Insect Development in Altered Gravitational Environment
Tischler, Marc E.
1996-01-01
When tobacco hornworm (Manduca sexta) larvae burrow underground (25-30 cm) to pupate, they reorient themselves to a relatively horizontal position indicating an ability to sense gravity. To evaluate their sensitivity to gravitational environment during metamorphosis, Manduca (pharate adults) were placed in a vertical (head-up) position. Distinct morphological changes, each one reflecting ensuing phases, were used to follow adult development. Five days after pupation, the vertical group showed accelerated (P less than 0.05) development and were nearly 4 phases ahead (P less than 0.0001) after 10 days. Differences in development in the vertical group were characterized further by increased (7-48%) hemolymph concentrations of 13 amino acids, but a decrease in cys and pro and no change in arg, his, met and val (trp, undetectable). Decreased (36%) turnover of injected H-3 - phenylalanine suggested slower utilization of amino acids contributed, at least partly, to the increased concentrations. Vertically-oriented Manduca also exhibited a greater (20 %, P less than 0.001) protein content in their flight muscles near the end of development. Analysis of hemolymph sugar levels showed a redistribution of sugars from the monosaccharide glucose to the disaccharide trehalose. Since injection of 20-hydroxyecdysone decreased (49%) turnover of H-3- phenylalanine in pharate adults and since ecdysteroids are known to increase flight muscle size and control adult development, these results are consistent with our measuring a greater (+80%, P less than 0.05) ecdysteroid titer in the vertically-oriented insects. These results suggest that gravity environment influences ecdysone output by the pharate adult. When we evaluated hemolymph flow in the head-up and control positions, we found that injected C-14-inulin was distributed somewhat more rapidly in the head-up group irrespective of the sight of injection (head or abdomen) likely because in the head-up position flow of the hemolymph is
Institute of Scientific and Technical Information of China (English)
Airong Qian; Shengmeng Di; Xiang Gao; Wei Zhang; Zongcheng Tian; Jingbao Li; Lifang Hu; Pengfei Yang; Dachuan Yin; Peng Shang
2009-01-01
The diamagnetic levitation as a novel ground-based model for simulating a reduced gravity environment has been widely applied in many fields.In this study,a special designed superconducting magnet,which can produce three apparent gravity levels (0,1,and 2 g),namely high magneto-gravitational environment (HMGE),was used to simulate space gravity environment.The effects of HMGE on osteoblast gene expression profile were investigated by microarray.Genes sensitive to diamagnetic levitation environment (0 g),gravity changes,and high magnetic field changes were sorted on the basis of typical cell func-tions.Cytoskeleton,as an intracellular load-bearing struc-ture,plays an important role in gravity perception.Therefore,13 cytoskeleton-related genes were chosen according to the results of microarray analysis,and the expressions of these genes were found to be altered under HMGE by real-time PCR.Based on the PCR results,the expressions of WASF2 (WAS protein family,member 2),WIPFI (WAS/WASL interacting protein family,member 1),paxillin:and talin 1 were further identified by western blot assay.Results indicated that WASF2 and WIPF1 were more sensitive to altered gravity levels,and talin 1 and paxillin were sensitive to both magnetic field and gravity changes.Our findings demonstrated that HMGE can affect osteoblast gene expression profile and cytoskele-ton-related genes expression.The identification of mechanosensitive genes may enhance our understandings to the mechanism of bone loss induced by microgravity and may provide some potential targets for preventing and treating bone loss or osteoporosis.
Altered Perspectives: Immersive Environments
Shipman, J. S.; Webley, P. W.
2016-12-01
Immersive environments provide an exciting experiential technology to visualize the natural world. Given the increasing accessibility of 360o cameras and virtual reality headsets we are now able to visualize artistic principles and scientific concepts in a fully immersive environment. The technology has become popular for photographers as well as designers, industry, educational groups, and museums. Here we show a sci-art perspective on the use of optics and light in the capture and manipulation of 360o images and video of geologic phenomena and cultural heritage sites in Alaska, England, and France. Additionally, we will generate intentionally altered perspectives to lend a surrealistic quality to the landscapes. Locations include the Catacombs of Paris, the Palace of Versailles, and the Northern Lights over Fairbanks, Alaska. Some 360o view cameras now use small portable dual lens technology extending beyond the 180o fish eye lens previously used, providing better coverage and image quality. Virtual reality headsets range in level of sophistication and cost, with the most affordable versions using smart phones and Google Cardboard viewers. The equipment used in this presentation includes a Ricoh Theta S spherical imaging camera. Here we will demonstrate the use of 360o imaging with attendees being able to be part of the immersive environment and experience our locations as if they were visiting themselves.
Effects of High Magneto-Gravitational Environment on Silkworm Embryogenesis
Tian, Zongcheng; Li, Muwang; Qian, Airong; Xu, Huiyun; Wang, Zhe; Di, Shengmeng; Yang, Pengfei; Hu, Lifang; Ding, Chong; Zhang, Wei; Luo, Mingzhi; Han, Jing; Gao, Xiang; Huang, Yongping; Shang, Peng
2010-04-01
The objective of this research was to observe whether silkworm embryos can survive in a high magneto-gravitational environment (HMGE) and what significant phenotype changes can be produced. The hatching rate, hatching time, life span, growth velocity and cocoon weight of silkworm were measured after silkworm embryos were exposed to HMGE (0 g, 12 T; 1 g, 16 T; and 2 g, 12 T) for a period of time. Compared with the control group, 0 g exposure resulted in a lower hatching rate and a shorter life span. Statistically insignificant morphological changes had been observed for larvae growth velocity, incidence of abnormal markings and weight of cocoons. These results suggest that the effect of HMGE on silkworm embryogenesis is not lethal. Bio-effects of silkworm embryogenesis at 0 g in a HMGE were similar with those of space flight. The hatching time, life span and hatching rates of silkworm may be potential phenotype markers related to exposure in a weightless environment.
Collisional disruption of gravitational aggregates in the tidal environment
Energy Technology Data Exchange (ETDEWEB)
Hyodo, Ryuki; Ohtsuki, Keiji [Department of Earth and Planetary Sciences, Kobe University, Kobe 657-8501 (Japan)
2014-05-20
The degree of disruption in collisions in free space is determined by specific impact energy, and the mass fraction of the largest remnant is a monotonically decreasing function of impact energy. However, it has not been shown whether such a relationship is applicable to collisions under the influence of a planet's tidal force, which is important in ring dynamics and satellite accretion. Here we examine the collisional disruption of gravitational aggregates in the tidal environment by using local N-body simulations. We find that outcomes of such a collision largely depend on the impact velocity, the direction of impact, and the radial distance from the planet. In the case of a strong tidal field corresponding to Saturn's F ring, collisions in the azimuthal direction are much more destructive than those in the radial direction. Numerical results of collisions sensitively depend on the impact velocity, and a complete disruption of aggregates can occur even in impacts with velocity much lower than their escape velocity. In such low-velocity collisions, the deformation of colliding aggregates plays an essential role in determining collision outcomes, because the physical size of the aggregate is comparable to its Hill radius. On the other hand, the dependence of collision outcomes on impact velocity becomes similar to the case in free space when the distance from the planet is sufficiently large. Our results are consistent with Cassini observations of the F ring, which suggest ongoing creation and disruption of aggregates within the ring.
The terrestrial gravitational wave environment from known sources
Webbink, Ronald F.
1993-01-01
The objective of this project was to produce a gravitational wave spectral line list of all known binary stars producing expected strain amplitudes at Earth in excess of h = 10 (exp -21), or gravitational wave fluxes in excess of F = 10 (exp -12) erg cm(exp -2) s(exp -1). These strain and flux limits lie above the anticipated detection thresholds for space-borne laser interferometers capable of detecting gravitational radiation in the 10 micron Hz to 1 Hz frequency range. The source list was intended to provide frequency (including each harmonic), amplitude and phase (for each polarization and harmonic), and celestial coordinates for each system, lacking only the orientation of the principal polarization axis with respect to the pole of the coordinate system, and the sign of the source phase and frequency (or, equivalently, of the sense of rotation of the strain tensor with time) from providing a complete source description. Such a spectral line list would lay essential groundwork for high-sensitivity, low-frequency searches for gravitational radiation.
Without gravity, you would float into space. Gravity pulls matter together: it holds us onto the Earth, it holds the Earth in orbit around the sun and it holds our solar system in orbit about the centre of the galaxy. Everything with mass feels the attraction of gravity. The strength of the attraction between 2 objects depends on their masses. Despite its omnipresence, gravity is the weakest of the 4 forces. It is insignificant at the scale of human beings: when a group of visitors walks past, gravity doesn't pull you towards them! At even smaller scales, the gravitational pull between the electron and the proton is about 1040 times weaker than the electromagnetic attraction between them. Text for the interactive: Why does the same mass weigh more on the Earth than on the moon ?
Qian, Airong; Zhang, Wei; Weng, Yuanyuan; Tian, Zongcheng; Di, Shengmeng; Yang, Pengfei; Yin, Dachuan; Hu, Lifang; Wang, Zhe; Xu, Huiyun; Shang, Peng
The aims of this study are to investigate the effects of gravitational environment produced by a superconducting magnet on osteoblast morphology, proliferation and adhesion. A superconducting magnet which can produce large gradient high magnetic field (LGHMF) and provide three apparent gravity levels (0g,1gand2g) was employed to simulate space gravity environment. The effects of LGHMF on osteoblast morphology, proliferation, adhesion and the gene expression of fibronectin and collagen I were detected by scanning electron microscopy, immunocytochemistry, adhesion assays and real time PCR, respectively, after exposure of osteoblasts to LGHMF for 24 h. Osteoblast morphology was affected by LGHMF (0g,1gand2g) and the most evident morphology alteration was observed at 0g condition. Proliferative abilities of MC3T3 and MG-63 cell were affected under LGHMF (0g,1gand2g) conditions compared to control condition. The adhesive abilities of MC3T3 and MG-63 cells to extracellular matrix (ECM) proteins (fibronectin, laminin, collagen IV) were also affected by LGHMF (0g,1gand2g), moreover, the effects of LGHMF on osteoblast adhesion to different ECM proteins were different. Fibronectin gene expression in MG63 cells under zero gravity condition was increased significantly compared to other conditions. Collagen I gene expression in MG-63 and MC3T3 cells was altered by both magnetic field and alerted gravity. The study indicates that the superconducting magnet which can produce LGHMF may be a novel ground-based space gravity simulator and can be used for biological experiment at cellular level.
Modelling glass alteration in an altered argillaceous environment
Bildstein, O.; Trotignon, L.; Pozo, C.; Jullien, M.
2007-05-01
The long term behaviour of materials such as glass, steel and clay has been investigated in the context of deep geological disposal of radioactive wastes. The interactions between vitrified wastes, canister corrosion products (CPs) and clay are studied using a modified version of the reaction-transport code Crunch, especially looking at pH changes and possible cementation at the interface with the clayey materials. These perturbations may indeed affect the lifetime of glass matrix in deep repositories, e.g., high pH enhances the rate of glass alteration. This work focuses on the argillite of Bure. The calculations were performed at 323 K with a glass alteration rate switching from a high initial rate to a residual rate according to the sorption capacity of CPs. The time at which this sorption capacity is saturated is crucial to the system in terms of wastes package lifetime. The results show that the glass alteration imposes a high pH value at the interface with CPs and clay: up to a value of 9.2, compared to 7.3 which is the initial pH value in the argillite. Experimental data show that the rate of glass alteration is much higher in such pH conditions. For a R7T7-type glass, the rate is about five times higher at pH 9 than at pH 7. This pH perturbation migrates through the clayey domain as a result of the migration of mobile elements such as boron and sodium, and despite the existence of strong pH buffers in the argillite. The cementation of porosity at the interface between glass and clay is predicted by the model due to the massive precipitation of iron corrosion products and glass alteration products. At this point of the evolution of the system, the pH starts to decrease and the alteration rate of the glass could be significantly reduced. This porosity clogging effect is difficult to confirm by experiments especially since existing data on short term experiments tend to show a pervasive precipitation of silica in the domain instead of a localized precipitation
Gravitational loading of a simulated launch alters mRNA expression in osteoblasts
Fitzgerald, J.; Hughes-Fulford, M.
1996-01-01
Serum-deprived mouse osteoblastic cells (MC3T3-E1a) were centrifuged under a regime designed to simulate a space shuttle launch (maximum of 3g). Messenger RNA levels for eight genes involved in bone growth and maintenance were determined using RT-PCR. Following 30 min of centrifugation, mRNA level for early response gene c-fos was significantly increased 89% (P gene osteocalcin was significantly decreased to 44% of control level (P basal mRNA level for TGFbeta3 was detected. In addition, no change in the steady-state synthesis of prostaglandin E2 was detected, possibly due to lack of lipid substrates in serum-deprived cells, suggesting that the increase in c-fos mRNA in response to gravitational loading is a result of mechanical stimulation. These results indicate that a small magnitude mechanical loading, such as that experienced during a shuttle launch, can alter mRNA levels in quiescent osteoblastic cells.
Parker, Donald E
2003-01-01
Preparation for extended travel by astronauts within the Solar System, including a possible manned mission to Mars, requires more complete understanding of adaptation to altered inertial environments. Improved understanding is needed to support development and evaluation of interventions to facilitate adaptations during transitions between those environments. Travel to another planet escalates the adaptive challenge because astronauts will experience prolonged exposure to microgravity before encountering a novel gravitational environment. This challenge would have to be met without ground support at the landing site. Evaluation of current adaptive status as well as intervention efficacy can be performed using perceptual, eye movement and postural measures. Due to discrepancies of adaptation magnitude and time-course among these measures, complete understanding of adaptation processes, as well as intervention evaluation, requires examination of all three. Previous research and theory that provide models for comprehending adaptation to altered inertial environments are briefly examined. Reports from astronauts of selected pre- in- and postflight self-motion illusions are described. The currently controversial tilt-translation reinterpretation hypothesis is reviewed and possible resolutions to the controversy are proposed. Finally, based on apparent gaps in our current knowledge, further research is proposed to achieve a more complete understanding of adaptation as well as to develop effective counter-measures.
Multi-robot path planning in a dynamic environment using improved gravitational search algorithm
Directory of Open Access Journals (Sweden)
P.K. Das
2016-09-01
Full Text Available This paper proposes a new methodology to optimize trajectory of the path for multi-robots using improved gravitational search algorithm (IGSA in a dynamic environment. GSA is improved based on memory information, social, cognitive factor of PSO (particle swarm optimization and then, population for next generation is decided by the greedy strategy. A path planning scheme has been developed using IGSA to optimally obtain the succeeding positions of the robots from the existing position. Finally, the analytical and experimental results of the multi-robot path planning have been compared with those obtained by IGSA, GSA and PSO in a similar environment. The simulation and the Khepera environmental results outperform IGSA as compared to GSA and PSO with respect to performance matrix.
Van Ombergen, Angelique; Wuyts, Floris L; Jeurissen, Ben; Sijbers, Jan; Vanhevel, Floris; Jillings, Steven; Parizel, Paul M; Sunaert, Stefan; Van de Heyning, Paul H; Dousset, Vincent; Laureys, Steven; Demertzi, Athena
2017-06-12
Spaceflight severely impacts the human body. However, little is known about how gravity and gravitational alterations affect the human brain. Here, we aimed at measuring the effects of acute exposure to gravity transitions. We exposed 28 naïve participants to repetitive alterations between normal, hyper- and microgravity induced by a parabolic flight (PF) and measured functional MRI connectivity changes. Scans were acquired before and after the PF. To mitigate motion sickness, PF participants received scopolamine prior to PF. To account for the scopolamine effects, 12 non-PF controls were scanned prior to and after scopolamine injection. Changes in functional connectivity were explored with the Intrinsic Connectivity Contrast (ICC). Seed-based analysis on the regions exhibiting localized changes was subsequently performed to understand the networks associated with the identified nodes. We found that the PF group was characterized by lower ICC scores in the right temporo-parietal junction (rTPJ), an area involved in multisensory integration and spatial tasks. The encompassed network revealed PF-related decreases in within- and inter-hemispheric anticorrelations between the rTPJ and the supramarginal gyri, indicating both altered vestibular and self-related functions. Our findings shed light on how the brain copes with gravity transitions, on gravity internalization and are relevant for the understanding of bodily self-consciousness.
Controlled Environments Enable Adaptive Management in Aquatic Ecosystems Under Altered Environments
Bubenheim, David L.
2016-01-01
Ecosystems worldwide are impacted by altered environment conditions resulting from climate, drought, and land use changes. Gaps in the science knowledge base regarding plant community response to these novel and rapid changes limit both science understanding and management of ecosystems. We describe how CE Technologies have enabled the rapid supply of gap-filling science, development of ecosystem simulation models, and remote sensing assessment tools to provide science-informed, adaptive management methods in the impacted aquatic ecosystem of the California Sacramento-San Joaquin River Delta. The Delta is the hub for California's water, supplying Southern California agriculture and urban communities as well as the San Francisco Bay area. The changes in environmental conditions including temperature, light, and water quality and associated expansion of invasive aquatic plants negatively impact water distribution and ecology of the San Francisco Bay/Delta complex. CE technologies define changes in resource use efficiencies, photosynthetic productivity, evapotranspiration, phenology, reproductive strategies, and spectral reflectance modifications in native and invasive species in response to altered conditions. We will discuss how the CE technologies play an enabling role in filling knowledge gaps regarding plant response to altered environments, parameterization and validation of ecosystem models, development of satellite-based, remote sensing tools, and operational management strategies.
Vestibular adaption to an altered gravitational environment: consequences for spatial orientation
Nooij, S.A.E.
2008-01-01
Earth's gravity is an omnipresent factor in human life and provides a strong reference for spatial orientation. Changes in the prevailing gravity level, like the transition to weightlessness during space flight, affect spatial orientation and require adaptation of many physiological processes involv
Probing the environment of gravitational wave transient sources with TeV afterglow emission
Zhu, Qin-Yu
2016-01-01
Recently, Advanced Laser Interferometer Gravitational-wave Observatory (aLIGO) detected gravitational wave (GW) transients from mergers of binary black holes (BHs). The system may also produce a wide-angle, relativistic outflow if the claimed short GRB detected by GBM is in real association with GW 150914. It was suggested that mergers of double neutron stars (or neutron star-black hole binaries), another promising source of GW transients, also produce fast, wide-angle outflows. In this paper, we calculate the high-energy gamma-ray emission arising from the blast waves driven by these wide-angle outflows. We find that TeV emission arising from the inverse-Compton process in the relativistic outflow resulted from mergers of binary BHs similar to those in GW 150914 could be detectable by ground-based IACT telescopes such as Cherenkov Telescope Array (CTA) if the sources occur in { a dense medium with density $n > 0.3 cm^{-3}$}. For neutron star-neutron star (NS-NS) and NS-BH mergers, TeV emission from the wide-...
Gorgiladze, G I; Bukiia, R D; Kalandarishvili, É L; Korotkova, E V; Taktakishvili, A D; Davitashvili, M T; Gelashvili, N Sh
2011-01-01
Light and scanning electron microscopy was used to study the morphological parameters and ultrastructure of Helix lucorum statocysts and statoliths in Pomatias rivulare statocysts after 56, 93 and 110-day exposure to microgravity aboard the ISS. Increased gravity was simulated by 30-d centrifugation at 6 g. On the first day of recovery, many statoconia and statoliths were found to carry numerous warts. Moreover, statoconia grew in number significantly as compared with the ground control. On the contrary centrifugation caused massive destruction of statoconia. In a month after orbital flight and centrifugation morphology of both statoconia and stastoliths was nearly normal. These results evidence, that the gravitational field is an important factor for the abiotic medium responsible for building up the inertial mass in the equilibrium organ of animals.
Micromégas: Altered Body-Environment Scaling in Literary Fiction.
Dieguez, Sebastian
2016-01-01
Architectonic embodiment postulates a bidirectional link between bodily awareness and the architectural environment. The standard size and features of the human body, for instance, are thought to influence the structure of interiors and buildings, as well as their perception and appreciation. Whereas architectural practice and theory, the visual arts and more recently the cognitive sciences have explored this relationship of humans with their crafted environments, many fictional literary works have long experimented with alterations of body-environment scaling. This so-called Gulliver theme - popular in the science-fiction genre but also in children's literature and philosophical satire - reveals, as a recurrent thought-experiment, our preoccupation with proportions and our fascination for the infinitely small and large. Here I provide an overview of the altered scaling theme in literature, including classics such as Voltaire's Micromégas, Swift's Gulliver's Travels, Caroll's Alice, and Matheson's The Shrinking man, closely examining issues relevant to architectonic embodiment such as: bodily, perceptual, cognitive, affective, and social changes related to alterations in body size relative to people, objects and architectural environments. I next provide a taxonomy of the Gulliver theme and highlight its main psychological features, and then proceed to review relevant work from cognitive science. Although fictional alterations of body-environment scaling far outreach current possibilities in experimental research, I argue that the peripetiae and morals outlined in the literary realm, as products of the human imagination, provide a unique window into the folk-psychology of body and space.
Hausrath, Elisabeth M; Tschauner, Oliver
2013-11-01
Fumaroles represent a very important potential habitat on Mars because they contain water and nutrients. Global deposition of volcanic sulfate aerosols may also have been an important soil-forming process affecting large areas of Mars. Here we identify alteration from the Senator fumarole, northwest Nevada, USA, and in low-temperature environments near the fumarole to help interpret fumarolic and acid vapor alteration of rocks and soils on Mars. We analyzed soil samples and fluorapatite, olivine, and basaltic glass placed at and near the fumarole in in situ mineral alteration experiments designed to measure weathering under natural field conditions. Using synchrotron X-ray diffraction, we clearly observe hydroxyl-carbonate-bearing fluorapatite as a fumarolic alteration product of the original material, fluorapatite. The composition of apatites as well as secondary phosphates has been previously used to infer magmatic conditions as well as fumarolic conditions on Mars. To our knowledge, the observations reported here represent the first documented instance of formation of hydroxyl-carbonate-bearing apatite from fluorapatite in a field experiment. Retreat of olivine surfaces, as well as abundant NH4-containing minerals, was also characteristic of fumarolic alteration. In contrast, alteration in the nearby low-temperature environment resulted in formation of large pits on olivine surfaces, which were clearly distinguishable from the fumarolic alteration. Raman signatures of some fumarolically impacted surfaces are consistent with detection of the biological molecules chlorophyll and scytenomin, potentially useful biosignatures. Observations of altered minerals on Mars may therefore help identify the environment of formation and understand the aqueous history and potential habitability of that planet.
Micromégas: altered body-environment scaling in literary fiction
Directory of Open Access Journals (Sweden)
Sebastian eDieguez
2016-04-01
Full Text Available Architectonic embodiment postulates a bidirectional link between bodily awareness and the architectural environment. The standard size and features of the human body, for instance, are thought to influence the structure of interiors and buildings, as well as their perception and appreciation. Whereas architectural practice and theory, the visual arts and more recently the cognitive sciences have explored this relationship of humans with their crafted environments, many fictional literary works have long experimented with alterations of body-environment scaling. This so-called Gulliver theme - popular in the science-fiction genre but also in children’s literature and philosophical satire – reveals, as a recurrent thought-experiment, our preoccupation with proportions and our fascination for the infinitely small and large. Here I provide an overview of the altered scaling theme in literature, including classics such as Voltaire’s Micromégas, Swift’s Gulliver’s Travels, Caroll’s Alice and Matheson’s The Shrinking man, closely examining issues relevant to architectonic embodiment such as: bodily, perceptual, cognitive, affective, and social changes related to alterations in body size relative to people, objects and architectural environments. I next provide a taxonomy of the Gulliver theme and highlight its main psychological features, and then proceed to review relevant work from cognitive science. Although fictional alterations of body-environment scaling far outreach current possibilities in experimental research, I argue that the peripetiae and morals outlined in the literary realm, as products of the human imagination, provide a unique window into the folk-psychology of body and space.
Micromégas: Altered Body–Environment Scaling in Literary Fiction
Dieguez, Sebastian
2016-01-01
Architectonic embodiment postulates a bidirectional link between bodily awareness and the architectural environment. The standard size and features of the human body, for instance, are thought to influence the structure of interiors and buildings, as well as their perception and appreciation. Whereas architectural practice and theory, the visual arts and more recently the cognitive sciences have explored this relationship of humans with their crafted environments, many fictional literary works have long experimented with alterations of body–environment scaling. This so-called Gulliver theme – popular in the science-fiction genre but also in children’s literature and philosophical satire – reveals, as a recurrent thought-experiment, our preoccupation with proportions and our fascination for the infinitely small and large. Here I provide an overview of the altered scaling theme in literature, including classics such as Voltaire’s Micromégas, Swift’s Gulliver’s Travels, Caroll’s Alice, and Matheson’s The Shrinking man, closely examining issues relevant to architectonic embodiment such as: bodily, perceptual, cognitive, affective, and social changes related to alterations in body size relative to people, objects and architectural environments. I next provide a taxonomy of the Gulliver theme and highlight its main psychological features, and then proceed to review relevant work from cognitive science. Although fictional alterations of body-environment scaling far outreach current possibilities in experimental research, I argue that the peripetiae and morals outlined in the literary realm, as products of the human imagination, provide a unique window into the folk-psychology of body and space. PMID:27148156
Gravitational lensing by gravitational waves
Bisnovatyi-Kogan, G. S.; Tsupko, O. Yu.
2008-01-01
Gravitational lensing by gravitational wave is considered. We notice that although final and initial direction of photons coincide, displacement between final and initial trajectories occurs. This displacement is calculated analytically for the plane gravitational wave pulse. Estimations for observations are discussed.
Foster, B. G.
1974-01-01
Preflight studies on Aeromonas proteolytica are reported to investigate the possibility of genetic alterations resulting in increased proteolysis in spacecraft environments. This organism may be present on human tissue and could pose medical problems if its endopeptidase and a hemolysin were to be produced in ususually high quantities or altered in such a way as to be more effective in their activities. Considered are: (1) Development of a nutrative holding medium for suspension of organisms; (2) the establishment of baseline information for the standardization of the assay for endopeptidase levels and hemolytic titers; (3) formulation of a method by which intracutaneous hemorrhage could be quantitated in guinea pig tissue; and (4) the responses of these organisms to parameters of spaceflight and experimentation.
Competition and soil resource environment alter plant–soil feedbacks for native and exotic grasses
Larios, Loralee; Suding, Katharine N.
2015-01-01
Feedbacks between plants and soil biota are increasingly identified as key determinants of species abundance patterns within plant communities. However, our understanding of how plant–soil feedbacks (PSFs) may contribute to invasions is limited by our understanding of how feedbacks may shift in the light of other ecological processes. Here we assess how the strength of PSFs may shift as soil microbial communities change along a gradient of soil nitrogen (N) availability and how these dynamics may be further altered by the presence of a competitor. We conducted a greenhouse experiment where we grew native Stipa pulchra and exotic Avena fatua, alone and in competition, in soils inoculated with conspecific and heterospecific soil microbial communities conditioned in low, ambient and high N environments. Stipa pulchra decreased in heterospecific soil and in the presence of a competitor, while the performance of the exotic A. fatua shifted with soil microbial communities from altered N environments. Moreover, competition and soil microbial communities from the high N environment eliminated the positive PSFs of Stipa. Our results highlight the importance of examining how individual PSFs may interact in a broader community context and contribute to the establishment, spread and dominance of invaders. PMID:25425557
Grigoryan, L. S.; Saakyan, G. S.
1984-09-01
The existence of a special gravitational vacuum is considered in this paper. A phenomenological method differing from the traditional Einsteinian formalization is utilized. Vacuum, metric and matter form a complex determined by field equations and at great distances from gravitational masses vacuum effects are small but could be large in powerful fields. Singularities and black holes justify the approach as well as the Ambartsmyan theory concerning the existence of supermassive and superdense prestallar bodies that then disintegrate. A theory for these superdense bodies is developed involving gravitational field equations that describe the vacuum by an energy momentum tensor and define the field and mass distribution. Computations based on the theory for gravitational radii with incompressible liquid models adequately reflecting real conditions indicate that a gravitational vacuum could have considerable effects on superdense stars and could have radical effects for very large masses.
Directory of Open Access Journals (Sweden)
Bronwen Martin
Full Text Available Reproductive capacity and nutritional input are tightly linked and animals' specific responses to alterations in their physical environment and food availability are crucial to ensuring sustainability of that species. We have assessed how alterations in dietary energy intake (both reductions and excess, as well as in food availability, via intermittent fasting (IF, affect the gonadal transcriptome of both male and female rats. Starting at four months of age, male and female rats were subjected to a 20% or 40% caloric restriction (CR dietary regime, every other day feeding (IF or a high fat-high glucose (HFG diet for six months. The transcriptional activity of the gonadal response to these variations in dietary energy intake was assessed at the individual gene level as well as at the parametric functional level. At the individual gene level, the females showed a higher degree of coherency in gonadal gene alterations to CR than the males. The gonadal transcriptional and hormonal response to IF was also significantly different between the male and female rats. The number of genes significantly regulated by IF in male animals was almost 5 times greater than in the females. These IF males also showed the highest testosterone to estrogen ratio in their plasma. Our data show that at the level of gonadal gene responses, the male rats on the IF regime adapt to their environment in a manner that is expected to increase the probability of eventual fertilization of females that the males predict are likely to be sub-fertile due to their perception of a food deficient environment.
Energy Technology Data Exchange (ETDEWEB)
Shnir, Ya. M., E-mail: shnir@theor.jinr.ru [Joint Institute for Nuclear Research (Russian Federation)
2015-12-15
We construct solutions of the 3 + 1 dimensional Faddeev–Skyrme model coupled to Einstein gravity. The solutions are static and asymptotically flat. They are characterized by a topological Hopf number. We investigate the dependence of the ADM masses of gravitating Hopfions on the gravitational coupling. When gravity is coupled to flat space solutions, a branch of gravitating Hopfion solutions arises and merges at a maximal value of the coupling constant with a second branch of solutions. This upper branch has no flat space limit. Instead, in the limit of a vanishing coupling constant, it connects to either the Bartnik–McKinnon or a generalized Bartnik–McKinnon solution. We further find that in the strong-coupling limit, there is no difference between the gravitating solitons of the Skyrme model and the Faddeev–Skyrme model.
Bini, Donato; Chicone, Carmen; Mashhoon, Bahram
2008-01-01
We study the linear post-Newtonian approximation to general relativity known as gravitoelectromagnetism (GEM); in particular, we examine the similarities and differences between GEM and electrodynamics. Notwithstanding some significant differences between them, we find that a special nonstationary metric in GEM can be employed to show {\\it explicitly} that it is possible to introduce gravitational induction within GEM in close analogy with Faraday's law of induction and Lenz's law in electrodynamics. Some of the physical implications of gravitational induction are briefly discussed.
Microbiome interplay: plants alter microbial abundance and diversity within the built environment.
Mahnert, Alexander; Moissl-Eichinger, Christine; Berg, Gabriele
2015-01-01
The built indoor microbiome has importance for human health. Residents leave their microbial fingerprint but nothing is known about the transfer from plants. Our hypothesis that indoor plants contribute substantially to the microbial abundance and diversity in the built environment was experimentally confirmed as proof of principle by analyzing the microbiome of the spider plant Chlorophytum comosum in relation to their surroundings. The abundance of Archaea, Bacteria, and Eukaryota (fungi) increased on surrounding floor and wall surfaces within 6 months of plant isolation in a cleaned indoor environment, whereas the microbial abundance on plant leaves and indoor air remained stable. We observed a microbiome shift: the bacterial diversity on surfaces increased significantly but fungal diversity decreased. The majority of cells were intact at the time of samplings and thus most probably alive including diverse Archaea as yet unknown phyllosphere inhabitants. LEfSe and network analysis showed that most microbes were dispersed from plant leaves to the surrounding surfaces. This led to an increase of specific taxa including spore-forming fungi with potential allergic potential but also beneficial plant-associated bacteria, e.g., Paenibacillus. This study demonstrates for the first time that plants can alter the microbiome of a built environment, which supports the significance of plants and provides insights into the complex interplay of plants, microbiomes and human beings.
Microbiome interplay: plants alter microbial abundance and diversity within the built environment
Directory of Open Access Journals (Sweden)
Alexander eMahnert
2015-08-01
Full Text Available The built indoor microbiome has importance for human health. Residents leave their microbial fingerprint but nothing is known about the transfer from plants. Our hypothesis that indoor plants contribute substantially to the microbial abundance and diversity in the built environment was experimentally confirmed as proof of principle by analyzing the microbiome of the spider plant Chlorophytum comosum in relation to their surroundings. The abundance of Archaea, Bacteria and Eukaryota (fungi increased on surrounding floor and wall surfaces within six months of plant isolation in a cleaned indoor environment, whereas the microbial abundance on plant leaves and indoor air remained stable. We observed a microbiome shift: the bacterial diversity on surfaces increased significantly but fungal diversity decreased. The majority of cells were intact at the time of samplings and thus most probably alive including diverse Archaea as yet unknown phyllosphere inhabitants. LEfSe and network analysis showed that most microbes were dispersed from plant leaves to the surrounding surfaces. This led to an increase of specific taxa including spore-forming fungi with potential allergic potential but also beneficial plant-associated bacteria, e.g. Paenibacillus. This study demonstrates for the first time that plants can alter the microbiome of a built environment, which supports the significance of plants and provides insights into the complex interplay of plants, microbiomes and human beings.
Gravitational waves from gravitational collapse
Energy Technology Data Exchange (ETDEWEB)
Fryer, Christopher L [Los Alamos National Laboratory; New, Kimberly C [Los Alamos National Laboratory
2008-01-01
Gravitational wave emission from stellar collapse has been studied for nearly four decades. Current state-of-the-art numerical investigations of collapse include those that use progenitors with more realistic angular momentum profiles, properly treat microphysics issues, account for general relativity, and examine non-axisymmetric effects in three dimensions. Such simulations predict that gravitational waves from various phenomena associated with gravitational collapse could be detectable with ground-based and space-based interferometric observatories. This review covers the entire range of stellar collapse sources of gravitational waves: from the accretion induced collapse of a white dwarf through the collapse down to neutron stars or black holes of massive stars to the collapse of supermassive stars.
Gravitational Waves from Gravitational Collapse
Directory of Open Access Journals (Sweden)
Chris L. Fryer
2011-01-01
Full Text Available Gravitational-wave emission from stellar collapse has been studied for nearly four decades. Current state-of-the-art numerical investigations of collapse include those that use progenitors with more realistic angular momentum profiles, properly treat microphysics issues, account for general relativity, and examine non-axisymmetric effects in three dimensions. Such simulations predict that gravitational waves from various phenomena associated with gravitational collapse could be detectable with ground-based and space-based interferometric observatories. This review covers the entire range of stellar collapse sources of gravitational waves: from the accretion-induced collapse of a white dwarf through the collapse down to neutron stars or black holes of massive stars to the collapse of supermassive stars.
Bartoli, Giacomo; Bottega, Stefania; Forino, Laura M C; Ciccarelli, Daniela; Spanò, Carmelina
2014-02-01
Cistus salviifolius is able to colonise one of the most extreme active geothermal alteration fields in terms of both soil acidity and hot temperatures. The analyses of morpho-functional and physiological characters, investigated in leaves of plants growing around fumaroles (G leaves) and in leaves developed by the same plants after transfer into growth chamber under controlled conditions (C leaves) evidenced the main adaptive traits developed by this pioneer plant in a stressful environment. These traits involved leaf shape and thickness, mesophyll compactness, stomatal and trichome densities, chloroplast size. Changes of functional and physiological traits concerned dry matter content, peroxide and lipid peroxidation, leaf area, relative water and pigment contents. A higher reducing power and antioxidant enzymatic activity were typical of G leaves. Though the high levels of stress parameters, G leaves showed stress-induced specific morphogenic and physiological responses putatively involved in their surviving in active geothermal habitats.
Cell-to-cell communication and cellular environment alter the somatostatin status of delta cells
Energy Technology Data Exchange (ETDEWEB)
Kelly, Catriona, E-mail: catriona.kelly@qub.ac.uk [SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine (United Kingdom); Flatt, Peter R.; McClenaghan, Neville H. [SAAD Centre for Pharmacy and Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine (United Kingdom)
2010-08-20
Research highlights: {yields} TGP52 cells display enhanced functionality in pseudoislet form. {yields} Somatostatin content was reduced, but secretion increased in high glucose conditions. {yields} Cellular interactions and environment alter the somatostatin status of TGP52 cells. -- Abstract: Introduction: Somatostatin, released from pancreatic delta cells, is a potent paracrine inhibitor of insulin and glucagon secretion. Islet cellular interactions and glucose homeostasis are essential to maintain normal patterns of insulin secretion. However, the importance of cell-to-cell communication and cellular environment in the regulation of somatostatin release remains unclear. Methods: This study employed the somatostatin-secreting TGP52 cell line maintained in DMEM:F12 (17.5 mM glucose) or DMEM (25 mM glucose) culture media. The effect of pseudoislet formation and culture medium on somatostatin content and release in response to a variety of stimuli was measured by somatostatin EIA. In addition, the effect of pseudoislet formation on cellular viability (MTT and LDH assays) and proliferation (BrdU ELISA) was determined. Results: TGP52 cells readily formed pseudoislets and showed enhanced functionality in three-dimensional form with increased E-cadherin expression irrespective of the culture environment used. However, culture in DMEM decreased cellular somatostatin content (P < 0.01) and increased somatostatin secretion in response to a variety of stimuli including arginine, calcium and PMA (P < 0.001) when compared with cells grown in DMEM:F12. Configuration of TGP52 cells as pseudoislets reduced the proliferative rate and increased cellular cytotoxicity irrespective of culture medium used. Conclusions: Somatostatin secretion is greatly facilitated by cell-to-cell interactions and E-cadherin expression. Cellular environment and extracellular glucose also significantly influence the function of delta cells.
Classical Gravitational Interactions and Gravitational Lorentz Force
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
In quantum gauge theory of gravity, the gravitational field is represented by gravitational gauge field.The field strength of gravitational gauge field has both gravitoelectric component and gravitomagnetic component. In classical level, gauge theory of gravity gives classical Newtonian gravitational interactions in a relativistic form. Besides,it gives gravitational Lorentz force, which is the gravitational force on a moving object in gravitomagnetic field The direction of gravitational Lorentz force is not the same as that of classical gravitational Newtonian force. Effects of gravitational Lorentz force should be detectable, and these effects can be used to discriminate gravitomagnetic field from ordinary electromagnetic magnetic field.
Chen, Siyuan; Sesana, Alberto; Del Pozzo, Walter
2017-09-01
We present a fast and versatile method to calculate the characteristic spectrum hc of the gravitational wave background (GWB) emitted by a population of eccentric massive black hole binaries (MBHBs). We fit the spectrum of a reference MBHB with a simple analytic function and show that the spectrum of any other MBHB can be derived from this reference spectrum via simple scalings of mass, redshift and frequency. We then apply our calculation to a realistic population of MBHBs evolving via three-body scattering of stars in galactic nuclei. We demonstrate that our analytic prescription satisfactorily describes the signal in the frequency band relevant to pulsar timing array (PTA) observations. Finally, we model the high-frequency steepening of the GWB to provide a complete description of the features characterizing the spectrum. For typical stellar distributions observed in massive galaxies, our calculation shows that three-body scattering alone is unlikely to affect the GWB in the PTA band and a low-frequency turnover in the spectrum is caused primarily by high eccentricities.
Dodelson, Scott
2017-01-01
Gravitational lensing is a consequence of general relativity, where the gravitational force due to a massive object bends the paths of light originating from distant objects lying behind it. Using very little general relativity and no higher level mathematics, this text presents the basics of gravitational lensing, focusing on the equations needed to understand the phenomena. It then applies them to a diverse set of topics, including multiply imaged objects, time delays, extrasolar planets, microlensing, cluster masses, galaxy shape measurements, cosmic shear, and lensing of the cosmic microwave background. This approach allows undergraduate students and others to get quickly up to speed on the basics and the important issues. The text will be especially relevant as large surveys such as LSST and Euclid begin to dominate the astronomical landscape. Designed for a one semester course, it is accessible to anyone with two years of undergraduate physics background.
Galtsov, D V
2001-01-01
Recent progress in the study of solitons and black holes in non-Abelian field theories coupled to gravity is reviewed. New topics include gravitational binding of monopoles, black holes with non-trivial topology, Lue-Weinberg bifurcation, asymptotically AdS lumps, solutions to the Freedman-Schwarz model with applications to holography, non-Abelian Born-Infeld solutions
Bassi, Angelo; Großardt, André; Ulbricht, Hendrik
2017-10-01
We discuss effects of loss of coherence in low energy quantum systems caused by or related to gravitation, referred to as gravitational decoherence. These effects, resulting from random metric fluctuations, for instance, promise to be accessible by relatively inexpensive table-top experiments, way before the scales where true quantum gravity effects become important. Therefore, they can provide a first experimental view on gravity in the quantum regime. We will survey models of decoherence induced both by classical and quantum gravitational fluctuations; it will be manifest that a clear understanding of gravitational decoherence is still lacking. Next we will review models where quantum theory is modified, under the assumption that gravity causes the collapse of the wave functions, when systems are large enough. These models challenge the quantum-gravity interplay, and can be tested experimentally. In the last part we have a look at the state of the art of experimental research. We will review efforts aiming at more and more accurate measurements of gravity (G and g) and ideas for measuring conventional and unconventional gravity effects on nonrelativistic quantum systems.
