that explain perturbative aspects of the theory but they fail describing non-perturbative phenomena, as confinement and dynamic chiral symmetry breaking. In this work we study the structure of the quark-gluon vertex in a non-perturbative regime examining QCD, checking results with QED, and working in the Schwinger-Dyson formalism.
Berry's Phase in Noncommutative Spaces
Institute of Scientific and Technical Information of China (English)
S. A. Alavi
2003-01-01
We discuss the perturbative aspects of noncommutative quantum mechanics. Then we study Berry's phase within the framework of noncommutative quantum mechanics. The results show deviations from the usual quantum mechanics, which depend on the parameter of space/space noncommutativity.
Abbas, Abbas M.; Khalil, Mohamed A.; Massoud, Usama; Santos, Fernando M.; Mesbah, Hany A.; Lethy, Ahmed; Soliman, Mamdouh; Ragab, El Said A.
2012-06-01
According to some new discoveries at Tap-Osiris Magna temple (West of Alexandria), there is potentiality to uncover a remarkable archeological finding at this site. Three years ago many significant archeological evidences have been discovered sustaining the idea that the tomb of Cleopatra and Anthony may be found in the Osiris temple inside Tap-Osiris Magna temple at a depth from 20 to 30 m. To confirm this idea, PHASE I was conducted in by joint application of Ground Penetrating Radar “GPR”, Electrical Resistivity Tomography “ERT” and Magnetometry. The results obtained from PHASE I could not confirm the existence of major tombs at this site. However, small possible cavities were strongly indicated which encouraged us to proceed in investigation of this site by using another geophysical approach including Very Low Frequency Electro Magnetic (VLF-EM) technique. VLF-EM data were collected along parallel lines covering the investigated site with a line-to-line spacing of 1 m. The point-to-point distance of 1 m along the same line was employed. The data were qualitatively interpreted by Fraser filtering process and quantitatively by 2-D VLF inversion of tipper data and forward modeling. Results obtained from VLF-EM interpretation are correlated with 2-D resistivity imaging and drilling information. Findings showed a highly resistive zone at a depth extended from about 25-45 m buried beneath Osiris temple, which could be indicated as the tomb of Cleopatra and Anthony. This result is supported by Fraser filtering and forward modeling results. The depth of archeological findings as indicated from the geophysical survey is correlated well with the depth expected by archeologists, as well as, the depth of discovered tombs outside Tap-Osiris Magna temple. This depth level has not been reached by drilling in this site. We hope that the site can be excavated in the future based on these geophysical results.
Chagelishvili, George; Hau, Jan-Niklas; Khujadze, George; Oberlack, Martin
2016-08-01
The linear dynamics of perturbations in smooth shear flows covers the transient exchange of energies between (1) the perturbations and the basic flow and (2) different perturbations modes. Canonically, the linear exchange of energies between the perturbations and the basic flow can be described in terms of the Orr and the lift-up mechanisms, correspondingly for two-dimensional (2D) and three-dimensional (3D) perturbations. In this paper the mechanical basis of the linear transient dynamics is introduced and analyzed for incompressible plane constant shear flows, where we consider the dynamics of virtual fluid particles in the framework of plane perturbations (i.e., perturbations with plane surfaces of constant phase) for the 2D and 3D case. It is shown that (1) the formation of a pressure perturbation field is the result of countermoving neighboring sets of incompressible fluid particles in the flow, (2) the keystone of the energy exchange mechanism between the basic flow and perturbations is the collision of fluid particles with the planes of constant pressure in accordance with the classical theory of elastic collision of particles with a rigid wall, making the pressure field the key player in this process, (3) the interplay of the collision process and the shear flow kinematics describes the transient growth of plane perturbations and captures the physics of the growth, and (4) the proposed mechanical picture allows us to reconstruct the linearized Euler equations in spectral space with a time-dependent shearwise wave number, the linearized Euler equations for Kelvin modes. This confirms the rigor of the presented analysis, which, moreover, yields a natural generalization of the proposed mechanical picture of the transient growth to the well-established linear phenomenon of vortex-wave-mode coupling.
Quantitative methods in classical perturbation theory.
Giorgilli, A.
Poincaré proved that the series commonly used in Celestial mechanics are typically non convergent, although their usefulness is generally evident. Recent work in perturbation theory has enlightened this conjecture of Poincaré, bringing into evidence that the series of perturbation theory, although non convergent in general, furnish nevertheless valuable approximations to the true orbits for a very large time, which in some practical cases could be comparable with the age of the universe. The aim of the author's paper is to introduce the quantitative methods of perturbation theory which allow to obtain such powerful results.
Density perturbation growth in teleparallel cosmology
Energy Technology Data Exchange (ETDEWEB)
Geng, Chao-Qiang [College of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing, 400065 (China); Wu, Yi-Peng, E-mail: geng@phys.nthu.edu.tw, E-mail: s9822508@m98.nthu.edu.tw [Department of Physics, National Tsing Hua University, Hsinchu, 300 Taiwan (China)
2013-04-01
We study the cosmological perturbations in teleparallel dark energy models in which there is a dynamical scalar field with a non-minimal coupling to gravity. We find that the propagating degrees of freedom are the same as in quintessence cosmology despite that variables of the perturbed vierbein field are greater than those in metric theories. We numerically show some evident discrepancy from general relativity in the evolutions of the perturbations on all scales of the universe. We also demonstrate that the gravitational interactions are enhanced during the unique tracker evolutions in these models.
HIV-associated memory B cell perturbations.
Hu, Zhiliang; Luo, Zhenwu; Wan, Zhuang; Wu, Hao; Li, Wei; Zhang, Tong; Jiang, Wei
2015-05-21
Memory B-cell depletion, hyperimmunoglobulinemia, and impaired vaccine responses are the hallmark of B cell perturbations inhuman immunodeficiency virus (HIV) disease. Although B cells are not the targets for HIV infection, there is evidence for B cell, especially memory B cell dysfunction in HIV disease mediated by other cells or HIV itself. This review will focus on HIV-associated phenotypic and functional alterations in memory B cells. Additionally, we will discuss the mechanism underlying these perturbations and the effect of anti-retroviral therapy (ART) on these perturbations.
Perturbative Semiclassical Trace Formulae for Harmonic Oscillators
DEFF Research Database (Denmark)
Møller-Andersen, Jakob; Ögren, Magnus
2015-01-01
In this article we extend previous semiclassical studies by including more general perturbative potentials of the harmonic oscillator in arbitrary spatial dimensions. Our starting point is a radial harmonic potential with an arbitrary even monomial perturbation, which we use to study the resulting...... U(D) to O(D) symmetry breaking. We derive the gross structure of the semiclassical spectrum from periodic orbit theory, in the form of a perturbative (ħ → 0) trace formula. We then show how to apply the results to even-order polynomial potentials, possibly including mean-field terms. We have drawn...
Perturbative loop corrections and nonlocal gravity
Maggiore, Michele
2016-01-01
Nonlocal gravity has been shown to provide a phenomenologically viable infrared modification of GR. A natural question is whether the required nonlocality can emerge from perturbative quantum loop corrections due to light particles. We show that this is not the case. For the value of the mass scale of the non-local models required by cosmology, the perturbative form factors obtained from the loop corrections, in the present cosmological epoch, are in the regime where they are local. The mechanism behind the generation of the required nonlocality must be more complex, possibly related to strong infrared effects and non-perturbative mass generation for the conformal mode.
Asymptotic stability of singularly perturbed differential equations
Artstein, Zvi
2017-02-01
Asymptotic stability is examined for singularly perturbed ordinary differential equations that may not possess a natural split into fast and slow motions. Rather, the right hand side of the equation is comprised of a singularly perturbed component and a regular one. The limit dynamics consists then of Young measures, with values being invariant measures of the fast contribution, drifted by the slow one. Relations between the asymptotic stability of the perturbed system and the limit dynamics are examined, and a Lyapunov functions criterion, based on averaging, is established.
Institute of Scientific and Technical Information of China (English)
常珊珊; 赵正予; 汪枫
2011-01-01
By heating the ionosphere with large ELF/VLF-modulated HF wave, a virtual antenna is produced in the ionosphere, which is an effective means to radiate ELF/VLF waves. This paper uses the modulated-heating models of Wang Feng (2009) to calculate the strength of the LF radiation source produced by HF heating, uses full-wave model to analyze attenuation and reflection of the LF wave transmitting downward, and with HAARP experiment parameter, simulates magnetic field of the LF signals on the sea, which is in PT order, according with the experimental data.%通过大功率ELF/VLF调幅高频波对电离层进行加热,形成电离层虚拟天线,可以作为发射ELF/VLF波的一种有效手段.本文使用汪枫(2009)的调制加热模型,计算高频加热电离层产生的低频辐射源强度,采用全波解算法分析辐射的低频波向下传播过程中的衰减和反射问题,并采用HAARP实验参数,模拟出在海面上接收到的低频信号强度为PT量级,与实验数据一致.模拟结果表明,加热泵波功率、低频调制波频率、以及加热纬度位置是影响ELF/VLF波辐射和传播的三个主要因素.
Marshall, R. A.; Snively, J. B.
2013-12-01
We present observations of thunderstorm-driven perturbations to the D-region ionosphere measured by VLF subionospheric remote sensing (VLF-SRS). VLF-SRS is sensitive to electron density and collision frequency disturbances in a narrow altitude range near 85 km along the great-circle-path (GCP) between a VLF transmitter and a receiver some thousands of km away. These disturbances are measured as amplitude and/or phase perturbations to the continuous VLF transmitter signal. On March 20, 2001, a prominent event was observed by VLF receivers in Colorado monitoring the VLF transmitter in Puerto Rico, exhibiting unusually strong amplitude perturbations of up to 0.6 dB, with periods of 1-3 minutes, but no detectable phase perturbations. As these periods are well below the minimum Brunt-Vaisala period of about 5 minutes, we hypothesize that they may be associated with thunderstorm-generated acoustic waves (AWs). The GCPs from this transmitter to the receivers passed through two thunderstorms at the time of the AW event, one near the southern tip of Florida and the other over the Florida panhandle. The apparent AW event lasted for about one hour and was observed on four near-parallel GCPs separated by a few tens of km at the thunderstorm location. This data shows that VLF-SRS may provide a new, high-time-resolution (better than 1 Hz) monitoring system for acoustic and gravity waves in the upper atmosphere. To investigate the hypothesized AW source for this event, we use a two-step simulation process. A nonlinear, compressible, atmospheric dynamics model is used to simulate acoustic wave propagation from a defined source near the ground to 200 km altitude. Case studies are constructed to investigate different source configurations and perturbations to ionospheric density profiles. The modified electron and neutral density are then input to a finite-difference electromagnetic code that simulates the VLF transmitter signal propagation to the receiver over a distance of ~5000
Dark Energy in a perturbed Weyl-Dirac Universe
Israelit, Mark
2012-01-01
In the framework of Weyl-Dirac's theory a perturbed universe is considered. It contains luminous matter, dark matter consisting of weylons as well dark energy (DE) presented by Dirac's gauge function,\\beta. A massive body creates a spherically symmetric gravitational field, that is regarded as the perturbation of the homogeneous and isotropic universe [20]. Around the perturbing mass the dark energy forms up a ball-like concentration that reaches the horizon. The energy-mass density of this DE ball, the pressure and mass are searched. It turns out that they all are negative. As negative pressure is necessary to get acceleration at the expanding phase and deceleration during contraction, the Weyl-Dirac DE is an appropriate candidate. The negative mass of the DE ball is universally repulsive, both positive-mass and negative-mass objects will be pushed away by the ball. The negative DE mass and the negative DE pressure can be regarded as causing and supporting the present cosmic acceleration.