Implications of the gravitational wave event GW150914
Miller, M. Coleman
2016-07-01
The era of gravitational-wave astronomy began on 14 September 2015, when the LIGO Scientific Collaboration detected the merger of two ˜30 M_⊙ black holes at a distance of {˜ }400 Mpc. This event has facilitated qualitatively new tests of gravitational theories, and has also produced exciting information about the astrophysical origin of black hole binaries. In this review we discuss the implications of this event for gravitational physics and astrophysics, as well as the expectations for future detections. In brief: (1) because the spins of the black holes could not be measured accurately and because mergers are not well calculated for modified theories of gravity, the current analysis of GW150914 does not place strong constraints on gravity variants that change only the generation of gravitational waves, but (2) it does strongly constrain alterations of the propagation of gravitational waves and alternatives to black holes. Finally, (3) many astrophysical models for the origin of heavy black hole binaries such as the GW150914 system are in play, but a reasonably robust conclusion that was reached even prior to the detection is that the environment of such systems needs to have a relatively low abundance of elements heavier than helium.
Mishima, Eikan; Fukuda, Shinji; Shima, Hisato; Hirayama, Akiyoshi; Akiyama, Yasutoshi; Takeuchi, Yoichi; Fukuda, Noriko N; Suzuki, Takehiro; Suzuki, Chitose; Yuri, Akinori; Kikuchi, Koichi; Tomioka, Yoshihisa; Ito, Sadayoshi; Soga, Tomoyoshi; Abe, Takaaki
2015-08-01
The accumulation of uremic toxins is involved in the progression of CKD. Various uremic toxins are derived from gut microbiota, and an imbalance of gut microbiota or dysbiosis is related to renal failure. However, the pathophysiologic mechanisms underlying the relationship between the gut microbiota and renal failure are still obscure. Using an adenine-induced renal failure mouse model, we evaluated the effects of the ClC-2 chloride channel activator lubiprostone (commonly used for the treatment of constipation) on CKD. Oral administration of lubiprostone (500 µg/kg per day) changed the fecal and intestinal properties in mice with renal failure. Additionally, lubiprostone treatment reduced the elevated BUN and protected against tubulointerstitial damage, renal fibrosis, and inflammation. Gut microbiome analysis of 16S rRNA genes in the renal failure mice showed that lubiprostone treatment altered their microbial composition, especially the recovery of the levels of the Lactobacillaceae family and Prevotella genus, which were significantly reduced in the renal failure mice. Furthermore, capillary electrophoresis-mass spectrometry-based metabolome analysis showed that lubiprostone treatment decreased the plasma level of uremic toxins, such as indoxyl sulfate and hippurate, which are derived from gut microbiota, and a more recently discovered uremic toxin, trans-aconitate. These results suggest that lubiprostone ameliorates the progression of CKD and the accumulation of uremic toxins by improving the gut microbiota and intestinal environment.
Gravitational Radiation from Oscillating Gravitational Dipole
De Aquino, Fran
2002-01-01
The concept of Gravitational Dipole is introduced starting from the recent discovery of negative gravitational mass (gr-qc/0005107 and physics/0205089). A simple experiment, a gravitational wave transmitter, to test this new concept of gravitational radiation source is presented.
Ciufolini, I; Moschella, U; Fre, P
2001-01-01
Gravitational waves (GWs) are a hot topic and promise to play a central role in astrophysics, cosmology, and theoretical physics. Technological developments have led us to the brink of their direct observation, which could become a reality in the coming years. The direct observation of GWs will open an entirely new field: GW astronomy. This is expected to bring a revolution in our knowledge of the universe by allowing the observation of previously unseen phenomena, such as the coalescence of compact objects (neutron stars and black holes), the fall of stars into supermassive black holes, stellar core collapses, big-bang relics, and the new and unexpected.With a wide range of contributions by leading scientists in the field, Gravitational Waves covers topics such as the basics of GWs, various advanced topics, GW detectors, astrophysics of GW sources, numerical applications, and several recent theoretical developments. The material is written at a level suitable for postgraduate students entering the field.
Bini, Donato; Cherubini, Christian; Chicone, Carmen; Mashhoon, Bahram
2008-01-01
We study the linear post-Newtonian approximation to general relativity known as gravitoelectromagnetism (GEM); in particular, we examine the similarities and differences between GEM and electrodynamics. Notwithstanding some significant differences between them, we find that a special nonstationary metric in GEM can be employed to show {\\it explicitly} that it is possible to introduce gravitational induction within GEM in close analogy with Faraday's law of induction and Lenz's law in electrod...
Hakim, Rémi
1994-01-01
Il existe à l'heure actuelle un certain nombre de théories relativistes de la gravitation compatibles avec l'expérience et l'observation. Toutefois, la relativité générale d'Einstein fut historiquement la première à fournir des résultats théoriques corrects en accord précis avec les faits.
Determination of Geochemical Characteristics of Glass Alteration Environments Using Boron Isotopes
Pauly, B. D.; Williams, L. B.; Hervig, R.; Zierenberg, R. A.; Schiffman, P.
2012-12-01
Palagonite (palagonitized sideromelane) is the initial, low-temperature alteration product of basaltic glass in the presence of water and/or water vapor. High-resolution transmission electron microscopy shows that palagonite is a mineraloid consisting of sheeted, smectite-like areas and amorphous areas. The presence of clay-like material raises the possibility for environmentally-controlled boron isotope fractionation during palagonitization, potentially similar to that observed due to formation of authigenic clay in bentonites. We measured boron isotope ratios in thin-sectioned palagonite samples using secondary-ion mass spectrometry (SIMS), and devised a procedure for in-situ removal of surface contaminants of boron as well as boron within the interlayers of this authigenic material, permitting determination of both bulk and tetrahedral boron isotopic ratios. The samples were basaltic hyaloclastites from submarine volcaniclastic, submarine volcanic, and marine phreatomagmatic environments. Measured tetrahedral boron isotopic ratios (δ11B) ranged from -7.7 (±2.2) to 43.6 (±0.9)‰. All samples with relatively heavy δ11B values also had relatively low initial porosities (determined by point counting), whereas all but one of the samples with relatively light δ11B values also had relatively high initial porosities. In previous clay mineralization studies, boron isotope fractionation has been shown to depend not only on temperature but also on the proportions of aqueous B(OH)3 and B(OH)4-, which is controlled by pH. At high pH, tetrahedral B(OH)4- is the dominant aqueous species, so relatively less B-isotope fractionation occurs than at low pH, where trigonal B(OH)3 is the dominant aqueous species. During palagonitization at high pH, the measured tetrahedral δ11B would be closer to δ11B of the water (less fractionation), whereas at low pH, the measured tetrahedral δ11B would be significantly lighter than δ11B of the water (more fractionation). Geochemical
Post-depositional alteration of benthic foraminifera in a methane seep environment
Schneider, Andrea; Cremiere, Antoine; Panieri, Giuliana; Lepland, Aivo; Knies, Jochen
2016-04-01
Benthic foraminifera tests from the sediment cores taken from the Vestnesa Ridge, one of the northernmost known marine methane hydrate reservoir, were studied for their visual appearance, mineral and stable carbon isotopic composition in order to explore their indicator potential in a methane seep environment. The Vestnesa Ridge is a sediment drift located in 1200m water depth at 79°N at Svalbard's northwestern continental margin. Observations of gas flares originating from pockmarks that are aligned along the crest of the ridge show ongoing methane emission. A distinct sediment layer containing a fossilized assemblage of chemosynthetic bivalves indicates methane seepage activity at least in the late Pleistocene. We have examined the state of preservation and geochemical characteristics of foraminifera tests from this bivalve shell horizon. Tests of the benthic foraminifera species Cassidulina neoteretis display a variable degree of post-depositional alteration and formation of diagenetic carbonate overgrowths on calcitic primary tests. Using binoculars, scanning electron microscope imagery and energy dispersive x-ray spectroscopy, we distinguish visually and mineralogically different diagenetic phases on the external and internal test surfaces. Pristine and smooth test surfaces act as nucleation templates for precipitation of authigenic Mg-calcite crystals causing complete filling of chambers and encrustation of the external test surfaces. The presence of Mg-calcite indicates the overgrowth is precipitating in sulfate-poor sediments. In addition to benthic foraminifera, we have studied the mineralogical and stable carbon and oxygen isotope composition of authigenic carbonate nodules found in the bivalve shell horizon. The mineralogical nature of the carbonates and overgrowths on the foraminifera tests were found to be identical. The δ13C value of the carbonate nodules is as low as -32.3‰ indicating their methane-derived origin. Authigenic carbonate coated
Gravitational redshift from rotating body having intense magnetic field
Dubey, Anuj Kumar
2016-01-01
It is well known fact that gravitational field can alter the space-time structure and gravitational redshift is its one example. Electromagnetic field can also alter the space-time similar to gravitational field. So electromagnetic field can give rise to an additional effect on gravitational redshift. There are many objects in nature, like neutron stars, magnetars etc which have high amount of rotation and magnetic field. In the present paper we will derive the expression of gravitational redshift from rotating body having intense magnetic field by using the action function of the electromagnetic fields.
Influence of gravitational lensing on gravitational radiation
Zakharov, A.
In a paper by Wang, Turner and Stebbins (PRL, Phys. Rev. Lett. 77 (1996) p.2875) an influence of gravitational lensing on increasing an estimated rate of gravitational radiation sources was considered. We show that the authors used the incorrect model for this case and thus they gave overestimated rate of possible events for possible sources of gravitational radiation for the advanced LIGO detector. We show also that if we would use a more correct model of gravitational lensing, one could conclude that more strong influence on increasing rate of estimated events of gravitational radiation for advanced LIGO detector could give gravitational lenses of galactic masses but not gravitational lenses of stellar masses as Wang et al. concluded. Moreover, binary gravitational lenses could give essential distortion of gravitational wave form template, especially gravitational wave template of periodic sources and the effect could be significant for templates of quasi-periodic sources which could be detected by a future gravitational wave space detector like LISA. Recently, the Galactic center was considered by Ruffa (ApJ, 1999) as a gravitational lens that focuses a gravitational wave energy to the Earth. The author used the wave optic approximation to solve this problem and concluded that amplification due to the gravitational lens focusing could be very huge. The conclusion is based on the perfect location of the gravitational wave source, namely the source lies very close to the line passing through the Earth and the gravitational lens (the Galactic Center), therefore the probability of the huge magnification of gravitational wave sources is negligible.
Alteration of Lunar Rock Surfaces through Interaction with the Space Environment
Frushour, A. M.; Noble, S. K; Christoffersen, R.; Keller, L P.
2014-01-01
Space weathering occurs on all ex-posed surfaces of lunar rocks, as well as on the surfaces of smaller grains in the lunar regolith. Space weather-ing alters these exposed surfaces primarily through the action of solar wind ions and micrometeorite impact processes. On lunar rocks specifically, the alteration products produced by space weathering form surface coatings known as patina. Patinas can have spectral reflectance properties different than the underlying rock. An understanding of patina composition and thickness is therefore important for interpreting re-motely sensed data from airless solar system bodies. The purpose of this study is to try to understand the physical and chemical properties of patina by expanding the number of patinas known and characterized in the lunar rock sample collection.
Hausmann, N; Fengler, S; Hennig, A; Franz-Wachtel, M; Hampp, R; Neef, M
2014-01-01
Callus cell cultures of Arabidopsis thaliana (cv. Columbia) were exposed to parabolic flights in order to assess molecular, short-term responses to altered gravity fields. Using transgenic cell lines, hydrogen peroxide (H2 O2 ) and cytosolic Ca(2+) were continuously monitored. In parallel, the metabolism of samples was chemically quenched (RNAlater, Ambion for RNA; acid/base for NADPH, NADP) at typical stages of a parabola [1 g before pull up; end of pull up (1.8 g), end of microgravity (20 s) and end of pull out (1.8 g)]. Cells exhibited an increase in both Ca(2+) and H2 O2 with the onset of microgravity, and a decline thereafter. This behaviour was accompanied by a decrease of the NADPH/NADP redox ratio, indicating Ca(2+) -dependent activation of a NADPH oxidase. Microarray analyses revealed concomitant expression profiles. At the end of the microgravity phase, 396 transcripts were specifically up-, while 485 were down-regulated. Up-regulation was dominated by Ca(2+) - and ROS-related gene products. The same material was also used for analysis of phosphopeptides with 2-D SDS PAGE. Relevant spots were identified by liquid chromatography-MS. With the exception of a chaperone (HSP 70-3), hypergravity (1.8 g) and microgravity modified different sets of proteins. These are partly involved in primary metabolism (glycolysis, gluconeogenesis, citrate cycle) and detoxification of ROS. Taken together, these data show that both gene expression and protein modulation jointly respond within seconds to alterations in the gravity field, with a focus on metabolic adaptation, signalling and control of ROS. © 2013 German Botanical Society and The Royal Botanical Society of the Netherlands.
Exposure to a novel stimulus environment alters patterns of lateralization in avian auditory cortex.
Yang, L M; Vicario, D S
2015-01-29
Perceptual filters formed early in development provide an initial means of parsing the incoming auditory stream. However, these filters may not remain fixed, and may be updated by subsequent auditory input, such that, even in an adult organism, the auditory system undergoes plastic changes to achieve a more efficient representation of the recent auditory environment. Songbirds are an excellent model system for experimental studies of auditory phenomena due to many parallels between song learning in birds and language acquisition in humans. In the present study, we explored the effects of passive immersion in a novel heterospecific auditory environment on neural responses in caudo-medial neostriatum (NCM), a songbird auditory area similar to the secondary auditory cortex in mammals. In zebra finches, a well-studied species of songbirds, NCM responds selectively to conspecific songs and contains a neuronal memory for tutor and other familiar conspecific songs. Adult male zebra finches were randomly assigned to either a conspecific or heterospecific auditory environment. After 2, 4 or 9 days of exposure, subjects were presented with heterospecific and conspecific songs during awake electrophysiological recording. The neural response strength and rate of adaptation to the testing stimuli were recorded bilaterally. Controls exposed to conspecific environment sounds exhibited the normal pattern of hemispheric lateralization with higher absolute response strength and faster adaptation in the right hemisphere. The pattern of lateralization was fully reversed in birds exposed to heterospecific environment for 4 or 9 days and partially reversed in birds exposed to heterospecific environment for 2 days. Our results show that brief passive exposure to a novel category of sounds was sufficient to induce a gradual reorganization of the left and right secondary auditory cortices. These changes may reflect modification of perceptual filters to form a more efficient representation
Potential Scenarios for Nanomaterial Release and Subsequent alteration in the Environment
Nowack, B.; Ranville, J.; Diamond, S.; Gallego-Urrea, J.; Metcalfe, C.; Rose, J.; Horne, N.; Koelmans, A.A.; Klaine, S.J.
2012-01-01
The risks associated with exposure to engineered nanomaterials (ENM) will be determined in part by the processes that control their environmental fate and transformation. These processes act not only on ENM that might be released directly into the environment, but more importantly also on ENM in
Parental thermal environment alters offspring sex ratio and fitness in an oviparous lizard.
Schwanz, Lisa E
2016-08-01
The environment experienced by parents can impact the phenotype of their offspring (parental effects), a critical component of organismal ecology and evolution in variable or changing environments. Although temperature is a central feature of the environment for ectotherms, its role in parental effects has been little explored until recently. Here, parental basking opportunity was manipulated in an oviparous lizard with temperature-dependent sex determination, the jacky dragon (Amphibolurus muricatus). Eggs were incubated at a temperature that typically produces a 50:50 sex ratio, and hatchlings were reared in a standard thermal environment. Offspring of parents in short bask conditions appeared to have better fitness outcomes in captive conditions than those of parents in long bask conditions - they had greater growth and survival as a function of their mass. In addition, the sex of offspring (male or female) depended on the interaction between parental treatment and egg mass, and treatment impacted whether sons or daughters grew larger in their first season. The interactive effects of treatment on offspring sex and growth are consistent with adaptive explanations for the existence of temperature-dependent sex determination in this species. Moreover, the greater performance recorded in short bask offspring may represent an anticipatory parental effect to aid offspring in predicted conditions of restricted thermal opportunity. Together, these responses constitute a crucial component of the population response to spatial or temporal variation in temperature.
Potential Scenarios for Nanomaterial Release and Subsequent alteration in the Environment
Nowack, B.; Ranville, J.; Diamond, S.; Gallego-Urrea, J.; Metcalfe, C.; Rose, J.; Horne, N.; Koelmans, A.A.; Klaine, S.J.
2012-01-01
The risks associated with exposure to engineered nanomaterials (ENM) will be determined in part by the processes that control their environmental fate and transformation. These processes act not only on ENM that might be released directly into the environment, but more importantly also on ENM in con
Alteration of a human intestinal microbiota under extreme life environment in the Antarctica.
Jin, Jong-Sik; Touyama, Mutsumi; Yamada, Shin; Yamazaki, Takashi; Benno, Yoshimi
2014-01-01
The human intestinal microbiota (HIM) settles from birth and continues to change phenotype by some factors (e.g. host's diet) throughout life. However, the effect of extreme life environment on human HIM composition is not well known. To understand HIM fluctuation under extreme life environment in humans, fecal samples were collected from six Japanese men on a long Antarctic expedition. They explored Antarctica for 3 months and collected their fecal samples at once-monthly intervals. Using terminal restriction fragment length polymorphism (T-RFLP) and real time polymerase chain reaction (PCR) analysis, the composition of HIM in six subjects was investigated. Three subjects presented restoration of HIM after the expedition compared versus before and during the expedition. Two thirds samples collected during the expedition belonged to the same cluster in dendrogram. However, all through the expedition, T-RFLP patterns showed interindividual variability. Especially, Bifidobacterium spp. showed a tendency to decrease during and restore after the expedition. A reduction of Bifidobacterium spp. was observed in five subjects the first 1 month of the expedition. Bacteroides thetaiotaomicron, which is thought to proliferate during emotional stress, significantly decreased in one subject, indicating that other factors in addition to emotional stress may affect the composition of HIM in this study. These findings could be helpful to understand the effect of extreme life environment on HIM.
Bubenheim, David; Potter, Christopher; Zhang, Minghua
2016-01-01
The California Sacramento-San Joaquin River Delta is the hub for California's water supply, conveying water from Northern to Southern California agriculture and communities while supporting important ecosystem services, agriculture, and communities in the Delta. Changes in climate, long-term drought, and water quality have all been suspected as playing role in the dramatic expansion of invasive aquatic plants and their impact on ecosystems of the San Francisco Bay / California Delta complex. NASA Ames Research Center, USDA-Agricultural Research Service, the State of California, UC Davis, and local governments have partnered under a USDA sponsored project (DRAAWP) to develop science-based, adaptive-management strategies for invasive aquatic plants in Sacramento-San Joaquin Delta. Critical to developing management strategies is to understand how the Delta is affected by both the magnitude of fluctuations in land-use and climate / drought induced altered environments and how the plants respond to these altered environments. We utilize the Soil Water Assessment Tool (SWAT), a watershed-scale model developed to quantify the impact of land management practices in large and complex watersheds on water quality, as the backbone for a customized Delta model - Delta-SWAT. The model uses land-use, soils, elevation, and hydrologic routing to characterize pesticide and nutrient transport from the Sacramento and San Joaquin rivers watersheds and loading into the Delta. Land-use within the Delta, as well as water extraction to supply those functions, and the resulting return of water to Delta waterways are included in Delta-SWAT. Hydrologic transport within the Delta has required significant attention to address the lack of elevation driven transport processes. Delta-SWAT water quality trend estimates are compared with water quality monitoring conducted throughout the Delta. Aquatic plant response to water quality and other environmental factors is carried out using a customized
Yamamuro, Yutaka
2008-10-01
Although it is recognized that the genetic background governs behavioral phenotypes, environmental factors also play a critical role in the development of various behavioral processes. The maternal environment has a major impact on pups, and the cross-fostering procedure is used to determine the influence of early life experiences. The present study examined the influence of maternal environment on behavioral traits in inbred Fischer 344 (F344) rats. F344/DuCrlCrlj and Wistar (Crlj:WI) pups were fostered from postnatal day 1 as follows: Wistar pups raised by Wistar dams, F344 raised by Wistar, Wistar raised by F344, and F344 raised by F344. At 10 weeks of age, rats were randomly assigned to an open-field test and social interaction test. In the open-field test, irrespective of the rearing conditions, the activity during the first 1 min was significantly lower in F344 rats than in Wistar rats. Latency to the onset of movement showed no difference between groups. In the social interaction test, the recognition performance during the first 1 min in F344 raised by F344 was significantly shorter than that in the other groups. The onset of recognition to a novel social partner in F344 raised by F344 was significantly delayed, and the delay disappeared upon cross-fostering by Wistar dams. These results raise the possibility that the behavioral phenotype of F344 rats results from the interplay of genetic factors and maternal environment during early life, and that F344 rats are a strain with high susceptibility to rearing conditions for the formation of their emotionality.
Directory of Open Access Journals (Sweden)
Katherine L Krynak
Full Text Available Recent global declines, extirpations and extinctions of wildlife caused by newly emergent diseases highlight the need to improve our knowledge of common environmental factors that affect the strength of immune defense traits. To achieve this goal, we examined the influence of acidification and shading of the larval environment on amphibian skin-associated innate immune defense traits, pre and post-metamorphosis, across two populations of American Bullfrogs (Rana catesbeiana, a species known for its wide-ranging environmental tolerance and introduced global distribution. We assessed treatment effects on 1 skin-associated microbial communities and 2 post-metamorphic antimicrobial peptide (AMP production and 3 AMP bioactivity against the fungal pathogen Batrachochytrium dendrobatidis (Bd. While habitat acidification did not affect survival, time to metamorphosis or juvenile mass, we found that a change in average pH from 7 to 6 caused a significant shift in the larval skin microbial community, an effect which disappeared after metamorphosis. Additionally, we found shifts in skin-associated microbial communities across life stages suggesting they are affected by the physiological or ecological changes associated with amphibian metamorphosis. Moreover, we found that post-metamorphic AMP production and bioactivity were significantly affected by the interactions between pH and shade treatments and interactive effects differed across populations. In contrast, there were no significant interactions between treatments on post-metamorphic microbial community structure suggesting that variation in AMPs did not affect microbial community structure within our study. Our findings indicate that commonly encountered variation in the larval environment (i.e. pond pH and degree of shading can have both immediate and long-term effects on the amphibian innate immune defense traits. Our work suggests that the susceptibility of amphibians to emerging diseases could be
Motor alterations associated with exposure to manganese in the environment in Mexico.
Rodríguez-Agudelo, Yaneth; Riojas-Rodríguez, Horacio; Ríos, Camilo; Rosas, Irma; Sabido Pedraza, Eva; Miranda, Javier; Siebe, Christina; Texcalac, José Luis; Santos-Burgoa, Carlos
2006-09-15
Overexposure to manganese (Mn) causes neurotoxicity (a Parkinson-like syndrome) or psychiatric damage ("manganese madness"). Several studies have shown alterations to motor and neural behavior associated with exposure to Mn in the workplace. However, there are few studies on the effects of environmental exposure of whole populations. We studied the risk of motor alterations in people living in a mining district in Mexico. We studied 288 individual people (168 women and 120 men) from eight communities at various distances from manganese extraction or processing facilities in the district of Molango. We measured manganese concentrations in airborne particles, water, soil and crops and evaluated the possible routes of Mn exposure. We also took samples of people's blood and determined their concentrations of Mn and lead (Pb). We used "Esquema de Diagnóstico Neuropsicológico" Ardila and Ostrosky-Solís's neuropsychological battery to evaluate motor functions. Concentrations of Mn in drinking water and maize grain were less than detection limits at most sampling sites. Manganese extractable by DTPA in soils ranged between 6 and 280 mg kg(-1) and means were largest close to Mn extraction or processing facilities. Air Mn concentration ranged between 0.003 and 5.86 microg/m(3); the mean value was 0.42 microg/m(3) and median was 0.10 microg/m(3), the average value (geometric mean) resulted to be 0.13 microg/m(3). Mean blood manganese concentration was 10.16 microg/l, and geometric mean 9.44 microg/l, ranged between 5.0 and 31.0 mcrog/l. We found no association between concentrations of Mn in blood and motor tests. There was a statistically significant association between Mn concentrations in air and motor tests that assessed the coordination of two movements (OR 3.69; 95% CI 0.9, 15.13) and position changes in hand movements (OR 3.09; CI 95% 1.07, 8.92). An association with tests evaluating conflictive reactions (task that explores verbal regulations of movements) was also
Takakura, Jun'ya; Nishimura, Takayuki; Choi, Damee; Egashira, Yuka; Watanuki, Shigeki
2015-10-01
A recent study showed that thermoregulatory-like cardiovascular responses can be invoked simply by exposure to visual information, even though the thermal environments are neutral and unchanged. However, it was not clear how such responses affect actual human body temperature regulation. We investigated whether such visually invoked physiological responses can substantively affect human core body temperature in a thermally challenging cold environment. Participants comprised 13 graduate or undergraduate students viewing different video images containing hot, cold, or no scenery, while room temperature was gradually lowered from 28 to 16 °C over 80 min. Rectal temperature, mean skin temperature, core to skin temperature gradient, and oxygen consumption were measured during the experiment. Rectal temperature was significantly lower when hot video images were presented compared to when control video images were presented. Oxygen consumption was comparable among all video images, but core to skin temperature gradient was significantly lower when hot video images were presented. This result suggests that visual information, even in the absence of thermal energy, can affect human thermodynamics and core body temperature.
Takakura, Jun'ya; Nishimura, Takayuki; Choi, Damee; Egashira, Yuka; Watanuki, Shigeki
2015-10-01
A recent study showed that thermoregulatory-like cardiovascular responses can be invoked simply by exposure to visual information, even though the thermal environments are neutral and unchanged. However, it was not clear how such responses affect actual human body temperature regulation. We investigated whether such visually invoked physiological responses can substantively affect human core body temperature in a thermally challenging cold environment. Participants comprised 13 graduate or undergraduate students viewing different video images containing hot, cold, or no scenery, while room temperature was gradually lowered from 28 to 16 °C over 80 min. Rectal temperature, mean skin temperature, core to skin temperature gradient, and oxygen consumption were measured during the experiment. Rectal temperature was significantly lower when hot video images were presented compared to when control video images were presented. Oxygen consumption was comparable among all video images, but core to skin temperature gradient was significantly lower when hot video images were presented. This result suggests that visual information, even in the absence of thermal energy, can affect human thermodynamics and core body temperature.
Cao, Peilin; Karpyn, Zuleima T.; Li, Li
2013-07-01
The interaction between wellbore cement and CO2 has the potential to alter cement properties and form preferential leakage pathways during geological carbon sequestration. This work investigates changes in wellbore cement integrity during continuous flooding of CO2-saturated brine. We created composite cement-sandstone core samples with a continuous gap in the cement zone in order to represent defects such as fractures and voids in wellbore cement. Volumetric and structural changes in the cement zone were monitored and quantified using X-ray Micro-Computed Tomography imaging. During an 8 day dynamic flow-through period, the fracture/void aperture increased significantly, whereas the host sandstone remained unaltered. The void volume increased at a faster rate in the early stage of the flow-through period than it did toward the end of the period. Compared to the apertures close to the core outlet, those located near the core inlet experienced more severe cement degradation, accompanied by a decrease in specific surface area, constituting evidence of a smoothing effect. Contrary to previous observations of the self-healing behavior of cement fractures, the in situ permeability on a parallel experiment increased by a factor of 8 after 10 days of flooding. Findings from this work will provide valuable insights applicable to the development of predictive models and for risk assessment under conditions relevant to CO2 sequestration.
Altered mechano-chemical environment in hip articular cartilage: effect of obesity.
Travascio, Francesco; Eltoukhy, Moataz; Cami, Sonila; Asfour, Shihab
2014-10-01
The production of extracellular matrix (ECM) components of articular cartilage is regulated, among other factors, by an intercellular signaling mechanism mediated by the interaction of cell surface receptors (CSR) with insulin-like growth factor-1 (IGF-1). In ECM, the presence of binding proteins (IGFBP) hinders IGF-1 delivery to CSR. It has been reported that levels of IGF-1 and IGFBP in obese population are, respectively, lower and higher than those found in normal population. In this study, an experimental-numerical approach was adopted to quantify the effect of this metabolic alteration found in obese population on the homeostasis of femoral hip cartilage. A new computational model, based on the mechano-electrochemical mixture theory, was developed to describe competitive binding kinetics of IGF-1 with IGFBP and CSR, and associated glycosaminoglycan (GAG) biosynthesis. Moreover, a gait analysis was carried out on obese and normal subjects to experimentally characterize mechanical loads on hip cartilage during walking. This information was deployed into the model to account for effects of physiologically relevant tissue deformation on GAG production in ECM. Numerical simulations were performed to compare GAG biosynthesis in femoral hip cartilage of normal and obese subjects. Results indicated that the lower ratio of IGF-1 to IGFBP found in obese population reduces cartilage GAG concentration up to 18 % when compared to normal population. Moreover, moderate physical activity, such as walking, has a modest beneficial effect on GAG production. The findings of this study suggest that IGF-1/IGFBP metabolic unbalance should be accounted for when considering the association of obesity with hip osteoarthritis.
Ascough, Philippa; Bird, Michael; Meredith, Will; Large, David; Snape, Colin; Manion, Corinne
2014-05-01
Natural and anthropogenic burning events are a key link in the global carbon cycle, substantially influencing atmospheric CO2 levels, and consuming c.8700 teragrams yr-1 of dry biomass [1,2,3]. An important result of this process is charcoal, when lignocellulosic structures in biomass (e.g. wood) are converted to aromatic domains with high chemical stability. Charcoal is therefore not readily re-oxidized to CO2, with estimates of 5-7 ky for the half-life of charcoal carbon in soils [3,4]. Charcoal's high carbon content coupled with high environmental resistance has led to the concept of biochar as a valuable means of global carbon sequestration, capable of carbon offsets comparable to annual anthropogenic fuel emissions [5,6,7]. Charcoal is not, however, an environmentally inert substance, and at least some components of charcoal are susceptible to alteration in depositional environments. Despite the importance of charcoal in global carbon cycling, the mechanisms by which charcoal is altered in the environment remain, as yet, poorly understood. This fact limits our ability to properly incorporate both natural environmental charcoal and biochar into global carbon budgets. This study aimed to improve understanding of charcoal alteration in the environment by examining the influence of production conditions, starting material and deposition environment on the physical and chemical characteristics of charcoal at a field site in the Daintree rainforest. These factors have been identified as critical in determining the dynamics of charcoal in depositional environments [8,9] and climatic conditions at the field site (in Tropical Queensland, Australia) are likely to result in extensive alteration of charcoal. Charcoal from wood (Nothofagus spp.), algae (Enteromorpha spp.), and sugarcane (Saccharum spp.) biomass was produced at temperatures over 300-500°C and exposed to conditions of varying pH and vegetation cover. The effect of these variables on charcoal chemistry
Fertility profile of post Fourniers gangrene patients：Does neoscrotal environment alter fertility?
Institute of Scientific and Technical Information of China (English)
Zulqarnain Masoodi; Imran Ahmad; Fahad Khurram
2012-01-01
Objective:To ascertain changes in fertility in post Fournier’s gangrene patients on account of changed scrotal environment. Methods: Sixty post Fournier’s patients were as cases and 50 non Fournier’s individuals aptlyserved as controls. All subjects were followed up for 1 year. Aspects of fertility were investigated by means of a seminogram at 6 months and analysis for volume, viscosity, sperm concentration, motility and morphology according to WHO guidelines was done. Ability of the couples to conceive children in 1 year was also noted. The control group was investigated similarly and values were compared for significance. Results:The seminogram results were found out to be highly significant as there was marked difference in values (chi-square value 6.28, P-value< 0.012) whereas there was no significant association between attaining pregnancy at 1 year in two groups. Conclusions:A readily palpable difference in the seminogram values observed in Fournier’s patients is the most significant finding of this study. Also highlighted was that despite such seminogram changes the overall ability of the couple to achieve pregnancy remains unaltered.
Directory of Open Access Journals (Sweden)
Masami Yoshioka
2013-04-01
Full Text Available Objective: During the perioperative period, oral ingestion is changed considerably in esophagectomy patients. The aim of this study was to investigate oral environment modifications in patients undergoing esophageal cancer treatments due to changes in dietary intake and swallowing functions. Material and Methods: Thirty patients who underwent operation for removal of esophageal cancer in Tokushima University Hospital were enrolled in this study. Results: It was found that 1 the flow rate of resting saliva decreased significantly at postoperative period by deprived feeding for one week, although it did not recover several days after oral ingestion began, 2 the accumulation of dental plaque and the number of mutans streptococci in saliva decreased significantly after operation, while both increased relatively quick when oral ingestion began, and 3 the swallowing function decreased significantly in the postoperative period. Conclusions: These results suggest that dental professionals should emphasize the importance of oral health care and provide instructions on plaque control to patients during the perioperative period of esophageal cancer treatment.
The zCOSMOS Redshift Survey: How group environment alters global downsizing trends
Iovino, A; Scodeggio, M; Knobel, C; Kovac, K; Lilly, S; Bolzonella, M; Tasca, L A M; Zamorani, G; Zucca, E; Caputi, K; Pozzetti, L; Oesch, P; Lamareille, F; Halliday, C; Bardelli, S; Finoguenov, A; Guzzo, L; Kampczyk, P; Maier, C; Tanaka, M; Vergani, D; Carollo, C M; Contini, T; Kneib, J -P; Le Fèvre, O; Mainieri, V; Renzini, A; Bongiorno, A; Coppa, G; De la Torre, S; de Ravel, L; Franzetti, P; Garilli, B; Le Borgne, J F; Le Brun, V; Mignoli, M; Pellò, R; Peng, Y; Pérez-Montero, E; Ricciardelli, E; Silverman, J D; Tresse, L; Abbas, U; Bottini, D; Cappi, A; Cassata, P; Cimatti, A; Koekemoer, A M; Leauthaud, A; MacCagni, D; Marinoni, C; McCracken, H J; Memeo, P; Meneux, B; Porciani, C; Scaramella, R; Schiminovich, D; Scoville, N
2009-01-01
We took advantage of the wealth of information provided by the first ~10000 galaxies of the zCOSMOS-bright survey and its group catalogue to study the complex interplay between group environment and galaxy properties. The classical indicator F_blue (fraction of blue galaxies) proved to be a simple but powerful diagnostic tool. We studied its variation for different luminosity and mass selected galaxy samples. Using rest-frame B-band selected samples, the groups galaxy population exhibits significant blueing as redshift increases, but maintains a lower F_blue with respect both to the global and the isolated galaxy population. However moving to mass selected samples it becomes apparent that such differences are largely due to the biased view imposed by the B-band luminosity selection, being driven by the population of lower mass, bright blue galaxies for which we miss the redder, equally low mass, counterparts. By focusing the analysis on narrow mass bins such that mass segregation becomes negligible we find th...
Detection of gravitational radiation
Energy Technology Data Exchange (ETDEWEB)
Holten, J.W. van [ed.
1994-12-31
In this report the main contributions presented at the named symposium are collected. These concern astrophysical sources of gravitational radiation, ultracryogenic gravitational wave experiments, read out and data analysis of gravitational wave antennas, cryogenic aspects of large mass cooling to mK temperatures, and metallurgical and engineering aspects of large Cu structure manufacturing. (HSI).
Herbivore body condition response in altered environments: mule deer and habitat management.
Directory of Open Access Journals (Sweden)
Eric J Bergman
Full Text Available The relationships between habitat, body condition, life history characteristics, and fitness components of ungulates are interwoven and of interest to researchers as they strive to understand the impacts of a changing environment. With the increased availability of portable ultrasound machines and the refinement of hormonal assays, assessment of ungulate body condition has become an accessible monitoring strategy. We employed body condition scoring, estimation of % ingesta-free body fat (%IFBF, assessment of free thyroid hormones (FT4 and FT3, and assessment of pregnancy, as metrics to determine if landscape-level habitat treatments affected body condition of adult (≥ 1.5 years old female mule deer (Odocoileus hemionus. All body condition related metrics were measured on 2 neighboring study areas--a reference area that had received no habitat treatments and a treatment study area that had received mechanical removal of pinyon pine (Pinyus edulis--Utah juniper (Juniperus osteosperma forest, chemical control of weeds, and reseeding with preferred mule deer browse species. A consistent trend of higher %IFBF was observed in the treatment study area [Formula: see text] than in the reference study area [Formula: see text], although variation of estimates was larger than hypothesized. A similar pattern was observed with higher thyroid hormones concentrations being observed in the treatment study area, but large amounts of variation within concentration estimates were also observed. The consistent pattern of higher body condition related estimates in our treatment study area provides evidence that large mammalian species are sensitive to landscape change, although variation within estimates underlie the challenge in detecting population level impacts stemming from environmental change.
Moinfar, Farid; Beham, Alfred; Friedrich, Gerhard; Deutsch, Alexander; Hrzenjak, Andelko; Luschin, Gero; Tavassoli, Fattaneh A
2008-05-01
Genetic abnormalities in microenvironmental tissues with subsequent alterations of reciprocal interactions between epithelial and mesenchymal cells play a key role in the breast carcinogenesis. Although a few reports have demonstrated abnormal fibroblastic functions in normal-appearing fibroblasts taken from the skins of breast cancer patients, the genetic basis of this phenomenon and its implication for carcinogenesis are unexplored. We analyzed 12 mastectomy specimens showing invasive ductal carcinomas. In each case, morphologically normal epidermis and dermis, carcinoma, normal stroma close to carcinoma, and stroma at a distant from carcinoma were microdissected. Metastatic-free lymphatic tissues from lymph nodes served as a control. Using PCR, DNA extracts were examined with 11 microsatellite markers known for a high frequency of allelic imbalances in breast cancer. Losses of heterozygosity and/or microsatellite instability were detected in 83% of the skin samples occurring either concurrently with or independently from the cancerous tissues. In 80% of these cases at least one microsatellite marker displayed loss of heterozygosity or microsatellite instability in the skin, which was absent in carcinoma. A total of 41% of samples showed alterations of certain loci observed exclusively in the carcinoma but not in the skin compartments. Our study suggests that breast cancer is not just a localized genetic disorder, but rather part of a larger field of genetic alterations/instabilities affecting multiple cell populations in the organ with various cellular elements, ultimately contributing to the manifestation of the more 'localized' carcinoma. These data indicate that more global assessment of tumor micro- and macro-environment is crucial for our understanding of breast carcinogenesis.
Directory of Open Access Journals (Sweden)
Mohammad M Alzahrani
2014-12-01
Full Text Available Distraction osteogenesis (DO is a surgical technique where gradual and controlled separation of two bony fragments following an osteotomy leads to the induction of new bone formation in the distracted gap. DO is used for limb lengthening, correction of bony deformities and the replacement of bone loss secondary to infection, trauma and tumors. Although DO gives satisfactory results in most cases, one major drawback of this technique is the prolonged period of time the external fixator has to be kept on until the newly formed bone consolidates thus leading to numerous complications. Numerous attempts at accelerating bone formation during DO have been reported. One specific approach is manipulation of the mechanical environment during DO by applying changes in the standard protocol of distraction. Attempts at changing this mechanical environment led to mixed results. Increasing the rate or applying acute distraction, led to poor bone formation in the distracted zone. On the other hand, the addition of compressive forces (such as weight bearing, alternating distraction with compression or by over-lengthening and then shortening has been reported to increase bone formation. It still remains unclear why these alterations may lead to changes in bone formation. While the cellular and molecular changes occurring during the standard DO protocol, specifically increased expression of transforming growth factor-β1, platelet derived growth factor, insulin-like growth factor, basic fibroblast growth factor, vascular endothelial growth factor, and bone morphogenic proteins have been extensively investigated, the literature is sparse on the changes occurring when this protocol is altered. It is the purpose of this article to review the pertinent literature on the changes in the expression of various proteins and molecules as a result of changes in the mechanical loading technique in DO and try to define potential future research directions.
Theory of gravitational interactions
Gasperini, Maurizio
2017-01-01
This is the second edition of a well-received book that is a modern, self-contained introduction to the theory of gravitational interactions. The new edition includes more details on gravitational waves of cosmological origin, the so-called brane world scenario, and gravitational time-delay effects. The first part of the book follows the traditional presentation of general relativity as a geometric theory of the macroscopic gravitational field, while the second, more advanced part discusses the deep analogies (and differences) between a geometric theory of gravity and the “gauge” theories of the other fundamental interactions. This fills a gap within the traditional approach to general relativity which usually leaves students puzzled about the role of gravity. The required notions of differential geometry are reduced to the minimum, allowing room for aspects of gravitational physics of current phenomenological and theoretical interest, such as the properties of gravitational waves, the gravitational inter...
Gravitational Higgs Mechanism in Neutron Star Interiors
Coates, Andrew; Sotiriou, Thomas P
2016-01-01
We suggest that nonminimally coupled scalar fields can lead to modifications of the microphysics in the interiors of relativistic stars. As a concrete example, we consider the generation of a non-zero photon mass in such high-density environments. This is achieved by means of a light gravitational scalar, and the scalarization phase transition in scalar-tensor theories of gravitation. Two distinct models are presented, and phenomenological implications are briefly discussed.
Gravitational waves from inflation
Guzzetti, M. C.; Bartolo, N.; Liguori, M.; Matarrese, S.
2016-09-01
The production of a stochastic background of gravitational waves is a fundamental prediction of any cosmological inflationary model. The features of such a signal encode unique information about the physics of the Early Universe and beyond, thus representing an exciting, powerful window on the origin and evolution of the Universe. We review the main mechanisms of gravitational-wave production, ranging from quantum fluctuations of the gravitational field to other mechanisms that can take place during or after inflation. These include e.g. gravitational waves generated as a consequence of extra particle production during inflation, or during the (p)reheating phase. Gravitational waves produced in inflation scenarios based on modified gravity theories and second-order gravitational waves are also considered. For each analyzed case, the expected power spectrum is given. We discuss the discriminating power among different models, associated with the validity/violation of the standard consistency relation between tensor-to-scalar ratio r and tensor spectral index nT. In light of the prospects for (directly/indirectly) detecting primordial gravitational waves, we give the expected present-day gravitational radiation spectral energy-density, highlighting the main characteristics imprinted by the cosmic thermal history, and we outline the signatures left by gravitational waves on the Cosmic Microwave Background and some imprints in the Large-Scale Structure of the Universe. Finally, current bounds and prospects of detection for inflationary gravitational waves are summarized.
Theory of gravitational interactions
Gasperini, Maurizio
2013-01-01
This reference textbook is an up-to-date and self-contained introduction to the theory of gravitational interactions. The first part of the book follows the traditional presentation of general relativity as a geometric theory of the macroscopic gravitational field. A second, advanced part then discusses the deep analogies (and differences) between a geometric theory of gravity and the gauge theories of the other fundamental interactions. This fills a gap which is present in the context of the traditional approach to general relativity, and which usually makes students puzzled about the role of gravity. The necessary notions of differential geometry are reduced to the minimum, leaving more room for those aspects of gravitational physics of current phenomenological and theoretical interest, such as the properties of gravitational waves, the gravitational interactions of spinors, and the supersymmetric and higher-dimensional generalization of the Einstein equations. Theory of Gravitational Interactions will be o...
Gravitational waves from inflation
Guzzetti, Maria Chiara; Liguori, Michele; Matarrese, Sabino
2016-01-01
The production of a stochastic background of gravitational waves is a fundamental prediction of any cosmological inflationary model. The features of such a signal encode unique information about the physics of the Early Universe and beyond, thus representing an exciting, powerful window on the origin and evolution of the Universe. We review the main mechanisms of gravitational-wave production, ranging from quantum fluctuations of the gravitational field to other mechanisms that can take place during or after inflation. These include e.g. gravitational waves generated as a consequence of extra particle production during inflation, or during the (p)reheating phase. Gravitational waves produced in inflation scenarios based on modified gravity theories and second-order gravitational waves are also considered. For each analyzed case, the expected power-spectrum is given. We discuss the discriminating power among different models, associated with the validity/violation of the standard consistency relation between t...
Hoffmann, William F
1964-01-01
Remarks on the observational basis of general relativity ; Riemannian geometry ; gravitation as geometry ; gravitational waves ; Mach's principle and experiments on mass anisotropy ; the many faces of Mach ; the significance for the solar system of time-varying gravitation ; relativity principles and the role of coordinates in physics ; the superdense star and the critical nucleon number ; gravitation and light ; possible effects on the solar system of φ waves if they exist ; the Lyttleton-Bondi universe and charge equality ; quantization of general relativity ; Mach's principle as boundary condition for Einstein's equations.
Twomey, Kate B; Alston, Mark; An, Shi-Qi; O'Connell, Oisin J; McCarthy, Yvonne; Swarbreck, David; Febrer, Melanie; Dow, J Maxwell; Plant, Barry J; Ryan, Robert P
2013-01-01
Chronic polymicrobial infections of the lung are the foremost cause of morbidity and mortality in cystic fibrosis (CF) patients. The composition of the microbial flora of the airway alters considerably during infection, particularly during patient exacerbation. An understanding of which organisms are growing, their environment and their behaviour in the airway is of importance for designing antibiotic treatment regimes and for patient prognosis. To this end, we have analysed sputum samples taken from separate cohorts of CF and non-CF subjects for metabolites and in parallel, and we have examined both isolated DNA and RNA for the presence of 16S rRNA genes and transcripts by high-throughput sequencing of amplicon or cDNA libraries. This analysis revealed that although the population size of all dominant orders of bacteria as measured by DNA- and RNA- based methods are similar, greater discrepancies are seen with less prevalent organisms, some of which we associated with CF for the first time. Additionally, we identified a strong relationship between the abundance of specific anaerobes and fluctuations in several metabolites including lactate and putrescine during patient exacerbation. This study has hence identified organisms whose occurrence within the CF microbiome has been hitherto unreported and has revealed potential metabolic biomarkers for exacerbation.
Directory of Open Access Journals (Sweden)
Kate B Twomey
Full Text Available Chronic polymicrobial infections of the lung are the foremost cause of morbidity and mortality in cystic fibrosis (CF patients. The composition of the microbial flora of the airway alters considerably during infection, particularly during patient exacerbation. An understanding of which organisms are growing, their environment and their behaviour in the airway is of importance for designing antibiotic treatment regimes and for patient prognosis. To this end, we have analysed sputum samples taken from separate cohorts of CF and non-CF subjects for metabolites and in parallel, and we have examined both isolated DNA and RNA for the presence of 16S rRNA genes and transcripts by high-throughput sequencing of amplicon or cDNA libraries. This analysis revealed that although the population size of all dominant orders of bacteria as measured by DNA- and RNA- based methods are similar, greater discrepancies are seen with less prevalent organisms, some of which we associated with CF for the first time. Additionally, we identified a strong relationship between the abundance of specific anaerobes and fluctuations in several metabolites including lactate and putrescine during patient exacerbation. This study has hence identified organisms whose occurrence within the CF microbiome has been hitherto unreported and has revealed potential metabolic biomarkers for exacerbation.
What about gravitation?; Et la gravitation?
Energy Technology Data Exchange (ETDEWEB)
Binetruy, P. [Ecole Polytechnique, CRNS/IN2P3, Lab. Astroparticule et Cosmologie (APC), 91 - Palaiseau (France); CEA Saclay, IRFU, 91 - Gif-sur-Yvette (France); Observatoire de Paris, 75 - Paris (France); Goldstein, C. [Centre National de la Recherche Scientifique (CNRS), 75 - Paris (France); Institut de Mathematiques de Jussieu, 75 - Paris (France); Ritter, J. [Paris-8 Univ. Vincennes saint Senis, 93 (France); Institut de Mathematiques de Jussieu, 75 - Paris (France); Smolin, L. [Waterloo Univ., Institut for Theoretical Physics, ON (Canada); Maldacena, J. [Ecole des Sciences de la Nature de l' Institut pour les Etudes Avancees de Princeton, New Jersey (United States); Quevedo, F. [Cambridge Univ. (United Kingdom); Burgess, C. [Universite McMaster, Perimeter Institute, Hamilton, Ontario (Canada)
2009-01-15
Particle's standard model does not include gravitation. A quantum theory of gravitation is today's quest of physics, it would shed light on vacuum energy or extra-dimensions. Till his death A.Einstein has worked on theories able to unify gravitation to electromagnetism but none has been backed by experimental data. Space and time seem continuous but the theory of the loop quantum gravitation theory presents them as tiny discrete entities. On the other hand, the string theory in its attempt to unify physics'law, describes a strange world that allows strings to vibrate in a number of dimensions that is far beyond what we see in our daily life. The latest development of the string theory show that the brief period of very fast expansion that the universe underwent just after the big-bang could be the consequence of the collision of our universe with another one in a gigantic and multi-dimensional world. Another theory explains that gravitation is an illusion in our 3-dimensional world and must be seen as a consequence of particle interactions in a 2-dimensional world. (A.C.)
R. Vlokh; M. Kostyrko
2006-01-01
Nonlinear effect of the gravitation field of spherically symmetric mass on the gravitational coefficient G has been analysed. In frame of the approaches of parametric optics and gravitation nonlinearity we have shown that the gravitation field of spherically symmetric mass can lead to changes in the gravitational coefficient G.
Schucking, Engelbert L
2008-01-01
The mantra about gravitation as curvature is a misnomer. The curvature tensor for a standard of rest does not describe acceleration in a gravitational field but the \\underline{gradient} of the acceleration (e.g. geodesic deviation). The gravitational field itself (Einstein 1907) is essentially an accelerated reference system. It is characterized by a field of orthonormal four-legs in a Riemann space with Lorentz metric. By viewing vectors at different events having identical leg-components as parallel (teleparallelism) the geometry in a gravitational field defines torsion. This formulation of Einstein's 1907 principle of equivalence uses the same Riemannian metric and the same 1916 field equations for his theory of gravitation and fulfills his vision of General Relativity.
Tiec, Alexandre Le
2016-01-01
The existence of gravitational radiation is a natural prediction of any relativistic description of the gravitational interaction. In this chapter, we focus on gravitational waves, as predicted by Einstein's general theory of relativity. First, we introduce those mathematical concepts that are necessary to properly formulate the physical theory, such as the notions of manifold, vector, tensor, metric, connection and curvature. Second, we motivate, formulate and then discuss Einstein's equation, which relates the geometry of spacetime to its matter content. Gravitational waves are later introduced as solutions of the linearized Einstein equation around flat spacetime. These waves are shown to propagate at the speed of light and to possess two polarization states. Gravitational waves can interact with matter, allowing for their direct detection by means of laser interferometers. Finally, Einstein's quadrupole formulas are derived and used to show that nonspherical compact objects moving at relativistic speeds a...
Jilek, Joseph L; Sant, Karilyn E; Cho, Katherine H; Reed, Matthew S; Pohl, Jan; Hansen, Jason M; Harris, Craig
2015-10-01
Ethanol (EtOH) is a reactive oxygen-generating teratogen involved in the etiology of structural and functional developmental defects. Embryonic nutrition, redox environment, and changes in the thiol proteome following EtOH exposures (1.56.0 mg/ml) were studied in rat whole embryo culture. Glutathione (GSH) and cysteine (Cys) concentrations with their respective intracellular redox potentials (Eh) were determined using high-performance liquid chromatography. EtOH reduced GSH and Cys concentrations in embryo (EMB) and visceral yolk sac (VYS) tissues, and also in yolk sac and amniotic fluids. These changes produced greater oxidation as indicated by increasingly positive Eh values. EtOH reduced histiotrophic nutrition pathway activities as measured by the clearance of fluorescin isothiocyanate (FITC)-albumin from culture media. A significant decrease in total FITC clearance was observed at all concentrations, reaching approximately 50% at the highest dose. EtOH-induced changes to the thiol proteome were measured in EMBs and VYSs using isotope-coded affinity tags. Decreased concentrations for specific proteins from cytoskeletal dynamics and endocytosis pathways (α-actinin, α-tubulin, cubilin, and actin-related protein 2); nuclear translocation (Ran and RanBP1); and maintenance of receptor-mediated endocytosis (cubilin) were observed. Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis also identified a decrease in ribosomal proteins in both EMB and VYS. Results show that EtOH interferes with nutrient uptake to reduce availability of amino acids and micronutrients required by the conceptus. Intracellular antioxidants such as GSH and Cys are depleted following EtOH and Eh values increase. Thiol proteome analysis in the EMB and VYS show selectively altered actin/cytoskeleton, endocytosis, ribosome biogenesis and function, nuclear transport, and stress-related responses. © The Author 2015. Published by Oxford University Press on behalf of the Society of
Data Quality Studies of Enhanced Interferometric Gravitational Wave Detectors
McIver, Jessica
2012-01-01
Data quality assessment plays an essential role in the quest to detect gravitational wave signals in data from the LIGO and Virgo interferometric gravitational wave detectors. Interferometer data contains a high rate of noise transients from the environment, the detector hardware, and the detector control systems. These transients severely limit the statistical significance of gravitational wave candidates of short duration and/or poorly modeled waveforms. This paper describes the data quality studies that have been performed in recent LIGO and Virgo observing runs to mitigate the impact of transient detector artifacts on the gravitational wave searches.
DEFF Research Database (Denmark)
Valentini, Chiara
2017-01-01
The term environment refers to the internal and external context in which organizations operate. For some scholars, environment is defined as an arrangement of political, economic, social and cultural factors existing in a given context that have an impact on organizational processes and structures....... For others, environment is a generic term describing a large variety of stakeholders and how these interact and act upon organizations. Organizations and their environment are mutually interdependent and organizational communications are highly affected by the environment. This entry examines the origin...... and development of organization-environment interdependence, the nature of the concept of environment and its relevance for communication scholarships and activities....
Solar gravitation and cosmology
Energy Technology Data Exchange (ETDEWEB)
Ferrari, J.A. (Departamento de Fisica, Facultad de Humanidades y Ciencias, Montevideo (Uruguay))
1984-08-11
The objective of this paper is to discuss some implications of a scalar of gravitation developed in a previous paper. At the beginning we shall show that, on the basis of a scalar theory of gravitation, it is possible to predict a gravitational light drag. The remainder of this paper is devoted to cosmology. We shall prove that Hubble's red shift, the existence of an age and an ''effective radius'' of the Universe can be deduced from a model of the universe that is Euclidean, infinite and nonexpanding. Finally, we discuss briefly Olbers' paradox and the thermal evolution of the universe.
Presenting Newtonian gravitation
Energy Technology Data Exchange (ETDEWEB)
Counihan, Martin [School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom)
2007-11-15
The basic principles of the Newtonian theory of gravitation are presented in a way which students may find more logically coherent, mathematically accessible and physically interesting than other approaches. After giving relatively simple derivations of the circular hodograph and the elliptical orbit from the inverse-square law, the concept of gravitational energy is developed from vector calculus. It is argued that the energy density of a gravitational field may reasonably be regarded as -g{sup 2}/8{pi}G, and that the inverse-square law may be replaced by a Schwarzschild-like force law without the need to invoke non-Euclidean geometry.
Smooth sandwich gravitational waves
Podolsky, J
1999-01-01
Gravitational waves which are smooth and contain two asymptotically flat regions are constructed from the homogeneous pp-waves vacuum solution. Motion of free test particles is calculated explicitly and the limit to an impulsive wave is also considered.
Gravitational lensing of quasars
Eigenbrod, Alexander
2013-01-01
The universe, in all its richness, diversity and complexity, is populated by a myriad of intriguing celestial objects. Among the most exotic of them are gravitationally lensed quasars. A quasar is an extremely bright nucleus of a galaxy, and when such an object is gravitationally lensed, multiple images of the quasar are produced – this phenomenon of cosmic mirage can provide invaluable insights on burning questions, such as the nature of dark matter and dark energy. After presenting the basics of modern cosmology, the book describes active galactic nuclei, the theory of gravitational lensing, and presents a particular numerical technique to improve the resolution of astronomical data. The book then enters the heart of the subject with the description of important applications of gravitational lensing of quasars, such as the measurement of the famous Hubble constant, the determination of the dark matter distribution in galaxies, and the observation of the mysterious inner parts of quasars with much higher r...
Ter-Kazarian, G T
1997-01-01
Suggested theory involves a drastic revision of a role of local internal symmetries in physical concept of curved geometry. Under the reflection of fields and their dynamics from Minkowski to Riemannian space a standard gauge principle of local internal symmetries is generalized. The gravitation gauge group is proposed, which is generated by hidden local internal symmetries. The developed mechanism enables one to infer Einstein's equation of gravitation, but only with strong difference from Einstein's theory at the vital point of well-defined energy-momentum tensor of gravitational field and conservation laws. The gravitational interaction as well as general distortion of manifold G(2.2.3) with hidden group U(1) was considered.
Energy Technology Data Exchange (ETDEWEB)
Ridgely, Charles T, E-mail: charles@ridgely.w [Thienes Engineering, Inc, La Mirada, CA 90638 (United States)
2011-03-15
When two gravitating bodies reside in a material medium, Newton's law of universal gravitation must be modified to account for the presence of the medium. A modified expression of Newton's law is known in the literature, but lacks a clear connection with existing gravitational theory. Newton's law in the presence of a homogeneous material medium is herein derived on the basis of classical, Newtonian gravitational theory and by a general relativistic use of Archimedes' principle. It is envisioned that the techniques presented herein will be most useful to graduate students and those undergraduate students having prior experience with vector analysis and potential theory.
Wilhelm, Klaus
2013-01-01
The study of the gravitational redshift -- a relative wavelength increase of $\\approx 2 \\times 10^{-6}$ was predicted for solar radiation by Einstein in 1908 -- is still an important subject in modern physics. In a dispute whether or not atom interferometry experiments can be employed for gravitational redshift measurements, two research teams have recently disagreed on the physical cause of the shift. Regardless of any discussion on the interferometer aspect -- we find that both groups of authors miss the important point that the ratio of gravitational to the electrostatic forces is generally very small. For instance, the gravitational force acting on an electron in a hydrogen atom situated in the Sun's photosphere to the electrostatic force between the proton and the electron is approximately $3 \\times 10^{-21}$. A comparison of this ratio with the predicted and observed solar redshift indicates a discrepancy of many orders of magnitude. Here we show, with Einstein's early assumption of the frequency of spe...
Gravitation and Duality Symmetry
D'Andrade, V C; Pereira, J G
2005-01-01
By generalizing the Hodge dual operator to the case of soldered bundles, and working in the context of the teleparallel equivalent of general relativity, an analysis of the duality symmetry in gravitation is performed. Although the basic conclusion is that, at least in the general case, gravitation does not present duality symmetry, there is a particular theory in which this symmetry is present. This theory is a self dual (or anti-self dual) teleparallel gravity in which, owing to the fact that it does not contribute to the gravitational interaction of fermions, the purely tensor part of torsion is assumed to vanish. The corresponding fermionic gravitational interaction is found to be chiral. Since duality is intimately related to renormalizability, this theory will probably be much more amenable to renormalization than teleparallel gravity or general relativity. Although obtained in the context of teleparallel gravity, these results must also be true for general relativity.
CERN. Geneva
2016-01-01
In the past year, the LIGO-Virgo Collaboration announced the first secure detection of gravitational waves. This discovery heralds the beginning of gravitational wave astronomy: the use of gravitational waves as a tool for studying the dense and dynamical universe. In this talk, I will describe the full spectrum of gravitational waves, from Hubble-scale modes, through waves with periods of years, hours and milliseconds. I will describe the different techniques one uses to measure the waves in these bands, current and planned facilities for implementing these techniques, and the broad range of sources which produce the radiation. I will discuss what we might expect to learn as more events and sources are measured, and as this field matures into a standard part of the astronomical milieu.
Potter-McIntyre, S. L.; Williams, J.; Phillips-Landers, C.; O'Connell, L.
2016-05-01
Microscopic and macroscopic biosignatures in modern spring deposits are compared with the Quaternary and Jurassic examples to show how these features are progressively altered and preserved on geologic time scales.
Directory of Open Access Journals (Sweden)
Stavroulakis N.
2008-04-01
Full Text Available The equations of gravitation together with the equations of electromagnetism in terms of the General Theory of Relativity allow to conceive an interdependence between the gravitational field and the electromagnetic field. However the technical difficulties of the relevant problems have precluded from expressing clearly this interdependence. Even the simple problem related to the field generated by a charged spherical mass is not correctly solved. In the present paper we reexamine from the outset this problem and propose a new solution.
Gravitationally confined relativistic neutrinos
Vayenas, C. G.; Fokas, A. S.; Grigoriou, D.
2017-09-01
Combining special relativity, the equivalence principle, and Newton’s universal gravitational law with gravitational rather than rest masses, one finds that gravitational interactions between relativistic neutrinos with kinetic energies above 50 MeV are very strong and can lead to the formation of gravitationally confined composite structures with the mass and other properties of hadrons. One may model such structures by considering three neutrinos moving symmetrically on a circular orbit under the influence of their gravitational attraction, and by assuming quantization of their angular momentum, as in the Bohr model of the H atom. The model contains no adjustable parameters and its solution, using a neutrino rest mass of 0.05 eV/c2, leads to composite state radii close to 1 fm and composite state masses close to 1 GeV/c2. Similar models of relativistic rotating electron - neutrino pairs give a mass of 81 GeV/c2, close to that of W bosons. This novel mechanism of generating mass suggests that the Higgs mass generation mechanism can be modeled as a latent gravitational field which gets activated by relativistic neutrinos.
Implications of the Gravitational Wave Event GW150914
Miller, M Coleman
2016-01-01
The era of gravitational-wave astronomy began on 14 September 2015, when the LIGO Scientific Collaboration detected the merger of two $\\sim 30 M_\\odot$ black holes at a distance of $\\sim 400$ Mpc. This event has facilitated qualitatively new tests of gravitational theories, and has also produced exciting information about the astrophysical origin of black hole binaries. In this review we discuss the implications of this event for gravitational physics and astrophysics, as well as the expectations for future detections. In brief: (1) because the spins of the black holes could not be measured accurately and because mergers are not well calculated for modified theories of gravity, the current analysis of GW150914 does not place strong constraints on gravity variants that change only the generation of gravitational waves, but (2) it does strongly constrain alterations of the propagation of gravitational waves and alternatives to black holes. Finally, (3) many astrophysical models for the origin of heavy black hol...
Warner, Nicholas H; Farmer, Jack D
2010-06-01
Jökulhlaups are terrestrial catastrophic outfloods, often triggered by subglacial volcanic eruptions. Similar volcano-ice interactions were likely important on Mars where magma/lava may have interacted with the planet's cryosphere to produce catastrophic floods. As a potential analogue to sediments deposited during martian floods, the Holocene sandurs of Iceland are dominated by basaltic clasts derived from the subglacial environment and deposited during jökulhlaups. Palagonite tuffs and breccias, present within the deposits, represent the primary alteration lithology. The surface abundance of palagonite on the sandurs is 1-20%. X-ray diffraction (XRD) analysis of palagonite breccias confirms a mineral assemblage of zeolites, smectites, low-quartz, and kaolinite. Oriented powder X-ray diffractograms (alteration mineral assemblage is consistent with low temperature (100-140 degrees C) hydrothermal alteration of basaltic material within the subglacial environment. These results suggest that potential martian analog sites that contain a similar suite of hydrated minerals may be indicative of past hydrothermal activity and locations where past habitable environments for microbial life may be found.
Universal decoherence due to gravitational time dilation
Pikovski, Igor; Costa, Fabio; Brukner, Caslav
2013-01-01
Phenomena inherent to quantum theory on curved space-time, such as Hawking radiation, are typically assumed to be only relevant at extreme physical conditions: at high energies and in strong gravitational fields. Here we consider low-energy quantum mechanics in the presence of weak gravitational time dilation and show that the latter leads to universal decoherence of quantum superpositions. Time dilation induces a universal coupling between internal degrees-of-freedom and the centre-of-mass of a composite particle and we show that the resulting entanglement causes the particle's position to decohere. We derive the decoherence timescale and show that the weak time dilation on Earth is already sufficient to decohere micro-scale objects. No coupling to an external environment is necessary, thus even completely isolated composite systems will decohere on curved space-time. In contrast to gravitational collapse models, no modification of quantum theory is assumed. General relativity therefore can account for the e...
The gravitational wave symphony of the Universe
Indian Academy of Sciences (India)
B S Sathyaprakash
2001-04-01
The new millennium will see the upcoming of several ground-based interferometric gravitational wave antennas. Within the next decade a space-based antenna may also begin to observe the distant Universe. These gravitational wave detectors will together operate as a network taking data continuously for several years, watching the transient and continuous phenomena occurring in the deep cores of astronomical objects and dense environs of the early Universe where gravity was extremely strong and highly nonlinear. The network will listen to the waves from rapidly spinning non-axisymmetric neutron stars, normal modes of black holes, binary black hole inspiral and merger, phase transitions in the early Universe, quantum ﬂuctuations resulting in a characteristic background in the early Universe. The gravitational wave antennas will open a new window to observe the dark Universe unreachable via other channels of astronomical observations.
Quantum Gravitational Decoherence of Light and Matter
Oniga, Teodora
2015-01-01
Real world quantum systems are open to perpetual influence from the wider environment. Vacuum gravitational fluctuations provide a most fundamental source of the environmental influence through their universal interactions with all forms of energy and matter causing decoherence. This may have subtle implications on precision laboratory experiments and astronomical observations and could limit the ultimate capacities for quantum technologies prone to decoherence. To establish the essential physical mechanism of decoherence under weak spacetime fluctuations, we carry out a sequence of analytical steps utilizing the Dirac constraint quantization and gauge invariant influence functional techniques, resulting in a general master equation of a compact form, that describes an open quantum gravitational system with arbitrary bosonic fields. An initial application of the theory is illustrated by the implied quantum gravitational dissipation of light as well as (non)relativistic massive or massless scalar particles. Re...
TU, H; Limousin, M; Cabanac, R; Marshall, P J; Fort, B; Treu, T; Péllo, R; Jullo, E; Kneib, J -P; Sygnet, J -F
2009-01-01
SL2SJ02176-0513 is a remarkable lens for the presence of two multiply-imaged systems at different redshifts lensed by a foreground massive galaxy at $z_{\\rm lens}=0.656$: a bright cusp arc at $z_{\\rm arc}=1.847$ and an additional double-image system at an estimated redshift of $z_{\\rm dbl}\\sim2.9$ based on photometry and lensing geometry. The system is located about 400 kpc away from the center of a massive group of galaxies. Mass estimates for the group are available from X-ray observations and satellite kinematics. Multicolor photometry provides an estimate of the stellar mass of the main lens galaxy. The lensing galaxy is modeled with two components (stars and dark matter), and we include the perturbing effect of the group environment, and all available constraints. We find that classic lensing degeneracies, e.g. between external convergence and mass density slope, are significantly reduced with respect to standard systems and infer tight constraints on the mass density profile: (i) the dark matter content...
DEFF Research Database (Denmark)
Talwara, Susheela; Grout, Brian William Wilson; Toldam-Andersen, Torben Bo
2015-01-01
Columnar apple trees (CATs) have radically-altered architecture (significantly shorter internodes and lateral branches) when compared to standard apple trees, attributed to a mutation of the Co gene involved in apical dominance. These changes in architecture have been associated with changes...
Energy Technology Data Exchange (ETDEWEB)
Ter-Kazarian, G. T. [Byurakan Astrophysical Observatory (Armenia)
1997-06-01
The suggested theory involves a drastic revision of the role of local internal symmetries in the physical concept of curved geometry. Under the reflection of fields and their dynamics from Minkowski to Riemannian space a standard gauge principle of local internal symmetries has been generalized. A gravitation gauge group is proposed, which is generated by hidden local internal symmetries. In all circumstances, it seemed to be of the greatest importance for the understanding of the physical nature of gravity. The most promising aspect in their approach so far is the fact that the energy-momentum conservation laws of gravitational interacting fields are formulated quite naturally by exploiting all the advantages of auxiliary shadow fields on flat shadow space. The mechanism developed here enables one to infer Einstein`s equation of gravitation, but only with a strong difference from Einstein`s theory at the vital point of well-defined energy-momentum tensor of gravitational field and conservation laws. The gravitational interaction as well as the general distortion of the manifold G(2.2.3) with hidden group U{sup loc} (1) has been considered.
Extended Theories of Gravitation
Directory of Open Access Journals (Sweden)
Fatibene Lorenzo
2013-09-01
Full Text Available Extended theories of gravitation are naturally singled out by an analysis inspired by the Ehelers-Pirani-Schild framework. In this framework the structure of spacetime is described by a Weyl geometry which is enforced by dynamics. Standard General Relativity is just one possible theory within the class of extended theories of gravitation. Also all Palatini f(R theories are shown to be extended theories of gravitation. This more general setting allows a more general interpretation scheme and more general possible couplings between gravity and matter. The definitions and constructions of extended theories will be reviewed. A general interpretation scheme will be considered for extended theories and some examples will be considered.
Cosmology of gravitational vacuum
Burdyuzha, V; Pacheco, J
2008-01-01
Production of gravitational vacuum defects and their contribution to the energy density of our Universe are discussed. These topological microstructures (defects) could be produced in the result of creation of the Universe from "nothing" when a gravitational vacuum condensate has appeared. They must be isotropically distributed over the isotropic expanding Universe. After Universe inflation these microdefects are smoothed, stretched and broken up. A part of them could survive and now they are perceived as the structures of Lambda-term and an unclustered dark matter. It is shown that the parametrization noninvariance of the Wheeler-De Witt equation can be used to describe phenomenologically vacuum topological defects of different dimensions (worm-holes, micromembranes, microstrings and monopoles). The mathematical illustration of these processes may be the spontaneous breaking of the local Lorentz-invariance of the quasi-classical equations of gravity. Probably the gravitational vacuum condensate has fixed tim...
Ohanian, Hans C
2013-01-01
The third edition of this classic textbook is a quantitative introduction for advanced undergraduates and graduate students. It gently guides students from Newton's gravitational theory to special relativity, and then to the relativistic theory of gravitation. General relativity is approached from several perspectives: as a theory constructed by analogy with Maxwell's electrodynamics, as a relativistic generalization of Newton's theory, and as a theory of curved spacetime. The authors provide a concise overview of the important concepts and formulas, coupled with the experimental results underpinning the latest research in the field. Numerous exercises in Newtonian gravitational theory and Maxwell's equations help students master essential concepts for advanced work in general relativity, while detailed spacetime diagrams encourage them to think in terms of four-dimensional geometry. Featuring comprehensive reviews of recent experimental and observational data, the text concludes with chapters on cosmology an...
A Gedankenexperiment in Gravitation
Gaspar, Yves
2011-01-01
In this paper we consider a thought experiment involving the effect of gravitation on an ideal scale containing a photon. If the tidal forces inherent to a gravitational field are neglected, then one is led to scenario which seems to bring about perpetual motion violating the first and second principle of thermodynamics. The tidal effects of gravity must neccessarily be included in order to obtain a consistent physical theory. As a result, Albert Einstein's thought experiments according to which the physical effects of inertia in an accelerated reference frame are equivalent to the effects of gravity in a frame at rest on the surface of a massive body must be reconsidered, since linearly accelerated frames do not produce tidal effects. We argue that the equivalence between inertial effects and gravitation can be restored for rotating frames and in this context a relation with the possible nature of quantum gravity is conjectured.
Perez, Jérôme
2007-01-01
Le présent document constitue le rapport de mon habilitation à diriger des recherches. Le sujet général est la gravitation qui constitue mon thème de recherche. Trois parties indépendantes forment le corps de ce document.Un essai de gravitation relativiste traite des propriétés dynamiques de l'Univers homogène et anisotrope. Un essai de gravitation classique rassemble trois de mes articles emblématiques sur ce sujet préfacés chacun d'une introduction. La dernière partie est consacrée à des in...
Kelly, Bernard J.
2010-01-01
Einstein's General Theory of Relativity is our best classical description of gravity, and informs modern astronomy and astrophysics at all scales: stellar, galactic, and cosmological. Among its surprising predictions is the existence of gravitational waves -- ripples in space-time that carry energy and momentum away from strongly interacting gravitating sources. In my talk, I will give an overview of the properties of this radiation, recent breakthroughs in computational physics allowing us to calculate the waveforms from galactic mergers, and the prospect of direct observation with interferometric detectors such as LIGO and LISA.
Energy Technology Data Exchange (ETDEWEB)
Pasterski, Sabrina; Strominger, Andrew; Zhiboedov, Alexander [Center for the Fundamental Laws of Nature, Harvard University,Cambridge, MA 02138 (United States)
2016-12-14
The conventional gravitational memory effect is a relative displacement in the position of two detectors induced by radiative energy flux. We find a new type of gravitational ‘spin memory’ in which beams on clockwise and counterclockwise orbits acquire a relative delay induced by radiative angular momentum flux. It has recently been shown that the displacement memory formula is a Fourier transform in time of Weinberg’s soft graviton theorem. Here we see that the spin memory formula is a Fourier transform in time of the recently-discovered subleading soft graviton theorem.
Gravitational Waves: The Evidence Mounts
Wick, Gerald L.
1970-01-01
Reviews the work of Weber and his colleagues in their attempts at detecting extraterrestial gravitational waves. Coincidence events recorded by special detectors provide the evidence for the existence of gravitational waves. Bibliography. (LC)
Gravitational Collapse End States
Joshi, Pankaj S.
2004-01-01
Recent developments on the final state of a gravitationally collapsing massive matter cloud are summarized and reviewed here. After a brief background on the problem, we point out how the black hole and naked singularity end states arise naturally in spherical collapse. We see that it is the geometry of trapped surfaces that governs this phenomena.
Gravitational lensing & stellar dynamics
Koopmans, L. V. E.; Mamon, GA; Combes, F; Deffayet, C; Fort, B
2006-01-01
Strong gravitational lensing and stellar dynamics provide two complementary and orthogonal constraints on the density profiles of galaxies. Based on spherically symmetric, scale-free, mass models, it is shown that the combination of both techniques is powerful in breaking the mass-sheet and mass-ani
Gravitational lensing & stellar dynamics
Koopmans, L. V. E.; Mamon, GA; Combes, F; Deffayet, C; Fort, B
2006-01-01
Strong gravitational lensing and stellar dynamics provide two complementary and orthogonal constraints on the density profiles of galaxies. Based on spherically symmetric, scale-free, mass models, it is shown that the combination of both techniques is powerful in breaking the mass-sheet and
Gravitational lensing & stellar dynamics
Koopmans, L. V. E.; Mamon, GA; Combes, F; Deffayet, C; Fort, B
2006-01-01
Strong gravitational lensing and stellar dynamics provide two complementary and orthogonal constraints on the density profiles of galaxies. Based on spherically symmetric, scale-free, mass models, it is shown that the combination of both techniques is powerful in breaking the mass-sheet and mass-ani
Nonlinear Gravitational Lagrangians revisited
Magnano, Guido
2016-01-01
The Legendre transformation method, applied in 1987 to deal with purely metric gravitational Lagrangians with nonlinear dependence on the Ricci tensor, is extended to metric-affine models and is shown to provide a concise and insightful comparison of the dynamical content of the two variational frameworks.
Gravitation radiation observations
Glass, E. N.
2017-01-01
The notion of gravitational radiation begins with electromagnetic radiation. In 1887 Heinrich Hertz, working in one room, generated and received electromagnetic radiation. Maxwell's equations describe the electromagnetic field. The quanta of electromagnetic radiation are spin 1 photons. They are fundamental to atomic physics and quantum electrodynamics.
Static Gravitational Global Monopoles
Liebling, S L
2000-01-01
Static solutions in spherical symmetry are found for gravitating global monopoles. Regular solutions lacking a horizon are found for $\\eta \\sqrt{3/8\\pi} \\approx 0.3455$ is consistent with findings that topological inflation begins at $\\eta \\approx 0.33$.
Quantum Decoherence During Inflation from Gravitational Nonlinearities
Nelson, Elliot
2016-01-01
We study the inflationary quantum-to-classical transition for the adiabatic curvature perturbation $\\zeta$ due to quantum decoherence, focusing on the role played by squeezed-limit mode couplings. We evolve the quantum state $\\Psi$ in the Schr\\"odinger picture, for a generic cubic coupling to additional environment degrees of freedom. Focusing on the case of minimal gravitational interactions, we find the evolution of the reduced density matrix for a given long-wavelength fluctuation by tracing out the other (mostly shorterwavelength) modes of $\\zeta$ as an environment. We show that inflation produces phase oscillations in the wave functional $\\Psi[\\zeta(\\mathbf{x})]$, which suppress off-diagonal components of the reduced density matrix, leaving a diagonal mixture of different classical configurations. Gravitational nonlinearities thus provide a minimal mechanism for generating classical stochastic perturbations from inflation. We identify the time when decoherence occurs, which is delayed after horizon cross...
Gutperlet, R.; Capperucci, R. M.; Bartholomä, A.; Kröncke, I.
2017-03-01
A survey was conducted in the Inner Jade tidal channel, the connection between the Jade Bay and the southern North Sea, to investigate the relationships between macrofauna community structure and environmental variables in a highly heterogeneous human disturbed environment. A manual expertise based classification of sidescan sonar records was successful in confirming the general relationship between backscatter intensity and sediment grain size in weakly disturbed environments. In highly disturbed environments, instead, the classification showed the influence of the topographic roughness over the sediment roughness in backscatter intensity. Low, but significant relationships between hydroacoustic classification and macrofauna community structure, as well as sediment distribution and the macrofaunal communities were identified. The most important impact on spatial community structure was the number of days after dredging/dumping activity for the JadeWeserPort, followed by sediment characteristics. Sand dominated western stations that were dredged for the JWP exhibited a characteristic macrofaunal community. Another distinct community occurred in stations with elevated mud content within the regularly dredged old navigation channel and in the undisturbed south eastern area. The macrofaunal communities in the north eastern undisturbed area coincided with elevated gravel and shell contents. This study stresses the problems of benthic habitat mapping in such a heterogeneous area.
Blas-Valdivia, Vanessa; Cano-Europa, Edgar; Martinez-Perez, Yoalli; Lezama-Palacios, Ruth; Franco-Colin, Margarita; Ortiz-Butron, Rocio
2015-10-01
The aim of this study was to investigate if a protective effect from hypothyroidism in acute liver failure resulted from reduced endoplasmic reticulum stress and changes to the redox environment. Twenty male Sprague-Dawley rats were divided in four groups: (1) euthyroid (sham surgery), (2) hypothyroid, (3) euthyroid (sham surgery)+thioacetamide and (4) hypothyroid+thioacetamide. Hypothyroidism was confirmed two weeks after thyroidectomy, and thioacetamide (TAA) (400mg/kg, ip) was administrated to the appropriate groups for three days with supportive therapy. Grades of encephalopathy in all animals were determined using behavioral tests. Animals were decapitated and their blood was obtained to assess liver function. The liver was dissected: the left lobe was used for histology and the right lobe was frozen for biochemical assays. Body weight, rectal temperature and T4 concentration were lower in hypothyroid groups. When measurements of oxidative stress markers, redox environment, γ-glutamylcysteine synthetase and glutathione-S-transferase were determined, we observed that hypothyroid animals with TAA compensated better with oxidative damage than euthyroid animals treated with TAA. Furthermore, we measured reduced expressions of GADD34, caspase-12 and GRP78 and subsequently less hypothyroidism-induced cellular damage in hypothyroid animals. We conclude that hypothyroidism protects against hepatic damage caused by TAA because it reduces endoplasmic reticulum stress and changes to the redox environment.
Gravitational Instabilities in Disks with Radiative Cooling
Mejia, A C; Pickett, M K; Mej\\'ia, Annie C.; Durisen, Richard H.; Pickett, Megan K.
2003-01-01
Previous simulations of self-gravitating protostellar disks have shown that, once developed, gravitational instabilities are enhanced by cooling the disk constantly during its evolution (Pickett et al. 2002). These earlier calculations included a very simple form of volumetric cooling, with a constant cooling time throughout the disk, which acted against the stabilizing effects of shock heating. The present work incorporates more realistic treatments of energy transport. The initial disk model extends from 2.3 to 40 AU, has a mass of 0.07 Msun and orbits a 0.5 Msun star. The models evolve for a period of over 2500 years, during which extensive spiral arms form. The disks structure is profoundly altered, transient clumps form in one case, but no permanent bound companion objects develop.
Gravitational Fragmentation in Galaxy Mergers: A Stability Criteria
Escala, Andres; del Valle, Luciano; Castillo, Esteban
2012-01-01
We study the gravitational stability of gaseous streams in the complex environment of a galaxy merger, because mergers are known to be places of ongoing massive cluster formation and bursts of star formation. We find an analytic stability parameter for case of gaseous streams orbiting around the merger remnant. We test our stability criteria using hydrodynamical simulations of galaxy mergers, obtaining satisfactory results. We find that our criteria successfully predicts the streams that will be gravitationally unstable to fragment into clumps.
Energy Technology Data Exchange (ETDEWEB)
Dill, H.G.; Wehner, H.; Kus, J. [Federal Institute for Geosciences and Natural Resources, P.O. Box 510163, D-30631 Hannover (Germany); Botz, R. [University Kiel, Geological-Paleontological Department, Olshausenstrasse 40-60, D-24118 Kiel (Germany); Berner, Z.; Stueben, D. [Technical University Karlsruhe, Institute for Mineralogy and Geochemistry, Fritz-Haber-Weg 2, D-76131 Karlsruhe (Germany); Al-Sayigh, A. [Sultan Qaboos University, Geological Dept. PO Box 36, Al-Khod (Oman)
2007-10-01
Paralic carbonaceous series intercalated among calcareous shelf sediments have seldom been investigated. During the early Eocene, calcareous and siliciclastic sediments were deposited on a wide shelf in front of low-reliefed hinterland in the Al Khawd region in NE Oman. The siliciclastic-calcareous sediments originated from strongly reworked debris of the Arabic Shield. The underlying Semail Ophiolite did not act as a direct source of debris but provided some heat to increase the maturity of carbonaceous rocks and modify the isotope signal of the calcareous minerals in the Rusayl Formation. A multidisciplinary approach involving sedimentology, mineralogy, chemistry, coal petrography and paleontology resulted in the establishment of nine stratigraphic lithofacies units and provides the reader with a full picture from deposition of the mixed carbonaceous-calcareous-siliciclastic rocks to the most recent stages of post-depositional alteration of the Paleogene formations. The calcareous Jafnayn Formation (lithofacies unit I) developed in a subtidal to intertidal regime, influenced episodically by storms. Deepening of the calcareous shelf towards younger series was ground to a halt by paleosols developing on a disconformity (lithofacies unit II) and heralding the onset of the Rusayl Formation. The stratigraphic lithofacies units III and IV reflect mangrove swamps which from time to time were flooded through washover fans from the open sea. The presence of Spinozonocolpites and the taxon Avicennia, which today belong to a coastal marsh vegetational community, furnish palynological evidence to the idea of extensive mangrove swamps in the Rusayl Formation [El Beialy, S.Y., 1998. Stratigraphic and palaeonenvironmental significance of Eocene palynomorphs from the Rusayl Shale Formation, Al Khawd, northern Oman. Review of Palaeobotany and Palynology 102, 249-258]. During the upper Rusayl Formation (lithofacies units V through VII) algal mats episodically flooded by marine
Molina, S J; Capani, F; Guelman, L R
2016-04-01
It has been previously shown that different extra-auditory alterations can be induced in animals exposed to noise at 15 days. However, data regarding exposure of younger animals, that do not have a functional auditory system, have not been obtained yet. Besides, the possibility to find a helpful strategy to restore these changes has not been explored so far. Therefore, the aims of the present work were to test age-related differences in diverse hippocampal-dependent behavioral measurements that might be affected in noise-exposed rats, as well as to evaluate the effectiveness of a potential neuroprotective strategy, the enriched environment (EE), on noise-induced behavioral alterations. Male Wistar rats of 7 and 15 days were exposed to moderate levels of noise for two hours. At weaning, animals were separated and reared either in standard or in EE cages for one week. At 28 days of age, different hippocampal-dependent behavioral assessments were performed. Results show that rats exposed to noise at 7 and 15 days were differentially affected. Moreover, EE was effective in restoring all altered variables when animals were exposed at 7 days, while a few were restored in rats exposed at 15 days. The present findings suggest that noise exposure was capable to trigger significant hippocampal-related behavioral alterations that were differentially affected, depending on the age of exposure. In addition, it could be proposed that hearing structures did not seem to be necessarily involved in the generation of noise-induced hippocampal-related behaviors, as they were observed even in animals with an immature auditory pathway. Finally, it could be hypothesized that the differential restoration achieved by EE rearing might also depend on the degree of maturation at the time of exposure and the variable evaluated, being younger animals more susceptible to environmental manipulations.