Perturbative Analysis of Gauged Matrix Models
Dijkgraaf, R; Kazakov, V A; Vafa, C; Dijkgraaf, Robbert; Gukov, Sergei; Kazakov, Vladimir A.; Vafa, Cumrun
2003-01-01
We analyze perturbative aspects of gauged matrix models, including those where classically the gauge symmetry is partially broken. Ghost fields play a crucial role in the Feynman rules for these vacua. We use this formalism to elucidate the fact that non-perturbative aspects of N=1 gauge theories can be computed systematically using perturbative techniques of matrix models, even if we do not possess an exact solution for the matrix model. As examples we show how the Seiberg-Witten solution for N=2 gauge theory, the Montonen-Olive modular invariance for N=1*, and the superpotential for the Leigh-Strassler deformation of N=4 can be systematically computed in perturbation theory of the matrix model/gauge theory (even though in some of these cases the exact answer can also be obtained by summing up planar diagrams of matrix models).
Simple Perturbation Example for Quantum Chemistry.
Goodfriend, P. L.
1985-01-01
Presents a simple example that illustrates various aspects of the Rayleigh-Schrodinger perturbation theory. The example is a particularly good one because it is straightforward and can be compared with both the exact solution and with experimental data. (JN)
Creating Statistically Anisotropic and Inhomogeneous Perturbations
Armendariz-Picon, C
2007-01-01
In almost all structure formation models, primordial perturbations are created within a homogeneous and isotropic universe, like the one we observe. Because their ensemble averages inherit the symmetries of the spacetime in which they are seeded, cosmological perturbations then happen to be statistically isotropic and homogeneous. Certain anomalies in the cosmic microwave background on the other hand suggest that perturbations do not satisfy these statistical properties, thereby challenging perhaps our understanding of structure formation. In this article we relax this tension. We show that if the universe contains an appropriate triad of scalar fields with spatially constant but non-zero gradients, it is possible to generate statistically anisotropic and inhomogeneous primordial perturbations, even though the energy momentum tensor of the triad itself is invariant under translations and rotations.
Gauge and motion in perturbation theory
Pound, Adam
2015-01-01
Through second order in perturbative general relativity, a small compact object in an external vacuum spacetime obeys a generalized equivalence principle: although it is accelerated with respect to the external background geometry, it is in free fall with respect to a certain \\emph{effective} vacuum geometry. However, this single principle takes very different mathematical forms, with very different behaviors, depending on how one treats perturbed motion. Furthermore, any description of perturbed motion can be altered by a gauge transformation. In this paper, I clarify the relationship between two treatments of perturbed motion and the gauge freedom in each. I first show explicitly how one common treatment, called the Gralla-Wald approximation, can be derived from a second, called the self-consistent approximation. I next present a general treatment of smooth gauge transformations in both approximations, in which I emphasise that the approximations' governing equations can be formulated in an invariant manner...
Perturbations of spiky strings in flat spacetimes
Bhattacharya, Soumya; Panigrahi, Kamal L
2016-01-01
Perturbations of a class of semiclassical strings known today as spiky strings, are studied using the well-known Jacobi equations for small normal deformations of an embedded timelike surface. It is shown that there exists finite normal perturbations of the spiky string worldsheets embedded in a $2+1$ dimensional flat spacetime. Such perturbations lead to a rounding off the spikes, which, in a way, demonstrates the stable nature of the unperturbed worldsheet. The same features appear for the dual spiky string solution and in the spiky as well as their dual solutions in $3+1$ dimensional flat spacetime. Our results are based on exact solutions of the corresponding Jacobi equations which we obtain and use while constructing the profiles of the perturbed configurations.
THE EIGENVALUE PERTURBATION BOUND FOR ARBITRARY MATRICES
Institute of Scientific and Technical Information of China (English)
Wen Li; Jian-xin Chen
2006-01-01
In this paper we present some new absolute and relative perturbation bounds for the eigenvalue for arbitrary matrices, which improves some recent results. The eigenvalue inclusion region is also discussed.
Cosmological perturbations in mimetic Horndeski gravity
Arroja, Frederico; Karmakar, Purnendu; Matarrese, Sabino
2016-01-01
We study linear scalar perturbations around a flat FLRW background in mimetic Horndeski gravity. In the absence of matter, we show that the Newtonian potential satisfies a second-order differential equation with no spatial derivatives. This implies that the sound speed for scalar perturbations is exactly zero on this background. We also show that in mimetic $G^3$ theories the sound speed is equally zero. We obtain the equation of motion for the comoving curvature perturbation (first order differential equation) and solve it to find that the comoving curvature perturbation is constant on all scales in mimetic Horndeski gravity. We find solutions for the Newtonian potential evolution equation in two simple models. Finally we show that the sound speed is zero on all backgrounds and therefore the system does not have any wave-like scalar degrees of freedom.
Rolling axions during inflation: perturbativity and signatures
Peloso, Marco; Unal, Caner
2016-01-01
The motion of a pseudo-scalar field $X$ during inflation naturally induces a significant amplification of the gauge fields to which it is coupled. The amplified gauge fields can source characteristic scalar and tensor primordial perturbations. Several phenomenological implications have been discussed in the cases in which (i) $X$ is the inflation, and (ii) $X$ is a field different from the inflation, that experiences a temporary speed up during inflation. In this second case, visible sourced gravitational waves (GW) can be produced at the CMB scales without affecting the scalar perturbations, even if the scale of inflation is several orders of magnitude below what is required to produce a visible vacuum GW signal. Perturbativity considerations can be used to limit the regime in which these results are under perturbative control. We revised limits recently claimed for the case (i), and we extend these considerations to the case (ii). We show that, in both cases, these limits are satisfied by the applications t...
Effective Field Theory of Cosmological Perturbations
Piazza, Federico
2013-01-01
The effective field theory of cosmological perturbations stems from considering a cosmological background solution as a state displaying spontaneous breaking of time translations and (adiabatic) perturbations as the related Nambu-Goldstone modes. With this insight, one can systematically develop a theory for the cosmological perturbations during inflation and, with minor modifications, also describe in full generality the gravitational interactions of dark energy, which are relevant for late-time cosmology. The formalism displays a unique set of Lagrangian operators containing an increasing number of cosmological perturbations and derivatives. We give an introductory description of the unitary gauge formalism for theories with broken gauge symmetry---that allows to write down the most general Lagrangian---and of the Stueckelberg "trick"---that allows to recover gauge invariance and to make the scalar field explicit. We show how to apply this formalism to gravity and cosmology and we reproduce the detailed ana...
General degeneracy in density functional perturbation theory
Palenik, Mark C.; Dunlap, Brett I.
2017-07-01
Degenerate perturbation theory from quantum mechanics is inadequate in density functional theory (DFT) because of nonlinearity in the Kohn-Sham potential. Herein, we develop the fully general perturbation theory for open-shell, degenerate systems in Kohn-Sham DFT, without assuming the presence of symmetry or equal occupation of degenerate orbitals. To demonstrate the resulting methodology, we apply it to the iron atom in the central field approximation, perturbed by an electric quadrupole. This system was chosen because it displays both symmetry required degeneracy, between the five 3 d orbitals, as well as accidental degeneracy, between the 3 d and 4 s orbitals. The quadrupole potential couples the degenerate 3 d and 4 s states, serving as an example of the most general perturbation.
Collision orbits in the presence of perturbations
Energy Technology Data Exchange (ETDEWEB)
Diaz-Cano, A. [Departamento de Algebra, Facultad de CC. Matematicas, Universidad Complutense de Madrid, Madrid (Spain)]. E-mail: antonio_diazcano@mat.ucm.es; Gonzalez-Gascon, F. [Departamento de Fisica Teorica II, Facultad de CC. Fisicas, Universidad Complutense de Madrid, Madrid (Spain)
2006-10-16
It is shown that for particles moving in a plane under the action of attracting central potentials and a perturbing force (potential but not central), orbits representing the falling down of the particle to the center of force exist.
Cosmological perturbations in teleparallel Loop Quantum Cosmology
Haro, Jaime
2013-01-01
Cosmological perturbations in Loop Quantum Cosmology (LQC) could be studied from two totally different ways. The first one, called holonomy corrected LQC, is performed in the Hamiltonian framework, where the Asthekar connection is replaced by a suitable sinus function (holonomy correction), in order to have a well-defined quantum analogue. The alternative approach is based in the fact that isotropic LQC could be also obtained as a particular case of teleparallel $F(T)$ gravity (teleparallel LQC). Then, working in the Lagrangian framework and using the well-know perturbation equations in $F(T)$ gravity, we have obtained, in teleparallel LQC, the equations for scalar and tensor perturbations, and the corresponding Mukhanov-Sasaki equations. For scalar perturbations, our equation only differs from the one obtained by holonomy corrections in the velocity of sound, leading both formulations, essentially to the same scale invariant power spectrum when a matter-dominated universe is considered. However for tensor pe...