Barreto, W; Rodriguez-Mueller, B
2016-01-01
Usually in computational physics, conclusions about realistic scenarios can be drawn from {\\it ab initio} idealized models. In some ways, the discovery of critical behavior in the gravitational collapse of a massless scalar field leads to the simulation of binary black holes, from its coalescence, to merging and ringdown. We have been lucky enough to have been working on a toy model to explore our way in as these events unfold. We revisited the gravitational instability of a kink problem. During that study, we confirmed a conjecture related to the mass gap, in the context of critical behavior, at the threshold of black hole formation. What is the meaning of this mass gap? Does it have physical relevance? This essay is about these issues.
Dimensions and Gravitational Waves
van Haasteren, Rutger
2014-10-01
High-precision timing of Galactic millisecond pulsars with radio telescopes holds great promise for the detection of astrophysical gravitational-waves in frequency range 10--100 nHz. Modern Bayesian data analysis methods rely mostly on Markov Chain Monte Carlo (MCMC) to explore the model parameter space when searching for signals in the pulsar timing data. Current challenges involve parameter spaces with large dimensionality, and linear algebra of high-dimensional systems. I will present sampling methods (taken from the Planck analysis team), and rank-reduction methods for large linear systems, that have enabled us to decrease the dimensionality of such problems. These methods are now being used to search for gravitational-waves in pulsar timing array projects. Especially our rank-reduction techniques are useful for any data analysis problem that involve large linear least-squares systems.
COSMOLOGY WITH GRAVITATIONAL LENSES
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Emilio E. Falco
2009-01-01
Full Text Available Gravitational lenses yield a very high rate of return on observational investment. Given their scarcity, their impact on our knowledge of the universe is very signi cant. In the weak- eld limit, lensing studies are based on well-established physics and thus o er a straightforward approach to pursue many currently pressing problems of astrophysics. Examples of these are the signi cance of dark matter and the density, age and size of the universe. I present recent developments in cosmological applications of gravitational lenses, regarding estimates of the Hubble constant using strong lensing of quasars. I describe our recent measurements of time delays for the images of SDSS J1004+4112, and discuss prospects for the future utilizing synoptic telescopes, planned and under construction.
Gravitationally induced quantum transitions
Landry, A.; Paranjape, M. B.
2016-06-01
In this paper, we calculate the probability for resonantly inducing transitions in quantum states due to time-dependent gravitational perturbations. Contrary to common wisdom, the probability of inducing transitions is not infinitesimally small. We consider a system of ultracold neutrons, which are organized according to the energy levels of the Schrödinger equation in the presence of the Earth's gravitational field. Transitions between energy levels are induced by an oscillating driving force of frequency ω . The driving force is created by oscillating a macroscopic mass in the neighborhood of the system of neutrons. The neutron lifetime is approximately 880 sec while the probability of transitions increases as t2. Hence, the optimal strategy is to drive the system for two lifetimes. The transition amplitude then is of the order of 1.06 ×10-5, and hence with a million ultracold neutrons, one should be able to observe transitions.
Gravitationally induced quantum transitions
Landry, A
2016-01-01
In this letter, we calculate the probability for resonantly induced transitions in quantum states due to time dependent gravitational perturbations. Contrary to common wisdom, the probability of inducing transitions is not infinitesimally small. We consider a system of ultra cold neutrons (UCN), which are organized according to the energy levels of the Schr\\"odinger equation in the presence of the earth's gravitational field. Transitions between energy levels are induced by an oscillating driving force of frequency $\\omega$. The driving force is created by oscillating a macroscopic mass in the neighbourhood of the system of neutrons. The neutrons decay in 880 seconds while the probability of transitions increase as $t^2$. Hence the optimal strategy is to drive the system for 2 lifetimes. The transition amplitude then is of the order of $1.06\\times 10^{-5}$ hence with a million ultra cold neutrons, one should be able to observe transitions.
Spacetime, Geometry and Gravitation
Sharan, Pankaj
2009-01-01
This introductory textbook on the general theory of relativity presents a solid foundation for those who want to learn about relativity. The subject is presented in a physically intuitive, but mathematically rigorous style. The topic of relativity is covered in a broad and deep manner. Besides, the aim is that after reading the book a student should not feel discouraged when she opens advanced texts on general relativity for further reading. The book consists of three parts: An introduction to the general theory of relativity. Geometrical mathematical background material. Topics that include the action principle, weak gravitational fields and gravitational waves, Schwarzschild and Kerr solution, and the Friedman equation in cosmology. The book is suitable for advanced graduates and graduates, but also for established researchers wishing to be educated about the field.
Burinskii, Alexander
2015-01-01
As is known, the gravitational and electromagnetic (EM) field of the Dirac electron is described by an over-extremal Kerr-Newman (KN) black hole (BH) solution which has the naked singular ring and two-sheeted topology. This space is regulated by the formation of a regular source based on the Higgs mechanism of broken symmetry. This source shares much in common with the known MIT- and SLAC-bag models, but has the important advantage, of being in accordance with gravitational and electromagnetic field of the external KN solution. The KN bag model is flexible. At rotations, it takes the shape of a thin disk, and similar to other bag models, under deformations it creates a string-like structure which is positioned along the sharp border of the disk.
Koehler, Wolfgang
2011-01-01
A new classical theory of gravitation within the framework of general relativity is presented. It is based on a matrix formulation of four-dimensional Riemann-spaces and uses no artificial fields or adjustable parameters. The geometrical stress-energy tensor is derived from a matrix-trace Lagrangian, which is not equivalent to the curvature scalar R. To enable a direct comparison with the Einstein-theory a tetrad formalism is utilized, which shows similarities to teleparallel gravitation theories, but uses complex tetrads. Matrix theory might solve a 27-year-old, fundamental problem of those theories (sec. 4.1). For the standard test cases (PPN scheme, Schwarzschild-solution) no differences to the Einstein-theory are found. However, the matrix theory exhibits novel, interesting vacuum solutions.
Gravitational instabilities of superspinars
Pani, Paolo; Berti, Emanuele; Cardoso, Vitor
2010-01-01
Superspinars are ultracompact objects whose mass M and angular momentum J violate the Kerr bound (cJ/GM^2>1). Recent studies analyzed the observable consequences of gravitational lensing and accretion around superspinars in astrophysical scenarios. In this paper we investigate the dynamical stability of superspinars to gravitational perturbations, considering either purely reflecting or perfectly absorbing boundary conditions at the "surface" of the superspinar. We find that these objects are unstable independently of the boundary conditions, and that the instability is strongest for relatively small values of the spin. Also, we give a physical interpretation of the various instabilities that we find. Our results (together with the well-known fact that accretion tends to spin superspinars down) imply that superspinars are very unlikely astrophysical alternatives to black holes.
Directory of Open Access Journals (Sweden)
Kristyn Dunlop
2015-02-01
Full Text Available The importance of the in utero environment as a contributor to later life metabolic disease has been demonstrated in both human and animal studies. In this review, we consider how disruption of normal fetal growth may impact skeletal muscle metabolic development, ultimately leading to insulin resistance and decreased insulin sensitivity, a key precursor to later life metabolic disease. In cases of intrauterine growth restriction (IUGR associated with hypoxia, where the fetus fails to reach its full growth potential, low birth weight (LBW is often the outcome, and early in postnatal life, LBW individuals display modifications in the insulin-signaling pathway, a critical precursor to insulin resistance. In this review, we will present literature detailing the classical development of insulin resistance in IUGR, but also discuss how this impaired development, when challenged with a postnatal Western diet, may potentially contribute to the development of later life insulin resistance. Considering the important role of the skeletal muscle in insulin resistance pathogenesis, understanding the in utero programmed origins of skeletal muscle deficiencies in insulin sensitivity and how they may interact with an adverse postnatal environment, is an important step in highlighting potential therapeutic options for LBW offspring born of pregnancies characterized by placental insufficiency.
Gravitational Lenses of Wormholes
Nandi, K K; Zhang, Y Z; Nandi, Kamal Kanti; Zakharov, Alexander V.; Zhang, Yuan-Zhong
2006-01-01
Gravitational lensing by traversable Lorentzian wormholes is a new possibility and is analyzed in the strong field limit. Wormhole solutions are considered in the Einstein minimally coupled theory and in the brane world model. The observables in both the theories show significant differences from those in the Schwarzschild black hole lensing. It is shown that the zero mass wormholes act as photon sinks. Some special features of the considered solutions are pointed out.
Extended Theories of Gravitation
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Fatibene Lorenzo
2013-09-01
Full Text Available Within the framework of extended theories of gravitation we shall discuss physical equivalences among different formalisms and classical tests. As suggested by the Ehlers-Pirani-Schild framework, the conformal invariance will be preserved and its effect on observational protocols discussed. Accordingly, we shall review standard tests showing how Palatini f(R-theories naturally passes solar system tests. Observation protocols will be discussed in this wider framework.
Gravitation and electromagnetism
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Sidharth, B.G. [Birla Science Centre, Adarsh Nagar, Hyderabad (India)
2001-06-01
The realms of gravitation, belonging to classical physics, and of electromagnetism, belonging to the theory of the electron and quantum mechanics have remained apart as two separate pillars, in spite of a century of effort by physicists to reconcile them. In this paper it is argued that if ideas of classical spacetime have been extended to include in addition to non-integrability non-commutavity also, then such a reconciliation is possible.
Can gravitation accelerate neutrinos?
Hojman, Sergio A.; Asenjo, Felipe A.
2012-01-01
The Lagrangian equations of motion for massive spinning test particles (tops) moving on a gravitational background using General Relativity are presented. The paths followed by tops are nongeodesic. An exact solution for the motion of tops on a Schwarzschild background which allows for superluminal propagation of tops is studied. It is shown that the solution becomes relevant for particles with small masses, such as neutrinos. This general result is used to calculate the necessary condition t...
Gravitational Waves Astronomy: a cornerstone for gravitational theories
Corda, Christian
2010-01-01
Realizing a gravitational wave (GW) astronomy in next years is a great challenge for the scientific community. By giving a significant amount of new information, GWs will be a cornerstone for a better understanding of gravitational physics. In this paper we re-discuss that the GW astronomy will permit to solve a captivating issue of gravitation. In fact, it will be the definitive test for Einstein's general relativity (GR), or, alternatively, a strong endorsement for extended theories of gravity (ETG).
Directory of Open Access Journals (Sweden)
Laura eMaggi
2011-10-01
Full Text Available In recent years several evidence demonstrated that some features of hippocampal biology, like neurogenesis, synaptic transmission, learning and memory performances are deeply modulated by social, motor and sensorial experiences. Fractalkine/CX3CL1 is a transmembrane chemokine abundantly expressed in the brain by neurons, where it modulates glutamatergic transmission and long-term plasticity processes regulating the intercellular communication between glia and neurons, being its specific receptor CX3CR1 expressed by microglia. In this paper we investigated the role of CX3CL1/CX3CR1 signaling on experience-dependent hippocampal plasticity processes. At this aim wt and CX3CR1GFP/GFP mice were exposed to long-lasting-enriched environment (EE and the effects on hippocampal functions were studied by electrophysiological recordings of long-term potentiation (LTP of synaptic activity, behavioral tests of learning and memory in the Morris water maze paradigm and analysis of neurogenesis in the subgranular zone of the dentate gyrus (DG.We found that CX3CR1 deficiency increases hippocampal plasticity and spatial memory blunting the potentiating effects of EE. In contrast, exposure to EE increased the number and migration of neural progenitors in the DG of both wt and CX3CR1GFP/GFP mice. These data indicate that CX3CL1/CX3CR1-mediated signaling is crucial for a normal experience-dependent modulation of hippocampal functions.
Gravitomagnetic corrections on gravitational waves
Capozziello, S; Forte, L; Garufi, F; Milano, L
2009-01-01
Gravitational waveforms and production could be considerably affected by gravitomagnetic corrections considered in relativistic theory of orbits. Beside the standard periastron effect of General Relativity, new nutation effects come out when c^{-3} corrections are taken into account. Such corrections emerge as soon as matter-current densities and vector gravitational potentials cannot be discarded into dynamics. We study the gravitational waves emitted through the capture, in the gravitational field of massive binary systems (e.g. a very massive black hole on which a stellar object is inspiralling) via the quadrupole approximation, considering precession and nutation effects. We present a numerical study to obtain the gravitational wave luminosity, the total energy output and the gravitational radiation amplitude. From a crude estimate of the expected number of events towards peculiar targets (e.g. globular clusters) and in particular, the rate of events per year for dense stellar clusters at the Galactic Cen...
Gravitational waves from stellar encounters
Capozziello, Salvatore
2008-01-01
The emission of gravitational waves from a system of massive objects interacting on elliptical, hyperbolic and parabolic orbits is studied in the quadrupole approximation. Analytical expressions are then derived for the gravitational wave luminosity, the total energy output and gravitational radiation amplitude. A crude estimate of the expected number of events towards peculiar targets (i.e. globular clusters) is also given. In particular, the rate of events per year is obtained for the dense stellar cluster at the Galactic Center.
Gravitational Waves, Sources, and Detectors
Schutz, Bernard F
2010-01-01
Notes of lectures for graduate students that were given at Lake Como in 1999, covering the theory of linearized gravitational waves, their sources, and the prospects at the time for detecting gravitational waves. The lectures remain of interest for pedagogical reasons, and in particular because they contain a treatment of current-quadrupole gravitational radiation (in connection with the r-modes of neutron stars) that is not readily available in other sources.
Piecewise flat gravitational waves
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Van de Meent, Maarten, E-mail: M.vandeMeent@uu.nl [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, PO Box 80.195, 3508 TD Utrecht (Netherlands)
2011-04-07
We examine the continuum limit of the piecewise flat locally finite gravity model introduced by 't Hooft. In the linear weak field limit, we find the energy-momentum tensor and metric perturbation of an arbitrary configuration of defects. The energy-momentum turns out to be restricted to satisfy certain conditions. The metric perturbation is mostly fixed by the energy-momentum except for its lightlike modes which reproduce linear gravitational waves, despite no such waves being present at the microscopic level.
Superstatistics and Gravitation
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Octavio Obregón
2010-09-01
Full Text Available We suggest to consider the spacetime as a non-equilibrium system with a long-term stationary state that possess as a spatio-temporally fluctuating quantity ß . These systems can be described by a superposition of several statistics, superstatistics. We propose a Gamma distribution for f(ß that depends on a parameter ρ1. By means of it the corresponding entropy is calculated, ρ1 is identified with the probability corresponding to this model. A generalized Newton’s law of gravitation is then obtained following the entropic force formulation. We discuss some of the difficulties to try to get an associated theory of gravity.
Testing alternate gravitational theories
Standish, E. M.
2010-01-01
The planetary ephemerides are used to examine different suggested forms of the gravitational equations of motion which could possibly cause the observed Pioneer Anomaly. It is shown that most of the forms would be unacceptable, including that generally assumed - a constant acceleration directed toward the Sun. The tests show that three other forms could not exist within 10 au's of the Sun. Only one suggested form would be compatible with the Pioneer Anomaly affecting Saturn or any other more inward planet. Additional planetary observations in the future may possibly eliminate this form also.
Gravitational Lensing & Stellar Dynamics
Koopmans, L V E
2005-01-01
Strong gravitational lensing and stellar dynamics provide two complementary and orthogonal constraints on the density profiles of galaxies. Based on spherically symmetric, scale-free, mass models, it is shown that the combination of both techniques is powerful in breaking the mass-sheet and mass-anisotropy degeneracies. Second, observational results are presented from the Lenses Structure & Dynamics (LSD) Survey and the Sloan Lens ACS (SLACS) Survey collaborations to illustrate this new methodology in constraining the dark and stellar density profiles, and mass structure, of early-type galaxies to redshifts of unity.
Pinning Down Gravitational Settling
Korn, A J; Grundahl, F; Barklem, P; Gustafsson, B; Korn, Andreas J.; Piskunov, Nikolai; Grundahl, Frank; Barklem, Paul; Gustafsson, Bengt
2006-01-01
We analyse high-resolution archival UVES data of turnoff and subgiant stars in the nearby globular cluster NGC 6397 ([Fe/H] = -2). Balmer-profile analyses are performed to derive reddening-free effective temperatures. Due to the limited S/N and uncertainties related to blaze removal, we find the data quality insufficient to exclude the existence of gravitational settling. If the newly derived effective temperatures are taken as a basis for an abundance analysis, the photospheric iron (Fe II) abundance in the turnoff stars is 0.11 dex lower than in the (well-mixed) subgiants.
Danzmann, K
2013-01-01
The last century has seen enormous progress in our understanding of the Universe. We know the life cycles of stars, the structure of galaxies, the remnants of the big bang, and have a general understanding of how the Universe evolved. We have come remarkably far using electromagnetic radiation as our tool for observing the Universe. However, gravity is the engine behind many of the processes in the Universe, and much of its action is dark. Opening a gravitational window on the Universe will let us go further than any alternative. Gravity has its own messenger: Gravitational waves, ripples in the fabric of spacetime. They travel essentially undisturbed and let us peer deep into the formation of the first seed black holes, exploring redshifts as large as z ~ 20, prior to the epoch of cosmic re-ionisation. Exquisite and unprecedented measurements of black hole masses and spins will make it possible to trace the history of black holes across all stages of galaxy evolution, and at the same time constrain any devia...
General Relativity and Gravitation
Ashtekar, Abhay; Berger, Beverly; Isenberg, James; MacCallum, Malcolm
2015-07-01
Part I. Einstein's Triumph: 1. 100 years of general relativity George F. R. Ellis; 2. Was Einstein right? Clifford M. Will; 3. Cosmology David Wands, Misao Sasaki, Eiichiro Komatsu, Roy Maartens and Malcolm A. H. MacCallum; 4. Relativistic astrophysics Peter Schneider, Ramesh Narayan, Jeffrey E. McClintock, Peter Mészáros and Martin J. Rees; Part II. New Window on the Universe: 5. Receiving gravitational waves Beverly K. Berger, Karsten Danzmann, Gabriela Gonzalez, Andrea Lommen, Guido Mueller, Albrecht Rüdiger and William Joseph Weber; 6. Sources of gravitational waves. Theory and observations Alessandra Buonanno and B. S. Sathyaprakash; Part III. Gravity is Geometry, After All: 7. Probing strong field gravity through numerical simulations Frans Pretorius, Matthew W. Choptuik and Luis Lehner; 8. The initial value problem of general relativity and its implications Gregory J. Galloway, Pengzi Miao and Richard Schoen; 9. Global behavior of solutions to Einstein's equations Stefanos Aretakis, James Isenberg, Vincent Moncrief and Igor Rodnianski; Part IV. Beyond Einstein: 10. Quantum fields in curved space-times Stefan Hollands and Robert M. Wald; 11. From general relativity to quantum gravity Abhay Ashtekar, Martin Reuter and Carlo Rovelli; 12. Quantum gravity via unification Henriette Elvang and Gary T. Horowitz.
Energy Technology Data Exchange (ETDEWEB)
Burinskii, A., E-mail: burinskii@mail.ru [Russian Academy of Sciences, Nuclear Safety Institute (Russian Federation)
2015-08-15
The Kerr–Newman (KN) black hole (BH) solution exhibits the external gravitational and electromagnetic field corresponding to that of the Dirac electron. For the large spin/mass ratio, a ≫ m, the BH loses horizons and acquires a naked singular ring creating two-sheeted topology. This space is regularized by the Higgs mechanism of symmetry breaking, leading to an extended particle that has a regular spinning core compatible with the external KN solution. We show that this core has much in common with the known MIT and SLAC bag models, but has the important advantage of being in accordance with the external gravitational and electromagnetic fields of the KN solution. A peculiar two-sheeted structure of Kerr’s gravity provides a framework for the implementation of the Higgs mechanism of symmetry breaking in configuration space in accordance with the concept of the electroweak sector of the Standard Model. Similar to other bag models, the KN bag is flexible and pliant to deformations. For parameters of a spinning electron, the bag takes the shape of a thin rotating disk of the Compton radius, with a ring–string structure and a quark-like singular pole formed at the sharp edge of this disk, indicating that the considered lepton bag forms a single bag–string–quark system.
Burinskii, A.
2015-08-01
The Kerr-Newman (KN) black hole (BH) solution exhibits the external gravitational and electromagnetic field corresponding to that of the Dirac electron. For the large spin/mass ratio, a ≫ m, the BH loses horizons and acquires a naked singular ring creating two-sheeted topology. This space is regularized by the Higgs mechanism of symmetry breaking, leading to an extended particle that has a regular spinning core compatible with the external KN solution. We show that this core has much in common with the known MIT and SLAC bag models, but has the important advantage of being in accordance with the external gravitational and electromagnetic fields of the KN solution. A peculiar two-sheeted structure of Kerr's gravity provides a framework for the implementation of the Higgs mechanism of symmetry breaking in configuration space in accordance with the concept of the electroweak sector of the Standard Model. Similar to other bag models, the KN bag is flexible and pliant to deformations. For parameters of a spinning electron, the bag takes the shape of a thin rotating disk of the Compton radius, with a ring-string structure and a quark-like singular pole formed at the sharp edge of this disk, indicating that the considered lepton bag forms a single bag-string-quark system.
Energy Technology Data Exchange (ETDEWEB)
Green, H.S. [Department of Physics and Mathematical Physics, University of Adelaide, Adelaide, SA (Australia)
1998-12-31
It is possible to construct the non-euclidean geometry of space-time from the information carried by neutral particles. Points are identified with the quantal events in which photons or neutrinos are created and annihilated, and represented by the relativistic density matrices of particles immediately after creation or before annihilation. From these, matrices representing subspaces in any number of dimensions are constructed, and the metric and curvature tensors are derived by an elementary algebraic method; these are similar in all respects to those of Riemannian geometry. The algebraic method is extended to obtain solutions of Einstein`s gravitational field equations for empty space, with a cosmological term. General relativity and quantum theory are unified by the quantal embedding of non-euclidean space-time, and the derivation of a generalisation, consistent with Einstein`s equations, of the special relativistic wave equations of particles of any spin within representations of SO(3) SO(4; 2). There are some novel results concerning the dependence of the scale of space-time on properties of the particles by means of which it is observed, and the gauge groups associated with gravitation. Copyright (1998) CSIRO Australia 33 refs.
Calcium signaling in plant cells in altered gravity
Kordyum, E. L.
2003-10-01
Changes in the intracellular Ca 2+ concentration in altered gravity (microgravity and clinostating) evidence that Ca 2+ signaling can play a fundamental role in biological effects of microgravity. Calcium as a second messenger is known to play a crucial role in stimulus - response coupling for many plant cellular signaling pathways. Its messenger functions are realized by transient changes in the cytosolic ion concentration induced by a variety of internal and external stimuli such as light, hormones, temperature, anoxia, salinity, and gravity. Although the first data on the changes in the calcium balance in plant cells under the influence of altered gravity have appeared in 80 th, a review highlighting the performed research and the possible significance of such Ca 2+ changes in the structural and metabolic rearrangements of plant cells in altered gravity is still lacking. In this paper, an attempt was made to summarize the available experimental results and to consider some hypotheses in this field of research. It is proposed to distinguish between cell gravisensing and cell graviperception; the former is related to cell structure and metabolism stability in the gravitational field and their changes in microgravity (cells not specialized to gravity perception), the latter is related to active use of a gravitational stimulus by cells presumebly specialized to gravity perception for realization of normal space orientation, growth, and vital activity (gravitropism, gravitaxis) in plants. The main experimental data concerning both redistribution of free Ca 2+ ions in plant cell organelles and the cell wall, and an increase in the intracellular Ca 2+ concentration under the influence of altered gravity are presented. Based on the gravitational decompensation hypothesis, the consequence of events occurring in gravisensing cells not specialized to gravity perception under altered gravity are considered in the following order: changes in the cytoplasmic membrane surface
Vignettes in Gravitation and Cosmology
Sriramkumar, L
2012-01-01
This book comprises expository articles on different aspects of gravitation and cosmology that are aimed at graduate students. The topics discussed are of contemporary interest assuming only an elementary introduction to gravitation and cosmology. The presentations are to a certain extent pedagogical in nature, and the material developed is not usually found in sufficient detail in recent textbooks in these areas.
Gravitational Correction to Vacuum Polarization
Jentschura, U D
2015-01-01
We consider the gravitational correction to (electronic) vacuum polarization in the presence of a gravitational background field. The Dirac propagators for the virtual fermions are modified to include the leading gravitational correction (potential term) which corresponds to a coordinate-dependent fermion mass. The mass term is assumed to be uniform over a length scale commensurate with the virtual electron-positron pair. The on-mass shell renormalization condition ensures that the gravitational correction vanishes on the mass shell of the photon, i.e., the speed of light is unaffected by the quantum field theoretical loop correction, in full agreement with the equivalence principle. Nontrivial corrections are obtained for off-shell, virtual photons. We compare our findings to other works on generalized Lorentz transformations and combined quantum-electrodynamic gravitational corrections to the speed of light which have recently appeared in the literature.
Gravitational Repulsion and Dirac Antimatter
Kowitt, Mark E.
1996-03-01
Based on an analogy with electron and hole dynamics in semiconductors, Dirac's relativistic electron equation is generalized to include a gravitational interaction using an electromagnetic-type approximation of the gravitational potential. With gravitational and inertial masses decoupled, the equation serves to extend Dirac's deduction of antimatter parameters to include the possibility of gravitational repulsion between matter and antimatter. Consequences for general relativity and related “antigravity” issues are considered, including the nature and gravitational behavior of virtual photons, virtual pairs, and negative-energy particles. Basic cosmological implications of antigravity are explored—in particular, potential contributions to inflation, expansion, and the general absence of detectable antimatter. Experimental and observational tests are noted, and new ones suggested.
Gravitational Effects upon Locomotion Posture
DeWitt, John K.; Bentley, Jason R.; Edwards, W. Brent; Perusek, Gail P.; Samorezov, Sergey
2008-01-01
Researchers use actual microgravity (AM) during parabolic flight and simulated microgravity (SM) obtained with horizontal suspension analogs to better understand the effect of gravity upon gait. In both environments, the gravitational force is replaced by an external load (EL) that returns the subject to the treadmill. However, when compared to normal gravity (N), researchers consistently find reduced ground reaction forces (GRF) and subtle kinematic differences (Schaffner et al., 2005). On the International Space Station, the EL is applied by elastic bungees attached to a waist and shoulder harness. While bungees can provide EL approaching body weight (BW), their force-length characteristics coupled with vertical oscillations of the body during gait result in a variable load. However, during locomotion in N, the EL is consistently equal to 100% body weight. Comparisons between AM and N have shown that during running, GRF are decreased in AM (Schaffner et al, 2005). Kinematic evaluations in the past have focussed on joint range of motion rather than joint posture at specific instances of the gait cycle. The reduced GRF in microgravity may be a result of differing hip, knee, and ankle positions during contact. The purpose of this investigation was to compare joint angles of the lower extremities during walking and running in AM, SM, and N. We hypothesized that in AM and SM, joints would be more flexed at heel strike (HS), mid-stance (MS) and toe-off (TO) than in N.
Gravitationally Generated Interactions
Capozziello, Salvatore; Fabbri, Luca; Vignolo, Stefano
2012-01-01
Starting from a 5D-Riemannian manifold, we show that a reduction mechanism to 4D-spacetimes reproduces Extended Theories of Gravity (ETGs) that are direct generalizations of Einstein's gravity. In this context, the gravitational degrees of freedom can be dealt under the standard of spacetime deformations. Besides, such deformations can be related to the mass spectra of particles. The intrinsic non-linearity of ETGs gives an energy-dependent running coupling, while torsion gives rise to interactions among spinors displaying the structure of the weak forces among fermions. We discuss how this scheme is compatible with the known observational evidence and suggest that eventual discrepancies could be detected in experiments, as ATLAS and CMS, today running at LHC (CERN). We finally discuss the consequences of the present approach in view of unification of physical interactions.
Feynman Lectures on Gravitation
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Borcherds, P
2003-05-21
In the early 1960s Feynman lectured to physics undergraduates and, with the assistance of his colleagues Leighton and Sands, produced the three-volume classic Feynman Lectures in Physics. These lectures were delivered in the mornings. In the afternoons Feynman was giving postgraduate lectures on gravitation. This book is based on notes compiled by two students on that course: Morinigo and Wagner. Their notes were checked and approved by Feynman and were available at Caltech. They have now been edited by Brian Hatfield and made more widely available. The book has a substantial preface by John Preskill and Kip Thorne, and an introduction entitled 'Quantum Gravity' by Brian Hatfield. You should read these before going on to the lectures themselves. Preskill and Thorne identify three categories of potential readers of this book. 1. Those with a postgraduate training in theoretical physics. 2. 'Readers with a solid undergraduate training in physics'. 3. 'Admirers of Feynman who do not have a strong physics background'. The title of the book is perhaps misleading: readers in category 2 who think that this book is an extension of the Feynman Lectures in Physics may be disappointed. It is not: it is a book aimed mainly at those in category 1. If you want to get to grips with gravitation (and general relativity) then you need to read an introductory text first e.g. General Relativity by I R Kenyon (Oxford: Oxford University Press) or A Unified Grand Tour of Theoretical Physics by Ian D Lawrie (Bristol: IoP). But there is no Royal Road. As pointed out in the preface and in the introduction, the book represents Feynman's thinking about gravitation some 40 years ago: the lecture course was part of his attempts to understand the subject himself, and for readers in all three categories it is this that makes the book one of interest: the opportunity to observe how a great physicist attempts to tackle some of the hardest challenges of physics
Solar rotation gravitational moments
Directory of Open Access Journals (Sweden)
A. Ajabshirizadeh
2005-09-01
Full Text Available Gravitational multipole moments of the Sun are still poorly known. Theoretically, the difficulty is mainly due to the differential rotation for which the velocity rate varies both on the surface and with the depth. From an observational point of view, the multipole moments cannot be directly measured. However, recent progresses have been made proving the existence of a strong radial differential rotation in a thin layer near the solar surface (the leptocline. Applying the theory of rotating stars, we will first compute values of J2 and J4 taking into account the radial gradient of rotation, then we will compare these values with the existing ones, giving a more complete review. We will explain some astrophysical outcomes, mainly on the relativistic Post Newtonian parameters. Finally we will conclude by indicating how space experiments (balloon SDS flights, Golf NG, Beppi-Colombo, Gaia... will be essential to unambiguously determine these parameters.
Bubble collision with gravitation
Hwang, Dong-il; Lee, Wonwoo; Yeom, Dong-han
2012-01-01
In this paper, we study vacuum bubble collisions with various potentials including gravitation, assuming spherical, planar, and hyperbolic symmetry. We use numerical calculations from double-null formalism. Spherical symmetry can mimic the formation of a black hole via multiple bubble collisions. Planar and especially hyperbolic symmetry describes two bubble collisions. We study both cases, when two true vacuum regions have the same field value or different field values, by varying tensions. For the latter case, we also test symmetric and asymmetric bubble collisions, and see details of causal structures. If the colliding energy is sufficient, then the vacuum can be destabilized, and it is also demonstrated. This double-null formalism can be a complementary approach in the context of bubble collisions.
Earth Gravitational Model 2020
Barnes, D.; Factor, J. K.; Holmes, S. A.; Ingalls, S.; Presicci, M. R.; Beale, J.; Fecher, T.
2015-12-01
The National Geospatial-Intelligence Agency [NGA], in conjunction with its U.S. and international partners, has begun preliminary work on its next Earth Gravitational Model, to replace EGM2008. The new 'Earth Gravitational Model 2020' [EGM2020] has an expected public release date of 2020, and will likely retain the same harmonic basis and resolution as EGM2008. As such, EGM2020 will be essentially an ellipsoidal harmonic model up to degree (n) and order (m) 2159, but will be released as a spherical harmonic model to degree 2190 and order 2159. EGM2020 will benefit from new data sources and procedures. Updated satellite gravity information from the GOCE and GRACE mission, will better support the lower harmonics, globally. Multiple new acquisitions (terrestrial, airborne and shipborne) of gravimetric data over specific geographical areas, will provide improved global coverage and resolution over the land, as well as for coastal and some ocean areas. Ongoing accumulation of satellite altimetry data as well as improvements in the treatment of this data, will better define the marine gravity field, most notably in polar and near-coastal regions. NGA and partners are evaluating different approaches for optimally combining the new GOCE/GRACE satellite gravity models with the terrestrial data. These include the latest methods employing a full covariance adjustment. NGA is also working to assess systematically the quality of its entire gravimetry database, towards correcting biases and other egregious errors where possible, and generating improved error models that will inform the final combination with the latest satellite gravity models. Outdated data gridding procedures have been replaced with improved approaches. For EGM2020, NGA intends to extract maximum value from the proprietary data that overlaps geographically with unrestricted data, whilst also making sure to respect and honor its proprietary agreements with its data-sharing partners.
New cylindrical gravitational soliton waves and gravitational Faraday rotation
Tomizawa, Shinya
2013-01-01
In terms of gravitational solitons, we study gravitational non-linear effects of gravitational solitary waves such as Faraday rotation. Applying the Pomeransky's procedure for inverse scattering method, which has been recently used for constructing stationary black hole solutions in five dimensions to a cylindrical spacetime in four dimensions, we construct a new cylindrically symmetric soliton solution. This is the first example to be applied to the cylindrically symmetric case. In particular, we clarify the difference from the Tomimatsu's single soliton solution, which was constructed by the Belinsky-Zakharov's procedure.
Gravitational gradients in gravitational wave detectors: data analysis methods
Garrison, David; Gonzalez, Gabriela; Khanna, Gaurav
2000-04-01
We present a method of analyzing seismic data at the sites of gravitational wave detectors to determine the possible influence of gravitational gradients as a noise source in the detectors. We use statistical methods to distinguish between local and gobal noise sources, as well as compare our findings to models of gravitational gradients (S. A. Hughes and K. S. Thorne, Physical Review D, Volume 58, 122002). We apply these methods to data taken at the Hanford LIGO site, and present preliminary results. This work was supported by Pennsylvannia State University and the National Science Foundation. We acknowledge the collaboration of the LIGO project while taking the data presented.
The Effect of Gravitational Focusing on Annual Modulation
Lee, Samuel K; Peter, Annika H G; Safdi, Benjamin R
2014-01-01
The scattering rate at dark-matter direct-detection experiments should modulate annually due to the Earth's orbit around the Sun. The rate is typically thought to be extremized around June 1, when the relative velocity of the Earth with respect to the dark-matter wind is maximal. We point out that gravitational focusing can alter this modulation phase. Unbound dark-matter particles are focused by the Sun's gravitational potential, affecting their phase-space density in the lab frame. Gravitational focusing can result in a significant overall shift in the annual-modulation phase, which is most relevant for dark matter with low scattering speeds. The induced phase shift for light O(10) GeV dark matter may also be significant, depending on the threshold energy of the experiment.
Noises in Detecting Relic Gravitational Wave
Institute of Scientific and Technical Information of China (English)
LEE Zhi-Jun; WAN Zhen-Zhu
2006-01-01
We analyse the three basic kinds of noises in detecting the relic gravitational wave (GW), which are the noises caused by the thermal radiation in the detecting cavity and by the scattering of the Gaussian beam in the detecting cavity, and noise in the microwave radiometers. The analysis shows that a reasonable signal-to-noise ratio may be achieved for a detecting device with a suitable geometric structure only when the temperature of the environment is no more than T = 0.6 K, and the power of the radiation of the Gaussian beam is no less than P = 105W.
Gravitational Lensing of Gravitational Waves from Merging Neutron Star Binaries
Energy Technology Data Exchange (ETDEWEB)
Wang, Y.; Stebbins, A.; Turner, E.L. [NASA/Fermilab Astrophysics Center, FNAL, Batavia, Illinois 60510 (United States)]|[Princeton University Observatory, Peyton Hall, Princeton, New Jersey 08544 (United States)
1996-09-01
We discuss the gravitational lensing of gravitational waves from merging neutron star binaries, in the context of advanced LIGO type gravitational wave detectors. An advanced LIGO should see unlensed inspiral events with a redshift distribution with cutoff at a redshift {ital z}{sub max}{lt}1 for {ital h}{le}0.8. Any inspiral events detected at {ital z}{approx_gt}{ital z}{sub max} should be lensed. We compute the expected total number of events which are present due to gravitational lensing and their redshift distribution for an advanced LIGO in a flat universe. If the matter fraction in compact lenses is close to 10{percent}, an advanced LIGO should see a few strongly lensed events per year with {rho}{approx_gt}5. {copyright} {ital 1996 The American Physical Society.}
Gravitational lensing of gravitational waves from merging neutron star binaries
Energy Technology Data Exchange (ETDEWEB)
Wang, Yun; Stebbins, Albert; Turner, Edwin L.
1996-05-01
We discuss the gravitational lensing of gravitational waves from merging neutron star binaries, in the context of advanced LIGO type gravitational wave detectors. We consider properties of the expected observational data with cut on the signal-to-noise ratio \\rho, i.e., \\rho>\\rho_0. An advanced LIGO should see unlensed inspiral events with a redshift distribution with cut-off at a redshift z_{\\rm max} < 1 for h \\leq 0.8. Any inspiral events detected at z>z_{\\rm max} should be lensed. We compute the expected total number of events which are present due to gravitational lensing and their redshift distribution for an advanced LIGO in a flat Universe. If the matter fraction in compact lenses is close to 10\\%, an advanced LIGO should see a few strongly lensed events per year with \\rho >5.
Phonon creation by gravitational waves
Sabín, Carlos; Ahmadi, Mehdi; Fuentes, Ivette
2014-01-01
We show that gravitational waves create phonons in a Bose-Einstein condensate (BEC). A traveling spacetime distortion produces particle creation resonances that correspond to the dynamical Casimir effect in a BEC phononic field contained in a cavity-type trap. We propose to use this effect to detect gravitational waves. The amplitude of the wave can be estimated applying recently developed relativistic quantum metrology techniques. We provide the optimal precision bound on the estimation of the wave's amplitude. Finally, we show that the parameter regime required to detect gravitational waves with this technique is within experimental reach.
Gravitational Wave - Gauge Field Oscillations
Caldwell, R R; Maksimova, N A
2016-01-01
Gravitational waves propagating through a stationary gauge field transform into gauge field waves and back again. When multiple families of flavor-space locked gauge fields are present, the gravitational and gauge field waves exhibit novel dynamics. At high frequencies, the system behaves like coupled oscillators in which the gravitational wave is the central pacemaker. Due to energy conservation and exchange among the oscillators, the wave amplitudes lie on a multi-dimensional sphere, reminiscent of neutrino flavor oscillations. This phenomenon has implications for cosmological scenarios based on flavor-space locked gauge fields.
Gravitational Instantons and Cosmological Constant
Cyriac, Josily
2015-01-01
The cosmological dynamics of an otherwise empty universe in the presence of vacuum fields is considered. Quantum fluctuations at the Planck scale leads to a dynamical topology of space-time at very small length scales, which is dominated by compact gravitational instantons. The Planck scale vacuum energy acts as a source for the curvature of the these compact gravitational instantons and decouples from the large scale energy momentum tensor of the universe, thus making the observable cosmological constant vanish. However, a Euclidean functional integral over all possible topologies of the gravitational instantons generates a small non-zero value for the large scale cosmological constant, which agrees with the present observations.
Directory of Open Access Journals (Sweden)
Pieter Rottiers
1999-12-01
Full Text Available In addition to eugenetic changes, cancerous cells exhibit extensive modifications in the expression levels of a variety of genes. The phenotypic switch observed after inoculation of T lymphoma cells into syngenic mice illustrates the active participation of tumoral environment in the induction of an aberrant gene expression pattern. To further substantiate this contribution, we performed polymerase chain reaction (PCR-based subtraction suppression hybridization (SSH to identify genes that are differentially expressed in tumor-derived EL4/13.3 cells compared to the same cells isolated from cultures. Besides a number of unknown genes, the subtracted library contained several known genes that have been reported to be expressed at increased levels in tumors and/or to contribute to carcinogenesis. Apart from clones representing translated transcripts, the subtracted library also contained a high number of clones representing B2 repeat elements, viz. short interspersed repetitive elements that are transcribed by RNA polymerase III. Northern blotting confirmed the induction of B2 transcripts in tumor tissue and also revealed induction of chimeric, B2 repeat-containing mRNA. The appearance of chimeric transcripts was accompanied by aberrant, shorter-than-full-length transcripts, specifically from upregulated genes. Accordingly, in addition to altered gene expression, tumoral environmental triggers constitute a potent mechanism to create an epigenetic diversity in cancers by inducing extensive transcript anomalies.
Kim, So Yeun; Kim, Choong H.; Sandilands, L. J.; Sohn, C. H.; Matsuno, J.; Takagi, H.; Kim, K. W.; Lee, Y. S.; Moon, S. J.; Noh, T. W.
2016-12-01
We investigated the electronic structure of [(SrIrO3)m,(SrTi O3)] (m =1 ,2 ,and ∞ ) superlattice (SL) thin films with optical spectroscopy and first principles calculations. Our optical results confirmed the existence of the Jeff= 1 /2 states in SL samples, similar to the bulk Ruddlesden-Popper series S rn+1I rnO3 n +1 iridates. Apart from this similarity, in the SL samples, we observed red shifts of the characteristic optical excitations in the Jeff= 1 /2 state and an enhancement of the low-energy spectral weight, which implies a reduction in the effective electron correlation for bands near the Fermi energy. The density functional theory plus Coulomb interactions (DFT +U ) calculations suggested that the SrTi O3 layer intervened between SrIr O3 layers in the SLs activated additional hopping channels between the Ir ions, thus increasing the bandwidth and reducing the effective strength of the correlations. This paper demonstrates that fabrication of iridium-based heterostructures can be used to finely tune electronic structures via alteration of their local orbital environments.
Gravitational Stokes parameters. [for electromagnetic and gravitational radiation in relativity
Anile, A. M.; Breuer, R. A.
1974-01-01
The electromagnetic and gravitational Stokes parameters are defined in the general theory of relativity. The general-relativistic equation of radiative transfer for polarized radiation is then derived in terms of the Stokes parameters for both high-frequency electromagnetic and gravitational waves. The concept of Stokes parameters is generalized for the most general class of metric theories of gravity, where six (instead of two) independent states of polarization are present.
Testing local Lorentz invariance with gravitational waves
Kostelecky, Alan
2016-01-01
The effects of local Lorentz violation on dispersion and birefringence of gravitational waves are investigated. The covariant dispersion relation for gravitational waves involving gauge-invariant Lorentz-violating operators of arbitrary mass dimension is constructed. The chirp signal from the gravitational-wave event GW150914 is used to place numerous first constraints on gravitational Lorentz violation.
Gravitational Waves From Supermassive Black Holes
di Girolamo, Tristano
2016-10-01
In this talk, I will present the first direct detections of gravitational waves from binary stellar-mass black hole mergers during the first observing run of the two detectors of the Advanced Laser Interferometer Gravitational-wave Observatory, which opened the field of gravitational-wave astronomy, and then discuss prospects for observing gravitational waves from supermassive black holes with future detectors.
Testing local Lorentz invariance with gravitational waves
Energy Technology Data Exchange (ETDEWEB)
Kostelecký, V. Alan, E-mail: kostelec@indiana.edu [Physics Department, Indiana University, Bloomington, IN 47405 (United States); Mewes, Matthew [Physics Department, California Polytechnic State University, San Luis Obispo, CA 93407 (United States)
2016-06-10
The effects of local Lorentz violation on dispersion and birefringence of gravitational waves are investigated. The covariant dispersion relation for gravitational waves involving gauge-invariant Lorentz-violating operators of arbitrary mass dimension is constructed. The chirp signal from the gravitational-wave event GW150914 is used to place numerous first constraints on gravitational Lorentz violation.
Considerations on Gravitational Wave in Economics
Ovidiu Racorean
2002-01-01
A proposal for a dynamical potential of population displacements (named gravitational potential) between economic regions will be given. For a particular ideal chosen case,the gravitational potential is acting as a wave. An equation of the wave form will be given for gravitational potential-gravitational wave in economics.
Current status of gravitational-wave observations
Fairhurst, Stephen; Guidi, Gianluca M.; Hello, Patrice; Whelan, John T; Woan, Graham
2009-01-01
The first generation of gravitational wave interferometric detectors has taken data at, or close to, their design sensitivity. This data has been searched for a broad range of gravitational wave signatures. An overview of gravitational wave search methods and results are presented. Searches for gravitational waves from unmodelled burst sources, compact binary coalescences, continuous wave sources and stochastic backgrounds are discussed.
Gravitational radiation sources and signatures
Finn, L S
2001-01-01
The goal of these lecture notes is to introduce the developing research area of gravitational-wave phenomenology. In more concrete terms, they are meant to provide an overview of gravitational-wave sources and an introduction to the interpretation of real gravitational wave detector data. They are, of course, limited in both regards. Either topic could be the subject of one or more books, and certainly more than the few lectures possible in a summer school. Nevertheless, it is possible to talk about the problems of data analysis and give something of their flavor, and do the same for gravitational wave sources that might be observed in the upcoming generation of sensitive detectors. These notes are an attempt to do just that.
Gravitational scattering of electromagnetic radiation
Brooker, J. T.; Janis, A. I.
1980-01-01
The scattering of electromagnetic radiation by linearized gravitational fields is studied to second order in a perturbation expansion. The incoming electromagnetic radiation can be of arbitrary multipole structure, and the gravitational fields are also taken to be advanced fields of arbitrary multipole structure. All electromagnetic multipole radiation is found to be scattered by gravitational monopole and time-varying dipole fields. No case has been found, however, in which any electromagnetic multipole radiation is scattered by gravitational fields of quadrupole or higher-order multipole structure. This lack of scattering is established for infinite classes of special cases, and is conjectured to hold in general. The results of the scattering analysis are applied to the case of electromagnetic radiation scattered by a moving mass. It is shown how the mass and velocity may be determined by a knowledge of the incident and scattered radiation.
Modified Entropic Gravitation in Superconductors
de Matos, Clovis Jacinto
2011-01-01
Verlinde recently developed a theoretical account of gravitation in terms of an entropic force. The central element in Verlinde's derivation is information and its relation with entropy through the holographic principle. The application of this approach to the case of superconductors requires to take into account that information associated with superconductor's quantum vacuum energy is not stored on Planck size surface elements, but in four volume cells with Planck-Einstein size. This has profound consequences on the type of gravitational force generated by the quantum vacuum condensate in superconductors, which is closely related with the cosmological repulsive acceleration responsible for the accelerated expansion of the Universe. Remarkably this new gravitational type force depends on the level of breaking of the weak equivalence principle for cooper pairs in a given superconducting material, which was previously derived by the author starting from similar principles. It is also shown that this new gravit...
Academic Training: Gravitational Waves Astronomy
2006-01-01
2006-2007 ACADEMIC TRAINING PROGRAMME LECTURE SERIES 16, 17, 18 October from 11:00 to 12:00 - Main Auditorium, bldg. 500 Gravitational Waves Astronomy M. LANDRY, LIGO Hanford Observatory, Richland, USA Gravitational wave astronomy is expected to become an observational field within the next decade. First direct detection of gravitational waves is possible with existing terrestrial-based detectors, and highly probable with proposed upgrades. In this three-part lecture series, we give an overview of the field, including material on gravitional wave sources, detection methods, some details of interferometric detectors, data analysis methods, and current results from observational data-taking runs of the LIGO and GEO projects. ENSEIGNEMENT ACADEMIQUE ACADEMIC TRAINING Françoise Benz 73127 academic.training@cern.ch If you wish to participate in one of the following courses, please tell to your supervisor and apply electronically from the course description pages that can be found on the Web at: http://www...
Gravitational N-body Simulations
Trenti, M
2008-01-01
Gravitational N-body simulations, that is numerical solutions of the equations of motions for N particles interacting gravitationally, are widely used tools in astrophysics, with applications from few body or solar system like systems all the way up to galactic and cosmological scales. In this article we present a summary review of the field highlighting the main methods for N-body simulations and the astrophysical context in which they are usually applied.
Long pendulums in gravitational gradients
Energy Technology Data Exchange (ETDEWEB)
Suits, B H [Physics Department, Michigan Technological University, Houghton, MI 49931 (United States)
2006-03-01
Previous results for long pendulums above a spherical Earth are generalized for arbitrary non-uniform gravitational fields in the limit of small oscillation. As is the case for the previous results, gravitational gradients are multiplied by the length of the string even though the string is assumed massless. The effect is shown to arise from the constraint on the motion imposed by the string. The significance of these results for real gradients is discussed. (letters and comments)
Atom gravimeters and gravitational redshift
Wolf, Peter; Borde, Christian J; Reynaud, Serge; Salomon, Christophe; Cohen-Tannoudji, Claude; 10.1038/nature09340
2010-01-01
In a recent paper, H. Mueller, A. Peters and S. Chu [A precision measurement of the gravitational redshift by the interference of matter waves, Nature 463, 926-929 (2010)] argued that atom interferometry experiments published a decade ago did in fact measure the gravitational redshift on the quantum clock operating at the very high Compton frequency associated with the rest mass of the Caesium atom. In the present Communication we show that this interpretation is incorrect.
Gravitational Waves III: Detecting Systems
Cattani, M.
2010-01-01
In a recent paper we have deduced the basic equations that predict the emission of gravitational waves (GW) according to the Einstein gravitation theory. In a subsequent paper these equations have been used to calculate the luminosities and the amplitudes of the waves generated by binary stars, pulsations of neutron stars, wobbling of deformed neutron stars, oscillating quadrupoles, rotating bars and collapsing and bouncing cores of supernovas. We show here how the GW could be detected in our...
Blagojević, Milutin
2012-01-01
During the last five decades, gravity, as one of the fundamental forces of nature, has been formulated as a gauge field theory of the Weyl-Cartan-Yang-Mills type. The resulting theory, the Poincar\\'e gauge theory of gravity, encompasses Einstein's gravitational theory as well as the teleparallel theory of gravity as subcases. In general, the spacetime structure is enriched by Cartan's torsion and the new theory can accommodate fermionic matter and its spin in a perfectly natural way. The present reprint volume contains articles from the most prominent proponents of the theory and is supplemented by detailed commentaries of the editors. This guided tour starts from special relativity and leads, in its first part, to general relativity and its gauge type extensions a la Weyl and Cartan. Subsequent stopping points are the theories of Yang-Mills and Utiyama and, as a particular vantage point, the theory of Sciama and Kibble. Later, the Poincar\\'e gauge theory and its generalizations are explored and specific topi...
Gravitational quantum cohomology
Eguchi, Tohru; Xiong, C S; Eguchi, Tohru; Hori, Kentaro; Xiong, Chuan Sheng
1996-01-01
We discuss how the theory of quantum cohomology may be generalized to ``gravitational quantum cohomology'' by studying topological sigma models coupled to two-dimensional gravity. We first consider sigma models defined on a general Fano manifold M (manifold with a positive first Chern class) and derive new recursion relations for its two point functions. We then derive bi-Hamiltonian structures of the theories and show that they are completely integrable at least at the level of genus 0. We next consider the subspace of the phase space where only a marginal perturbation (with a parameter t) is turned on and construct Lax operators (superpotentials) L whose residue integrals reproduce correlation functions. In the case of M=CP^N the Lax operator is given by L= Z_1+Z_2+\\cdots +Z_N+e^tZ_1^{-1}Z_2^{-1}\\cdots Z_N^{-1} and agrees with the potential of the affine Toda theory of the A_N type. We also obtain Lax operators for various Fano manifolds; Grassmannians, rational surfaces etc. In these examples the number of...
Gravitational wave in Lorentz violating gravity
Li, Xin; Chang, Zhe(State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, 100049, Beijing, China)
2011-01-01
By making use of the weak gravitational field approximation, we obtain a linearized solution of the gravitational vacuum field equation in an anisotropic spacetime. The plane-wave solution and dispersion relation of gravitational wave is presented explicitly. There is possibility that the speed of gravitational wave is larger than the speed of light and the casuality still holds. We show that the energy-momentum of gravitational wave in the ansiotropic spacetime is still well defined and cons...
Hypergravity-induced altered behavior in Drosophila
Hosamani, Ravikumar; Wan, Judy; Marcu, Oana; Bhattacharya, Sharmila
2012-07-01
Microgravity and mechanical stress are important factors of the spaceflight environment, and affect astronaut health and behavior. Structural, functional, and behavioral mechanisms of all cells and organisms are adapted to Earth's gravitational force, 1G, while altered gravity can pose challenges to their adaptability to this new environment. On ground, hypergravity paradigms have been used to predict and complement studies on microgravity. Even small changes that take place at a molecular and genetic level during altered gravity may result in changes in phenotypic behavior. Drosophila provides a robust and simple, yet very reliable model system to understand the complexity of hypergravity-induced altered behavior, due to availability of a plethora of genetic tools. Locomotor behavior is a sensitive parameter that reflects the array of molecular adaptive mechanisms recruited during exposure to altered gravity. Thus, understanding the genetic basis of this behavior in a hypergravity environment could potentially extend our understanding of mechanisms of adaptation in microgravity. In our laboratory we are trying to dissect out the cellular and molecular mechanisms underlying hypergravity-induced oxidative stress, and its potential consequences on behavioral alterations by using Drosophila as a model system. In the present study, we employed pan-neuronal and mushroom body specific knock-down adult flies by using Gal4/UAS system to express inverted repeat transgenes (RNAi) to monitor and quantify the hypergravity-induced behavior in Drosophila. We established that acute hypergravity (3G for 60 min) causes a significant and robust decrease in the locomotor behavior in adult Drosophila, and that this change is dependent on genes related to Parkinson's disease, such as DJ-1α , DJ-1β , and parkin. In addition, we also showed that anatomically the control of this behavior is significantly processed in the mushroom body region of the fly brain. This work links a molecular
Directory of Open Access Journals (Sweden)
Md Shahidul Haque
2016-12-01
Full Text Available Arsenic is a major toxicant impairing in diverse metabolic alterations of the organisms and the mechanism of adaptive response is yet to be identified. In the present study, effects of different doses of arsenic in liver of Channa punctata on the regulation of metabolic activities were done. C. punctata, a variety of fresh water fish were exposed to 1, 10 and 1000 μM concentration of Na2HAsO4 for 1 h. The amount of protein, in response to 1, 10 and 1000 μM concentration of arsenic were augmented by 184.47% (2.84-folds, 202.82% (3.0- folds and 317.49% (4.17-folds, respectively and was found to be higher for 1000 μM dose. Cholesterol contents in liver were similarly exaggerated by 517.45% (6.17-folds, 308.13% (4.1-folds and 286.41% (3.86-folds, respectively. However, the higher response was found for 1 μM dose of Na2HAsO4. Similar stimulatory effects on triglyceride level were observed in response to arsenic. Na2HAsO4 causes 443.74% (5.43-folds, 533.11% (6.33-folds and 548.48% (6.48-folds enhanced triglyceride level in liver respectively and the effects were pronounced for 1000 μM concentration. Our findings conclude that arsenic is involved in impairment of metabolic activities in liver of the species of fish and gives an impact to the environment for survival.
Strong gravitational lensing of gravitational waves in Einstein Telescope
Energy Technology Data Exchange (ETDEWEB)
Piórkowska, Aleksandra; Biesiada, Marek [Department of Astrophysics and Cosmology, Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Zhu, Zong-Hong, E-mail: aleksandra.piorkowska@us.edu.pl, E-mail: marek.biesiada@us.edu.pl, E-mail: zhuzh@bnu.edu.cn [Department of Astronomy, Beijing Normal University, Beijing 100875 (China)
2013-10-01
Gravitational wave experiments have entered a new stage which gets us closer to the opening a new observational window on the Universe. In particular, the Einstein Telescope (ET) is designed to have a fantastic sensitivity that will provide with tens or hundreds of thousand NS-NS inspiral events per year up to the redshift z = 2. Some of such events should be gravitationally lensed by intervening galaxies. We explore the prospects of observing gravitationally lensed inspiral NS-NS events in the Einstein telescope. Being conservative we consider the lens population of elliptical galaxies. It turns out that depending on the local insipral rate ET should detect from one per decade detection in the pessimistic case to a tens of detections per year for the most optimistic case. The detection of gravitationally lensed source in gravitational wave detectors would be an invaluable source of information concerning cosmography, complementary to standard ones (like supernovae or BAO) independent of the local cosmic distance ladder calibrations.
Gravitational Radiation from Ultra High Energy Cosmic Rays in Models with Large Extra Dimensions
Koch, B; Bleicher, M; Koch, Ben; Drescher, Hans-Joachim; Bleicher, Marcus
2006-01-01
The effects of classical gravitational radiation in models with large extra dimensions are investigated for ultra high energy cosmic rays (CRs). The cross sections are implemented into a simulation package (SENECA) for high energy hadron induced CR air showers. We predict that gravitational radiation from quasi-elastic scattering could be observed at incident CR energies above $10^9$ GeV for a setting with more than two extra dimensions. It is further shown that this gravitational energy loss can alter the energy reconstruction for CR energies $E_{\\rm CR}\\ge 5\\cdot 10^9$ GeV.
On the use of measured time delays in gravitational lenses to determine the Hubble constant
Alcock, C.; Anderson, N.
1985-01-01
Gravitational lenses are rare in the known samples of quasars, indicating that the conditions involved in their formation are unusual. In particular, the distribution of matter along the light rays from the observer through the deflector to the quasar may be very different from mean conditions. It is shown that reasonable deviations in the density of matter along the beams can significantly alter the relationship between time delays and the Hubble constant, and it is concluded that gravitational lenses are not promising estimators of this constant. However, should an independent, precise determination of the Hubble constant become available, gravitational lenses could be used to probe long-range density fluctuations.
Magnetized black holes in an external gravitational field
Kunz, Jutta; Nedkova, Petya; Yazadjiev, Stoytcho
2017-07-01
We obtain a family of exact solutions describing magnetized black holes in an external gravitational field. Locally the solutions can be interpreted as representing the near-horizon region of a black hole, which interacts with a surrounding matter distribution producing a strong magnetic field. Thus, the solutions reflect the influence of both a gravitational and an electromagnetic external potential in the strong field regime. The static members in the family are generalizations of the Schwarzschild solution in the described environment, while the rotating ones generalize the magnetized Reissner-Nordström solution when the influence of an external gravitational source is also taken into account. Technically, the solutions are obtained by means of a Harrison transformation, applied on the (electro-)vacuum distorted black holes constructed by Bretón et al. We examine the thermodynamical properties of the solutions, and compare them with the corresponding isolated black holes, and with the particular cases when the interaction with only one of the external potentials is taken into account. For the static black holes the influence of the external gravitational and magnetic fields is factorized in a sense, both affecting different properties, and leaving the rest intact. For the rotating solutions the external gravitational and magnetic fields are coupled through the conditions for avoiding conical singularities. The Meissner effect is observed for extremal rotating solutions only in the zero-charge limit, similar to the magnetized Reissner-Nordström black hole.
Gravitational agglomeration of post-HCDA LMFBR nonspherical aerosols
Tuttle, R. F.
1980-12-01
A theoretical investigation of collisional dynamics of two particle interactions in a gravitational field is reported. This research is unique in that it is the first attempt at modeling the hydrodynamic interactions between a nonspherical particle and a spherical particle undergoing gravitational collisions in an LMFBR environment. Basic definitions and expressions are developed for nonspherical particles and related to spherical particles by means of shape factors. Using volume equivalent diameter as the defining length in the gravitational collision kernel, the aerodynamic shape factor, k, the density correction factor, alpha, and the gravitational collision shape factor, beta, are used to correct the collision kernel for the case of collisions between aerosol agglomerates. The Navier-Stokes equation in oblate spheroidal coordinates is solved to model a nonspherical particle and then the dynamic equations for two particle motions are developed. A computer program NGCEFF is constructed, the Navier-Stokes equation is solved by the finite difference method, and the dynamical equations are solved by Gear's method. It is concluded that the aerosol gravitational collision shape factor can be determined by further theoretical work based on the concepts and methods developed in this dissertation.
Modified entropic gravitation in superconductors
Energy Technology Data Exchange (ETDEWEB)
Matos, Clovis Jacinto de, E-mail: clovis.de.matos@esa.int [European Space Agency, 8-10 rue Mario Nikis, 75015 Paris (France)
2012-01-15
Verlinde recently developed a theoretical account of gravitation in terms of an entropic force. The central element in Verlinde's derivation is information and its relation with entropy through the holographic principle. The application of this approach to the case of superconductors requires to take into account that information associated with superconductor's quantum vacuum energy is not stored on Planck size surface elements, but in four volume cells with Planck-Einstein size. This has profound consequences on the type of gravitational force generated by the quantum vacuum condensate in superconductors, which is closely related with the cosmological repulsive acceleration responsible for the accelerated expansion of the Universe. Remarkably this new gravitational type force depends on the level of breaking of the weak equivalence principle for cooper pairs in a given superconducting material, which was previously derived by the author starting from similar principles. It is also shown that this new gravitational force can be interpreted as a surface force. The experimental detection of this new repulsive gravitational-type force appears to be challenging.
Gravitational Collapse of Gravitational Waves in 3D Numerical Relativity
Alcubierre, M; Brügmann, B; Lanfermann, G; Seidel, E; Suen, W M; Tobias, M; Alcubierre, Miguel; Allen, Gabrielle; Bruegmann, Bernd; Lanfermann, Gerd; Seidel, Edward; Suen, Wai-Mo; Tobias, Malcolm
2000-01-01
We demonstrate that evolutions of three-dimensional, strongly non-linear gravitational waves can be followed in numerical relativity, hence allowing many interesting studies of both fundamental and observational consequences. We study the evolution of time-symmetric, axisymmetric {\\it and} non-axisymmetric Brill waves, including waves so strong that they collapse to form black holes under their own self-gravity. The critical amplitude for black hole formation is determined. The gravitational waves emitted in the black hole formation process are compared to those emitted in the head-on collision of two Misner black holes.
Spin gravitational resonance and graviton detection
Quach, James Q
2016-01-01
We develop a gravitational analogue of spin magnetic resonance, called spin gravitational resonance, whereby a gravitational wave interacts with a magnetic field to produce a spin transition. In particular, an external magnetic field separates the energy spin states of a spin-1/2 particle, and the presence of the gravitational wave produces a perturbation in the components of the magnetic field orthogonal to the gravitational wave propagation. In this framework we test Dyson's conjecture that individual gravitons cannot be detected. Although we find no fundamental laws preventing single gravitons being detected with spin gravitational resonance, we show that it cannot be used in practice, in support of Dyson's conjecture.
A new formula of the Gravitational Curvature for the prism
Grazia D'Urso, Maria
2017-04-01
Gravitational Curvatures (GC) are the components of the third-order gravitational tensor and physically represent the rate of change of the gravity gradient. While scalar, vector and second-order tensor quantities of the Earth's gravitational field have extensively been studied and their properties have been well understood [1], the first successful terrestrial measurements of the third-order vertical gravitational gradients have been recently performed in [2] by atom interferometry sensors in laboratory environment. Possible benefits of the airborne third-order gravitational gradients for exploration geophysics are discussed in [3] while Brieden et al. (2010) [4] have proposed a new satellite mission called OPTical Interferometry for global Mass change detection from space (OPTIMA) sensing the third-order gravitational gradients in space. Moreover, exploitation of GC for modelling the Earth's gravitational field has been object of recent studies [5-7]. We extend the approach presented by the author in previous papers [8-10] by evaluating the algebraic expression of the third-order gravitational tensor for a prism. Comparisons with previous results [11-12] are also included. [1] Freeden W, Schreiner M (2009) Spherical functions of mathematical geosciences. A scalar, vectorial, and tensorial setup. In: Advances in geophysical and environmental mechanics and mathematics. Springer, Berlin [2] Rosi G, Cacciapuoti L, Sorrentino F, Menchetti M, Prevedelli M, Tino GM (2015) Measurements of the gravity-field curvature by atom interferometry. Phys Rev Lett 114:013001 [3] Di Francesco D, Meyer T, Christensen A, FitzGerald D (2009) Gravity gradiometry - today and tomorrow. In: 11th SAGA Biennial technical meeting and exhibition, 13-18 September 2009, Switzerland, pp 80-83 [4] Brieden P, Müller J, Flury J, Heinzel G (2010) The mission OPTIMA - novelties and benefit. In: Geotechnologien science report No. 17, Potsdam, pp 134-139 [5] Šprlák M, Novák P (2015) Integral
Gravitational baryogenesis after anisotropic inflation
Fukushima, Mitsuhiro; Mizuno, Shuntaro; Maeda, Kei-ichi
2016-05-01
The gravitational baryogensis may not generate a sufficient baryon asymmetry in the standard thermal history of the Universe when we take into account the gravitino problem. Hence, it has been suggested that anisotropy of the Universe can enhance the generation of the baryon asymmetry through the increase of the time change of the Ricci scalar curvature. We study the gravitational baryogenesis in the presence of anisotropy, which is produced at the end of an anisotropic inflation. Although we confirm that the generated baryon asymmetry is enhanced compared with the original isotropic cosmological model, taking into account the constraint on the anisotropy by the recent CMB observations, we find that it is still difficult to obtain the observed baryon asymmetry only through the gravitational baryogenesis without suffering from the gravitino problem.
Thought Experiments on Gravitational Forces
Lynden-Bell, Donald
2013-01-01
Large contributions to the near closure of the Universe and to the acceleration of its expansion are due to the gravitation of components of the stress-energy tensor other than its mass density. To familiarise astronomers with the gravitation of these components we conduct thought experiments on gravity, analogous to the real experiments that our forebears conducted on electricity. By analogy to the forces due to electric currents we investigate the gravitational forces due to the flows of momentum, angular momentum, and energy along a cylinder. Under tension the gravity of the cylinder decreases but the 'closure' of the 3-space around it increases. When the cylinder carries a torque the flow of angular momentum along it leads to a novel helical interpretation of Levi-Civita's external metric and a novel relativistic effect. Energy currents give gravomagnetic effects in which parallel currents repel and antiparallel currents attract, though such effects must be added to those of static gravity. The gravity of...
Gravitational Lensing - Einstein's Unfinished Symphony
Treu, Tommaso
2014-01-01
Gravitational lensing - the deflection of light rays by gravitating matter - has become a major tool in the armoury of the modern cosmologist. Proposed nearly a hundred years ago as a key feature of Einstein's theory of General Relativity, we trace the historical development since its verification at a solar eclipse in 1919. Einstein was apparently cautious about its practical utility and the subject lay dormant observationally for nearly 60 years. Nonetheless there has been rapid progress over the past twenty years. The technique allows astronomers to chart the distribution of dark matter on large and small scales thereby testing predictions of the standard cosmological model which assumes dark matter comprises a massive weakly-interacting particle. By measuring distances and tracing the growth of dark matter structure over cosmic time, gravitational lensing also holds great promise in determining whether the dark energy, postulated to explain the accelerated cosmic expansion, is a vacuum energy density or a...
Chirality and gravitational parity violation.
Bargueño, Pedro
2015-06-01
In this review, parity-violating gravitational potentials are presented as possible sources of both true and false chirality. In particular, whereas phenomenological long-range spin-dependent gravitational potentials contain both truly and falsely chiral terms, it is shown that there are models that extend general relativity including also coupling of fermionic degrees of freedom to gravity in the presence of torsion, which give place to short-range truly chiral interactions similar to that usually considered in molecular physics. Physical mechanisms which give place to gravitational parity violation together with the expected size of the effects and their experimental constraints are discussed. Finally, the possible role of parity-violating gravity in the origin of homochirality and a road map for future research works in quantum chemistry is presented.
Gravitational collapse and naked singularities
Indian Academy of Sciences (India)
Tomohiro Harada
2004-10-01
Gravitational collapse is one of the most striking phenomena in gravitational physics. The cosmic censorship conjecture has provided strong motivation for research in this field. In the absence of a general proof for censorship, many examples have been proposed, in which naked singularity is the outcome of gravitational collapse. Recent developments have revealed that there are examples of naked singularity formation in the collapse of physically reasonable matter fields, although the stability of these examples is still uncertain. We propose the concept of `effective naked singularities', which will be quite helpful because general relativity has limitation in its application at the high-energy end. The appearance of naked singularities is not detestable but can open a window for the new physics of strongly curved space-times.
Gravitational waves and multimessenger astronomy
Directory of Open Access Journals (Sweden)
Ricci Fulvio
2016-01-01
Full Text Available It is widely expected that in the coming quinquennium the first gravitational wave signal will be directly detected. The ground-based advanced LIGO and Virgo detectors are being upgraded to a sensitivity level such that we expect to be measure a significant binary merger rate. Gravitational waves events are likely to be accompanied by electromagnetic counterparts and neutrino emission carrying complementary information to those associated to the gravitational signals. If it becomes possible to measure all these forms of radiation in concert, we will end up an impressive increase in the comprehension of the whole phenomenon. In the following we summarize the scientific outcome of the interferometric detectors in the past configuration. Then we focus on some of the potentialities of the advanced detectors once used in the new context of the multimessenger astronomy.
Gravitational waves and multimessenger astronomy
Ricci, Fulvio
2016-07-01
It is widely expected that in the coming quinquennium the first gravitational wave signal will be directly detected. The ground-based advanced LIGO and Virgo detectors are being upgraded to a sensitivity level such that we expect to be measure a significant binary merger rate. Gravitational waves events are likely to be accompanied by electromagnetic counterparts and neutrino emission carrying complementary information to those associated to the gravitational signals. If it becomes possible to measure all these forms of radiation in concert, we will end up an impressive increase in the comprehension of the whole phenomenon. In the following we summarize the scientific outcome of the interferometric detectors in the past configuration. Then we focus on some of the potentialities of the advanced detectors once used in the new context of the multimessenger astronomy.
Gravitational Baryogenesis after Anisotropic Inflation
Fukushima, Mitsuhiro; Maeda, Kei-ichi
2016-01-01
The gravitational baryogensis may not generate a sufficient baryon asymmetry in the standard thermal history of the Universe when we take into account the gravitino problem. Hence it has been suggested that anisotropy of the Universe can enhance the generation of the baryon asymmetry through the increase of the time change of the Ricci scalar curvature. We study the gravitational baryogenesis in the presence of anisotropy, which is produced at the end of an anisotropic inflation. Although we confirm that the generated baryon asymmetry is enhanced compared with the original isotropic cosmological model, taking into account the constraint on the anisotropy by the recent CMB observations, we find that it is still difficult to obtain the observed baryon asymmetry only through the gravitational baryogenesis without suffering from the gravitino problem.
Gravitational Instabilities in Circumstellar Disks
Kratter, Kaitlin M
2016-01-01
[Abridged] Star and planet formation are the complex outcomes of gravitational collapse and angular momentum transport mediated by protostellar and protoplanetary disks. In this review we focus on the role of gravitational instability in this process. We begin with a brief overview of the observational evidence for massive disks that might be subject to gravitational instability, and then highlight the diverse ways in which the instability manifests itself in protostellar and protoplanetary disks: the generation of spiral arms, small scale turbulence-like density fluctuations, and fragmentation of the disk itself. We present the analytic theory that describes the linear growth phase of the instability, supplemented with a survey of numerical simulations that aim to capture the non-linear evolution. We emphasize the role of thermodynamics and large scale infall in controlling the outcome of the instability. Despite apparent controversies in the literature, we show a remarkable level of agreement between analyt...
Gravitational Origin of Dark Matter
Babichev, Eugeny; Raidal, Martti; Schmidt-May, Angnis; Urban, Federico; Veermäe, Hardi; von Strauss, Mikael
2016-01-01
Observational evidence for the existence of Dark Matter is limited to its gravitational effects. The extensive program for dedicated searches has yielded null results so far, challenging the most popular models. Here we propose that this is the case because the very existence of cold Dark Matter is a manifestation of gravity itself. The consistent bimetric theory of gravity, the only known ghost-free extension of General Relativity involving a massless and a massive spin-2 field, automatically contains a perfect Dark Matter candidate. We demonstrate that the massive spin-2 particle can be heavy, stable on cosmological scales, and that it interacts with matter only through a gravitational type of coupling. Remarkably, these features persist in the same region of parameter space where bimetric theory satisfies the current gravity tests. We show that the observed Dark Matter abundance can be generated via freeze-in and suggest possible particle physics and gravitational signatures of our bimetric Dark Matter mod...
The postulates of gravitational thermodynamics
Martínez, E A
1996-01-01
The general principles and logical structure of a thermodynamic formalism that incorporates strongly self-gravitating systems are presented. This framework generalizes and simplifies the formulation of thermodynamics developed by Callen. The definition of extensive variables, the homogeneity properties of intensive parameters, and the fundamental problem of gravitational thermodynamics are discussed in detail. In particular, extensive parameters include quasilocal quantities and are naturally incorporated into a set of basic general postulates for thermodynamics. These include additivity of entropies (Massieu functions) and the generalized second law. Fundamental equations are no longer homogeneous first-order functions of their extensive variables. It is shown that the postulates lead to a formal resolution of the fundamental problem despite non-additivity of extensive parameters and thermodynamic potentials. Therefore, all the results of (gravitational) thermodynamics are an outgrowth of these postulates. T...
Quantum gravitational effects on boundary
Park, I Y
2016-01-01
Quantum gravitational effects may hold the key to some of the outstanding problems in theoretical physics. In this work we analyze the perturbative quantum effects on the boundary of a gravitational system and Dirichlet boundary condtion imposed at the classical level. Our analysis reveals that for a black hole solution there exists a clash between the quantum effects and Dirichlet boundary condition: the solution of the one-particle-irreducible (1PI) action no longer obeys the Dirichlet boundary condition. The analysis also suggests that the violation of the Dirichlet boundary condition should be tied with a certain mechanism of information storage on the boundary.
Natural wormholes as gravitational lenses
Cramer, J G; Morris, M S; Visser, M; Benford, G; Landis, G A; Cramer, John G; Forward, Robert L; Morris, Michael S; Visser, Matt; Benford, Gregory; Landis, Geoffrey A
1995-01-01
Visser has suggested traversable 3-dimensional wormholes that could plausibly form naturally during Big Bang inflation. A wormhole mouth embedded in high mass density might accrete mass, giving the other mouth a net *negative* mass of unusual gravitational properties. The lensing of such a gravitationally negative anomalous compact halo object (GNACHO) will enhance background stars with a time profile that is observable and qualitatively different from that recently observed for massive compact halo objects (MACHOs) of positive mass. We recommend that MACHO search data be analyzed for GNACHOs.
General relativity and gravitational waves
Weber, J
2004-01-01
An internationally famous physicist and electrical engineer, the author of this text was a pioneer in the investigation of gravitational waves. Joseph Weber's General Relativity and Gravitational Waves offers a classic treatment of the subject. Appropriate for upper-level undergraduates and graduate students, this text remains ever relevant. Brief but thorough in its introduction to the foundations of general relativity, it also examines the elements of Riemannian geometry and tensor calculus applicable to this field.Approximately a quarter of the contents explores theoretical and experimenta
Gravitational-wave mediated preheating
Directory of Open Access Journals (Sweden)
Stephon Alexander
2015-04-01
Full Text Available We propose a new preheating mechanism through the coupling of the gravitational field to both the inflaton and matter fields, without direct inflaton–matter couplings. The inflaton transfers power to the matter fields through interactions with gravitational waves, which are exponentially enhanced due to an inflation–graviton coupling. One such coupling is the product of the inflaton to the Pontryagin density, as in dynamical Chern–Simons gravity. The energy scales involved are constrained by requiring that preheating happens fast during matter domination.
Lee, Inah; Knierim, James J.
2007-01-01
Subfields of the hippocampus display differential dynamics in processing a spatial environment, especially when changes are introduced to the environment. Specifically, when familiar cues in the environment are spatially rearranged, place cells in the CA3 subfield tend to rotate with a particular set of cues (e.g., proximal cues), maintaining a…
Precise Gravitational Tests via the SEE Mission: A Proposal for Space-Based Measurements
Sanders, Alvin J
2010-01-01
The objective of a SEE mission is to support development of unification theory by carrying out sensitive gravitational tests capable of determining whether various alternative theories are compatible with nature. Gravitation is a key "missing link" in unification theory. Nearly all unification theories incorporate gravity at a fundamental level, and therefore precise measurements of gravitational forces will place important constraints on unification theories. Ground-based gravitational measurements to the accuracy required are impossible due to the many sources of noise present in the terrestrial environment. The proposed space-based Satellite Energy Exchange (SEE) mission will measure several important parameters to an accuracy between 100 and 10,000 times better than current or planned measurement capabilities. It will test for time variation of the gravitational "constant" G and for violations of the weak equivalence principle (WEP) and the inverse-square-law (ISL), and it will determine G. It is well-kno...
Gravitational-wave implications for structure formation: a second-order approach
Pazouli, Despoina
2015-01-01
Gravitational waves are propagating undulations in the spacetime fabric, which interact very weakly with their environment. In cosmology, gravitational-wave distortions are produced by most of the inflationary scenarios and their anticipated detection should open a new window to the early universe. Motivated by the relative lack of studies on the potential implications of gravitational radiation for the large-scale structure of the universe, we consider its coupling to density perturbations during the post-recombination era. We do so by assuming an Einstein-de Sitter background cosmology and by employing a second-order perturbation study. At this perturbative level and on superhorizon scales, we find that gravitational radiation adds a distinct and faster growing mode to the standard linear solution for the density contrast. Given the expected weakness of cosmological gravitational waves, however, the effect of the new mode is currently subdominant and it could start becoming noticeable only in the far future...
Merging Black Holes and Gravitational Waves
Centrella, Joan
2009-01-01
This talk will focus on simulations of binary black hole mergers and the gravitational wave signals they produce. Applications to gravitational wave detection with LISA, and electronagnetic counterparts, will be highlighted.
Gravitating BPS dyons witout a dilaton
Lee, C; Lee, Choonkyu; Park, Q Han
1996-01-01
We describe curved-space BPS dyon solutions, the ADM mass of which saturates the gravitational version of the Bogomol'nyi bound. This generalizes self-gravitating BPS monopole solutions of Gibbons et al. when there is no dilaton.
Gravitational waves carrying orbital angular momentum
Bialynicki-Birula, Iwo
2015-01-01
Spinorial formalism is used to map every electromagnetic wave into the gravitational wave (within the linearized gravity). In this way we can obtain the gravitational counterparts of Bessel, Laguerre-Gauss, and other light beams carrying orbital angular momentum.
Precursory singularities in spherical gravitational collapse
Lake, Kayll
1992-05-01
General conditions are developed for the formation of naked precursory ('shell-focusing') singularities in spherical gravitational collapse. These singularities owe their nakedness to the fact that the gravitational potential fails to be single valued prior to the onset of a true gravitational singularity. It is argued that they do not violate the spirit of cosmic censorship. Rather, they may well be an essentially generic feature of relativistic gravitational collapse.
The gravitational-wave memory effect
Favata, Marc
2010-01-01
The nonlinear memory effect is a slowly-growing, non-oscillatory contribution to the gravitational-wave amplitude. It originates from gravitational waves that are sourced by the previously emitted waves. In an ideal gravitational-wave interferometer a gravitational-wave with memory causes a permanent displacement of the test masses that persists after the wave has passed. Surprisingly, the nonlinear memory affects the signal amplitude starting at leading (Newtonian-quadrupole) order. Despite ...
On the polarization of nonlinear gravitational waves
Poplawski, Nikodem J.
2011-01-01
We derive a relation between the two polarization modes of a plane, linear gravitational wave in the second-order approximation. Since these two polarizations are not independent, an initially monochromatic gravitational wave loses its periodic character due to the nonlinearity of the Einstein field equations. Accordingly, real gravitational waves may differ from solutions of the linearized field equations, which are being assumed in gravitational-wave detectors.
Normalization of Gravitational Acceleration Models
Eckman, Randy A.; Brown, Aaron J.; Adamo, Daniel R.
2011-01-01
Unlike the uniform density spherical shell approximations of Newton, the con- sequence of spaceflight in the real universe is that gravitational fields are sensitive to the nonsphericity of their generating central bodies. The gravitational potential of a nonspherical central body is typically resolved using spherical harmonic approximations. However, attempting to directly calculate the spherical harmonic approximations results in at least two singularities which must be removed in order to generalize the method and solve for any possible orbit, including polar orbits. Three unique algorithms have been developed to eliminate these singularities by Samuel Pines [1], Bill Lear [2], and Robert Gottlieb [3]. This paper documents the methodical normalization of two1 of the three known formulations for singularity-free gravitational acceleration (namely, the Lear [2] and Gottlieb [3] algorithms) and formulates a general method for defining normalization parameters used to generate normalized Legendre Polynomials and ALFs for any algorithm. A treatment of the conventional formulation of the gravitational potential and acceleration is also provided, in addition to a brief overview of the philosophical differences between the three known singularity-free algorithms.
Plausibility Arguments and Universal Gravitation
Cunha, Ricardo F. F.; Tort, A. C.
2017-01-01
Newton's law of universal gravitation underpins our understanding of the dynamics of the Solar System and of a good portion of the observable universe. Generally, in the classroom or in textbooks, the law is presented initially in a qualitative way and at some point during the exposition its mathematical formulation is written on the blackboard…
Gravitational lensing in plasmic medium
Energy Technology Data Exchange (ETDEWEB)
Bisnovatyi-Kogan, G. S., E-mail: gkogan@iki.rssi.ru; Tsupko, O. Yu., E-mail: tsupko@iki.rssi.ru [Russian Academy of Sciences, Space Research Institute (Russian Federation)
2015-07-15
The influence of plasma on different effects of gravitational lensing is reviewed. Using the Hamiltonian approach for geometrical optics in a medium in the presence of gravity, an exact formula for the photon deflection angle by a black hole (or another body with a Schwarzschild metric) embedded in plasma with a spherically symmetric density distribution is derived. The deflection angle in this case is determined by the mutual combination of different factors: gravity, dispersion, and refraction. While the effects of deflection by the gravity in vacuum and the refractive deflection in a nonhomogeneous medium are well known, the new effect is that, in the case of a homogeneous plasma, in the absence of refractive deflection, the gravitational deflection differs from the vacuum deflection and depends on the photon frequency. In the presence of a plasma nonhomogeneity, the chromatic refractive deflection also occurs, so the presence of plasma always makes gravitational lensing chromatic. In particular, the presence of plasma leads to different angular positions of the same image if it is observed at different wavelengths. It is discussed in detail how to apply the presented formulas for the calculation of the deflection angle in different situations. Gravitational lensing in plasma beyond the weak deflection approximation is also considered.