Microwave Background Anisotropies from Scaling Seed Perturbations
Durrer, R; Durrer, Ruth; Sakellariadou, Mairi
1997-01-01
We study microwave background anisotropies induced by scaling seed perturbations in a universe dominated by cold dark matter. Using a gauge invariant linear perturbation analysis, we solve the perturbation equations on super-horizon scales, for CMB anisotropies triggered by generic gravitational seeds. We find that perturbations induced by seeds -- under very mild restrictions -- are nearly isocurvature. Thus, compensation, which is mainly the consequence of physically sensible initial conditions, is very generic. We then restrict our study to the case of scaling sources, motivated by global scalar fields. We parameterize the energy momentum tensor of the source by ``seed functions'' and calculate the Sachs-Wolfe and acoustic contributions to the CMB anisotropies. We discuss the dependence of the anisotropy spectrum on the parameters of the model considered. Even within the restricted class of models investigated in this work, we find a surprising variety of results for the position and height of the first ac...
Adiabatic perturbations in coupled scalar field cosmologies
Beyer, Joschka
2014-01-01
We present a comprehensive and gauge invariant treatment of perturbations around cosmological scaling solutions for two canonical scalar fields coupled through a common potential in the early universe, in the presence of neutrinos, photons and baryons, but excluding cold dark matter. This setup is relevant for analyzing cosmic perturbations in scalar field models of dark matter with a coupling to a quintessence field. We put strong restrictions on the shape of the common potential and adopt a matrix-eigensystem approach to determine the dominant perturbations modes in such models. Similar to recent results in scenarios where standard cold dark matter couples to quintessence, we show that the stability of the adiabatic perturbation mode can be an issue for this class of scalar field dark matter models, but only for specific choices of the common potential. For an exponential coupling potential, a rather common shape arising naturally in many instances, this problem can be avoided. We explicitly calculate the d...
Borries, Claudia; Mahrous, Ayman M.; Ellahouny, Nada M.; Badeke, Ronny
2016-11-01
Strong ionospheric perturbations were generated by the intense geomagnetic storm on 17 March 2015. In this article, we are studying perturbations in the European-African sector observed in the total electron content (TEC). Focal points are wavelike phenomena considered as large-scale traveling ionospheric disturbances (LSTIDs). In the European-African sector, the storm produced three different types of LSTIDs: (1) a concurrent TEC perturbation at all latitudes simultaneously; (2) one LSTID propagating toward the equator, having very large wave parameters (wavelength: ≈3600 km, period: ≈120 min, and speed: ≈500 m/s); and (3) several LSTIDs propagating toward the equator with typical wave parameters (wavelength: ≈2100 km, period: ≈60 min, and speed ≈600 m/s). The third type of LSTIDs is considered to be exited as most LSTIDs either due to variations in the Joule heating or variations in the Lorentz force, whereas the first two perturbation types are rather unusual in their appearance. They occurred during the partial recovery phase when the geomagnetic perturbations were minor and the interplanetary magnetic field turned northward. A westward prompt penetration electric field is considered to excite the first perturbation signature, which indicates a sudden TEC depletion. For the second LSTID type, variations in the Lorentz force because of perturbed electric fields and a minor particle precipitation effect are extracted as possible excitation mechanisms.
Kanekar, Neeta; Aruin, Alexander S
2014-06-01
The ability to maintain balance deteriorates with increasing age. Anticipatory and compensatory postural adjustments (APAs and CPAs, respectively), both, are known to be affected in the elderly. We examined the effect of aging on the ability of older adults to utilize APAs and its effect on subsequent control of posture (CPAs). Ten elderly individuals were exposed to external predictable and unpredictable perturbations applied to the upper body in the sagittal plane. Body kinematics, electromyographic activity of 13 muscles, and ground reaction forces were analyzed during the anticipatory and compensatory phases of postural control. The elderly were capable of recognizing an upcoming predictable perturbation and activated muscles prior to it. However, the older adults used different muscle strategies and sequence of muscle recruitment than that reported in young adults. Additionally, when the perturbations were unpredictable, no APAs were seen which resulted in large CPAs and greater peak displacements of the center of pressure (COP) and center of mass (COM) following perturbations. As opposed to this, when the perturbations were predictable, APAs were seen in older adults resulting in significantly smaller CPAs. The presence and utilization of APAs in older adults also improved postural stability following the perturbation as seen by significantly smaller COP and COM peak displacements. Using APAs in older adults significantly reduces the need for large CPAs, resulting in greater postural stability following a perturbation. The results provide a foundation for investigating the role of training in improving the interplay between anticipatory and compensatory postural control in older adults.
Observing Quantum Tunneling in Perturbation Series
Suzuki, H; Suzuki, Hiroshi; Yasuta, Hirofumi
1997-01-01
It is well-known that the quantum tunneling makes conventional perturbation series non-Borel summable. We use this fact reversely and attempt to extract the decay width of the false-vacuum from the actual perturbation series of the vacuum energy density (vacuum bubble diagrams). It is confirmed that, at least in quantum mechanical examples, our proposal provides a complimentary approach to the the conventional instanton calculus in the strong coupling region.
Tuning Leaky Nanocavity Resonances - Perturbation Treatment
Shlafman, Michael; Salzman, Joseph
2010-01-01
Adiabatic frequency tuning of finite-lifetime-nanocavity electromagnetic modes affects also their quality-factor (Q). Perturbative Q change resulting from (real) frequency tuning, is a controllable parameter. Here, the influence of dielectric constant modulation (DCM) on cavity resonances is presented, by first order perturbation analysis for a 3D cavity with radiation losses. Semi-analytical expressions for DCM induced cavity mode frequency and Q changes are derived. The obtained results are in good agreement with numerical calculations.
Alternative perturbation approaches in classical mechanics
Energy Technology Data Exchange (ETDEWEB)
Amore, Paolo [Facultad de Ciencias, Universidad de Colima, Bernal DIaz del Castillo 340, Colima, Colima (Mexico); Raya, Alfredo [Facultad de Ciencias, Universidad de Colima, Bernal DIaz del Castillo 340, Colima, Colima (Mexico); Fernandez, Francisco M [INIFTA (Conicet, UNLP), Blvd. 113 y 64 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)
2005-11-01
We discuss two alternative methods, based on the Lindstedt-Poincare technique, for the removal of secular terms from the equations of perturbation theory. We calculate the period of an anharmonic oscillator by means of both approaches and show that one of them is more accurate for all values of the coupling constant. We believe that present discussion and comparison may be a suitable exercise for teaching perturbation theory in advanced undergraduate courses on classical mechanics.
Double Soft Theorem for Perturbative Gravity
Saha, Arnab Priya
2016-01-01
Following up on the recent work of Cachazo, He and Yuan \\cite{arXiv:1503.04816 [hep-th]}, we derive the double soft graviton theorem in perturbative gravity. We show that the double soft theorem derived using CHY formula precisely matches with the perturbative computation involving Feynman diagrams. In particular, we find how certain delicate limits of Feynman diagrams play an important role in obtaining this equivalence.
Reflection and transmission of conformal perturbation defects
Brunner, Ilka
2015-01-01
We consider reflection and transmission of interfaces which implement renormalisation group flows between conformal fixed points in two dimensions. Such an RG interface is constructed from the identity defect in the ultraviolet CFT by perturbing the theory on one side of the defect line. We compute reflection and transmission coefficients in perturbation theory to third order in the coupling constant and check our calculations against exact constructions of RG interfaces between coset models.
Density Perturbation Growth in Teleparallel Cosmology
Geng, Chao-Qiang
2012-01-01
We study the cosmological perturbations in teleparallel dark energy models in which there is a dynamical scalar field with a non-minimal coupling to gravity. We find that the propagating degrees of freedom are the same as in quintessence cosmology despite that variables of the perturbed vierbein field are greater than those in metric theories. The resulting growth evolution shows that gravitational interactions are enhanced during the unique tracker evolution of teleparallel dark energy models.
Non-perturbative renormalization in kaon decays
Donini, Andrea; Martinelli, G; Rossi, G C; Talevi, M; Testa, M; Vladikas, A
1996-01-01
We discuss the application of the MPSTV non-perturbative method \\cite{NPM} to the operators relevant to kaon decays. This enables us to reappraise the long-standing question of the $\\Delta I=1/2$ rule, which involves power-divergent subtractions that cannot be evaluated in perturbation theory. We also study the mixing with dimension-six operators and discuss its implications to the chiral behaviour of the $B_K$ parameter.
Cosmological scalar field perturbations can grow
Alcubierre, Miguel; Diez-Tejedor, Alberto; Torres, José M
2015-01-01
It has been argued that the small perturbations in the energy density to the homogeneous and isotropic configurations of a canonical scalar field in an expanding universe do not grow. We show that this is not true in general, and clarify the root of the misunderstanding. We revisit a simple model in which the linear perturbations grow like those in the standard cold dark matter scenario, but with the Jeans length at the scale of the Compton wavelength of the scalar particle.
Perturbative partition function for squashed S^5
Imamura, Yosuke
2012-01-01
We compute the index of 6d N=(1,0) theories on S^5xR containing vector and hypermultiplets. We only consider the perturbative sector without instantons. By compactifying R to S^1 with a twisted boundary condition and taking the small radius limit, we derive the perturbative partition function on a squashed S^5. The 1-loop partition function is represented in a simple form with the triple sine function.
General degeneracy in density functional perturbation theory
Palenik, Mark C
2016-01-01
Degenerate perturbation theory from quantum mechanics is inadequate in density functional theory (DFT) because of nonlinearity in the Kohn-Sham potential. We develop the fully general degenerate perturbation theory for DFT without assuming that the degeneracy is required by symmetry. The resulting methodology is applied to the iron atom ground state in order to demonstrate the effects of degeneracy that appears both due to symmetry requirements and accidentally, between different representations of the symmetry group.
PRIMAL PERTURBATION SIMPLEX ALGORITHMS FOR LINEAR PROGRAMMING
Institute of Scientific and Technical Information of China (English)
Ping-qi Pan
2000-01-01
In this paper, we propose two new perturbation simplex variants. Solving linear programming problems without introducing artificial variables, each of the two uses the dual pivot rule to achieve primal feasibility, and then the primal pivot rule to achieve optimality. The second algorithm, a modification of the first, is designed to handle highly degenerate problems more etficiently. Some interesting results concerning merit of the perturbation are established. Numerical results from preliminary tests are also reported.
Scalar Perturbations on the background of Linearly and Nonlinearly Charged BTZ Black Holes
Tang, Zi-Yu; Zangeneh, Mahdi Kord; Wang, Bin; Saavedra, Joel
2016-01-01
We investigate the spacetime properties of BTZ black holes in Maxwell field and BornInfeld field and find rich properties in the spacetime structures when the model parameters vary. Employing the Landau-Lifshitz theory, we examine the thermodynamical phase transition in the charged BTZ holes. We further study the dynamical perturbation in the background of the charged BTZ black holes and find different properties of dynamical perturbations for the extreme and nonextreme charged BTZ black holes, which can serve as a new physical signal to indicate the phase transition between them.
Gauge and motion in perturbation theory
Pound, Adam
2015-08-01
Through second order in perturbative general relativity, a small compact object in an external vacuum spacetime obeys a generalized equivalence principle: although it is accelerated with respect to the external background geometry, it is in free fall with respect to a certain effective vacuum geometry. However, this single principle takes very different mathematical forms, with very different behaviors, depending on how one treats perturbed motion. Furthermore, any description of perturbed motion can be altered by a gauge transformation. In this paper, I clarify the relationship between two treatments of perturbed motion and the gauge freedom in each. I first show explicitly how one common treatment, called the Gralla-Wald approximation, can be derived from a second, called the self-consistent approximation. I next present a general treatment of smooth gauge transformations in both approximations, in which I emphasize that the approximations' governing equations can be formulated in an invariant manner. All of these analyses are carried through second perturbative order, but the methods are general enough to go to any order. Furthermore, the tools I develop, and many of the results, should have broad applicability to any description of perturbed motion, including osculating-geodesic and two-timescale descriptions.
Hajian, K; Sheikh-Jabbari, M M
2014-01-01
In arXiv:1310.3727 we formulated and derived the three universal laws governing Near Horizon Extremal Geometries (NHEG). In this work we focus on the Entropy Perturbation Law (EPL) which, similarly to the first law of black hole thermodynamics, relates perturbations of the charges labeling perturbations around a given NHEG to the corresponding entropy perturbation. We show that field perturbations governed by the linearized equations of motion and symmetry conditions which we carefully specify, satisfy the EPL. We also show that these perturbations are limited to those coming from difference of two NHEG solutions (i.e. variations on the NHEG solution parameter space). Our analysis and discussions shed light on the "no-dynamics" statements of arXiv:0906.2380 and arXiv:0906.2376.
SOLVABILITY FOR NONLINEAR ELLIPTIC EQUATION WITH BOUNDARY PERTURBATION
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The solvability of nonlinear elliptic equation with boundary perturbation is considered. The perturbed solution of original problem is obtained and the uniformly valid expansion of solution is proved.
Moldovan, Iren-Adelina; Petruta Constantin, Angela; Emilian Toader, Victorin; Toma-Danila, Dragos; Biagi, Pier Francesco; Maggipinto, Tommaso; Dolea, Paul; Septimiu Moldovan, Adrian
2014-05-01
Based on scientific evidences supporting the causality between earthquake preparatory stages, space weather and solar activity and different types of electromagnetic (EM) disturbances together with the benefit of having full access at ground and space based EM data, INFREP proposes a complex and cross correlated investigation of phenomena that occur in the coupled system Lithosphere-Atmosphere-Ionsophere in order to identify possible causes responsible for anomalous effects observed in the propagation characteristics of radio waves, especially at low (LF) and very low frequency (VLF). INFREP, a network of VLF (20-60 kHz) and LF (150-300 kHz) radio receivers, was put into operation in Europe in 2009, having as principal goal, the study of disturbances produced by the earthquakes on the propagation properties of these signals. The Romanian NIEP VLF / LF monitoring system consisting in a radio receiver -made by Elettronika S.R.L. (Italy) and provided by the Bari University- and the infrastructure that is necessary to record and transmit the collected data, is a part of the international initiative INFREP. The NIEP VLF / LF receiver installed in Romania was put into operation in February 2009 in Bucharest and relocated to the Black-Sea shore (Dobruja Seismologic Observatory) in December 2009. The first development of the Romanian EM monitoring system was needed because after changing the receiving site from Bucharest to Eforie we obtained unsatisfactory monitoring data, characterized by large fluctuations of the received signals' intensities. Trying to understand this behavior has led to the conclusion that the electric component of the electromagnetic field was possibly influenced by the local conditions. Starting from this observation we have run some tests and changed the vertical antenna with a loop-type antenna that is more appropriate in highly electric-field polluted environments. Since the amount of recorded data is huge, for streamlining the research process
Adaptive control of rotating magnetic perturbations in HBT-EP using GPU processing
Rath, N.; Angelini, S.; Bialek, J.; Byrne, P. J.; DeBono, B.; Hughes, P.; Levesque, J. P.; Mauel, M. E.; Navratil, G. A.; Peng, Q.; Rhodes, D.; Stoafer, C.
2013-08-01
Feedback control has become a crucial tool in the research on magnetic confinement of plasmas for achieving controlled nuclear fusion. We present the first experimental results from a novel feedback control system that, for the first time, employs a graphics processing unit (GPU) for microsecond-latency, real-time control computations. The system was tested on the HBT-EP tokamak using an adaptive control algorithm for control of rotating magnetic perturbations. The algorithm assumes that perturbations of known shape are rotating rigidly, but dynamically derives and updates the rotation frequency to improve phase and gain accuracy of the control signals. Experiments were set up to control four rotating n = 1 perturbations at different poloidal angles. The perturbations are treated as coupled in frequency but independent of amplitude and phase, so that the system effectively controls a helical n = 1 perturbation with unknown poloidal spectrum. The control system suppresses the amplitude of the dominant 8 kHz mode by up to 60%. Deviation from the optimal feedback phase combines suppression with a speed up or slow down of the mode rotation frequency. The feedback performance is found to exceed previous results obtained with an FPGA- and Kalman-filter based control system without requiring any tuning of system model parameters.
Perturbations of ultralight vector field dark matter
Cembranos, J. A. R.; Maroto, A. L.; Núñez Jareño, S. J.
2017-02-01
We study the dynamics of cosmological perturbations in models of dark matter based on ultralight coherent vector fields. Very much as for scalar field dark matter, we find two different regimes in the evolution: for modes with {k}^2≪ Hma, we have a particle-like behaviour indistinguishable from cold dark matter, whereas for modes with {k}^2≫ Hma, we get a wave-like behaviour in which the sound speed is non-vanishing and of order c s 2 ≃ k 2/ m 2 a 2. This implies that, also in these models, structure formation could be suppressed on small scales. However, unlike the scalar case, the fact that the background evolution contains a non-vanishing homogeneous vector field implies that, in general, the evolution of the three kinds of perturbations (scalar, vector and tensor) can no longer be decoupled at the linear level. More specifically, in the particle regime, the three types of perturbations are actually decoupled, whereas in the wave regime, the three vector field perturbations generate one scalar-tensor and two vector-tensor perturbations in the metric. Also in the wave regime, we find that a non-vanishing anisotropic stress is present in the perturbed energy-momentum tensor giving rise to a gravitational slip of order ( Φ - Ψ)/ Φ ˜ c s 2 . Moreover in this regime the amplitude of the tensor to scalar ratio of the scalar-tensor modes is also h/ Φ ˜ c s 2 . This implies that small-scale density perturbations are necessarily associated to the presence of gravity waves in this model. We compare their spectrum with the sensitivity of present and future gravity waves detectors.
Acoustic anisotropic wavefields through perturbation theory
Alkhalifah, Tariq Ali
2013-09-01
Solving the anisotropic acoustic wave equation numerically using finite-difference methods introduces many problems and media restriction requirements, and it rarely contributes to the ability to resolve the anisotropy parameters. Among these restrictions are the inability to handle media with η<0 and the presence of shear-wave artifacts in the solution. Both limitations do not exist in the solution of the elliptical anisotropic acoustic wave equation. Using perturbation theory in developing the solution of the anisotropic acoustic wave equation allows direct access to the desired limitation-free solutions, that is, solutions perturbed from the elliptical anisotropic background medium. It also provides a platform for parameter estimation because of the ability to isolate the wavefield dependency on the perturbed anisotropy parameters. As a result, I derive partial differential equations that relate changes in the wavefield to perturbations in the anisotropy parameters. The solutions of the perturbation equations represented the coefficients of a Taylor-series-type expansion of the wavefield as a function of the perturbed parameter, which is in this case η or the tilt of the symmetry axis. The expansion with respect to the symmetry axis allows use of an acoustic transversely isotropic media with a vertical symmetry axis (VTI) kernel to estimate the background wavefield and the corresponding perturbation coefficients. The VTI extrapolation kernel is about one-fourth the cost of the transversely isotropic model with a tilt in the symmetry axis kernel. Thus, for a small symmetry axis tilt, the cost of migration using a first-order expansion can be reduced. The effectiveness of the approach was demonstrated on the Marmousi model.
The perturbative structure of spin glass field theory
Temesvári, T.
2014-03-01
Cubic replicated field theory is used to study the glassy phase of the short-range Ising spin glass just below the transition temperature, and for systems above, at, and slightly below the upper critical dimension six. The order parameter function is computed up to two-loop order. There are two, well-separated bands in the mass spectrum, just as in mean field theory. The small mass band acts as an infrared cutoff, whereas contributions from the large mass region can be computed perturbatively (d>6), or interpreted by the ɛ-expansion around the critical fixed point (d=6-ɛ). The one-loop calculation of the (momentum-dependent) longitudinal mass, and the whole replicon sector is also presented. The innocuous behavior of the replicon masses while crossing the upper critical dimension shows that the ultrametric replica symmetry broken phase remains stable below six dimensions.
The perturbative structure of spin glass field theory
Energy Technology Data Exchange (ETDEWEB)
Temesvári, T., E-mail: temtam@helios.elte.hu
2014-03-15
Cubic replicated field theory is used to study the glassy phase of the short-range Ising spin glass just below the transition temperature, and for systems above, at, and slightly below the upper critical dimension six. The order parameter function is computed up to two-loop order. There are two, well-separated bands in the mass spectrum, just as in mean field theory. The small mass band acts as an infrared cutoff, whereas contributions from the large mass region can be computed perturbatively (d>6), or interpreted by the ϵ-expansion around the critical fixed point (d=6−ϵ). The one-loop calculation of the (momentum-dependent) longitudinal mass, and the whole replicon sector is also presented. The innocuous behavior of the replicon masses while crossing the upper critical dimension shows that the ultrametric replica symmetry broken phase remains stable below six dimensions.
Exponential time-dependent perturbation theory in rotationally inelastic scattering
Cross, R. J.