Cosmological Acceleration from Gravitational Waves
Marochnik, Leonid
2015-01-01
It is shown that the classical gravitational waves of super-horizon wavelengths are able to form the de Sitter accelerated expansion of the empty (with no matter fields) Universe. The contemporary Universe is about 70% empty and asymptotically is going to become completely empty, so the effect caused by emptiness should be already very noticeable. It could manifest itself as the dark energy.
Academic Training: Gravitational Waves Astronomy
2006-01-01
2006-2007 ACADEMIC TRAINING PROGRAMME LECTURE SERIES 16, 17, 18 October from 11:00 to 12:00 - Main Auditorium, bldg. 500 Gravitational Waves Astronomy M. LANDRY, LIGO Hanford Observatory, Richland, USA Gravitational wave astronomy is expected to become an observational field within the next decade. First direct detection of gravitational waves is possible with existing terrestrial-based detectors, and highly probable with proposed upgrades. In this three-part lecture series, we give an overview of the field, including material on gravitional wave sources, detection methods, some details of interferometric detectors, data analysis methods, and current results from observational data-taking runs of the LIGO and GEO projects.ENSEIGNEMENT ACADEMIQUE ACADEMIC TRAINING Françoise Benz 73127 academic.training@cern.ch If you wish to participate in one of the following courses, please tell to your supervisor and apply electronically from the course description pages that can be found on the Web at: http://www.cern...
On black holes and gravitational waves
Loinger, Angelo
2002-01-01
Black holes and gravitational waves are theoretical entities of today astrophysics. Various observed phenomena have been associated with the concept of black hole ; until now, nobody has detected gravitational waves. The essays contained in this book aim at showing that the concept of black holes arises from a misinterpretation of general relativity and that gravitational waves cannot exist.
Unification of Electromagnetic Interactions and Gravitational Interactions
Institute of Scientific and Technical Information of China (English)
WUNing
2002-01-01
Unified theory of gravitational interactions and electromagnetic interactions is discussed in this paper.Based on gauge principle,electromagnetic interactions and gravitational interactions are formulated in the same manner and are unified in a semi-direct product group of U(1) Abelian gauge group and gravitational gauge group.
Unification of Electromagnetic Interactions and Gravitational Interactions
Institute of Scientific and Technical Information of China (English)
WU Ning
2002-01-01
Unified theory of gravitational interactions and electromagnetic interactions is discussed in this paper.Based on gauge principle, electromagnetic interactions and gravitational interactions are formulated in the same mannerand are unified in a semi-direct product group of U(1) Abelian gauge group and gravitational gauge group.
Gravitational Gauge Interactions of Dirac Field
Institute of Scientific and Technical Information of China (English)
WU Ning
2004-01-01
Gravitational interactions of Dirac field are studied in this paper. Based on gauge principle, quantum gauge theory of gravity, which is perturbatively renormalizable, is formulated in the Minkowski space-time. In quantum gauge theory of gravity, gravity is treated as a kind of fundamental interactions, which is transmitted by gravitational gauge tield, and Dirac field couples to gravitational field through gravitational gauge covariant derivative. Based on this theory, we can easily explain gravitational phase effect, which has already been detected by COW experiment.
Gravitational Waves in Effective Quantum Gravity
Energy Technology Data Exchange (ETDEWEB)
Calmet, Xavier; Kuntz, Ibere; Mohapatra, Sonali [University of Sussex, Physics and Astronomy, Brighton (United Kingdom)
2016-08-15
In this short paper we investigate quantum gravitational effects on Einstein's equations using Effective Field Theory techniques. We consider the leading order quantum gravitational correction to the wave equation. Besides the usual massless mode, we find a pair of modes with complex masses. These massive particles have a width and could thus lead to a damping of gravitational waves if excited in violent astrophysical processes producing gravitational waves such as e.g. black hole mergers. We discuss the consequences for gravitational wave events such as GW 150914 recently observed by the Advanced LIGO collaboration. (orig.)
Gravitational cooling of self-gravitating Bose-Condensates
Guzman, F S
2006-01-01
Equilibrium configurations for a self-gravitating scalar field with self-interaction are constructed. The corresponding Schr\\"odinger-Poisson (SP) system is solved using finite differences assuming spherical symmetry. It is shown that equilibrium configurations of the SP system are late-time attractor solutions for initially quite arbitrary density profiles, which relax and virialize through the emission of scalar field bursts; a process dubbed gravitational cooling. Among other potential applications, these results indicate that scalar field dark matter models (in its different flavors) tolerate the introduction of a self-interaction term in the SP equations. This study can be useful in exploring models in which dark matter in galaxies is not point-like.
Spherical gravitational curvature boundary-value problem
Šprlák, Michal; Novák, Pavel
2016-08-01
Values of scalar, vector and second-order tensor parameters of the Earth's gravitational field have been collected by various sensors in geodesy and geophysics. Such observables have been widely exploited in different parametrization methods for the gravitational field modelling. Moreover, theoretical aspects of these quantities have extensively been studied and well understood. On the other hand, new sensors for observing gravitational curvatures, i.e., components of the third-order gravitational tensor, are currently under development. As the gravitational curvatures represent new types of observables, their exploitation for modelling of the Earth's gravitational field is a subject of this study. Firstly, the gravitational curvature tensor is decomposed into six parts which are expanded in terms of third-order tensor spherical harmonics. Secondly, gravitational curvature boundary-value problems defined for four combinations of the gravitational curvatures are formulated and solved in spectral and spatial domains. Thirdly, properties of the corresponding sub-integral kernels are investigated. The presented mathematical formulations reveal some important properties of the gravitational curvatures and extend the so-called Meissl scheme, i.e., an important theoretical framework that relates various parameters of the Earth's gravitational field.
Impact of Planetary Gravitation on High Precision Neutral Atom Measurements
Kucharek, H.; Galli, A.; Wurz, P.; Moebius, E.; Lee, M. A.; Park, J.; Fuselier, S. A.; Bzowski, M.; Schwadron, N.; McComas, D. J.
2015-12-01
Measurements of energetic neutral atoms (ENAs) have been extremely successful in providing very important information on physical processes inside and outside our heliosphere. For instance, recent IBEX observations provided new insights into the local interstellar environment and improved measurements of the interstellar He temperature, velocity, and direction of the interstellar flow vector. Since particle collisions are rare and radiation pressure is negligible for these neutrals, gravitational forces mainly determine the trajectories of neutral He atoms. Depending on the distance of an ENA to the source of a gravitational field and its relative speed and direction this can result in a significant deflection and acceleration. In this presentation we study the impact of the gravitational effects of the Earth, Moon, and Jupiter on ENA measurements performed in Earth orbit. We show that planetary gravitational effects do not significantly affect the interstellar neutral gas parameters obtained from IBEX observations. We further study the possibility whether the He focusing cone of the Sun or Jupiter could be measured by IBEX, and whether these cones could be used as an independent measure of the interstellar He temperature. These topics are of particular importance for future missions such as IMAP, which will provide ENA images for a broader energy range and with better sensitivity and resolution.
Gravitational waves from compact objects
Institute of Scientific and Technical Information of China (English)
José Antonio de Freitas Pacheco
2010-01-01
Large ground-based laser beam interferometers are presently in operation both in the USA (LIGO) and in Europe (VIRGO) and potential sources that might be detected by these instruments are revisited. The present generation of detectors does not have a sensitivity high enough to probe a significant volume of the universe and,consequently, predicted event rates are very low. The planned advanced generation of interferometers will probably be able to detect, for the first time, a gravitational signal. Advanced LIGO and EGO instruments are expected to detect few (some): binary coalescences consisting of either two neutron stars, two black holes or a neutron star and a black hole. In space, the sensitivity of the planned LISA spacecraft constellation will allow the detection of the gravitational signals, even within a "pessimistic" range of possible signals, produced during the capture of compact objects by supermassive black holes, at a rate of a few tens per year.
Classifying self-gravitating radiations
Kim, Hyeong-Chan
2016-01-01
We study static systems of self-gravitating radiations confined in a sphere by using numerical and analytic calculations. We classify and analyze the solutions systematically. Due to the scaling symmetry, any solution can be represented as a segment of a solution curve on a plane of two-dimensional scale invariant variables. We find that a system can be conveniently parametrized by three parameters representing the solution curve, the scaling, and the system size, instead of the parameters defined at the outer boundary. The solution curves are classified to three types representing regular solutions, conically singular solutions with, and without an object which resembles an event horizon up to causal disconnectedness. For the last type, the behavior of a self-gravitating system is simple enough to allow analytic calculations.
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.
Conformal Anomalies and Gravitational Waves
Meissner, Krzysztof A
2016-01-01
We argue that the presence of conformal anomalies in gravitational theories can lead to observable modifications to Einstein's equations via the induced anomalous effective actions, whose non-localities can overwhelm the smallness of the Planck scale. The fact that no such effects have been seen in recent cosmological or gravitational wave observations therefore imposes strong restrictions on the field content of possible extensions of Einstein's theory: all viable theories should have vanishing conformal anomalies. We then show that, among presently known theories, a complete cancellation of conformal anomalies in $D=4$ for both the $C^2$ invariant and the Euler (Gauss-Bonnet) invariant $E_4$ can only be achieved for $N$-extended supergravities with $N\\geq 5$, as well as for M theory compactified to four dimensions.
Quantum walks and gravitational waves
Arnault, Pablo; Debbasch, Fabrice
2017-08-01
A new family of discrete-time quantum walks (DTQWs) propagating on a regular (1 + 2)D spacetime lattice is introduced. The continuum limit of these DTQWs is shown to coincide with the dynamics of a Dirac fermion coupled to an arbitrary relativistic gravitational field. This family is used to model the influence of arbitrary linear gravitational waves (GWs) on DTQWs. Pure shear GWs are studied in detail. We show that on large spatial scales, the spatial deformation generated by the wave induces a rescaling of the eigen-energies by a certain anisotropic factor which can be computed exactly. The effect of pure shear GWs on fermion interference patterns is also investigated, both on large scales and on scales comparable to the lattice spacing.
Gravitational wave science from space
Gair, Jonathan R.
2016-05-01
The rich millihertz gravitational wave band can only be accessed with a space- based detector. The technology for such a detector will be demonstrated by the LISA Pathfinder satellite that is due to launch this year and ESA has selected gravitational wave detection from space as the science theme to be addressed by the L3 large mission to be launched around 2034. In this article we will discuss the sources that such an instrument will observe, and how the numbers of events and precision of parameter determination are affected by modifications to the, as yet not finalised, mission design. We will also describe some of the exciting scientific applications of these observations, to astrophysics, fundamental physics and cosmology.
A gravitating electroweak bag model
Burinskii, Alexander
2016-02-01
Gravitational and electromagnetic (EM) field of electron is described by the Kerr-Newman (KN) black hole solution with a topological defect. Regularization of this defect by the Higgs field leads to the smooth source which shares much in common with the known MIT- and SLAC- bag models, but has the advantage, of matching gravitational and electromagnetic fields of the electron. This model is flexible, and the rotating KN bag takes the shape of a thin disk with a circular string positioned on the sharp border of the disk. We consider the lowest excitations of the KN solution and the corresponding deformations of the bag surface, setting a preliminary correspondence with electroweak sector of the SM.
Loop Quantum Cosmology Gravitational Baryogenesis
Odintsov, S D
2016-01-01
Loop Quantum Cosmology is an appealing quantum completion of classical cosmology, which brings along various theoretical features which in many cases offer remedy or modify various classical cosmology aspects. In this paper we address the gravitational baryogenesis mechanism in the context of Loop Quantum Cosmology. As we demonstrate, when Loop Quantum Cosmology effects are taken into account in the resulting Friedmann equations for a flat Friedmann-Robertson-Walker Universe, then even for a radiation dominated Universe, the predicted baryon-to-entropy ratio from the gravitational baryogenesis mechanism is non-zero, in contrast to the Einstein-Hilbert case, in which case the baryon-to-entropy ratio is zero. We also discuss various other cases apart from the radiation domination case, and we discuss how the baryon-to-entropy ratio is affected from the parameters of the quantum theory. In addition, we use illustrative exact solutions of Loop Quantum Cosmology and we investigate under which circumstances the bar...
A Classical Model of Gravitation
Directory of Open Access Journals (Sweden)
Wagener P.
2008-07-01
Full Text Available A classical model of gravitation is proposed with time as an independent coordinate. The dynamics of the model is determined by a proposed Lagrangian. Applying the canonical equations of motion to its associated Hamiltonian gives conservation equa- tions of energy, total angular momentum and the z component of the angular momen- tum. These lead to a Keplerian orbit in three dimensions, which gives the observed values of perihelion precession and bending of light by a massive object. An expression for gravitational redshift is derived by accepting the local validity of special relativity at all points in space. Exact expressions for the GEM relations, as well as their associated Lorentz-type force, are derived. An expression for Mach’s Principle is also derived.
The gravitational dynamics of galaxies
Indian Academy of Sciences (India)
Rajaram Nityananda
2009-07-01
The broad area of galactic dynamics is presented for a physics audience, with the requisite astronomy background in outline, and focusing on gravitational effects. The basic underlying model is a large number of particles (which could be stars or dark matter) moving in their self-consistent gravitational potential. The effects of two-particle correlations/scattering, although weak, can be cumulative and hence important for a class of systems such as star clusters which are hence termed collisional. On the larger scale of galaxies, we have collisionless behaviour which is different and in some ways richer. The basic ideas and applications in both these regimes are described, and some issues highlighted in conclusion.
Conformal gravity and "gravitational bubbles"
Berezin, V A; Eroshenko, Yu N
2015-01-01
We describe the general structure of the spherically symmetric solutions in the Weyl conformal gravity. The corresponding Bach equations are derived for the special type of metrics, which can be considered as the representative of the general class. The complete set of the pure vacuum solutions, consisting of two classes, is found. The first one contains the solutions with constant two-dimensional curvature scalar, and the representatives are the famous Robertson--Walker metrics. We called one of them the "gravitational bubbles", which is compact and with zero Weyl tensor. These "gravitational bubbles" are the pure vacuum curved space-times (without any material sources, including the cosmological constant), which are absolutely impossible in General Relativity. This phenomenon makes it easier to create the universe from "nothing". The second class consists of the solutions with varying curvature scalar. We found its representative as the one-parameter family, which can be conformally covered by the thee-para...
Bayesian Inference on Gravitational Waves
Directory of Open Access Journals (Sweden)
Asad Ali
2015-12-01
Full Text Available The Bayesian approach is increasingly becoming popular among the astrophysics data analysis communities. However, the Pakistan statistics communities are unaware of this fertile interaction between the two disciplines. Bayesian methods have been in use to address astronomical problems since the very birth of the Bayes probability in eighteenth century. Today the Bayesian methods for the detection and parameter estimation of gravitational waves have solid theoretical grounds with a strong promise for the realistic applications. This article aims to introduce the Pakistan statistics communities to the applications of Bayesian Monte Carlo methods in the analysis of gravitational wave data with an overview of the Bayesian signal detection and estimation methods and demonstration by a couple of simplified examples.
Gravitational lens surveys with LOFAR
Wucknitz, O
2008-01-01
Deep surveys planned as a Key Science Project of LOFAR provide completely new opportunities for gravitational lens searches. For the first time do large-scale surveys reach the resolution required for a direct selection of lens candidates using morphological criteria. We briefly describe the strategies that we will use to exploit this potential. The long baselines of an international E-LOFAR are essential for this project.
Self-gravitating accretion discs
Lodato, G.
2008-01-01
I review recent progresses in the dynamics and the evolution of self-gravitating accretion discs. Accretion discs are a fundamental component of several astrophysical systems on very diverse scales, and can be found around supermassive black holes in Active Galactic Nuclei (AGN), and also in our Galaxy around stellar mass compact objects and around young stars. Notwithstanding the specific differences arising from such diversity in physical extent, all these systems share a common feature whe...
Gravitational Global Monopoles with Horizons
Maison, D
1999-01-01
We give arguments for the existence of ``radial excitations'' of gravitational global monopoles with any number of zeros of the Higgs field and present numerical results for solutions with up to two zeros. All these solutions possess a de Sitter like cosmological horizon, outside of which they become singular. In addition we study corresponding static ``hairy'' black hole solutions, representing black holes sitting inside a global monopole core. In particular, we determine their existence domains as a function of their horizon radius rh.
Gravitational Baryogenesis in Anisotropic Universe
Saaidi, Kh
2010-01-01
The interaction between Ricci scalar curvature and the baryon number current, dynamically breaks CPT in an expanding universe and leads to baryon asymmetry. Using this kind of interaction and study the gravitational baryogenesis in the Bianchi type I universe. We find out the effect of anisotropy of the universe on the baryon asymmetry for the case which the equation of state parameter, $\\omega$, is dependent to time.
Gravitational Instabilities in Circumstellar Disks
Kratter, Kaitlin; Lodato, Giuseppe
2016-09-01
Star and planet formation are the complex outcomes of gravitational collapse and angular momentum transport mediated by protostellar and protoplanetary disks. In this review, we focus on the role of gravitational instability in this process. We begin with a brief overview of the observational evidence for massive disks that might be subject to gravitational instability and then highlight the diverse ways in which the instability manifests itself in protostellar and protoplanetary disks: the generation of spiral arms, small-scale turbulence-like density fluctuations, and fragmentation of the disk itself. We present the analytic theory that describes the linear growth phase of the instability supplemented with a survey of numerical simulations that aim to capture the nonlinear evolution. We emphasize the role of thermodynamics and large-scale infall in controlling the outcome of the instability. Despite apparent controversies in the literature, we show a remarkable level of agreement between analytic predictions and numerical results. In the next part of our review, we focus on the astrophysical consequences of the instability. We show that the disks most likely to be gravitationally unstable are young and relatively massive compared with their host star, Md/M*≥0.1. They will develop quasi-stable spiral arms that process infall from the background cloud. Although instability is less likely at later times, once infall becomes less important, the manifestations of the instability are more varied. In this regime, the disk thermodynamics, often regulated by stellar irradiation, dictates the development and evolution of the instability. In some cases the instability may lead to fragmentation into bound companions. These companions are more likely to be brown dwarfs or stars than planetary mass objects. Finally, we highlight open questions related to the development of a turbulent cascade in thin disks and the role of mode-mode coupling in setting the maximum angular
Cylindrical Collapse and Gravitational Waves
Herrera, L
2005-01-01
We study the matching conditions for a collapsing anisotropic cylindrical perfect fluid, and we show that its radial pressure is non zero on the surface of the cylinder and proportional to the time dependent part of the field produced by the collapsing fluid. This result resembles the one that arises for the radiation - though non-gravitational - in the spherically symmetric collapsing dissipative fluid, in the diffusion approximation.
Gravitating Dyons in Vaidya Geometry
Tripathi, Buddhi Vallabh; Dehnen, Heinz; Purohit, K D
2014-01-01
Gravitating monopoles and dyons in Einstein-Yang-Mills (EYM) or Einstein-Yang-Mills-Higgs (EYMH) systems have been extensively studied for various curved spacetimes, including those of black holes. We construct dyonic solutions of the EYMH theory in Vaidya spacetime using a set of generalized Julia-Zee ansatz for the fields. It is found that the dyonic charge is static in nature and it does not contribute to the energy of the null dust.
Energy Technology Data Exchange (ETDEWEB)
J Shearer; K Rosenkoetter; P Callan; C Pham
2011-12-31
The influence of a single octarepeat expansion on the Cu{sup II} and Zn{sup II} coordination environments within the octarepeat domain of the human prion protein is examined. Using X-ray absorption spectroscopy and diethyl pyrocarbonate labeling studies, we find that at low copper concentrations the 'normal' octarepeat domain (four PHGGGWGQ repeats) coordinates Zn{sup II} in an (N/O){sub 6} coordination environment with two histidine residues and Cu{sup II} in a redox-inactive (N/O){sub 4} coordination environment using one imidazole residue. Expansion of the octarepeat region by one repeat (five PHGGGWGQ repeats) yields a three-histidine (N/O){sub 6} coordination environment for Zn{sup II} and a two-histidine (N/O){sub 4} coordination environment for Cu{sup II} at low copper concentrations. This Cu{sup II}[(N/O){sub 2}-histidine{sub 2}] coordination motif is redox-active and capable of generating H{sub 2}O{sub 2} under reducing aerobic conditions.
The 1987-1988 NASA space/gravitational biology accomplishments
Halstead, Thora W. (Editor)
1988-01-01
Individual technical summaries of research projects of the NASA Space/Gravitational Biology Program, for research conducted during the period January 1987 to April 1988 are presented. This Program is concerned with using the characteristics of the space environment, particularly microgravity, as a tool to advance knowledge in the biological sciences; understanding how gravity has shaped and affected life on earth; and understanding how the space environment affects both plant and animal species. The summaries for each project include a description of the research, a list of the accomplishments, an explanation of the significance of the accomplishments, and a list of publications.
The 1985-86 NASA space/gravitational biology accomplishments
1987-01-01
Individual Technical summaries of research projects of NASA's Space/Gravitational Biology Program are presented. This Program is concerned with using the unique characteristics of the space environment, particularly microgravity, as a tool to advance knowledge in the biological sciences; understanding how gravity has shaped and affected life on Earth; and understanding how the space environment affects both plant and animal species. The summaries for each project include a description of the research, a listing of the accomplishments, an explanation of the significance of the accomplishments, and a list of publications.
The 1986-87 NASA space/gravitational biology accomplishments
Halstead, Thora W. (Editor)
1987-01-01
This report consists of individual technical summaries of research projects of NASA's Space/Gravitational Biology program, for research conducted during the period January 1986 to April 1987. This program utilizes the unique characteristics of the space environment, particularly microgravity, as a tool to advance knowledge in the biological sciences; understanding how gravity has shaped and affected life on Earth; and understanding how the space environment affects both plant and animal species. The summaries for each project include a description of the research, a list of accomplishments, an explanation of the significance of the accomplishments, and a list of publications.
The 1988-1989 NASA Space/Gravitational Biology Accomplishments
Halstead, Thora W. (Editor)
1990-01-01
This report consists of individual technical summaries of research projects of NASA's space/gravitational biology program, for research conducted during the period May 1988 to April 1989. This program is concerned with using the unique characteristics of the space environment, particularly microgravity, as a tool to advance knowledge in the biological sciences; understanding how gravity has shaped and affected life on Earth; and understanding how the space environment affects both plant and animal species. The summaries for each project include a description of the research, a list of the accomplishments, an explanation of the significance of the accomplishments, and a list of publications.
Gravitational Gauge Interactions of Scalar Field
Institute of Scientific and Technical Information of China (English)
WUNing
2003-01-01
Quantum gauge theory of gravity is formulated based on gauge principle. Because the Lagrangian has strict local gravitational gauge symmetry, gravitational gauge theory is a perturbatively renormalizable quantum theory. Gravitational gauge interactions of scalar field are studied in this paper. In quantum gauge theory of gravity, scalar field minimal couples to gravitational field through gravitational gauge covariant derivative. Comparing the Lagrangian for scalar field in quantum gauge theory of gravity with the corresponding Lagrangian in quantum fields in curved space-time, the definition for metric in curved space-time in geometry picture of gravity can be obtained, which is expressed by gravitational gauge field. In classical level, the Lagrangian and Hamiltonian approaches are also discussed.
Gravitational Gauge Interactions of Scalar Field
Institute of Scientific and Technical Information of China (English)
WU Ning
2003-01-01
Quantum gauge theory of gravity is formulated based on gauge principle. Because the Lagrangian hasstrict local gravitational gauge symmetry, gravitational gauge theory is a perturbatively renormalizable quantum theory.Gravitational gauge interactions of scalar field are studied in this paper. In quantum gauge theory of gravity, scalar fieldminimal couples to gravitational field through gravitational gauge covariant derivative. Comparing the Lagrangian forscalar field in quantum gauge theory of gravity with the corresponding Lagrangian in quantum fields in curved space-time, the definition for metric in curved space-time in geometry picture of gravity can be obtained, which is expressedby gravitational gauge field. In classical level, the Lagrangian and Hamiltonian approaches are also discussed.
Universal Gravitation as Lorentz-covariant Dynamics
Kauffmann, Steven Kenneth
2014-01-01
Einstein's equivalence principle implies that the acceleration of a particle in a "specified" gravitational field is independent of its mass. While this is certainly true to great accuracy for bodies we observe in the Earth's gravitational field, a hypothetical body of mass comparable to the Earth's would perceptibly cause the Earth to fall toward it, which would feed back into the strength as a function of time of the Earth's gravitational field affecting that body. In short, Einstein's equivalence principle isn't exact, but is an approximation that ignores recoil of the "specified" gravitational field, which sheds light on why general relativity has no clearly delineated native embodiment of conserved four-momentum. Einstein's 1905 relativity of course doesn't have the inexactitudes he unwittingly built into GR, so it is natural to explore a Lorentz-covariant gravitational theory patterned directly on electromagnetism, wherein a system's zero-divergence overall stress-energy, including all gravitational fee...
Journal of Gravitational Physiology, Volume 12, Number 1
Fuller, Charles A. (Editor); Cogoli, Augusto (Editor); Hargens, Alan R. (Editor); Smith, Arthur H. (Editor)
2005-01-01
The following topics were covered: System Specificity in Responsiveness to Intermittent -Gx Gravitation during Simulated Microgravity in Rats; A Brief Overview of Animal Hypergravity Studies; Neurovestibular Adaptation to Short Radius Centrifugation; Effect of Artificial Gravity with Exercise Load by Using Short-Arm Centrifuge with Bicycle Ergometer as a Countermeasure Against Disused Osteoporosis; Perception of Body Vertical in Microgravity during Parabolic Flight; Virtual Environment a Behavioral and Countermeasure Tool for Assisted Gesture in Weightlessness: Experiments during Parabolic Flight; Artificial Gravity: Physiological Perspectives for Long-Term Space Exploration; Comparison of the Effects of DL-threo-Beta-Benzyloxyaspartate on the Glutamate Release from Synaptosomes before and after Exposure of Rats to Artificial Gravity; Do Perception and Postrotatory Vestibulo-Ocular Reflex Share the Same Gravity Reference?; Vestibular Adaptation to Changing Gravity Levels and the Orientation of Listing's Plane; Compound Mechanism Hypothesis on +Gz - Induced Brain Injury and Dysfunction of Learning and Memory; Environmental Challenge Impairs Prefrontal Brain Functions; Effect of 6-Days of Support Withdrawal on Characteristics of Balance Function; Hypergravity-Induced Changes of Neuronal Activities in CA1 Region of Rat Hippocampus; Audiological Findings in Antiorthostatic Position Modelling Microgravitation; Investigating Human Cognitive Performance during Spaceflight; The Relevance of the Minimization of Torque Exchange with the Environment in Weightlessness is Confirmed by Asimulation Study; Characteristics of the Eyes Pursuit Function during Readaptation to Terrestrial Gravity after Prolonged Flights Aboard the International Space Station; Comparison of Cognitive Performance Tests for Promethazine Pharmacodynamics in Human Subjects; Structural Reappraisal of Dendritic Tree of Cerebellar Purkinje Cell for Novel Functional Modeling of Elementary Sensorimotor Adaptive
Response of massive bodies to gravitational waves
Hannibal, L; Hannibal, Ludger; Warkall, Jens
2000-01-01
The repsonse of a massive body to gravitational waves is decribed on the microscopic level, taking the metric perturbations of the electromagnetic and gravitational forces into account. The effects found substantially differ from those obtained in the commonly used oscillator model. The electromagnetic coupling induces a dominant surface effect, the gravitational coupling gives rise to the excitation of quadrupole modes, but several oredes of magnitude smaller.
Gravitational waves from binary black holes
Indian Academy of Sciences (India)
Bala R Iyer
2011-07-01
It is almost a century since Einstein predicted the existence of gravitational waves as one of the consequences of his general theory of relativity. A brief historical overview including Chandrasekhar’s contribution to the subject is ﬁrst presented. The current status of the experimental search for gravitational waves and the attendant theoretical insights into the two-body problem in general relativity arising from computations of gravitational waves from binary black holes are then broadly reviewed.
Generalized Gravitational Entropy from Various Matter Fields
Huang, Wung-Hong
2016-01-01
The generalized gravitational entropy proposed in recent by Lewkowycz and Maldacena [1] is extended to the systems of Boson fields, Fermion fields and Maxwell fields which have arbitrary frequency and mode numbers on the BTZ spacetime. We find the associated regular wave solution in each case and use it to calculate the exact gravitational entropy. The results show that there is a threshold frequency below which the Fermion fields could not contribute the generalized gravitational entropy. Al...
On Gravitational Entropy of de Sitter Universe
Ulhoa, S C
2013-01-01
The paper deals with the calculation of the gravitational entropy in the context of teleparallel gravity for de Sitter space-time. In such a theory it is possible to define gravitational energy and pressure, thus we use those expressions to construct the gravitational entropy. We interpret the cosmological constant as the temperature and write the first law of thermodynamics. In the limit $\\Lambda\\ll 1$ we find that the entropy is proportional to volume and $\\Delta S\\geq 0$.
Gravitational Couplings on D-brane Revisited
Ghodsi, Ahmad
2016-01-01
Gravitational couplings in bulk space-time include those terms which are fixed by scattering amplitude of strings and ambiguous terms that are coming from the field redefinitions. These field redefinitions can be fixed in the bulk by ghost-free condition. In this paper we have revised the effective gravitational couplings on D-branes by including the field redefinitions. We find the gravitational effective action up to $\\alpha'^2$-order.
Star Formation in the LMC: Gravitational Instability and Dynamical Triggering
Chu, Y H; Yang, C C
2007-01-01
Evidence for triggered star formation is difficult to establish because energy feedback from massive stars tend to erase the interstellar conditions that led to the star formation. Young stellar objects (YSOs) mark sites of {\\it current} star formation whose ambient conditions have not been significantly altered. Spitzer observations of the Large Magellanic Cloud (LMC) effectively reveal massive YSOs. The inventory of massive YSOs, in conjunction with surveys of interstellar medium, allows us to examine the conditions for star formation: spontaneous or triggered. We examine the relationship between star formation and gravitational instability on a global scale, and we present evidence of triggered star formation on local scales in the LMC.
Gravitational studies in cellular and developmental biology
Spooner, B. S.
1992-01-01
The paucity of data on the role of gravity in cellular and developmental biology has been examined, and a hypothesis has been generated that unifies potential gravity sensitivity in both plant and animal systems. This hypothesis considers the macromolecular order and functional importance of the extracellular matrix compartment, the intracellular cytoskeleton compartment, and the connecting plasma membrane-signal transduction compartment of plant and animal systems as potentially sensitive to alterations in the unit gravity environment in which they evolved.
Dixon's extended bodies and weak gravitational waves
Bini, Donato; Geralico, Andrea; Ortolan, Antonello
2009-01-01
General relativity considers Dixon's theory as the standard theory to deal with the motion of extended bodies in a given gravitational background. We discuss here the features of the "reaction" of an extended body to the passage of a weak gravitational wave. We find that the body acquires a dipolar moment induced by its quadrupole structure. Furthermore, we derive the "world function" for the weak field limit of a gravitational wave background and use it to estimate the deviation between geodesics and the world lines of structured bodies. Measuring such deviations, due to the existence of cumulative effects, should be favorite with respect to measuring the amplitude of the gravitational wave itself.
Gravitational Wave Detection with Michelson Interferometers
Sivasubramanian, S; Widom, A
2003-01-01
Electromagnetic methods recently proposed for detecting gravitational waves modify the Michelson phase shift analysis (historically employed for special relativity). We suggest that a frequency modulation analysis is more suited to general relativity. An incident photon in the presence of a very long wavelength gravitational wave will have a finite probability of being returned as a final photon with a frequency shift whose magnitude is equal to the gravitational wave frequency. The effect is due to the non-linear coupling between electromagnetic and gravitational waves. The frequency modulation is derived directly from the Maxwell-Einstein equations.
Astrophysical Gravitational Wave Sources Literature Catalog
National Aeronautics and Space Administration — Numerically-generated gravitational waveforms for circular inspiral into Kerr black holes. These waveforms were developed using Scott Hughes' black hole perturbation...
Gravitational phase operator and cosmic strings
Anandan, Jeeva S
1996-01-01
A quantum equivalence principle is formulated by means of a gravitational phase operator which is an element of the Poincare group. This is applied to the spinning cosmic string which suggests that it may contain gravitational torsion. A new exact solution of the Einstein- Cartan-Sciama-Kibble equations for the gravitational field with torsion is obtained everywhere for a cosmic string with uniform energy density, spin density and flux. A novel effect due to the quantized gravitational field of the cosmic string on the wave function of a particle outside the string is used to show that spacetime points are not meaningful in quantum gravity.
Physics, Astrophysics and Cosmology with Gravitational Waves
Directory of Open Access Journals (Sweden)
Sathyaprakash B. S.
2009-03-01
Full Text Available Gravitational wave detectors are already operating at interesting sensitivity levels, and they have an upgrade path that should result in secure detections by 2014. We review the physics of gravitational waves, how they interact with detectors (bars and interferometers, and how these detectors operate. We study the most likely sources of gravitational waves and review the data analysis methods that are used to extract their signals from detector noise. Then we consider the consequences of gravitational wave detections and observations for physics, astrophysics, and cosmology.
Gravitational Wave Astrophysics: Opening the New Frontier
Centrella, Joan
2012-01-01
A new era in astronomy will begin when the gravitational wave window onto the universe opens in approx. 5 years, as ground-based detectors make the first detections in the high-frequency regime. Since the universe is nearly transparent to gravitational waves, these signals carry direct information about their sources - such as masses, spins, luminosity distances, and orbital parameters - through dense, obscured regions across cosmic time. This talk will explore gravitational waves as cosmic messengers, highlighting key sources and opportunities for multi-messenger astronomy across the gravitational wave spectrum.
Baryons, Neutrinos, Feedback and Weak Gravitational Lensing
Harnois-Déraps, Joachim; Viola, Massimo; Heymans, Catherine
2014-01-01
(Abridged) The effect of baryonic feedback on the dark matter mass distribution is generally considered to be a nuisance to weak gravitational lensing. Measurements of cosmological parameters are affected as feedback alters the cosmic shear signal on angular scales smaller than a few arcminutes. Recent progress on the numerical modelling of baryon physics has shown that this effect could be so large that, rather than being a nuisance, the effect can be constrained with current weak lensing surveys, hence providing an alternative astrophysical insight on one of the most challenging questions of galaxy formation. In order to perform our analysis, we construct an analytic fitting formula that describes the effect of the baryons on the mass power spectrum. This fitting formula is based on three scenarios of the OWL hydrodynamical simulations. It is specifically calibrated for $z<1.5$, where it models the simulations to an accuracy that is better than $2\\%$ for scales $k<10 h\\mbox{Mpc}^{-1}$ and better than ...
Gravitational Lensing Accuracy Testing 2010 (GREAT10) Challenge Handbook
Kitching, Thomas; Gill, Mandeep; Harmeling, Stefan; Heymans, Catherine; Massey, Richard; Rowe, Barnaby; Schrabback, Tim; Voigt, Lisa; Balan, Sreekumar; Bernstein, Gary; Bethge, Matthias; Bridle, Sarah; Courbin, Frederic; Gentile, Marc; Heavens, Alan; Hirsch, Michael; Hosseini, Reshad; Kiessling, Alina; Kirk, Donnacha; Kuijken, Konrad; Mandelbaum, Rachel; Moghaddam, Baback; Nurbaeva, Guldariya; Paulin-Henriksson, Stephane; Rassat, Anais; Rhodes, Jason; Schölkopf, Bernhard; Shawe-Taylor, John; Shmakova, Marina; Taylor, Andy; Velander, Malin; van Waerbeke, Ludovic; Witherick, Dugan; Wittman, David
2010-01-01
GRavitational lEnsing Accuracy Testing 2010 (GREAT10) is a public image analysis challenge aimed at the development of algorithms to analyse astronomical images. Specifically the challenge is to measure varying image distortions in the presence of a variable convolution kernel, pixelization and noise. This is the second in a series of challenges set to the astronomy, computer science and statistics communities, providing a structured environment in which methods can be improved and tested in preparation for planned astronomical surveys. GREAT10 extends upon previous work by introducing variable fields into the challenge. The 'Galaxy Challenge' involves the precise measurement of galaxy shape distortions, quantified locally by two parameters called shear, in the presence of a known convolution kernel. Crucially, the convolution kernel and the simulated gravitational lensing shape distortion both now vary as a function of position within the images, as is the case for real data. In addition we introduce the 'St...
Gravitational Focusing and the Star Cluster Initial Mass Function
Kuznetsova, Aleksandra; Hartmann, Lee; Burkert, Andreas
2017-02-01
We discuss the possibility that gravitational focusing is responsible for the power-law mass function of star clusters N({log}M)\\propto {M}-1. This power law can be produced asymptotically when the mass accretion rate of an object depends upon the mass of the accreting body, as \\dot{M}\\propto {M}2. Although Bondi–Hoyle–Lyttleton accretion formally produces this dependence on mass in a uniform medium, realistic environments are much more complicated. However, numerical simulations in SPH that allow for sink formation yield such an asymptotic power-law mass function. We perform pure N-body simulations to isolate the effects of gravity from those of gas physics and to show that clusters naturally result with the power-law mass distribution. We also consider the physical conditions necessary to produce clusters on appropriate timescales. Our results help support the idea that gravitationally dominated accretion is the most likely mechanism for producing the cluster mass function.
Chaotic zones around gravitating binaries
Shevchenko, Ivan I
2014-01-01
The extent of the continuous zone of chaotic orbits of a small-mass tertiary around a system of two gravitationally bound bodies (a double star, a double black hole, a binary asteroid, etc.) is estimated analytically, in function of the tertiary's orbital eccentricity. The separatrix map theory is used to demonstrate that the central continuous chaos zone emerges due to overlapping of the orbital resonances corresponding to the integer ratios p:1 between the tertiary and the binary periods. The binary's mass ratio, above which such a chaotic zone is universally present, is also estimated.
The Scales of Gravitational Lensing
De Paolis, Francesco; Ingrosso, Gabriele; Manni, Luigi; Nucita, Achille; Strafella, Francesco
2016-01-01
After exactly a century since the formulation of the general theory of relativity, the phenomenon of gravitational lensing is still an extremely powerful method for investigating in astrophysics and cosmology. Indeed, it is adopted to study the distribution of the stellar component in the Milky Way, to study dark matter and dark energy on very large scales and even to discover exoplanets. Moreover, thanks to technological developments, it will allow the measure of the physical parameters (mass, angular momentum and electric charge) of supermassive black holes in the center of ours and nearby galaxies.
Matrix Models and Gravitational Corrections
Dijkgraaf, R; Temurhan, M; Dijkgraaf, Robbert; Sinkovics, Annamaria; Temurhan, Mine
2002-01-01
We provide evidence of the relation between supersymmetric gauge theories and matrix models beyond the planar limit. We compute gravitational R^2 couplings in gauge theories perturbatively, by summing genus one matrix model diagrams. These diagrams give the leading 1/N^2 corrections in the large N limit of the matrix model and can be related to twist field correlators in a collective conformal field theory. In the case of softly broken SU(N) N=2 super Yang-Mills theories, we find that these exact solutions of the matrix models agree with results obtained by topological field theory methods.
Gravitational entropy of cosmic expansion
Sussman, Roberto A
2014-01-01
We apply a recent proposal to define "gravitational entropy" to the expansion of cosmic voids within the framework of non-perturbative General Relativity. By considering CDM void configurations compatible with basic observational constraints, we show that this entropy grows from post-inflationary conditions towards a final asymptotic value in a late time fully non-linear regime described by the Lemaitre-Tolman-Bondi (LTB) dust models. A qualitatively analogous behavior occurs if we assume a positive cosmological constant consistent with a $\\Lambda$-CDM background model. However, the $\\Lambda$ term introduces a significant suppression of entropy growth with the terminal equilibrium value reached at a much faster rate.
Gravitational Waves from Warped Spacetime
Randall, Lisa; Randall, Lisa; Servant, Geraldine
2007-01-01
We argue that the RSI model can provide a strong signature in gravitational waves. This signal is a relic stochastic background generated during the cosmological phase transition from an AdS-Schwarschild phase to the RS1 geometry that should occur at a temperature in the TeV range. We estimate the amplitude of the signal in terms of the parameters of the potential stabilizing the radion and show that over much of the parameter region in which the phase transition completes, a signal should be detectable at the planned space interferometer, LISA.
Moduli destabilization via gravitational collapse
Energy Technology Data Exchange (ETDEWEB)
Hwang, Dong-il [Sogang Univ., Seoul (Korea, Republic of). Center for Quantum Spacetime; Pedro, Francisco G. [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany). Theory Group; Yeom, Dong-han [Sogang Univ., Seoul (Korea, Republic of). Center for Quantum Spacetime; Kyoto Univ. (Japan). Yukawa Inst. for Theoretical Physics
2013-06-15
We examine the interplay between gravitational collapse and moduli stability in the context of black hole formation. We perform numerical simulations of the collapse using the double null formalism and show that the very dense regions one expects to find in the process of black hole formation are able to destabilize the volume modulus. We establish that the effects of the destabilization will be visible to an observer at infinity, opening up a window to a region in spacetime where standard model's couplings and masses can differ significantly from their background values.
The Scales of Gravitational Lensing
Directory of Open Access Journals (Sweden)
Francesco De Paolis
2016-03-01
Full Text Available After exactly a century since the formulation of the general theory of relativity, the phenomenon of gravitational lensing is still an extremely powerful method for investigating in astrophysics and cosmology. Indeed, it is adopted to study the distribution of the stellar component in the Milky Way, to study dark matter and dark energy on very large scales and even to discover exoplanets. Moreover, thanks to technological developments, it will allow the measure of the physical parameters (mass, angular momentum and electric charge of supermassive black holes in the center of ours and nearby galaxies.
Exploring gravitational theories beyond Horndeski
Gleyzes, Jérôme; Piazza, Federico; Vernizzi, Filippo
2014-01-01
We have recently proposed a new class of gravitational scalar-tensor theories free from ghost instabilities. As they generalize Horndeski theories, or "generalized" galileons, we call them G$^3$. These theories possess a simple formulation when the time hypersurfaces are chosen to coincide with the uniform scalar field hypersurfaces. We confirm that they do not suffer from Ostrogradski instabilities by presenting the details of the Hamiltonian formulation. We examine the coupling between these theories and matter. Moreover, we investigate how they transform under a disformal redefinition of the metric. Remarkably, these theories are preserved by disformal transformations, which also allow subfamilies of G$^3$ to be mapped into Horndeski theories.
The Future of Gravitational Optics
Blandford, R D
2001-01-01
In this speculative, millenial essay, I try to anticipate what sort of novel gravitational optics investigations might be observed, after it becomes possible to map and monitor roughly a trillion sources (of which a billion may be usefully variable) comprehensively throughout electromagnetic and other spectra over the whole sky. Existing techniques suffice to produce three dimensional maps of the dark matter distribution of the accessible universe, to explore black hole spacetimes and to magnify images of the first luminous sources, terrestrial planets and compact objects.
Gravitational effects on inflaton decay
Energy Technology Data Exchange (ETDEWEB)
Ema, Yohei; Jinno, Ryusuke; Mukaida, Kyohei [Department of Physics, University of Tokyo,Tokyo 113-0033 (Japan); Nakayama, Kazunori [Department of Physics, University of Tokyo,Tokyo 113-0033 (Japan); Kavli IPMU, TODIAS, University of Tokyo,Kashiwa 277-8583 (Japan)
2015-05-22
We point out that the inflaton inevitably couples to all non-conformally coupled matters gravitationally through an oscillation in the Hubble parameter or the cosmic scale factor. It leads to particle production during the inflaton oscillation regime, which is most efficient just after inflation. Moreover, the analysis is extended to the model with non-minimal inflaton couplings to gravity, in which the Hubble parameter oscillates more violently. We apply our results to the graviton production by the inflaton: gravitons are also produced just after inflation, but the non-minimal coupling does not induce inflaton decay into the graviton pair.
Gravitational Effects on Inflaton Decay
Ema, Yohei; Mukaida, Kyohei; Nakayama, Kazunori
2015-01-01
We point out that the inflaton inevitably couples to all non-conformally coupled matters gravitationally through an oscillation in the Hubble parameter or the cosmic scale factor. It leads to particle production during the inflaton oscillation regime, which is most efficient just after inflation. Moreover, the analysis is extended to the model with non-minimal inflaton couplings to gravity, in which the Hubble parameter oscillates more violently. We apply our results to the graviton production by the inflaton: gravitons are also produced just after inflation, but the non-minimal coupling does not induce inflaton decay into the graviton pair.
$f(T)$ gravitational baryogenesis
Oikonomou, V K
2016-01-01
We investigate the gravitational baryogenesis mechanism in a universe governed by $f(T)$ gravity. We consider two possible baryogenesis terms, and we calculate the resulting baryon-to-entropy ratio in the case where the background cosmology is determined by either simple teleparallel gravity or by three specific, viable, $f(T)$ models. As we show, $f(T)$ gravity can provide a baryogenesis mechanism in agreement with observations. Reversely, one can use the observed value of baryon-to-entropy ratio in order to constrain the various models.
Solitary waves in a self-gravitating opposite polarity dust-plasma medium
Energy Technology Data Exchange (ETDEWEB)
Mamun, A. A.; Schlickeiser, R. [Institut für Theoretische Physik, Lehrstuhl IV, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum (Germany)
2015-10-15
A more general and realistic dusty plasma model, namely, self-gravitating opposite polarity dust-plasma system (containing inertial positive and negative dust, and inertialess ions and electrons following Maxwellian distribution) is considered. The possibility for the formation of solitary electrostatic and self-gravitational potential structures in such a dust-plasma system is thoroughly examined. The standard reductive perturbation method, which is valid for small but finite amplitude solitary structures, is employed. The parametric regimes for the existence of solitary electrostatic and self-gravitational potential structures, and their basic properties (viz., polarity, amplitude, width, and speed) are found to be significantly modified by the combined effects of positively charged dust component and self-gravitational field. The applications of the present investigation in different space dusty plasma environments and laboratory dusty plasma devices are briefly discussed.
Omnidirectional Gravitational Wave Detector with a Laser-Interferometric Gravitational Compass
Maia, M D; Sousa, Claudio M G; Magalhaes, Nadja S; Frajuca, Carlos
2016-01-01
Based on the Szekeres-Pirani gravitational compass we suggest the addition of a fourth, non-coplanar mass/mirror to the presently existing laser based gravitational wave observatories, enabling them to operate omnidirectionally, to filter out ambiguous interpretations and to point out the direction of the gravitational wave source.
Institute of Scientific and Technical Information of China (English)
QIAN Shang-Wu
2005-01-01
Based on the new metric theory of gravitation suggested by the author of this article, it gives a possible theoretical interpretation on the famous experiment done by D.R. Long in 1976, i.e. the distance-dependent effect of the gravitational constant in Newton's theory of gravitation.
Pitoňák, Martin; Šprlák, Michal; Hamáčková, Eliška; Novák, Pavel
2016-04-01
Regional recovery of the disturbing gravitational potential in the area of Central Europe from satellite gravitational gradients data is discussed in this contribution. The disturbing gravitational potential is obtained by inverting surface integral formulas which transform the disturbing gravitational potential onto disturbing gravitational gradients in the spherical local north-oriented frame. Two numerical approaches that solve the inverse problem are considered. In the first approach, the integral formulas are rigorously decomposed into two parts, that is, the effects of the gradient data within near and distant zones. While the effect of the near zone data is sought as an inverse problem, the effect of the distant zone data is synthesized from the global gravitational model GGM05S using spectral weights given by truncation error coefficients up to the degree 150. In the second approach, a reference gravitational field up to the degree 180 is applied to reduce and smooth measured gravitational gradients. In both cases we recovered the disturbing gravitational potential from each of the four well-measured gravitational gradients of the GOCE satellite separately as well as from their combination. Obtained results are compared with the EGM2008, DIR-r2, TIM-r2 and SPW-r2 global gravitational models. The best fit was achieved for EGM2008 and the second approach combining all four well-measured gravitational gradients with rms of 1.231 m2 s-2.
Prasanna, A R
2017-01-01
This book suitable for post graduates in Physics and Astrophysics aims at introducing the theory of general relativity as an important background for doing astrophysics. Starting from a detailed discussion of the various mathematical concepts for doing general relativity, the book introduces the geometric description of gravity. It gives a brief historical perspective to classical mechanics and electrodynamics making an attempt to establish the necessity of special relativity as propounded by Einstein extending to General Relativity. This book is a good starting point for post graduates wanting to pursue the modern topics of Cosmology, High energy astrophysics and related areas.
Interaction of gravitational waves with superconductors
Energy Technology Data Exchange (ETDEWEB)
Inan, N.A.; Thompson, J.J. [University of California, Schools of Natural Sciences, Merced, CA (United States); Chiao, R.Y. [University of California, Schools of Natural Sciences and Engineering, Merced, CA (United States)
2017-06-15
Applying the Helmholtz Decomposition theorem to linearized General Relativity leads to a gauge-invariant formulation where the transverse-traceless part of the metric perturbation describes gravitational waves in matter. Gravitational waves incident on a superconductor can be described by a linear London-like constituent equation characterized by a ''gravitational shear modulus'' and a corresponding plasma frequency and penetration depth. Electric-like and magnetic-like gravitational tensor fields are defined in terms of the strain field of a gravitational wave. It is shown that in the DC limit, the magnetic-like tensor field is expelled from the superconductor in a gravitational Meissner-like effect. The Cooper pair density is described by the Ginzburg-Landau theory embedded in curved space-time. The ionic lattice is modeled by quantum harmonic oscillators coupled to gravitational waves and characterized by quasi-energy eigenvalues for the phonon modes. The formulation predicts the possibility of a dynamical Casimir effect since the zero-point energy of the ionic lattice phonons is found to be modulated by the gravitational wave, in a quantum analog of a ''Weber-bar effect.'' Applying periodic thermodynamics and the Debye model in the low-temperature limit leads to a free energy density for the ionic lattice. Lastly, we relate the gravitational strain of space to the strain of matter to show that the response to a gravitational wave is far less for the Cooper pair density than for the ionic lattice. This predicts a charge separation effect in the superconductor as a result of the gravitational wave. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Tourrenc, Philippe
1992-01-01
La relativité générale a cessé d'être une pure théorie justifiée par les "trois tests classiques" disponibles il y a trente ans. Des pulsars, vrais laboratoires de gravitation relativiste, ont été découverts et étudiés. A l'automne 1991 les Etats-Unis ont pris la décision de construire deux détecteurs interférométriques d'ondes gravitationnelles. Au début de l'été 1992, le ministre français de la Recherche et de l'Espace a pris un engagement de même nature concernant le projet VIRGO, projet franco-italien de construction d'une antenne interférométrique. La gravitation relativiste est devenue un riche domaine d'observation et d'expérimentation. Cet ouvrage est un manuel de physique dont les intentions et le contenu se veulent adaptés au contexte scientifique actuel. Il doit beaucoup aux divers enseignements donnés par l'auteur, principalement l'enseignement de relativité générale en maîtrise de physique à l'université Pierre et Marie Curie (Paris VI). Dans la première partie, l...
Gravitational waves from axion monodromy
Energy Technology Data Exchange (ETDEWEB)
Hebecker, Arthur; Jaeckel, Joerg; Rompineve, Fabrizio; Witkowski, Lukas T. [Institute for Theoretical Physics, University of Heidelberg,Philosophenweg 19, 69120 Heidelberg (Germany)
2016-11-02
Large field inflation is arguably the simplest and most natural variant of slow-roll inflation. Axion monodromy may be the most promising framework for realising this scenario. As one of its defining features, the long-range polynomial potential possesses short-range, instantonic modulations. These can give rise to a series of local minima in the post-inflationary region of the potential. We show that for certain parameter choices the inflaton populates more than one of these vacua inside a single Hubble patch. This corresponds to a dynamical phase decomposition, analogously to what happens in the course of thermal first-order phase transitions. In the subsequent process of bubble wall collisions, the lowest-lying axionic minimum eventually takes over all space. Our main result is that this violent process sources gravitational waves, very much like in the case of a first-order phase transition. We compute the energy density and peak frequency of the signal, which can lie anywhere in the mHz-GHz range, possibly within reach of next-generation interferometers. We also note that this “dynamical phase decomposition' phenomenon and its gravitational wave signal are more general and may apply to other inflationary or reheating scenarios with axions and modulated potentials.
Gravitational-wave Mission Study
Mcnamara, Paul; Jennrich, Oliver; Stebbins, Robin T.
2014-01-01
In November 2013, ESA selected the science theme, the "Gravitational Universe," for its third large mission opportunity, known as L3, under its Cosmic Vision Programme. The planned launch date is 2034. ESA is considering a 20% participation by an international partner, and NASA's Astrophysics Division has indicated an interest in participating. We have studied the design consequences of a NASA contribution, evaluated the science benefits and identified the technology requirements for hardware that could be delivered by NASA. The European community proposed a strawman mission concept, called eLISA, having two measurement arms, derived from the well studied LISA (Laser Interferometer Space Antenna) concept. The US community is promoting a mission concept known as SGO Mid (Space-based Gravitational-wave Observatory Mid-sized), a three arm LISA-like concept. If NASA were to partner with ESA, the eLISA concept could be transformed to SGO Mid by the addition of a third arm, augmenting science, reducing risk and reducing non-recurring engineering costs. The characteristics of the mission concepts and the relative science performance of eLISA, SGO Mid and LISA are described. Note that all results are based on models, methods and assumptions used in NASA studies
Relativity in Combinatorial Gravitational Fields
Directory of Open Access Journals (Sweden)
Mao Linfan
2010-04-01
Full Text Available A combinatorial spacetime $(mathscr{C}_G| uboverline{t}$ is a smoothly combinatorial manifold $mathscr{C}$ underlying a graph $G$ evolving on a time vector $overline{t}$. As we known, Einstein's general relativity is suitable for use only in one spacetime. What is its disguise in a combinatorial spacetime? Applying combinatorial Riemannian geometry enables us to present a combinatorial spacetime model for the Universe and suggest a generalized Einstein gravitational equation in such model. Forfinding its solutions, a generalized relativity principle, called projective principle is proposed, i.e., a physics law ina combinatorial spacetime is invariant under a projection on its a subspace and then a spherically symmetric multi-solutions ofgeneralized Einstein gravitational equations in vacuum or charged body are found. We also consider the geometrical structure in such solutions with physical formations, and conclude that an ultimate theory for the Universe maybe established if all such spacetimes in ${f R}^3$. Otherwise, our theory is only an approximate theory and endless forever.
Confusion in Cosmology and Gravitation
Corda, C.; Katebi, R.; Schmidt, N. O.
2016-10-01
In a series of papers, Santilli and collaborators released various strong statements against the general theory of relativity (GTR) and the standard ΛCDM model of cosmology. In this paper we show that such claims are due to misunderstandings of basic concepts of gravitation and cosmology. In particular, we show that Santilli and collaborators demonstrated neither that the GTR is wrong, nor that the Universe is not expanding. We also show that the so-called iso-gravitation theory (IGT) of Santilli is in macroscopic contrast with geodesic motion and, in turn, with the Equivalence Principle (EP) and must therefore be ultimately rejected. Finally, we show that, although the so called iso-redshift could represent an interesting alternative (similar to the tired light theory historically proposed by Zwicky) to the Universe expansion from a qualitative point of view, it must be rejected from a quantitative point of view because the effect of iso-redshift is 10-6 smaller than the effect requested to achieve the cosmological redshift.
Quasar evolution and gravitational collapse
Energy Technology Data Exchange (ETDEWEB)
Cavaliere, A.; Giallongo, E.; Vagnetti, F.; Messina, A.
1983-06-01
The paper presents three convergent results concerning the sources in theactive nuclei of quasars and radio galaxies that derive their power fromconversion of gravitational energy. We first derive, for several leading modelsbased on liberation of gravitational energy from mass in a compact supply, thelaws governing the secular change L of the primary power driving the individual sources, and identify their common and key property: L increases, and eventually decreases, linearly or faster with the power itself, so that the associated time scales t/sub s/ = L/Vertical BarLVertical Bar obey dt/sub s/, (L)/dL<0. We then describe a general statistical framework to populate with sources the (luminosity, cosmic time)-plane, based on a continuity equation that embodies a given L. We show how the main features of the populations depend primarily on L, while the memory of the initial details is easily erased. With L as derived above, we obtain basic evolutions of the density (L>0) and of the luminosity (L<0) type, with a global differential character. Finally we compute the full evolution functions, comprising a brightening (L>0) and a dimming (L<0) phase, corresponding to three such models. Sub-Eddington accretion onto a massive black hole from a star cluster that self-destroys by collisions is close to reproduce the general course of the empirical models for the optical QSO population.
Gravitational waves from axion monodromy
Hebecker, Arthur; Jaeckel, Joerg; Rompineve, Fabrizio; Witkowski, Lukas T.
2016-11-01
Large field inflation is arguably the simplest and most natural variant of slow-roll inflation. Axion monodromy may be the most promising framework for realising this scenario. As one of its defining features, the long-range polynomial potential possesses short-range, instantonic modulations. These can give rise to a series of local minima in the post-inflationary region of the potential. We show that for certain parameter choices the inflaton populates more than one of these vacua inside a single Hubble patch. This corresponds to a dynamical phase decomposition, analogously to what happens in the course of thermal first-order phase transitions. In the subsequent process of bubble wall collisions, the lowest-lying axionic minimum eventually takes over all space. Our main result is that this violent process sources gravitational waves, very much like in the case of a first-order phase transition. We compute the energy density and peak frequency of the signal, which can lie anywhere in the mHz-GHz range, possibly within reach of next-generation interferometers. We also note that this ``dynamical phase decomposition" phenomenon and its gravitational wave signal are more general and may apply to other inflationary or reheating scenarios with axions and modulated potentials.
Gravitational Waves: Elusive Cosmic Messengers
Centrella, Joan
2007-01-01
The final merger of two black holes is expected to be the strongest g ravitational wave source for ground-based interferometers such as LIG O, VIRGO, and GE0600, as well as the space-based interferometer LISA. Observing these sources with gravitational wave detectors requires t hat we know the radiation waveforms they emit. Since these mergers ta ke place in regions of extreme gravity, we need to solve Einstein's equations of general relativity on a computer in order to calculate t hese waveforms. For more than 30 years, scientists have tried to comp ute black hole mergers using the methods of numerical relativity. The resulting computer codes have been plagued by instabilities, causing them to crash well before the black holes in the binary could comple te even a single orbit. Within the past few years, however, this situ ation has changed dramatically, with a series of remarkable breakthro ughs. This talk will focus on new simulations that are revealing the dynamics and waveforms of binary black hole mergers, and their applic ations in gravitational wave detection, data analysis, and astrophysi cs.
Gravitational instabilities in astrophysical fluids
Tohline, Joel E.
1990-01-01
Over the past decade, the significant advancements that have been made in the development of computational tools and numerical techniques have allowed astrophysicists to begin to model accurately the nonlinear growth of gravitational instabilities in a variety of physical systems. The fragmentation or rotationally driven fission of dynamically evolving, self-gravitating ``drops and bubbles'' is now routinely modeled in full three-dimensional generality as we attempt to understand the behavior of protostellar clouds, rotating stars, galaxies, and even the primordial soup that defined the birth of the universe. A brief review is presented here of the general insights that have been gained from studies of this type, followed by a somewhat more detailed description of work, currently underway, that is designed to explain the process of binary star formation. A short video animation sequence, developed in conjunction with some of the research being reviewed, illustrates the basic-nature of the fission instability in rotating stars and of an instability that can arise in a massive disk that forms in a protostellar cloud.
Conformal anomalies and gravitational waves
Meissner, Krzysztof A.; Nicolai, Hermann
2017-09-01
We argue that the presence of conformal anomalies in gravitational theories can lead to observable modifications to Einstein's equations via the induced anomalous effective actions, whose non-localities can overwhelm the smallness of the Planck scale. The fact that no such effects have been seen in recent cosmological or gravitational wave observations therefore imposes strong restrictions on the field content of possible extensions of Einstein's theory: all viable theories should have vanishing conformal anomalies. We then show that a complete cancellation of conformal anomalies in D = 4 for both the C2 invariant and the Euler (Gauss-Bonnet) invariant E4 can only be achieved for N-extended supergravity multiplets with N ⩾ 5, as well as for M theory compactified to four dimensions. Although there remain open questions, in particular concerning the true significance of conformal anomalies in non-conformal theories, as well as their possible gauge dependence for spin s ⩾3/2, these cancellations suggest a hidden conformal structure of unknown type in these theories.
Gravitational Zoology: Fish as Model Systems for understanding Motion Sickness Susceptibility
Anken, R.; Rahmann, H.
During the entire evolution of life on Earth, the development of all organisms took place under constant gravity conditions, against which they achieved specific countermeasures for compensation and adaptation. On this background, it is still an open question to which extent altered gravity such as hyper- or microgravity (centrifuge/spaceflight) affects the normal individual development, either on the systemic level of the whole organism or on the level of individual organs or even single cells. The present review provides information on this topic, focusing on the effects of altered gravity on developing fish as model systems even for higher vertebrates including humans, with special emphasis on the effect of altered gravity on behaviour and particularly on the developing brain and vestibular system. Overall, the results speak in favour of the following concept: Short -term altered gravity ( 1 day) can induce transitional aberrant behaviour due to malfunctions of the inner ear, originating from asymmetric otoliths or, generally, from a mismatch between canal and otolith afferents. The vanishing aberrant behaviour is due to a reweighing of sensory inputs and neurovestibular compensation, probably on bioelectrical basis. During long- term altered gravity (several days and more), step by step neuroplastic reactivities on molecular basis (i.e., molecular facilitation) in the brain and inner ears possibly activate feedback mechanisms between the CNS and the vestibular organs for the regain of normal behaviour. The following areas of research with animals at altered gravity need to be addressed in the future: 1. Maintenance of animals through two complete life cycles in the space environment (developmental deficiencies?). 2. Investigation of the peripheral and c ntral vestibular system by ground-based studiese (mutants, hypergravity experiments...), focusing on plasticity in developing animals as well as in adults. 3. Investigation of the effect of microgravity during
Gravitational radiation from a rotating magnetic dipole
Hacyan, Shahen
2016-01-01
The gravitational radiation emitted by a rotating magnetic dipole is calculated. Formulas for the polarization amplitudes and the radiated power are obtained in closed forms, considering both the near and radiation zones of the dipole. For a neutron star, a comparison is made with other sources of gravitational and electromagnetic radiation.
Singularities from colliding plane gravitational waves
Tipler, Frank J.
1980-12-01
A simple geometrical argument is given which shows that a collision between two plane gravitational waves must result in singularities. The argument suggests that these singularities are a peculiar feature of plane waves, because singularities are also a consequence of a collision between self-gravitating plane waves of other fields with arbitrarily small energy density.
Singularities from colliding plane gravitational waves
Energy Technology Data Exchange (ETDEWEB)
Tipler, F.J.
1980-12-15
A simple geometrical argument is given which shows that a collision between two plane gravitational waves must result in singularities. The argument suggests that these singularities are a peculiar feature of plane waves, because singularities are also a consequence of a collision between self-gravitating plane waves of other fields with arbitrarily small energy density.
Gravitational force between two electrons in superconductors
de Matos, Clovis Jacinto
2007-01-01
The attractive gravitational force between two electrons in superconductors is deduced from the Eddington-Dirac large number relation, together with Beck and Mackey electromagnetic model of vacuum energy in superconductors. This force is estimated to be weaker than the gravitational attraction between two electrons in the vacuum.
Vanishing Vierbein in Gauge Theories of Gravitation
Jadczyk, A
1999-01-01
We discuss the problem of a degenerate vierbein in the framework of gauge theories of gravitation (thus including torsion). We discuss two examples: Hanson-Regge gravitational instanton and Einstein-Rose bridge.We argue that a region of space-time with vanishing vierbein but smooth principal connection can be, in principle, detected by scattering experiments.
Pure Gravitational Back-Reaction Observables
Tsamis, N C
2013-01-01
After discussing the various issues regarding and requirements on pure quantum gravitational observables in homogeneous-isotropic conditions, we construct a composite operator observable satisfying most of them. We also expand it to first order in the loop counting parameter and suggest it as a physical quantifier of gravitational back-reaction in an initially inflating cosmology.
Workshop on gravitational waves and relativistic astrophysics
Indian Academy of Sciences (India)
Patrick Das Gupta
2004-10-01
Discussions related to gravitational wave experiments viz. LIGO and LISA as well as to observations of supermassive black holes dominated the workshop sessions on gravitational waves and relativistic astrophysics in the ICGC-2004. A summary of seven papers that were presented in these workshop sessions has been provided in this article.
Onthe static and spherically symmetric gravitational field
Gottlieb, Ioan; Maftei, Gheorghe; Mociutchi, Cleopatra
Starting from a generalization of Einstein 's theory of gravitation, proposed by one of the authors (Cleopatra Mociutchi), the authors study a particular spherical symmetric case. Among other one obtain the compatibility conditions for the existence of the static and spherically symmetruic gravitational filed in the case of extended Einstein equation.
Gravitational Perturbation in Topological Phonon Space
Institute of Scientific and Technical Information of China (English)
李芳昱; 罗俊; 唐孟希
1994-01-01
The effect of gravitational wave (GW) on phonon in crystal lattice space with spiral dislocation is expressed as a gravitational perturbation in topological phonon space with background of the spiral dislocation.This is a new-type effect form of the GW field to the phonon.The corresponding phonon solutions are given.
A distinguishing gravitational property for gravitational equation in higher dimensions
Energy Technology Data Exchange (ETDEWEB)
Dadhich, Naresh [Jamia Millia Islamia, Centre for Theoretical Physics, New Delhi (India); Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Pune (India)
2016-03-15
It is well known that Einstein gravity is kinematic (meaning that there is no non-trivial vacuum solution; i.e. the Riemann tensor vanishes whenever the Ricci tensor does so) in 3 dimension because the Riemann tensor is entirely given in terms of the Ricci tensor. Could this property be universalized for all odd dimensions in a generalized theory? The answer is yes, and this property uniquely singles out pure Lovelock (it has only one Nth order term in the action) gravity for which the Nth order Lovelock-Riemann tensor is indeed given in terms of the corresponding Ricci tensor for all odd, d = 2N + 1, dimensions. This feature of gravity is realized only in higher dimensions and it uniquely picks out pure Lovelock gravity from all other generalizations of Einstein gravity. It serves as a good distinguishing and guiding criterion for the gravitational equation in higher dimensions. (orig.)
A discerning gravitational property for gravitational equation in higher dimensions
Dadhich, Naresh
2015-01-01
It is well-known that Einstein gravity is kinematic (no non-trivial vacuum solution;i.e. Riemann vanishes whenever Ricci does so) in $3$ dimension because Riemann is entirely given in terms of Ricci. Could this property be universalized for all odd dimensions in a generalized theory? The answer is yes, and this property uniquely singles out pure Lovelock (it has only one $N$th order term in action) gravity for which $N$th order Lovelock Riemann tensor is indeed given in terms of corresponding Ricci for all odd $d=2N+1$ dimensions. This feature of gravity is realized only in higher dimensions and it uniquely picks out pure Lovelock gravity from all other generalizations of Einstein gravity. It serves as a good discerning and guiding criterion for gravitational equation in higher dimensions.
Gravitational Mass, Its Mechanics - What It Is; How It Operates
Ellman, Roger
1999-01-01
The earlier paper, Inertial Mass, Its Mechanics - What It Is; How It Operates, developed the mechanics of inertial mass. The present paper is for the purpose of equivalently developing gravitation. The behavior of gravitation is well known, as described by Newton's Law of Gravitation. But just what gravitational mass is, how gravitational behavior comes about, what in material reality produces the effects of gravitational mass, has been little understood. The only extant hypotheses involve th...
Probing Cosmic Superstrings with Gravitational Waves
Sousa, Lara
2016-01-01
We compute the stochastic gravitational wave background generated by cosmic superstrings using a semi-analytical velocity-dependent model to describe their dynamics. We show that heavier string types may leave distinctive signatures on the stochastic gravitational wave background spectrum within the reach of present and upcoming gravitational wave detectors. We examine the physically motivated scenario in which the physical size of loops is determined by the gravitational backreaction scale and use NANOGRAV data to derive a conservative constraint of $G\\mu_F<3.2 \\times 10^{-9}$ on the tension of fundamental strings. We demonstrate that approximating the gravitational wave spectrum generated by cosmic superstring networks using the spectrum generated by ordinary cosmic strings with reduced intercommuting probability (which is often done in the literature) leads, in general, to weaker observational constraints on $G\\mu_F$. We show that the inclusion of heavier string types is required for a more accurate cha...
The conceptual origins of gravitational lensing
Valls-Gabaud, David
2012-01-01
We critically examine the evidence available of the early ideas on the bending of light due to a gravitational attraction, which led to the concept of gravitational lenses, and attempt to present an undistorted historical perspective. Contrary to a widespread but baseless claim, Newton was not the precursor to the idea, and the first Query in his {\\sl Opticks} is totally unrelated to this phenomenon. We briefly review the roles of Voltaire, Marat, Cavendish, Soldner and Einstein in their attempts to quantify the gravitational deflection of light. The first, but unpublished, calculations of the lensing effect produced by this deflection are found in Einstein's 1912 notebooks, where he derived the lensing equation and the formation of images in a gravitational lens. The brief 1924 paper by Chwolson which presents, without calculations, the formation of double images and rings by a gravitational lens passed mostly unnoticed. The unjustly forgotten and true pioneer of the subject is F. Link, who not only publishe...
Probing inflation models with gravitational waves
Domcke, Valerie
2016-01-01
A direct detection of primordial gravitational waves is the ultimate probe for any inflation model. While current CMB bounds predict the generic scale-invariant gravitational wave spectrum from slow-roll inflation to be below the reach of upcoming gravitational wave interferometers, this prospect may dramatically change if the inflaton is a pseudoscalar. In this case, a coupling to any abelian gauge field leads to a tachyonic instability for the latter and hence to a new source of gravitational waves, directly related to the dynamics of inflation. In this contribution we discuss how this setup enables the upcoming gravitational wave interferometers advanced LIGO/VIRGO and eLISA to probe the microphysics of inflation, distinguishing between different universality classes of single-field slow-roll inflation models. We find that the prime candidate for an early detection is a Starobinsky-like model.
Optics in a nonlinear gravitational wave
Harte, Abraham I
2015-01-01
Gravitational waves can act like gravitational lenses, affecting the observed positions, brightnesses, and redshifts of distant objects. Exact expressions for such effects are derived here, allowing for arbitrarily-moving sources and observers in the presence of plane-symmetric gravitational waves. The commonly-used predictions of linear perturbation theory are shown to be generically overshadowed---even for very weak gravitational waves---by nonlinear effects when considering observations of sufficiently distant sources; higher-order perturbative corrections involve secularly-growing terms which cannot necessarily be neglected. Even on more moderate scales where linear effects remain at least marginally dominant, nonlinear corrections are qualitatively different from their linear counterparts. There is a sense in which they can, for example, mimic the existence of a third type of gravitational wave polarization.
Optics in a nonlinear gravitational plane wave
Harte, Abraham I.
2015-09-01
Gravitational waves can act like gravitational lenses, affecting the observed positions, brightnesses, and redshifts of distant objects. Exact expressions for such effects are derived here in general relativity, allowing for arbitrarily-moving sources and observers in the presence of plane-symmetric gravitational waves. At least for freely falling sources and observers, it is shown that the commonly-used predictions of linear perturbation theory can be generically overshadowed by nonlinear effects; even for very weak gravitational waves, higher-order perturbative corrections involve secularly-growing terms which cannot necessarily be neglected when considering observations of sufficiently distant sources. Even on more moderate scales where linear effects remain at least marginally dominant, nonlinear corrections are qualitatively different from their linear counterparts. There is a sense in which they can, for example, mimic the existence of a third type of gravitational wave polarization.
Mead, Carver
2015-01-01
Gravitational coupling of the propagation four-vectors of matter wave functions is formulated in flat space-time. Coupling at the momentum level rather than at the "force-law" level greatly simplifies many calculations. This locally Lorentz-invariant approach (G4v) treats electromagnetic and gravitational coupling on an equal footing. Classical mechanics emerges from the incoherent aggregation of matter wave functions. The theory reproduces, to first order beyond Newton, the standard GR results for Gravity-Probe B, deflection of light by massive bodies, precession of orbits, gravitational red shift, and total gravitational-wave energy radiated by a circular binary system. Its predictions of total radiated energy from highly eccentric Kepler systems are slightly larger than those of similar GR treatments. G4v predictions differ markedly from those of GR for the gravitational-wave radiation patterns from rotating massive systems, and for the LIGO antenna pattern. The predicted antenna patterns have been shown t...
Gravitational wave signal from massive gravity
Gumrukcuoglu, A Emir; Lin, Chunshan; Mukohyama, Shinji; Tanahashi, Norihiro
2012-01-01
We discuss the detectability of gravitational waves with a time dependent mass contribution, by means of the stochastic gravitational wave observations. Such a mass term typically arises in the cosmological solutions of massive gravity theories. We conduct the analysis based on a general quadratic action, and thus the results apply universally to any massive gravity theories in which modification of general relativity appears primarily in the tensor modes. The primary manifestation of the modification in the gravitational wave spectrum is a sharp peak. The position and height of the peak carry information on the present value of the mass term, as well as the duration of the inflationary stage. We also discuss the detectability of such a gravitational wave signal using the future-planned gravitational wave observatories.
Gravity's kiss the detection of gravitational waves
Collins, Harry
2017-01-01
Scientists have been trying to confirm the existence of gravitational waves for fifty years. Then, in September 2015, came a "very interesting event" (as the cautious subject line in a physicist's email read) that proved to be the first detection of gravitational waves. In Gravity's Kiss, Harry Collins -- who has been watching the science of gravitational wave detection for forty-three of those fifty years and has written three previous books about it -- offers a final, fascinating account, written in real time, of the unfolding of one of the most remarkable scientific discoveries ever made. Predicted by Einstein in his theory of general relativity, gravitational waves carry energy from the collision or explosion of stars. Dying binary stars, for example, rotate faster and faster around each other until they merge, emitting a burst of gravitational waves. It is only with the development of extraordinarily sensitive, highly sophisticated detectors that physicists can now confirm Einstein's prediction. This is...
Fundamentals of interferometric gravitational wave detectors
Saulson, Peter R
2017-01-01
LIGO's recent discovery of gravitational waves was headline news around the world. Many people will want to understand more about what a gravitational wave is, how LIGO works, and how LIGO functions as a detector of gravitational waves.This book aims to communicate the basic logic of interferometric gravitational wave detectors to students who are new to the field. It assumes that the reader has a basic knowledge of physics, but no special familiarity with gravitational waves, with general relativity, or with the special techniques of experimental physics. All of the necessary ideas are developed in the book.The first edition was published in 1994. Since the book is aimed at explaining the physical ideas behind the design of LIGO, it stands the test of time. For the second edition, an Epilogue has been added; it brings the treatment of technical details up to date, and provides references that would allow a student to become proficient with today's designs.
Comparing numerical and analytic approximate gravitational waveforms
Afshari, Nousha; Lovelace, Geoffrey; SXS Collaboration
2016-03-01
A direct observation of gravitational waves will test Einstein's theory of general relativity under the most extreme conditions. The Laser Interferometer Gravitational-Wave Observatory, or LIGO, began searching for gravitational waves in September 2015 with three times the sensitivity of initial LIGO. To help Advanced LIGO detect as many gravitational waves as possible, a major research effort is underway to accurately predict the expected waves. In this poster, I will explore how the gravitational waveform produced by a long binary-black-hole inspiral, merger, and ringdown is affected by how fast the larger black hole spins. In particular, I will present results from simulations of merging black holes, completed using the Spectral Einstein Code (black-holes.org/SpEC.html), including some new, long simulations designed to mimic black hole-neutron star mergers. I will present comparisons of the numerical waveforms with analytic approximations.
Directory of Open Access Journals (Sweden)
A P Baltensperger
Full Text Available Climate change is acting to reallocate biomes, shift the distribution of species, and alter community assemblages in Alaska. Predictions regarding how these changes will affect the biodiversity and interspecific relationships of small mammals are necessary to pro-actively inform conservation planning. We used a set of online occurrence records and machine learning methods to create bioclimatic envelope models for 17 species of small mammals (rodents and shrews across Alaska. Models formed the basis for sets of species-specific distribution maps for 2010 and were projected forward using the IPCC (Intergovernmental Panel on Climate Change A2 scenario to predict distributions of the same species for 2100. We found that distributions of cold-climate, northern, and interior small mammal species experienced large decreases in area while shifting northward, upward in elevation, and inland across the state. In contrast, many southern and continental species expanded throughout Alaska, and also moved down-slope and toward the coast. Statewide community assemblages remained constant for 15 of the 17 species, but distributional shifts resulted in novel species assemblages in several regions. Overall biodiversity patterns were similar for both time frames, but followed general species distribution movement trends. Biodiversity losses occurred in the Yukon-Kuskokwim Delta and Seward Peninsula while the Beaufort Coastal Plain and western Brooks Range experienced modest gains in species richness as distributions shifted to form novel assemblages. Quantitative species distribution and biodiversity change projections should help land managers to develop adaptive strategies for conserving dispersal corridors, small mammal biodiversity, and ecosystem functionality into the future.
Gravitating fluids with Lie symmetries
Msomi, A M; Maharaj, S D
2010-01-01
We analyse the underlying nonlinear partial differential equation which arises in the study of gravitating flat fluid plates of embedding class one. Our interest in this equation lies in discussing new solutions that can be found by means of Lie point symmetries. The method utilised reduces the partial differential equation to an ordinary differential equation according to the Lie symmetry admitted. We show that a class of solutions found previously can be characterised by a particular Lie generator. Several new families of solutions are found explicitly. In particular we find the relevant ordinary differential equation for all one-dimensional optimal subgroups; in several cases the ordinary differential equation can be solved in general. We are in a position to characterise particular solutions with a linear barotropic equation of state.
Folding gravitational-wave interferometers
Sanders, J. R.; Ballmer, Stefan W.
2017-01-01
The sensitivity of kilometer-scale terrestrial gravitational wave interferometers is limited by mirror coating thermal noise. Alternative interferometer topologies can mitigate the impact of thermal noise on interferometer noise curves. In this work, we explore the impact of introducing a single folding mirror into the arm cavities of dual-recycled Fabry–Perot interferometers. While simple folding alone does not reduce the mirror coating thermal noise, it makes the folding mirror the critical mirror, opening up a variety of design and upgrade options. Improvements to the folding mirror thermal noise through crystalline coatings or cryogenic cooling can increase interferometer range by as much as a factor of two over the Advanced LIGO reference design.
Classifying self-gravitating radiations
Kim, Hyeong-Chan
2017-02-01
We study a static system of self-gravitating radiations confined in a sphere by using numerical and analytical calculations. Because of the scaling symmetry of radiations, most of the main properties of a solution can be represented as a segment of a solution curve on a plane of two-dimensional scale invariant variables. We define an "approximate horizon" (AH) from the analogy with an apparent horizon. Any solution curve contains a unique point that corresponds to the AH. A given solution is uniquely labeled by three parameters representing the solution curve, the size of the AH, and the sphere size, which are an alternative to the data at the outer boundary. Various geometrical properties including the existence of an AH and the behaviors around the center can be identified from the parameters. We additionally present an analytic solution of the radiations on the verge of forming a black hole. Analytic formulas for the central mass of the naked singularity are given.
Gravitational action with null boundaries
Lehner, Luis; Poisson, Eric; Sorkin, Rafael D
2016-01-01
We present a complete discussion of the boundary term in the action functional of general relativity when the boundary includes null segments in addition to the more usual timelike and spacelike segments. We confirm that ambiguities appear in the contribution from a null segment, because it depends on an arbitrary choice of parametrization for the generators. We also show that similar ambiguities appear in the contribution from a codimension-two surface at which a null segment is joined to another (spacelike, timelike, or null) segment. The parametrization ambiguity can be tamed by insisting that the null generators be affinely parametrized; this forces each null contribution to the boundary action to vanish, but leaves intact the fredom to rescale the affine parameter by a constant factor on each generator. Once a choice of parametrization is made, the ambiguity in the joint contributions can be eliminated by formulating well-motivated rules that ensure the additivity of the gravitational action. Enforcing t...
Gravitational Collapse in Gravity's Rainbow
Ali, Ahmed Farag; Majumder, Barun; Mistry, Ravi
2015-01-01
In this paper, we will analyze the gravitational collapse in the framework of gravity's rainbow. We will demonstrate that the position of the horizon for a particle inside the black hole depends on the energy of that particle. It will also be observe that the position of the horizon for a particle falling radially into the black hole also depends on its energy. Thus, it is possible for a particle coming from outside to interact with a particle inside the black, and take some information outside the black hole. This is because for both these particles the position of horizon is different. So, even though the particle from inside the black hole is in its own horizon, it is not in the horizon of the particle coming from outside. Thus, we will demonstrate that in gravity's rainbow information can get out of a black hole.
Gauss-Bonnet Gravitational Baryogenesis
Odintsov, S D
2016-01-01
In this letter we study some variant forms of gravitational baryogenesis by using higher order terms containing the partial derivative of the Gauss-Bonnet scalar coupled to the baryonic current. This scenario extends the well known theory that uses a similar coupling between the Ricci scalar and the baryonic current. One appealing feature of the scenario we study is that the predicted baryon asymmetry during a radiation domination era is non-zero. We calculate the baryon to entropy ratio for the Gauss-Bonnet term and by using the observational constraints we investigate which are the allowed forms of the $R+F(\\mathcal{G})$ gravity controlling the evolution. Also we briefly discuss some alternative higher order terms that can generate a non-zero baryon asymmetry, even in the conformal invariance limit.
Gauss-Bonnet gravitational baryogenesis
Odintsov, S. D.; Oikonomou, V. K.
2016-09-01
In this letter we study some variant forms of gravitational baryogenesis by using higher order terms containing the partial derivative of the Gauss-Bonnet scalar coupled to the baryonic current. This scenario extends the well known theory that uses a similar coupling between the Ricci scalar and the baryonic current. One appealing feature of the scenario we study is that the predicted baryon asymmetry during a radiation domination era is non-zero. We calculate the baryon to entropy ratio for the Gauss-Bonnet term and by using the observational constraints we investigate which are the allowed forms of the R + F (G) gravity controlling the evolution. Also we briefly discuss some alternative higher order terms that can generate a non-zero baryon asymmetry, even in the conformal invariance limit.
Exploring gravitational theories beyond Horndeski
Gleyzes, Jérôme; Langlois, David; Piazza, Federico; Vernizzi, Filippo
2015-02-01
We have recently proposed a new class of gravitational scalar-tensor theories free from Ostrogradski instabilities, in ref. [1]. As they generalize Horndeski theories, or "generalized" galileons, we call them G3. These theories possess a simple formulation when the time hypersurfaces are chosen to coincide with the uniform scalar field hypersurfaces. We confirm that they contain only three propagating degrees of freedom by presenting the details of the Hamiltonian formulation. We examine the coupling between these theories and matter. Moreover, we investigate how they transform under a disformal redefinition of the metric. Remarkably, these theories are preserved by disformal transformations that depend on the scalar field gradient, which also allow to map subfamilies of G3 into Horndeski theories.