1983-08-01
An exponential form of time-dependent perturbation theory (the Magnus approximation) is developed for rotationally inelastic scattering. A phase-shift matrix is calculated as an integral in time over the anisotropic part of the potential. The trajectory used for this integral is specified by the diagonal part of the potential matrix and the arithmetic average of the initial and final velocities and the average orbital angular momentum. The exponential of the phase-shift matrix gives the scattering matrix and the various cross sections. A special representation is used where the orbital angular momentum is either treated classically or may be frozen out to yield the orbital sudden approximation. Calculations on Ar+N2 and Ar+TIF show that the theory generally gives very good agreement with accurate calculations, even where the orbital sudden approximation (coupled-states) results are seriously in error.
Forward modeling of gyrosynchrotron intensity perturbations by sausage modes
Energy Technology Data Exchange (ETDEWEB)
Reznikova, V. E.; Van Doorsselaere, T. [Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B box 2400, B-3001 Leuven (Belgium); Antolin, P., E-mail: Veronika.Reznikova@wis.kuleuven.be [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
2014-04-20
To determine the observable radio signatures of the fast sausage standing wave, we examine gyrosynchrotron (GS) emission modulation using a linear three-dimensional magnetohydrodynamic model of a plasma cylinder. Effects of the line-of-sight angle and instrumental resolution on perturbations of the GS intensity are analyzed for two models: a base model with strong Razin suppression and a low-density model in which the Razin effect was unimportant. Our finding contradicts previous predictions made with simpler models: an in-phase variation of intensity between low (f < f {sub peak}) and high (f > f {sub peak}) frequencies is found for the low-density model and an anti-phase variation for the base model in the case of a viewing angle of 45°. The spatially inhomogeneous character of the oscillating emission source and the spatial resolution of the model are found to have a significant effect on the resulting intensity.
Rolling axions during inflation: perturbativity and signatures
Peloso, Marco; Sorbo, Lorenzo; Unal, Caner
2016-09-01
The motion of a pseudo-scalar field X during inflation naturally induces a significant amplification of the gauge fields to which it is coupled. The amplified gauge fields can source characteristic scalar and tensor primordial perturbations. Several phenomenological implications have been discussed in the cases in which (i) X is the inflaton, and (ii) X is a field different from the inflaton, that experiences a temporary speed up during inflation. In this second case, visible sourced gravitational waves (GW) can be produced at the CMB scales without affecting the scalar perturbations, even if the scale of inflation is several orders of magnitude below what is required to produce a visible vacuum GW signal. Perturbativity considerations can be used to limit the regime in which these results are under perturbative control. We revised limits recently claimed for the case (i), and we extend these considerations to the case (ii). We show that, in both cases, these limits are satisfied by the applications that generate signals at CMB scales. Applications that generate gravitational waves and primordial black holes at much smaller scales are at the limit of the validity of this perturbativity analysis, so we expect those results to be valid up to possibly order one corrections.
Cosmological perturbations on the Phantom brane
Bag, Satadru; Shtanov, Yuri; Sahni, Varun
2016-01-01
We obtain a closed system of equations for scalar perturbations in a multi-component braneworld. Our braneworld possesses a phantom-like equation of state at late times, $w_{\\rm eff} < -1$, but no big-rip future singularity. In addition to matter and radiation, the braneworld possesses a new effective degree of freedom - the 'Weyl fluid' or 'dark radiation'. Setting initial conditions on super-Hubble spatial scales at the epoch of radiation domination, we evolve perturbations of radiation, pressureless matter and the Weyl fluid until the present epoch. We observe a gradual decrease in the amplitude of the Weyl-fluid perturbations after Hubble-radius crossing, which results in a negligible effect of the Weyl fluid on the evolution of matter perturbations on spatial scales relevant for structure formation. Consequently, the quasi-static approximation of Koyama and Maartens provides a good fit to the exact results during the matter-dominated epoch. We find that the late-time growth of density perturbations on...
Four-Dimensional Spin Foam Perturbation Theory
Directory of Open Access Journals (Sweden)
João Faria Martins
2011-10-01
Full Text Available We define a four-dimensional spin-foam perturbation theory for the BF-theory with a B∧B potential term defined for a compact semi-simple Lie group G on a compact orientable 4-manifold M. This is done by using the formal spin foam perturbative series coming from the spin-foam generating functional. We then regularize the terms in the perturbative series by passing to the category of representations of the quantum group U_q(g where g is the Lie algebra of G and q is a root of unity. The Chain-Mail formalism can be used to calculate the perturbative terms when the vector space of intertwiners Λ⊗Λ→A, where A is the adjoint representation of g, is 1-dimensional for each irrep Λ. We calculate the partition function Z in the dilute-gas limit for a special class of triangulations of restricted local complexity, which we conjecture to exist on any 4-manifold M. We prove that the first-order perturbative contribution vanishes for finite triangulations, so that we define a dilute-gas limit by using the second-order contribution. We show that Z is an analytic continuation of the Crane-Yetter partition function. Furthermore, we relate Z to the partition function for the F∧F theory.
Local perturbations perturb—exponentially–locally
Energy Technology Data Exchange (ETDEWEB)
De Roeck, W., E-mail: wojciech.deroeck@fys.kuleuven.be; Schütz, M., E-mail: marius.schutz@fys.kuleuven.be [Instituut voor Theoretische Fysica, K. U. Leuven, Celestijnenlaan 200D, B-3001 Heverlee (Belgium)
2015-06-15
We elaborate on the principle that for gapped quantum spin systems with local interaction, “local perturbations [in the Hamiltonian] perturb locally [the groundstate].” This principle was established by Bachmann et al. [Commun. Math. Phys. 309, 835–871 (2012)], relying on the “spectral flow technique” or “quasi-adiabatic continuation” [M. B. Hastings, Phys. Rev. B 69, 104431 (2004)] to obtain locality estimates with sub-exponential decay in the distance to the spatial support of the perturbation. We use ideas of Hamza et al. [J. Math. Phys. 50, 095213 (2009)] to obtain similarly a transformation between gapped eigenvectors and their perturbations that is local with exponential decay. This allows to improve locality bounds on the effect of perturbations on the low lying states in certain gapped models with a unique “bulk ground state” or “topological quantum order.” We also give some estimate on the exponential decay of correlations in models with impurities where some relevant correlations decay faster than one would naively infer from the global gap of the system, as one also expects in disordered systems with a localized groundstate.
Institute of Scientific and Technical Information of China (English)
钟先琼; 向安平; 程科
2011-01-01
According to the extended nonlinear Schr(o)dinger equation including quintic nonlinearity in optical fibers,modulation instability (MI) based generation of high-repetition-rate optical pulse trains is numerically demonstrated by using the optical wave with its phase perturbed by Gaussian-typed continuous spectrum instead of conventional monochromatic one. The results show that,the pulse trains can also be generated due to MI effect like the conventional case.However,being different from the conventional case,the generated pulse trains here consist of limited number of pulses which are generally not equal in width,intensity,and interval.And the pulse number increases with the propagation distance.Moreover,when the other parameters are the same,the positive quintic nonlinearity can make the pulse width and interval shorten,which means that the positive quintic nonlinearity is beneficial to generate higher repetition rate pulse trains.While the negative one takes the opposite.The numerically calculated chirps developed during the generation process of pulse trains indicate that,both the chirps and their variations with the distance are highly nonmonotonic,and the quintic nonlinearity will change both the chirp range and the chirp amount.%根据包含五阶非线性的扩展非线性薛定谔方程,数值研究了高斯型连续谱相位扰动而不是传统单色扰动下基于调制不稳定性的高重复率脉冲串产生.结果表明:脉冲串也能像传统情形那样形成,但却呈现出不同的特性.如脉冲数目有限,且各脉冲的高度、强度及间距不等.脉冲数目随传输距离增加而增加.而五阶非线性能使脉冲宽度和间距变小因而有利于高重复率脉冲串产生,负五阶非线性则相反.对脉冲串形成过程中演变啁啾的数值计算表明,啁啾及其随距离的变化都是高度非单调的,五阶非线性将改变啁啾的范围和量值.
Perturbative analysis of gauged matrix models
Dijkgraaf, Robbert; Gukov, Sergei; Kazakov, Vladimir A.; Vafa, Cumrun
2003-08-01
We analyze perturbative aspects of gauged matrix models, including those where classically the gauge symmetry is partially broken. Ghost fields play a crucial role in the Feynman rules for these vacua. We use this formalism to elucidate the fact that nonperturbative aspects of N=1 gauge theories can be computed systematically using perturbative techniques of matrix models, even if we do not possess an exact solution for the matrix model. As examples we show how the Seiberg-Witten solution for N=2 gauge theory, the Montonen-Olive modular invariance for N=1*, and the superpotential for the Leigh-Strassler deformation of N=4 can be systematically computed in perturbation theory of the matrix model or gauge theory (even though in some of these cases an exact answer can also be obtained by summing up planar diagrams of matrix models).
Perturbation calculation of thermodynamic density of states.
Brown, G; Schulthess, T C; Nicholson, D M; Eisenbach, M; Stocks, G M
2011-12-01
The density of states g (ε) is frequently used to calculate the temperature-dependent properties of a thermodynamic system. Here a derivation is given for calculating the warped density of states g*(ε) resulting from the addition of a perturbation. The method is validated for a classical Heisenberg model of bcc Fe and the errors in the free energy are shown to be second order in the perturbation. Taking the perturbation to be the difference between a first-principles quantum-mechanical energy and a corresponding classical energy, this method can significantly reduce the computational effort required to calculate g(ε) for quantum systems using the Wang-Landau approach.
Non-perturbative quantum geometry III
Krefl, Daniel
2016-08-01
The Nekrasov-Shatashvili limit of the refined topological string on toric Calabi-Yau manifolds and the resulting quantum geometry is studied from a non-perturbative perspective. The quantum differential and thus the quantum periods exhibit Stokes phenomena over the combined string coupling and quantized Kähler moduli space. We outline that the underlying formalism of exact quantization is generally applicable to points in moduli space featuring massless hypermultiplets, leading to non-perturbative band splitting. Our prime example is local ℙ1 + ℙ1 near a conifold point in moduli space. In particular, we will present numerical evidence that in a Stokes chamber of interest the string based quantum geometry reproduces the non-perturbative corrections for the Nekrasov-Shatashvili limit of 4d supersymmetric SU(2) gauge theory at strong coupling found in the previous part of this series. A preliminary discussion of local ℙ2 near the conifold point in moduli space is also provided.
Elementary Theorems Regarding Blue Isocurvature Perturbations
Chung, Daniel J H
2015-01-01
Blue CDM-photon isocurvature perturbations are attractive in terms of observability and may be typical from the perspective of generic mass relations in supergravity. We present and apply three theorems useful for blue isocurvature perturbations arising from linear spectator scalar fields. In the process, we give a more precise formula for the blue spectrum associated with the work of 0904.3800, which can in a parametric corner give a factor of O(10) correction. We explain how a conserved current associated with Peccei-Quinn symmetry plays a crucial role and explicitly plot several example spectra including the breaks in the spectra. We also resolve a little puzzle arising from a naive multiplication of isocurvature expression that sheds light on the gravitational imprint of the adiabatic perturbations on the fields responsible for blue isocurvature fluctuations.
Chiral Perturbation Theory With Lattice Regularization
Ouimet, P P A
2005-01-01
In this work, alternative methods to regularize chiral perturbation theory are discussed. First, Long Distance Regularization will be considered in the presence of the decuplet of the lightest spin 32 baryons for several different observables. This serves motivation and introduction to the use of the lattice regulator for chiral perturbation theory. The mesonic, baryonic and anomalous sectors of chiral perturbation theory will be formulated on a lattice of space time points. The consistency of the lattice as a regulator will be discussed in the context of the meson and baryon masses. Order a effects will also be discussed for the baryon masses, sigma terms and magnetic moments. The work will close with an attempt to derive an effective Wess-Zumino-Witten Lagrangian for Wilson fermions at non-zero a. Following this discussion, there will be a proposal for a phenomenologically useful WZW Lagrangian at non-zero a.
Non-Perturbative Quantum Geometry III
Krefl, Daniel
2016-01-01
The Nekrasov-Shatashvili limit of the refined topological string on toric Calabi-Yau manifolds and the resulting quantum geometry is studied from a non-perturbative perspective. The quantum differential and thus the quantum periods exhibit Stockes phenomena over the combined string coupling and quantized Kaehler moduli space. We outline that the underlying formalism of exact quantization is generally applicable to points in moduli space featuring massless hypermultiplets, leading to non-perturbative band splitting. Our prime example is local P1xP1 near a conifold point in moduli space. In particular, we will present numerical evidence that in a Stockes chamber of interest the string based quantum geometry reproduces the non-perturbative corrections for the Nekrasov-Shatashvili limit of 4d supersymmetric SU(2) gauge theory at strong coupling found in the previous part of this series. A preliminary discussion of local P2 near the conifold point in moduli space is also provided.
Gaugeon Formalism for Perturbative Quantum Gravity
Upadhyay, Sudhaker
2014-01-01
In this paper we investigate the Yokoyama gaugeon formalism for perturbative quantum gravity in general curved spacetime. Within the gaugeon formalism, we extend the configuration space by introducing vector gaugeon fields describing quantum gauge freedom. Such extended theory of perturbative gravity admits quantum gauge transformations leading to an natural shift in the gauge parameter. Further we impose the Gupta-Bleuler type subsidiary condition to remove the unphysical gaugeon modes. To replace the Gupta-Bleuler type condition by more acceptable Kugo-Ojima type subsidiary condition we analyse the BRST symmetric gaugeon formalism. Further, the physical Hilbert space is constructed for the perturbative quantum gravity which remains invariant under both the BRST symmetry and quantum gauge transformations.
Cosmological Perturbations in Extended Massive Gravity
Gumrukcuoglu, A Emir; Lin, Chunshan; Mukohyama, Shinji; Trodden, Mark
2013-01-01
We study cosmological perturbations around self-accelerating solutions to two extensions of nonlinear massive gravity: the quasi-dilaton theory and the mass-varying theory. We examine stability of the cosmological solutions, and the extent to which the vanishing of the kinetic terms for scalar and vector perturbations of self-accelerating solutions in massive gravity is generic when the theory is extended. We find that these kinetic terms are in general non-vanishing in both extensions, though there are constraints on the parameters and background evolution from demanding that they have the correct sign. In particular, the self-accelerating solutions of the quasi-dilaton theory are always unstable to scalar perturbations with wavelength shorter than the Hubble length.
Note on the semiclassicality of cosmological perturbations
Donà, Pietro; Marcianò, Antonino
2016-12-01
Moving from the consideration that matter fields must be treated in terms of their fundamental quantum counterparts, we show straightforward arguments, within the framework of ordinary quantum mechanics and quantum field theory, in order to convince readers that cosmological perturbations must be addressed in term of the semiclassical limit of the expectation value of quantum fields. We first take into account cosmological perturbations originated by a quantum scalar field, and then extend our treatment in order to account for the expectation values of bilinears of Dirac fermion fields. The latter can indeed transform as scalar quantities under diffeomorphisms, as well as all the other bilinear of the Dirac fields that belong to the Clifford algebra. This is the first of a series of works that is intended to prove that cosmological quantum perturbations can actually be accounted for in terms of Dirac fermion fields, which must be treated as fundamental quantum objects, and their dynamics.
Cosmological Perturbations with Multiple Fluids and Fields
Hwang, J
2002-01-01
We consider the evolution of perturbed cosmological spacetime with multiple fluid and field system in Einstein gravity. Equations are presented in gauge-ready forms, and are presented using the adiabatic and isocurvature perturbation variables. We present equations in the general background with $K$ and $\\Lambda$. We also clarify the conditions for conserved adiabatic and isocurvature perturbations in the large-scale limit. One interesting conclusion is that, for ideal fluid system, although the isocurvature modes can seed the adiabatic mode in the large-scale limit, the isocurvature modes decouple from the adiabatic one which is not the case for the field system. Useful sets of equations readily applicable to the quintessence models and the warm inflation scenario can be found in this work. An application to the scaling regime with an exponential field potential is made in the Appendix.
甚低频拖曳天线的稳态动力学研究%Research on the Steady Dynamic of VLF Trailing Antenna on an Aircraft
Institute of Scientific and Technical Information of China (English)
郑小洪; 侯志强; 韩维; 李冀鑫
2012-01-01
甚低频(Very low frequency,VLF)拖曳天线力学特征和控制是飞机对潜通信系统进一步深入论证需要解决的关键问题之一,而对其稳态动力学研究是进行甚低频拖曳天线力学特征和控制研究的基础.通过对载机盘旋时甚低频天线运动状态及其受力进行分析,应用牛顿定律建立机载甚低频拖曳天线稳态动力学模型.运用打靶法对其稳态动力学模型进行求解,分析载机速度、倾斜角和天线末端锥袋质量对天线末端锥袋量纲一半径和天线垂直度的影响.仿真结果表明在阻力系数较小时,在一定的倾斜角和载机飞行速度范围内其垂直度和天线末端量纲一半径存在多值情况,会导致拖曳天线系统的不稳定;在一定的阻力系数下,减小飞机速度,增加载机的倾斜角,能够提高甚低频拖曳天线的垂直度;单一增加天线末端锥袋质量来提高垂直度是不可行的.%The dynamic character and control of very low frequency(VLF) trailing antenna on a aircraft is one of most important problems which needs to research. The steady dynamic is the base of the dynamic character and control of the VLF trailing antenna. The mathematics model based Newton law of the trailing antenna is founded, and solved via a shooting technique. The influences of the angle of bank and the velocity of aircraft to the non-dismensionalization end radius and verticality are researched. The result shows that under the low drag, for certain ranges of the angle of bank and the velocity, the equilibrium solution is multi volume; under certain ranges of air drag, it is possible to descend the velocity of the aircraft and increase the bank angle to improve the verticality of the antenna. But it's impossible to increase the mass of the drogue only to improve the verticality of the antenna.
Operator Decomposition Framework for Perturbation Theory
Energy Technology Data Exchange (ETDEWEB)
Abdel-Khalik, Hany S.; Wang, Congjian; Bang, Young Suk [North Carolina State University, Raleigh (United States)
2012-05-15
This summary describes a new framework for perturbation theory intended to improve its performance, in terms of the associated computational cost and the complexity of implementation, for routine reactor calculations in support of design, analysis, and regulation. Since its first introduction in reactor analysis by Winger, perturbation theory has assumed an aura of sophistication with regard to its implementation and its capabilities. Only few reactor physicists, typically mathematically proficient, have contributed to its development, with the general body of the nuclear engineering community remaining unaware of its current status, capabilities, and challenges. Given its perceived sophistication and the small body of community users, the application of perturbation theory has been limited to investigatory analyses only. It is safe to say that the nuclear community is split into two groups, a small one which understands the theory and, and a much bigger group with the perceived notion that perturbation theory is nothing but a fancy mathematical approach that has very little use in practice. Over the past three years, research has demonstrated two goals. First, reduce the computational cost of perturbation theory in order to enable its use for routine reactor calculations. Second, expose some of the myth about perturbation theory and present it in a form that is simple and relatable in order to stimulate the interest of nuclear practitioners, especially those who are currently working on the development of next generation reactor design and analysis tools. The operator decomposition approach has its roots in linear algebra and can be easily understood by code developers, especially those involved in the design of iterative numerical solution strategies
Evolution of perturbed accelerating relativistic shock waves
Palma, G; Vietri, M; Del Zanna, L
2008-01-01
We study the evolution of an accelerating hyperrelativistic shock under the presence of upstream inhomogeneities wrinkling the discontinuity surface. The investigation is conducted by means of numerical simulations using the PLUTO code for astrophysical fluid dynamics. The reliability and robustness of the code are demonstrated against well known results coming from the linear perturbation theory. We then follow the nonlinear evolution of two classes of perturbing upstream atmospheres and conclude that no lasting wrinkle can be preserved indefinitely by the flow. Finally we derive analytically a description of the geometrical effects of a turbulent upstream ambient on the discontinuity surface.
Scalar and tensor perturbation in vacuum inflation
Huang, Zhiqiang
2016-01-01
It was recently proposed that a small true vacuum universe can inflate spontaneously, in principle. In this paper, this model is completed with experimental results. There should be matter creation in vacuum inflation due to quantum fluctuations, and the matter created will influence the inflation simultaneously. We derive cosmological perturbations in this vacuum inflation model and express them with Hubble flow-functions. By comparing the perturbations with the experimental results, we can determine all the parameters in this model. Finally, we calculate the evolution of the matter density with the determined parameters and show that the matter produced in inflation roughly fits the observations at present.
Matter Density Perturbations in Modified Teleparallel Theories
Wu, Yi-Peng
2012-01-01
We study the matter density perturbations in modified teleparallel gravity theories, where extra degrees of freedom arise from the local Lorentz violation in the tangent space. We formulate a vierbein perturbation with variables addressing all the 16 components of the vierbein field. By assuming the perfect fluid matter source, we examine the cosmological implication of the 6 unfamiliar new degrees of freedom in modified $f(T)$ gravity theories. We find that despite the new modes in the vierbein scenario provide no explicit significant effect in the small-scale regime, they exhibit some deviation from the standard general relativity results in super-horizon scales.
Robustness of braneworld scenarios against tensorial perturbations
Bazeia, D; Menezes, R; Olmo, Gonzalo J; Rubiera-Garcia, D
2015-01-01
Inspired by the peculiarities of the effective geometry of crystalline structures, we reconsider thick brane scenarios from a metric-affine perspective. We show that for a rather general family of theories of gravity, whose Lagrangian is an arbitrary function of the metric and the Ricci tensor, the background and scalar field equations can be written in first-order form, and tensorial perturbations have a non negative definite spectrum, which makes them stable under linear perturbations regardless of the form of the gravity Lagrangian. We find, in particular, that the tensorial zero modes are exactly the same as predicted by Einstein's theory regardless of the scalar field and gravitational Lagrangians.
Non-perturbative QCD and hadron physics
Cobos-Martínez, J. J.
2016-10-01
A brief exposition of contemporary non-perturbative methods based on the Schwinger-Dyson (SDE) and Bethe-Salpeter equations (BSE) of Quantum Chromodynamics (QCD) and their application to hadron physics is given. These equations provide a non-perturbative continuum formulation of QCD and are a powerful and promising tool for the study of hadron physics. Results on some properties of hadrons based on this approach, with particular attention to the pion distribution amplitude, elastic, and transition electromagnetic form factors, and their comparison to experimental data are presented.
Vector Meson Masses in Chiral Perturbation Theory
Bijnens, J; Talavera, P
1997-01-01
We discuss the vector meson masses within the context of Chiral Perturbation Theory performing an expansion in terms of the momenta, quark masses and 1/Nc. We extend the previous analysis to include isospin breaking effects and also include up to order p^4. We discuss vector meson chiral perturbation theory in some detail and present a derivation from a relativistic lagrangian. The unknown coefficients are estimated in various ways. We also discuss the relevance of electromagnetic corrections and the implications of the present calculation for the determination of quark masses.
Perturbations of C*-algebraic Invariants
DEFF Research Database (Denmark)
Christensen, Erik; Sinclair, Allan M.; Smith, Roger R.;
2010-01-01
The setting of the article is the so-called theory of perturbations of algebras of operators. It is shown that several of the properties a C*-algebra may have are preseved under pertubations. The main result states that Pisier's concept finite length is a stasble property.......The setting of the article is the so-called theory of perturbations of algebras of operators. It is shown that several of the properties a C*-algebra may have are preseved under pertubations. The main result states that Pisier's concept finite length is a stasble property....
A generalized perturbation program for CANDU reactor
Energy Technology Data Exchange (ETDEWEB)
Kim, Do Heon; Kim, Jong Kyung [Hanyang University, Seoul (Korea, Republic of); Choi, Hang Bok; Roh, Gyu Hong [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of); Yang, Won Sik [Chosun University, Kwangju (Korea, Republic of)
1998-12-31
A generalized perturbation program has been developed for the purpose of estimating zonal power variation of a CANDU reactor upon refueling operation. The forward and adjoint calculation modules of RFSP code were used to construct the generalized perturbation program. The numerical algorithm for the generalized adjoint flux calculation was verified by comparing the zone power estimates upon refueling with those of forward calculation. It was, however, noticed that the truncation error from the iteration process of the generalized adjoint flux is not negligible. 2 refs., 1 figs., 1 tab. (Author)
Taming perturbative divergences in asymptotically safe gravity
Energy Technology Data Exchange (ETDEWEB)
Benedetti, Dario, E-mail: dbenedetti@perimeterinstitute.c [Perimeter Institute for Theoretical Physics, 31 Caroline St. N, N2L 2Y5, Waterloo ON (Canada); Machado, Pedro F., E-mail: p.f.machado@uu.n [Institute for Theoretical Physics, Utrecht University, 3508 TD Utrecht (Netherlands); Saueressig, Frank, E-mail: Frank.Saueressig@cea.f [Institut de Physique Theorique, CEA Saclay, F-91191 Gif-Sur-Yvette Cedex (France); CNRS URA 2306, F-91191 Gif-Sur-Yvette Cedex (France)
2010-01-01
We use functional renormalization group methods to study gravity minimally coupled to a free scalar field. This setup provides the prototype of a gravitational theory which is perturbatively non-renormalizable at one-loop level, but may possess a non-trivial renormalization group fixed point controlling its UV behavior. We show that such a fixed point indeed exists within the truncations considered, lending strong support to the conjectured asymptotic safety of the theory. In particular, we demonstrate that the counterterms responsible for its perturbative non-renormalizability have no qualitative effect on this feature.
Death to perturbative QCD in exclusive processes?
Energy Technology Data Exchange (ETDEWEB)
Eckardt, R.; Hansper, J.; Gari, M.F. [Institut fuer Theoretische Physik, Bochum (Germany)
1994-04-01
The authors discuss the question of whether perturbative QCD is applicable in calculations of exclusive processes at available momentum transfers. They show that the currently used method of determining hadronic quark distribution amplitudes from QCD sum rules yields wave functions which are completely undetermined because the polynomial expansion diverges. Because of the indeterminacy of the wave functions no statement can be made at present as to whether perturbative QCD is valid. The authors emphasize the necessity of a rigorous discussion of the subject and the importance of experimental data in the range of interest.
Perturbative approach to Markovian open quantum systems.
Li, Andy C Y; Petruccione, F; Koch, Jens
2014-05-08
The exact treatment of Markovian open quantum systems, when based on numerical diagonalization of the Liouville super-operator or averaging over quantum trajectories, is severely limited by Hilbert space size. Perturbation theory, standard in the investigation of closed quantum systems, has remained much less developed for open quantum systems where a direct application to the Lindblad master equation is desirable. We present such a perturbative treatment which will be useful for an analytical understanding of open quantum systems and for numerical calculation of system observables which would otherwise be impractical.
Perturbative QCD at finite temperature and density
Niégawa, A
1997-01-01
This is a comprehensive review on the perturbative hot QCD including the recent developments. The main body of the review is concentrated upon dealing with physical quantities like reaction rates. Contents: \\S1. Introduction, \\S2. Perturbative thermal field theory: Feynman rules, \\S3. Reaction-rate formula, \\S4. Hard-thermal-loop resummation scheme in hot QCD, \\S5. Effective action, \\S6. Hard modes with $|P^2| \\leq O (g^2 T^2)$, hard-thermal-loop resummation scheme, \\S9. Conclusions.
Perturbative renormalization of the electric field correlator
Christensen, C
2016-01-01
The momentum diffusion coefficient of a heavy quark in a hot QCD plasma can be extracted as a transport coefficient related to the correlator of two colour-electric fields dressing a Polyakov loop. We determine the perturbative renormalization factor for a particular lattice discretization of this correlator within Wilson's SU(3) gauge theory, finding a ~12% NLO correction for values of the bare coupling used in the current generation of simulations. The impact of this result on existing lattice determinations is commented upon, and a possibility for non-perturbative renormalization through the gradient flow is pointed out.
Perturbative renormalization of the electric field correlator
Directory of Open Access Journals (Sweden)
C. Christensen
2016-04-01
Full Text Available The momentum diffusion coefficient of a heavy quark in a hot QCD plasma can be extracted as a transport coefficient related to the correlator of two colour-electric fields dressing a Polyakov loop. We determine the perturbative renormalization factor for a particular lattice discretization of this correlator within Wilson's SU(3 gauge theory, finding a ∼12% NLO correction for values of the bare coupling used in the current generation of simulations. The impact of this result on existing lattice determinations is commented upon, and a possibility for non-perturbative renormalization through the gradient flow is pointed out.
Perturbative renormalization of the electric field correlator
Christensen, C.; Laine, M.
2016-04-01
The momentum diffusion coefficient of a heavy quark in a hot QCD plasma can be extracted as a transport coefficient related to the correlator of two colour-electric fields dressing a Polyakov loop. We determine the perturbative renormalization factor for a particular lattice discretization of this correlator within Wilson's SU(3) gauge theory, finding a ∼ 12% NLO correction for values of the bare coupling used in the current generation of simulations. The impact of this result on existing lattice determinations is commented upon, and a possibility for non-perturbative renormalization through the gradient flow is pointed out.
Perturbation of Wavelet and Gabor Frames
Institute of Scientific and Technical Information of China (English)
Ivana Carrizo; Sergio Favier
2003-01-01
In this work two aspects of theory of frames are presented: a side necessary condition on irregular wavelet frames is obtained, another perturbation of wavelet and Gabor frames is considered. Specifically,we present the results obtained on frame stability when one disturbs the mother of wavelet frame, or the parameter of dilatation, and in Gabor frames when the generating function or the parameter of translation are perturbed. In all cases we work without demanding compactness of the support, neither on the generating function, nor on its Fourier transform.
Perturbative and nonperturbative renormalization in lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Goeckeler, M. [Regensburg Univ. (Germany). Institut fuer Theoretische Physik; Horsley, R. [University of Edinburgh (United Kingdom). School of Physics and Astronomy; Perlt, H. [Leipzig Univ. (DE). Institut fuer Theoretische Physik] (and others)
2010-03-15
We investigate the perturbative and nonperturbative renormalization of composite operators in lattice QCD restricting ourselves to operators that are bilinear in the quark fields (quark-antiquark operators). These include operators which are relevant to the calculation of moments of hadronic structure functions. The nonperturbative computations are based on Monte Carlo simulations with two flavors of clover fermions and utilize the Rome-Southampton method also known as the RI-MOM scheme. We compare the results of this approach with various estimates from lattice perturbation theory, in particular with recent two-loop calculations. (orig.)
Manifestly Covariant Gauge-invariant Cosmological Perturbation Theory
Miedema, P G
2010-01-01
It is shown that a first-order cosmological perturbation theory for the open, flat and closed Friedmann-Lemaitre-Robertson-Walker universes admits one, and only one, gauge-invariant variable which describes the perturbation to the energy density and which becomes equal to the usual Newtonian energy density in the non-relativistic limit. The same holds true for the perturbation to the particle number density. Using these two new variables, a new manifestly gauge-invariant cosmological perturbation theory has been developed. Density perturbations evolve diabatically. Perturbations in the total energy density are gravitationally coupled to perturbations in the particle number density, irrespective of the nature of the particles. There is, in first-order, no back-reaction of perturbations to the global expansion of the universe. Small-scale perturbations in the radiation-dominated era oscillate with an increasing amplitude, whereas in older, less precise treatments, oscillating perturbations are found with a decr...
On Self-adjustment of Social Conventions to Small Perturbations
Institute of Scientific and Technical Information of China (English)
JIANG Yi-Chuan
2008-01-01
@@ We present a model for self-adjustment of social conventions to small perturbations, and investigate how pertur-bations can influence the convergence of social convention in different situations.The experimental results show that the sensitivity of social conventions is determined by not only the perturbations themselves but also the agent adjustment functions for the perturbations; and social conventions are more sensitive to the outlier agent number than to the strategy fluctuation magnitudes and localities of perturbations.
Homotopy perturbation method for Ozone decomposition of the second order in aqueous solutions
Directory of Open Access Journals (Sweden)
Ayati Z.
2015-05-01
Full Text Available In this article the problem of mass transfer of ozone of the second order from a gaseous phase into an aqueous phase has been studied. Homotopy perturbation method is employed to derive an analytical approximation to the solutions of the system of differential equations governing on the problem. Some parametric studies have been included. The effects of the temperature and hydroxyl ion reaction order to the solutions are illustrated by some plots
Reduction of some perturbed Keplerian problems
Energy Technology Data Exchange (ETDEWEB)
Inarrea, Manuel [Universidad de La Rioja, Area de Fisica, 26006 Logrono (Spain); Lanchares, Victor [Universidad de La Rioja, Departamento de Matematicas y Computacion, 26004 Logrono (Spain)] e-mail: vlancha@dmc.unirioja.es; Palacian, Jesus F. [Universidad Publica de Navarra, Departamento de Matematica e Informatica, 31006 Pamplona (Spain); Pascual, Ana I. [Universidad de La Rioja, Departamento de Matematicas y Computacion, 26004 Logrono (Spain); Salas, J. Pablo [Universidad de La Rioja, Area de Fisica, 26006 Logrono (Spain); Yanguas, Patricia [Universidad Publica de Navarra, Departamento de Matematica e Informatica, 31006 Pamplona (Spain)
2006-01-01
Perturbed Hamiltonian Keplerian systems enjoying some discrete and continuous symmetries can be brought to a one degree of freedom system containing the main qualitative features of the original one. This reduced system is defined in a compact set of the plane where the qualitative dynamics can be studied in a systematic way.
Homological Perturbation Theory and Mirror Symmetry
Institute of Scientific and Technical Information of China (English)
Jian ZHOU
2003-01-01
We explain how deformation theories of geometric objects such as complex structures,Poisson structures and holomorphic bundle structures lead to differential Gerstenhaber or Poisson al-gebras. We use homological perturbation theory to construct A∞ algebra structures on the cohomology,and their canonically defined deformations. Such constructions are used to formulate a version of A∞algebraic mirror symmetry.
Baryon form factors in chiral perturbation theory
Kubis, B; Kubis, Bastian; Meissner, Ulf-G.
2001-01-01
We analyze the electromagnetic form factors of the ground state baryon octet to fourth order in relativistic baryon chiral perturbation theory. Predictions for the \\Sigma^- charge radius and the \\Lambda-\\Sigma^0 transition moment are found to be in excellent agreement with the available experimental information. Furthermore, the convergence behavior of the hyperon charge radii is shown to be more than satisfactory.
Characterizing heterogeneous cellular responses to perturbations.
Slack, Michael D; Martinez, Elisabeth D; Wu, Lani F; Altschuler, Steven J
2008-12-01
Cellular populations have been widely observed to respond heterogeneously to perturbation. However, interpreting the observed heterogeneity is an extremely challenging problem because of the complexity of possible cellular phenotypes, the large dimension of potential perturbations, and the lack of methods for separating meaningful biological information from noise. Here, we develop an image-based approach to characterize cellular phenotypes based on patterns of signaling marker colocalization. Heterogeneous cellular populations are characterized as mixtures of phenotypically distinct subpopulations, and responses to perturbations are summarized succinctly as probabilistic redistributions of these mixtures. We apply our method to characterize the heterogeneous responses of cancer cells to a panel of drugs. We find that cells treated with drugs of (dis-)similar mechanism exhibit (dis-)similar patterns of heterogeneity. Despite the observed phenotypic diversity of cells observed within our data, low-complexity models of heterogeneity were sufficient to distinguish most classes of drug mechanism. Our approach offers a computational framework for assessing the complexity of cellular heterogeneity, investigating the degree to which perturbations induce redistributions of a limited, but nontrivial, repertoire of underlying states and revealing functional significance contained within distinct patterns of heterogeneous responses.
Electromagnetic Nondestructive Testing by Perturbation Homotopy Method
Directory of Open Access Journals (Sweden)
Liang Ding
2014-01-01
Full Text Available Now electromagnetic nondestructive testing methods have been applied to many fields of engineering. But traditional electromagnetic methods (usually based on least square and local iteration just roughly give the information of location, scale, and quality. In this paper we consider inverse electromagnetic problem which is concerned with the estimation of electric conductivity of Maxwell's equations (2D and 3D. A perturbation homotopy method combined with damping Gauss-Newton methods is applied to the inverse electromagnetic problem. This method differs from traditional homotopy method. The structure of homotopy function is similar to Tikhonov functional. Sets of solutions are produced by perturbation for every homotopy parameter λ=λi, i=0,…,L. At each iterative step of the algorithm, we add stochastic perturbation to numerical solutions. The previous solution and perturbation solution are regarded as the initial value in the next iteration. Although the number of solution in set increased, it increased the likelihood of obtaining correct solution. Results exhibits clear advantages over damping Gauss-Newton method and testify that it is an available method, especially on aspects of wide convergence and precision.
Non-perturbative Heavy Quark Effective Theory
DEFF Research Database (Denmark)
Della Morte, Michele; Heitger, Jochen; Simma, Hubert;
2015-01-01
We review a lattice strategy how to non-perturbatively determine the coefficients in the HQET expansion of all components of the heavy-light axial and vector currents, including 1/m_h-corrections. We also discuss recent preliminary results on the form factors parameterizing semi-leptonic B-decays...
Non-perturbative Heavy Quark Effective Theory
DEFF Research Database (Denmark)
Della Morte, Michele; Heitger, Jochen; Simma, Hubert
2015-01-01
We review a lattice strategy how to non-perturbatively determine the coefficients in the HQET expansion of all components of the heavy-light axial and vector currents, including 1/m_h-corrections. We also discuss recent preliminary results on the form factors parameterizing semi-leptonic B-decays...
The Kepler Problem with Anisotropic Perturbations
Diacu, Florin; Santoprete, Manuele
2009-01-01
We study a 2-body problem given by the sum of the Newtonian potential and an anisotropic perturbation that is a homogeneous function of degree $-\\beta$, $\\beta\\ge 2$. For $\\beta>2$, the sets of initial conditions leading to collisions/ejections and the one leading to escapes/captures have positive measure. For $\\beta>2$ and $\\beta\
Perturbations of ultralight vector field dark matter
Cembranos, J A R; Jareño, S J Núñez
2016-01-01
We study the dynamics of cosmological perturbations in models of dark matter based on ultralight coherent vector fields. Very much as for scalar field dark matter, we find two different regimes in the evolution: for modes with $k^2\\ll {\\cal H}ma$, we have a particle-like behaviour indistinguishable from cold dark matter, whereas for modes with $k^2\\gg {\\cal H}ma$, we get a wave-like behaviour in which the sound speed is non-vanishing and of order $c_s^2\\simeq k^2/m^2a^2$. This implies that, also in these models, structure formation could be suppressed on small scales. However, unlike the scalar case, the fact that the background evolution contains a non-vanishing homogeneous vector field implies that, in general, the evolution of the three kinds of perturbations (scalar, vector and tensor) can no longer be decoupled at the linear level. More specifically, in the particle regime, the three types of perturbations are actually decoupled, whereas in the wave regime, the three vector field perturbations generate o...
Cosmological perturbations from the Standard Model Higgs
Energy Technology Data Exchange (ETDEWEB)
Simone, Andrea De [SISSA, Via Bonomea 265, I-34136 Trieste (Italy); Riotto, Antonio, E-mail: andrea.desimone@sissa.it, E-mail: antonio.riotto@unige.ch [Department of Theoretical Physics and Center for Astroparticle Physics (CAP), 24 quai E. Ansermet, CH-1211 Geneva 4 (Switzerland)
2013-02-01
We propose that the Standard Model (SM) Higgs is responsible for generating the cosmological perturbations of the universe by acting as an isocurvature mode during a de Sitter inflationary stage. In view of the recent ATLAS and CMS results for the Higgs mass, this can happen if the Hubble rate during inflation is in the range (10{sup 10}−10{sup 14}) GeV (depending on the SM parameters). Implications for the detection of primordial tensor perturbations through the B-mode of CMB polarization via the PLANCK satellite are discussed. For example, if the Higgs mass value is confirmed to be m{sub h} = 125.5 GeV and m{sub t},α{sub s} are at their central values, our mechanism predicts tensor perturbations too small to be detected in the near future. On the other hand, if tensor perturbations will be detected by PLANCK through the B-mode of CMB, then there is a definite relation between the Higgs and top masses, making the mechanism predictive and falsifiable.
Quenched chiral perturbation theory to one loop
Colangelo, Gilberto; Pallante, Elisabetta
1998-01-01
We calculate the divergences of the generating functional of quenched chiral perturbation theory at one loop, and renormalize the theory by an appropriate definition of the counterterms. We show that the quenched chiral logarithms can be accounted for by defining a renormalized B0 parameter which, a
Quenched Chiral Perturbation Theory to one loop
Colangelo, G.; Pallante, E.
1998-01-01
The divergences of the generating functional of quenched Chiral Perturbation theory (qCHPT) to one loop are computed in closed form. We show how the quenched chiral logarithms can be reabsorbed in the renormalization of the B0 parameter of the leading order Lagrangian. Finally, we do the chiral powe