Gravitational Forces on the Branes
Arnowitt, R L
2005-01-01
We examine the gravitational forces in a brane-world scenario felt by point particles on two 3-branes bounding a 5-dimensional AdS space with $S^{1}/Z_2$ symmetry. The particles are treated as perturbations on the vacuum metric and coordinate conditions are chosen so that no brane bending effects occur. We make an ADM type decomposition of the metric tensor and solve Einstein's equations to linear order in the static limit. While no stabilization mechanism is assumed, all the 5D Einstein equations are solved and are seen to have a consistent solution. We find that Newton's law is reproduced on the Planck brane at the origin while particles on the TeV brane a distance $y_2$ from the origin experience an attractive force that has a growing exponential dependence on the brane position.
Gravitational Instability of a Kink
Barreto, W; Lehner, L; Winicour, J
1996-01-01
We study the equilibria of a self-gravitating scalar field in the region outside a reflecting barrier. By introducing a potential difference between the barrier and infinity, we create a kink which cannot decay to a zero energy state. In the realm of small amplitude, the kink decays to a known static solution of the Einstein-Klein-Gordon equation. However, for larger kinks the static equilibria are degenerate, forming a system with two energy levels. The upper level is unstable and, under small perturbations, decays to the lower energy stable equilibrium. Under large perturbations, the unstable upper level undergoes collapse to a black hole. The equilibrium of the system provides a remarkably simple and beautiful illustration of a turning point instability.
Kofinas, Georgios
2013-01-01
We raise on theoretical grounds the question of the physical relevance of Israel matching conditions and their generalizations to higher codimensions, the standard cornerstone of the braneworld and other membrane scenarios. Our reasoning is twofold: First, the incapability of the conventional matching conditions to accept the Nambu-Goto probe limit (even the geodesic limit of the Israel matching conditions is not acceptable since being the geodesic equation a kinematical fact it should be preserved for all gravitational theories or defects, which is not the case for these conditions). Second, in our D-dimensional spacetime (maybe D=4), classical defects of any possible codimension should be compatible. These matching conditions fail to accept codimension-2 and 3 defects for D=4 (which represents effectively the spacetime at certain length and energy scales) and most probably fail to accept high enough codimensional defects for any D since there is no high enough Lovelock density to support them. Here, we prop...
Astrophysical Applications of Gravitational Microlensing
Mao, Shude
2012-01-01
Since the first discovery of microlensing events nearly two decades ago, gravitational microlensing has accumulated tens of TBytes of data and developed into a powerful astrophysical technique with diverse applications. The review starts with a theoretical overview of the field and then proceeds to discuss the scientific highlights. (1) Microlensing observations toward the Magellanic Clouds rule out the Milky Way halo being dominated by MAssive Compact Halo Objects (MACHOs). This confirms most dark matter is non-baryonic, consistent with other observations. (2) Microlensing has discovered about 20 extrasolar planets (16 published), including the first two Jupiter-Saturn like systems and the only "cold Neptunes" yet detected. They probe a different part of the parameter space and will likely provide the most stringent test of core accretion theory of planet formation. (3) Microlensing provides a unique way to measure the mass of isolated stars, including brown dwarfs to normal stars. Half a dozen or so stellar...
Braneworld Black Hole Gravitational Lensing
Liang, Jun
2017-04-01
A class of braneworld black holes, which I called as Bronnikov-Melnikov-Dehen (BMD) black holes, are studied as gravitational lenses. I obtain the deflection angle in the strong deflection limit, and further calculate the angular positions and magnifications of relativistic images as well as the time delay between different relativistic images. I also compare the results with those obtained for Schwarzschild and two braneworld black holes, i.e., the tidal Reissner-Nordström (R-N) and the Casadio-Fabbri-Mazzacurati (CFM) black holes. Supported by Natural Science Foundation of Education Department of Shannxi Provincial Government under Grant No. 15JK1077, and Doctorial Scientific Research Starting Fund of Shannxi University of Science and Technology under Grant No. BJ12-02
Gravitation, Causality, and Quantum Consistency
Hertzberg, Mark P
2016-01-01
We examine the role of consistency with causality and quantum mechanics in determining the properties of gravitation. We begin by constructing two different classes of interacting theories of massless spin 2 particles -- gravitons. One involves coupling the graviton with the lowest number of derivatives to matter, the other involves coupling the graviton with higher derivatives to matter, making use of the linearized Riemann tensor. The first class requires an infinite tower of terms for consistency, which is known to lead uniquely to general relativity. The second class only requires a finite number of terms for consistency, which appears as a new class of theories of massless spin 2. We recap the causal consistency of general relativity and show how this fails in the second class for the special case of coupling to photons, exploiting related calculations in the literature. In an upcoming publication [1] this result is generalized to a much broader set of theories. Then, as a causal modification of general ...
Inflation with large gravitational waves
Vikman, A
2006-01-01
It is well known that in manifestly Lorentz invariant theories with nontrivial kinetic terms, perturbations around some classical backgrounds can travel faster than light. These exotic "supersonic" models may have interesting consequences for cosmology and astrophysics. In particular, one can show that in such theories the contribution of the gravitational waves to the CMB fluctuations can be significantly larger than that in standard inflationary models. This increase of the tensor-to-scalar perturbation ratio leads to a larger B-component of the CMB polarization, thus making the prospects for future detection much more promising. Interestingly, the spectral index of scalar perturbations and mass of the scalar field considered in the model are practically indistinguishable from the standard case. Whereas the energy scale of inflation and hence the reheating temperature can be much higher compared to a simple chaotic inflation.
Horizon Thermodynamics and Gravitational Tension
Widom, A; Srivastava, Y N
2016-01-01
We consider the thermodynamics of a horizon surface from the viewpoint of the vacuum tension $\\tau =(c^4/4G )$. Numerically, $\\tau \\approx 3.026\\times 10^{43}$ Newton. In order of magnitude, this is the tension that has been proposed for microscopic string models of gravity. However, after decades of hard work on string theory models of gravity, there is no firm scientific evidence that such models of gravity apply empirically. Our purpose is thereby to discuss the gravitational tension in terms of the conventional Einstein general theory of relativity that apparently does explain much and maybe all of presently known experimental gravity data. The central result is that matter on the horizon surface is bound by the entropy-area law by tension in the closely analogous sense that the Wilson action-area law also describes a surface confinement.
Three hundred years of gravitation
Hawking, Stephen William
1987-01-01
To commemorate the 300th anniversary of the publication of Isaac Newton's Philosophiae Naturalis Principia Mathematica, Stephen Hawking and Werner Israel have assembled a series of unique review papers by many of the world's foremost researchers in cosmology, relativity and particle physics. The resulting volume reflects the significant and exciting advances that have been made in these fields since the editor's acclaimed volume published in 1979: General Relativity: An Einstein Centenary Survey. Newton's immense contribution to the physical sciences is assessed, and its relevance to today's physics made clear. The international contributors then chart the major developments in the study of gravitation, from Newtonian gravity to black hole physics. In the fields of galaxy formation, inflationary and quantum cosmology, and superstring unification, the book provides important overviews written by workers involved in many of the advances described. By shaping such a wide-ranging and scholarly series of articles ...
Gravitational Effects on Human Physiology.
Atomi, Yoriko
2015-01-01
Physical working capacity decreases with age and also in microgravity. Regardless of age, increased physical activity can always improve the physical adaptability of the body, although the mechanisms of this adaptability are unknown. Physical exercise produces various mechanical stimuli in the body, and these stimuli may be essential for cell survival in organisms. The cytoskeleton plays an important role in maintaining cell shape and tension development, and in various molecular and/or cellular organelles involved in cellular trafficking. Both intra and extracellular stimuli send signals through the cytoskeleton to the nucleus and modulate gene expression via an intrinsic property, namely the "dynamic instability" of cytoskeletal proteins. αB-crystallin is an important chaperone for cytoskeletal proteins in muscle cells. Decreases in the levels of αB-crystallin are specifically associated with a marked decrease in muscle mass (atrophy) in a rat hindlimb suspension model that mimics muscle and bone atrophy that occurs in space and increases with passive stretch. Moreover, immunofluorescence data show complete co-localization of αB-crystallin and the tubulin/microtubule system in myoblast cells. This association was further confirmed in biochemical experiments carried out in vitro showing that αB-crystallin acts as a chaperone for heat-denatured tubulin and prevents microtubule disassembly induced by calcium. Physical activity induces the constitutive expression of αB-crystallin, which helps to maintain the homeostasis of cytoskeleton dynamics in response to gravitational forces. This relationship between chaperone expression levels and regulation of cytoskeletal dynamics observed in slow anti-gravitational muscles as well as in mammalian striated muscles, such as those in the heart, diaphragm and tongue, may have been especially essential for human evolution in particular. Elucidation of the intrinsic properties of the tubulin/microtubule and chaperone
Kofinas, Georgios; Irakleidou, Maria
2014-03-01
We raise on theoretical grounds the question of the physical relevance of Israel matching conditions and their generalizations to higher codimensions, the standard cornerstone of the braneworld and other membrane scenarios. Our reasoning is based on the incapability of the conventional matching conditions to accept the Nambu-Goto probe limit, the inconsistency of codimension-2 and -3 classical defects for D=4 and the probable inconsistency of high enough codimensional defects for any D since there is no high enough Lovelock density to support them. We propose alternative matching conditions which seem to overcome the previous puzzles. Instead of varying the brane-bulk action with respect to the bulk metric at the brane position, we vary with respect to the brane embedding fields so that the gravitational backreaction is included ("gravitating Nambu-Goto matching conditions"). Here, we consider in detail the case of a codimension-2 brane in 6-dim Einstein-Gauss-Bonnet gravity, prove its consistency for an axially symmetric cosmological configuration and show that the theory possesses richer structure compared to the standard theory. The cosmologies found have the Friedmann behavior and extra correction terms. For a radiation brane one solution avoids a cosmological singularity and undergoes accelerated expansion near the minimum scale factor. In the presence of an induced gravity term, there naturally appears in the theory the effective cosmological constant scale λ /(M64rc2), which for a brane tension λ ˜M64 (e.g. TeV4) and rc˜H0-1 gives the observed value of the cosmological constant.
Klubicová, Katarína; Danchenko, Maksym; Skultety, Ludovit; Berezhna, Valentyna V; Rashydov, Namik M; Hajduch, Martin
2013-11-01
Starting in 2007, we have grown soybean (Glycine max [L.] Merr. variety Soniachna) and flax (Linum usitatissimum, L. variety Kyivskyi) in the radio-contaminated Chernobyl area and analyzed the seed proteomes. In the second-generation flax seeds, we detected a 12% increase in oil content. To characterize the bases for this increase, seed development has been studied. Flax seeds were harvested in biological triplicate at 2, 4, and 6 weeks after flowering and at maturity from plants grown in nonradioactive and radio-contaminated plots in the Chernobyl area for two generations. Quantitative proteomic analyses based on 2-D gel electrophoresis (2-DE) allowed us to establish developmental profiles for 199 2-DE spots in both plots, out of which 79 were reliably identified by tandem mass spectrometry. The data suggest a statistically significant increased abundance of proteins associated with pyruvate biosynthesis via cytoplasmic glycolysis, L-malate decarboxylation, isocitrate dehydrogenation, and ethanol oxidation to acetaldehyde in early stages of seed development. This was followed by statistically significant increased abundance of ketoacyl-[acylcarrier protein] synthase I related to condensation of malonyl-ACP with elongating fatty acid chains. On the basis of these and previous data, we propose a preliminary model for plant adaptation to growth in a radio-contaminated environment. One aspect of the model suggests that changes in carbon assimilation and fatty acid biosynthesis are an integral part of plant adaptation.
Gravitating sphalerons in the Skyrme model
Shnir, Ya
2015-01-01
We construct self-gravitating axially symmetric sphaleron solutions of the 3+1 dimensional Skyrme model coupled to Einstein gravity. The solutions are static and asymptotically flat, they are characterized by two integers n and m, where n is the winding numbers of the constituents and the second integer m defines type of the solution. These configuration correspond to the chains of charge n Skyrmions and charge -n anti-Skyrmions placed along the axis of symmetry in alternating order. We investigate the dependency of the masses of the gravitating sphalerons on the gravitational coupling. We find new chains of self-gravitating |n| = 1 Skyrmions-anti-Skyrmions (S-A) which emerge at some critical non-zero value of the gravitational coupling and do not have flat space limit. In contrast, the branches of self-gravitating |n| $\\ge$ 2 S-A chains emerge from the corresponding flat space configurations. In both cases these branches merge at some maximal value of the effective gravitational coupling the branches of diff...
Effect of gravitational focusing on annual modulation in dark-matter direct-detection experiments.
Lee, Samuel K; Lisanti, Mariangela; Peter, Annika H G; Safdi, Benjamin R
2014-01-10
The scattering rate in dark-matter direct-detection experiments should modulate annually due to Earth's orbit around the Sun. The rate is typically thought to be extremized around June 1, when the relative velocity of Earth with respect to the dark-matter wind is maximal. We point out that gravitational focusing can alter this modulation phase. Unbound dark-matter particles are focused by the Sun's gravitational potential, affecting their phase-space density in the lab frame. Gravitational focusing can result in a significant overall shift in the annual-modulation phase, which is most relevant for dark matter with low scattering speeds. The induced phase shift for light O(10) GeV dark matter may also be significant, depending on the threshold energy of the experiment.
Chiral Gravitational Waves from Chiral Fermions
Anber, Mohamed M
2016-01-01
We report on a new mechanism that leads to the generation of primordial chiral gravitational waves, and hence, the violation of the parity symmetry in the Universe. We show that nonperturbative production of fermions with a definite helicity is accompanied by the generation of chiral gravitational waves. This is a generic and model-independent phenomenon that can occur during inflation, reheating and radiation eras, and can leave imprints in the cosmic microwave background polarization and may be observed in future ground- and space-based interferometers. We also discuss a specific model where chiral gravitational waves are generated via the production of light chiral fermions during pseudoscalar inflation.
A Gravitational Edge Detection for Multispectral Images
Directory of Open Access Journals (Sweden)
Genyun Sun
2013-07-01
Full Text Available Gravitational edge detection is one of the new edge detection algorithms that is based on the law of gravity. This algorithm assumes that each image pixel is a celestial body with a mass represented by its grayscale intensity and their interactions are based on the Newtonian laws of gravity. In this article, a multispectral version of the algorithm is introduced. The method uses gravitational techniques in combination with metric tensor to detect edges of multispectral images including color images. To evaluate the performances of the proposed algorithm, several experiments are performed. The experimental results confirm the efficiency of the multispectral gravitational edge detection.
Gravitational Wave & Relativity Impact Electronic Communication & Engineering
Directory of Open Access Journals (Sweden)
Zakaria Shahrudin
2017-01-01
Full Text Available About a few months ago (Feb 11, 2016, the LIGO (Laser Interferometer Gravitational-Wave Observatory scientist team researchers made an announcement that they had confirmed the gravitational wave already detected on Sept 14, 2015 (by LIGO’s twin detectors in Livingston, Louisiana and Hanford, Washington. The wave was predicted by Einstein back in 1916 with his theory of General Relativity. This paper is about gravitational wave and relativity theory that may contribute to the field of Telecommunication and other engineering as well.
The theory of space, time and gravitation
Fock, V
2015-01-01
The Theory of Space, Time, and Gravitation, 2nd Revised Edition focuses on Relativity Theory and Einstein's Theory of Gravitation and correction of the misinterpretation of the Einsteinian Gravitation Theory. The book first offers information on the theory of relativity and the theory of relativity in tensor form. Discussions focus on comparison of distances and lengths in moving reference frames; comparison of time differences in moving reference frames; position of a body in space at a given instant in a fixed reference frame; and proof of the linearity of the transformation linking two iner
Chiral gravitational waves from chiral fermions
Anber, Mohamed M.; Sabancilar, Eray
2017-07-01
We report on a new mechanism that leads to the generation of primordial chiral gravitational waves, and hence, the violation of the parity symmetry in the Universe. We show that nonperturbative production of fermions with a definite helicity is accompanied by the generation of chiral gravitational waves. This is a generic and model-independent phenomenon that can occur during inflation, reheating and radiation eras, and can leave imprints in the cosmic microwave background polarization and may be observed in future ground- and space-based interferometers. We also discuss a specific model where chiral gravitational waves are generated via the production of light chiral fermions during pseudoscalar inflation.
Gravitational brainwaves, quantum fluctuations and stochastic quantization
Bar, D
2007-01-01
It is known that the biological activity of the brain involves radiation of electric waves. These waves result from ionic currents and charges traveling among the brain's neurons. But it is obvious that these ions and charges are carried by their relevant masses which should give rise, according to the gravitational theory, to extremely weak gravitational waves. We use in the following the stochastic quantization (SQ) theory to calculate the probability to find a large ensemble of brains radiating similar gravitational waves. We also use this SQ theory to derive the equilibrium state related to the known Lamb shift.
Non-Euclidean Geometry and Gravitation
Directory of Open Access Journals (Sweden)
Stavroulakis N.
2006-04-01
Full Text Available A great deal of misunderstandings and mathematical errors are involved in the currently accepted theory of the gravitational field generated by an isotropic spherical mass. The purpose of the present paper is to provide a short account of the rigorous mathematical theory and exhibit a new formulation of the problem. The solution of the corresponding equations of gravitation points out several new and unusual features of the stationary gravitational field which are related to the non-Euclidean structure of the space. Moreover it precludes the black hole from being a mathematical and physical notion.
Gravitational radiation in dynamical noncommutative spaces
Alavi, S A
2015-01-01
The gravitational radiation in dynamical non-commutative spaces (DNCS) is explored. we derive the corrections due to dynamical noncommutativity on the gravitational potential. We obtain the DNC corrections on the angular velocity as well as the radiated power of the system. By calculating the period decay of the system and using the observational data we obtain an upper bound for the DNS parameter {\\tau} . We also study quantum interference induced by gravitational potential in usual non-commutative and dynamical non-commutative spaces. The phase difference induced by gravity is calculated on two different paths and then, it is compared with the phase difference induced by gravity in commutative space.
Electromagnetic Effects in Superconductors in Gravitational Field
Ahmedov, B J
2005-01-01
The general relativistic modifications to the resistive state in superconductors of second type in the presence of a stationary gravitational field are studied. Some superconducting devices that can measure the gravitational field by its red-shift effect on the frequency of radiation are suggested. It has been shown that by varying the orientation of a superconductor with respect to the earth gravitational field, a corresponding varying contribution to AC Josephson frequency would be added by gravity. A magnetic flux (being proportional to angular velocity of rotation $\\Omega$) through a rotating hollow superconducting cylinder with the radial gradient of temperature $\
Relic Gravitational Waves and Their Detection
Grishchuk, L P
2001-01-01
The range of expected amplitudes and spectral slopes of relic (squeezed)gravitational waves, predicted by theory and partially supported byobservations, is within the reach of sensitive gravity-wave detectors. In themost favorable case, the detection of relic gravitational waves can be achievedby the cross-correlation of outputs of the initial laser interferometers inLIGO, VIRGO, GEO600. In the more realistic case, the sensitivity of advancedground-based and space-based laser interferometers will be needed. The specificstatistical signature of relic gravitational waves, associated with thephenomenon of squeezing, is a potential reserve for further improvement of thesignal to noise ratio.
Newtorites in bar detectors of gravitational wave
Ronga, F
2016-01-01
The detection of particles with only gravitational interactions (Newtorites) in gravitational bar detectors was studied in 1984 by Bernard, De Rujula and Lautrup. The negative results of dark matter searches suggest to look to exotic possibilities like Newtorites. The limits obtained with the Nautilus bar detector will be presented and the possible improvements will be discussed. Since the gravitational coupling is very weak, the possible limits are very far from what is needed for dark matter, but for large masses are the best limits obtained on the Earth. An update of limits for MACRO particles will be given.
Generalized gravitational entropy from total derivative action
Dong, Xi; Miao, Rong-Xin
2015-12-01
We investigate the generalized gravitational entropy from total derivative terms in the gravitational action. Following the method of Lewkowycz and Maldacena, we find that the generalized gravitational entropy from total derivatives vanishes. We compare our results with the work of Astaneh, Patrushev, and Solodukhin. We find that if total derivatives produced nonzero entropy, the holographic and the field-theoretic universal terms of entanglement entropy would not match. Furthermore, the second law of thermodynamics could be violated if the entropy of total derivatives did not vanish.
Generalized Gravitational Entropy from Total Derivative Action
Dong, Xi
2015-01-01
We investigate the generalized gravitational entropy from total derivative terms in the gravitational action. Following the method of Lewkowycz and Maldacena, we find that the generalized gravitational entropy from total derivatives vanishes. We compare our results with the work of Astaneh, Patrushev, and Solodukhin. We find that if total derivatives produced nonzero entropy, the holographic and the field-theoretic universal terms of entanglement entropy would not match. Furthermore, the second law of thermodynamics could be violated if the entropy of total derivatives did not vanish.
Baehr, Hans
2015-01-01
Protoplanetary disks fragment due to gravitational instability when there is enough mass for self-gravitation, described by the Toomre parameter, and when heat can be lost at a rate comparable to the local dynamical timescale, described by t_c=beta Omega^-1. Simulations of self-gravitating disks show that the cooling parameter has a rough critical value at beta_crit=3. When below beta_crit, gas overdensities will contract under their own gravity and fragment into bound objects while otherwise maintaining a steady state of gravitoturbulence. However, previous studies of the critical cooling parameter have found dependence on simulation resolution, indicating that the simulation of self-gravitating protoplanetary disks is not so straightforward. In particular, the simplicity of the cooling timescale t_c prevents fragments from being disrupted by pressure support as temperatures rise. We alter the cooling law so that the cooling timescale is dependent on local surface density fluctuations, a means of incorporati...
Thermal gravitational waves in accelerating universe
Directory of Open Access Journals (Sweden)
B Ghayour
2013-10-01
Full Text Available Gravitational waves are considered in thermal vacuum state. The amplitude and spectral energy density of gravitational waves are found enhanced in thermal vacuum state compared to its zero temperature counterpart. Therefore, the allowed amount of enhancement depends on the upper bound of WMAP-5 and WMAP-7 for the amplitude and spectral energy density of gravitational waves. The enhancement of amplitude and spectral energy density of the waves in thermal vacuum state is consistent with current accelerating phase of the universe. The enhancement feature of amplitude and spectral energy density of the waves is independent of the expansion model of the universe and hence the thermal effect accounts for it. Therefore, existence of thermal gravitational waves is not ruled out
Gravitational wave astronomy: the current status
Blair, David; Zhao, Chunnong; Wen, Linqing; Chu, Qi; Fang, Qi; Cai, RongGen; Gao, JiangRui; Lin, XueChun; Liu, Dong; Wu, Ling-An; Zhu, ZongHong; Reitze, David H; Arai, Koji; Zhang, Fan; Flaminio, Raffaele; Zhu, Xingjiang; Hobbs, George; Manchester, Richard N; Shannon, Ryan M; Baccigalupi, Carlo; Xu, Peng; Bian, Xing; Cao, Zhoujian; Chang, ZiJing; Dong, Peng; Gong, XueFei; Huang, ShuangLin; Ju, Peng; Luo, ZiRen; Qiang, Li'E; Tang, WenLin; Wan, XiaoYun; Wang, Yue; Xu, ShengNian; Zhang, YunLong; Zhang, HaiPeng; Lau, Yun-Kau; Ni, Wei-Tou
2016-01-01
In the centenary year of Einstein's General Theory of Relativity, this paper reviews the current status of gravitational wave astronomy across a spectrum which stretches from attohertz to kilohertz frequencies. Sect. 1 of this paper reviews the historical development of gravitational wave astronomy from Einstein's first prediction to our current understanding the spectrum. It is shown that detection of signals in the audio frequency spectrum can be expected very soon, and that a north-south pair of next generation detectors would provide large scientific benefits. Sect. 2 reviews the theory of gravitational waves and the principles of detection using laser interferometry. The state of the art Advanced LIGO detectors are then described. These detectors have a high chance of detecting the first events in the near future. Sect. 3 reviews the KAGRA detector currently under development in Japan, which will be the first laser interferometer detector to use cryogenic test masses. Sect. 4 of this paper reviews gravit...
Hunting for dark particles with gravitational waves
Energy Technology Data Exchange (ETDEWEB)
Giudice, Gian F.; McCullough, Matthew; Urbano, Alfredo [CERN, Theoretical Physics Department,Geneva (Switzerland)
2016-10-03
The LIGO observation of gravitational waves from a binary black hole merger has begun a new era in fundamental physics. If new dark sector particles, be they bosons or fermions, can coalesce into exotic compact objects (ECOs) of astronomical size, then the first evidence for such objects, and their underlying microphysical description, may arise in gravitational wave observations. In this work we study how the macroscopic properties of ECOs are related to their microscopic properties, such as dark particle mass and couplings. We then demonstrate the smoking gun exotic signatures that would provide observational evidence for ECOs, and hence new particles, in terrestrial gravitational wave observatories. Finally, we discuss how gravitational waves can test a core concept in general relativity: Hawking’s area theorem.
Gravitation and quantummechanical localization of macroobjects
Diósi, L
2015-01-01
We propose nonlinear Schr\\"odinger equation with gravitational self-interacting term. The separability conditions of Bialynicki-Birula are satisfied in asymptotic sense. Solitonlike solutions were found.
Update on gravitational-wave research
Grishchuk, L P
2003-01-01
The recently assembled laser-beam detectors of gravitational waves are approaching the planned level of sensitivity. In the coming 1 - 2 years, we may be observing the rare but powerful events of inspiral and merger of binary stellar-mass black holes. More likely, we will have to wait for a few years longer, until the advanced detectors become operational. Their sensitivity will be sufficient to meet the most cautious evaluations of the strength and event rates of astrophysical sources of gravitational waves. The experimental and theoretical work related to the space-based laser-beam detectors is also actively pursued. The current gravitational wave research is broad and interesting. Experimental innovations, source modelling, methods of data analysis, theoretical issues of principle are being studied and developed at the same time. The race for direct detection of relatively high-frequency waves is accompanied by vigorous efforts to discover the very low-frequency relic gravitational waves through the measur...
Looking for Lorentz violation with gravitational waves
Schreck, M
2016-01-01
The current letter has been inspired by the recent direct detection of gravitational waves reported by Advanced LIGO. In this context, a particular Lorentz-violating framework for classical, massive particles is on the focus. The latter is characterized by a preferred direction in spacetime comprised of CPT-odd components with mass dimension 1. Curvature effects in spacetime, which are caused by a propagating gravitational wave, are assumed to deform the otherwise constant background field. In accordance with spontaneous Lorentz violation, a particular choice for the vector field is taken, which was proposed elsewhere. The geodesic equations for a particle that is subject to this type of Lorentz violation are obtained. Subsequently, their numerical solutions are computed and discussed. The particular model considered leads to changes in the particle trajectory, which interferometric gravitational-wave experiments could be sensitive for. Since such effects have not been observed in the gravitational-wave event...
Testing the Gravitational Redshift with Atomic Gravimeters?
Wolf, Peter; Bordé, Christian J; Reynaud, Serge; Salomon, Christophe; Cohen-Tannoudji, Claude
2011-01-01
Atom interferometers allow the measurement of the acceleration of freely falling atoms with respect to an experimental platform at rest on Earth's surface. Such experiments have been used to test the universality of free fall by comparing the acceleration of the atoms to that of a classical freely falling object. In a recent paper, M\\"uller, Peters and Chu [Nature {\\bf 463}, 926-929 (2010)] argued that atom interferometers also provide a very accurate test of the gravitational redshift (or universality of clock rates). Considering the atom as a clock operating at the Compton frequency associated with the rest mass, they claimed that the interferometer measures the gravitational redshift between the atom-clocks in the two paths of the interferometer at different values of gravitational potentials. In the present paper we analyze this claim in the frame of general relativity and of different alternative theories, and conclude that the interpretation of atom interferometers as testing the gravitational redshift ...
The gravitational-wave memory effect
Favata, Marc
2010-01-01
The nonlinear memory effect is a slowly-growing, non-oscillatory contribution to the gravitational-wave amplitude. It originates from gravitational waves that are sourced by the previously emitted waves. In an ideal gravitational-wave interferometer a gravitational-wave with memory causes a permanent displacement of the test masses that persists after the wave has passed. Surprisingly, the nonlinear memory affects the signal amplitude starting at leading (Newtonian-quadrupole) order. Despite this fact, the nonlinear memory is not easily extracted from current numerical relativity simulations. After reviewing the linear and nonlinear memory I summarize some recent work, including: (1) computations of the memory contribution to the inspiral waveform amplitude (thus completing the waveform to third post-Newtonian order); (2) the first calculations of the nonlinear memory that include all phases of binary black hole coalescence (inspiral, merger, ringdown); and (3) realistic estimates of the detectability of the ...
Gravitational Waves from Coalescing Binary Sources
Maia, M D
2010-01-01
Coalescing binary systems (eg pulsars, neutron stars and black holes) are the most likely sources of gravitational radiation, yet to be detected on or near Earth, where the local gravitational field is negligible and the Poincar\\'e symmetry rules. On the other hand, the general theory of gravitational waves emitted by axially symmetric rotating sources predicts the existence of a non-vanishing news function. The existence of such function implies that, for a distant observer, the asymptotic group of isometries, the BMS group, has a translational symmetry that depends on the orbit periodicity of the source, thus breaking the isotropy o the Poincar\\'e translations. These results suggest the application of the asymptotic BMS-covariant wave equation to obtain a proper theoretical basis for the gravitational waves observations.
Exact plane gravitational waves and electromagnetic fields
Montanari, E; Montanari, Enrico; Calura, Mirco
2000-01-01
The behaviour of a "test" electromagnetic field in the background of an exactgravitational plane wave is investigated in the framework of Einstein's generalrelativity. We have expressed the general solution to the de Rham equations asa Fourier-like integral. In the general case we have reduced the problem to aset of ordinary differential equations and have explicitly written the solutionin the case of linear polarization of the gravitational wave. We have expressedour results by means of Fermi Normal Coordinates (FNC), which define the properreference frame of the laboratory. Moreover we have provided some "gedankenexperiments", showing that an external gravitational wave induces measurableeffects of non tidal nature via electromagnetic interaction. Consequently it isnot possible to eliminate gravitational effects on electromagnetic field, evenin an arbitrarily small spatial region around an observer freely falling in thefield of a gravitational wave. This is opposite to the case of mechanicalinteraction invo...
Cosmological inference using gravitational wave observations alone
Del Pozzo, Walter; Messenger, Chris
2015-01-01
Gravitational waves emitted during the coalescence of binary neutron star systems are self-calibrating signals. As such they can provide a direct measurement of the luminosity distance to a source without the need for a cosmic distance scale ladder. In general, however, the corresponding redshift measurement needs to be obtained electromagnetically since it is totally degenerate with the total mass of the system. Nevertheless, recent Fisher matrix studies has shown that if information about the equation of state of the neutron stars is available, it is indeed possible to extract redshift information from the gravitational wave signal alone. Therefore, measuring the cosmological parameters in pure gravitational wave fashion is possible. Furthermore, the huge number of sources potentially observable by the Einstein Telescope has led to speculations that the gravitational wave measurement is potentially competitive with traditional methods. The Einstein telescope is a conceptual study for a third generation grav...
Sources of Gravitational Waves: Theory and Observations
Buonanno, Alessandra
2014-01-01
Gravitational-wave astronomy will soon become a new tool for observing the Universe. Detecting and interpreting gravitational waves will require deep theoretical insights into astronomical sources. The past three decades have seen remarkable progress in analytical and numerical computations of the source dynamics, development of search algorithms and analysis of data from detectors with unprecedented sensitivity. This Chapter is devoted to examine the advances and future challenges in understanding the dynamics of binary and isolated compact-object systems, expected cosmological sources, their amplitudes and rates, and highlights of results from gravitational-wave observations. All of this is a testament to the readiness of the community to open a new window for observing the cosmos, a century after gravitational waves were first predicted by Albert Einstein.
Approximation methods in gravitational-radiation theory
Will, C. M.
1986-02-01
The observation of gravitational-radiation damping in the binary pulsar PSR 1913+16 and the ongoing experimental search for gravitational waves of extraterrestrial origin have made the theory of gravitational radiation an active branch of classical general relativity. In calculations of gravitational radiation, approximation methods play a crucial role. The author summarizes recent developments in two areas in which approximations are important: (1) the quadrupole approximation, which determines the energy flux and the radiation reaction forces in weak-field, slow-motion, source-within-the-near-zone systems such as the binary pulsar; and (2) the normal modes of oscillation of black holes, where the Wentzel-Kramers-Brillouin approximation gives accurate estimates of the complex frequencies of the modes.
Reheating After Quintessential Inflation and Gravitational Waves
Tashiro, H; Sasaki, M; Tashiro, Hiroyuki; Chiba, Takeshi; Sasaki, Misao
2004-01-01
We investigate the dependence of the gravitational wave spectrum from quintessential inflation on the reheating process. We consider two extreme reheating processes. One is the gravitational reheating by particle creation in the expanding universe in which the beginning of the radiation dominated epoch is delayed due to the presence of the epoch of domination of the kinetic energy of the inflaton (kination). The other is the instant preheating considered by Felder et al. in which the Universe becomes radiation dominated soon after the end of inflation. We find that the spectrum of the gravitational waves at $\\sim 100$ GHz is quite sensitive to the reheating process. Conversely, the detection or non-detection of primordial gravitational waves at $\\sim$100 MHz would provide useful information regarding the reheating process in quintessential inflation.
Hunting for dark particles with gravitational waves
Giudice, Gian F.; McCullough, Matthew; Urbano, Alfredo
2016-10-01
The LIGO observation of gravitational waves from a binary black hole merger has begun a new era in fundamental physics. If new dark sector particles, be they bosons or fermions, can coalesce into exotic compact objects (ECOs) of astronomical size, then the first evidence for such objects, and their underlying microphysical description, may arise in gravitational wave observations. In this work we study how the macroscopic properties of ECOs are related to their microscopic properties, such as dark particle mass and couplings. We then demonstrate the smoking gun exotic signatures that would provide observational evidence for ECOs, and hence new particles, in terrestrial gravitational wave observatories. Finally, we discuss how gravitational waves can test a core concept in general relativity: Hawking's area theorem.
Gravitational Waves and Time Domain Astronomy
Centrella, Joan; Nissanke, Samaya; Williams, Roy
2012-01-01
The gravitational wave window onto the universe will open in roughly five years, when Advanced LIGO and Virgo achieve the first detections of high frequency gravitational waves, most likely coming from compact binary mergers. Electromagnetic follow-up of these triggers, using radio, optical, and high energy telescopes, promises exciting opportunities in multi-messenger time domain astronomy. In the decade, space-based observations of low frequency gravitational waves from massive black hole mergers, and their electromagnetic counterparts, will open up further vistas for discovery. This two-part workshop featured brief presentations and stimulating discussions on the challenges and opportunities presented by gravitational wave astronomy. Highlights from the workshop, with the emphasis on strategies for electromagnetic follow-up, are presented in this report.
The gravitational field and brain function
Mei, Lei; Zhou, Chuan-Dai; Lan, Jing-Quan; Wang, Zhi-Ging; Wu, Wen-Can; Xue, Xin-Min
The frontal cortex is recognized as the highest adaptive control center of the human brain. The principle of the ``frontalization'' of human brain function offers new possibilities for brain research in space. There is evolutionary and experimental evidence indicating the validity of the principle, including it's role in nervous response to gravitational stimulation. The gravitational field is considered here as one of the more constant and comprehensive factors acting on brain evolution, which has undergone some successive crucial steps: ``encephalization'', ``corticalization'', ``lateralization'' and ``frontalization''. The dominating effects of electrical responses from the frontal cortex have been discovered 1) in experiments under gravitational stimulus; and 2) in processes potentially relating to gravitational adaptation, such as memory and learning, sensory information processing, motor programing, and brain state control. A brain research experiment during space flight is suggested to test the role of the frontal cortex in space adaptation and it's potentiality in brain control.
Self-gravitating fluid tori with charge
Karas, Vladimir; Trova, Audrey; Kovar, Jiri
2017-08-01
We have been developing an analytical approach to study equilibria of self-gravitating charged fluid embedded in the gravitational and magnetic fields of a central body. Our calculations provide a toy-model scenario for gaseous/dusty tori surrounding supermassive black holes in galactic nuclei. While the central black hole dominates the gravitational field and remains electrically neutral, the surrounding material has a non-negligible self-gravitational effect on the torus structure. Moreover, by charging mechanisms it also acquires non-zero electric charge density. These two influences need to be taken into account to achieve a self-consistent picture (based on Trova et al., ApJSS, 226, id. 12, 2016).
Universal Spin Structure in Gauge Gravitation Theory
Giachetta, G; Sardanashvily, G
1997-01-01
Building on the universal covering group of the general linear group, we introduce the composite spinor bundle whose subbundles are Lorentz spin structures associated with different gravitational fields. General covariant transformations of this composite spinor bundle are canonically defined.
Geometrical vs wave optics under gravitational waves
Angélil, Raymond
2015-01-01
We present some new derivations of the effect of a plane gravitational wave on a light ray. A simple interpretation of the results is that a gravitational wave causes a phase modulation of electromagnetic waves. We arrive at this picture from two contrasting directions, namely null geodesics and Maxwell's equations, or, geometric and wave optics. Under geometric optics, we express the geodesic equations in Hamiltonian form and solve perturbatively for the effect of gravitational waves. We find that the well-known time-delay formula for light generalizes trivially to massive particles. We also recover, by way of a Hamilton-Jacobi equation, the phase modulation obtained under wave optics. Turning then to wave optics, rather than solving Maxwell's equations directly for the fields, as in most previous approaches, we derive a perturbed wave equation (perturbed by the gravitational wave) for the electromagnetic four-potential. From this wave equation it follows that the four-potential and the electric and magnetic...
Hunting for Dark Particles with Gravitational Waves
Giudice, Gian F.; Urbano, Alfredo
2016-01-01
The LIGO observation of gravitational waves from a binary black hole merger has begun a new era in fundamental physics. If new dark sector particles, be they bosons or fermions, can coalesce into exotic compact objects (ECOs) of astronomical size, then the first evidence for such objects, and their underlying microphysical description, may arise in gravitational wave observations. In this work we study how the macroscopic properties of ECOs are related to their microscopic properties, such as dark particle mass and couplings. We then demonstrate the smoking gun exotic signatures that would provide observational evidence for ECOs, and hence new particles, in terrestrial gravitational wave observatories. Finally, we discuss how gravitational waves can test a core concept in general relativity: Hawking's area theorem.
Environmental Effects for Gravitational-wave Astrophysics
Barausse, Enrico; Pani, Paolo
2014-01-01
The upcoming detection of gravitational waves by terrestrial interferometers will usher in the era of gravitational-wave astronomy. This will be particularly true when space-based detectors will come of age and measure the mass and spin of massive black holes with exquisite precision and up to very high redshifts, thus allowing for better understanding of the symbiotic evolution of black holes with galaxies, and for high-precision tests of General Relativity in strong-field, highly-dynamical regimes. Such ambitious goals require that astrophysical environmental pollution of gravitational-wave signals be constrained to negligible levels, so that neither detection nor estimation of the source parameters are significantly affected. Here, we consider the main sources for space-based detectors -the inspiral, merger and ringdown of massive black-hole binaries and extreme mass-ratio inspirals- and account for various effects on their gravitational waveforms, including electromagnetic fields, cosmological evolution, ...
Gravitational Waves from Oscillons after Inflation
Antusch, Stefan; Cefalà, Francesco; Orani, Stefano
2017-01-01
We investigate the production of gravitational waves during preheating after inflation in the common case of field potentials that are asymmetric around the minimum. In particular, we study the impact of oscillons, comparatively long lived and spatially localized regions where a scalar field (e.g., the inflaton) oscillates with large amplitude. Contrary to a previous study, which considered a symmetric potential, we find that oscillons in asymmetric potentials associated with a phase transition can generate a pronounced peak in the spectrum of gravitational waves that largely exceeds the linear preheating spectrum. We discuss the possible implications of this enhanced amplitude of gravitational waves. For instance, for low scale inflation models, the contribution from the oscillons can strongly enhance the observation prospects at current and future gravitational wave detectors.
Gravitational Wave Physics with Binary Love Relations
Yagi, Kent; Yunes, Nicolas
2016-03-01
Gravitational waves from the late inspiral of neutron star binaries encode rich information about their internal structure at supranuclear densities through their tidal deformabilities. However, extracting the individual tidal deformabilities of the components of a binary is challenging with future ground-based gravitational wave interferometers due to degeneracies between them. We overcome this difficulty by finding new, approximate universal relations between the individual tidal deformabilities that depend on the mass ratio of the two stars and are insensitive to their internal structure. Such relations have applications not only to gravitational wave astrophysics, but also to nuclear physics as they improve the measurement accuracy of tidal parameters. Moreover, the relations improve our ability to test extreme gravity and perform cosmology with gravitational waves emitted from neutron star binaries.
Some Remarks on Gravitational Global Monopoles
Maison, D; Maison, Dieter; Liebling, Steven L.
1999-01-01
Using mainly analytical arguments, we derive the exact relation static gravitational global monopoles. For this value, the global monopole bifurcates with the de Sitter solution obtained for vanishing Higgs field. In addition, we analyze the stability properties of the solutions.
Planar Gravitational Corrections For Supersymmetric Gauge Theories
Dijkgraaf, R; Ooguri, H; Vafa, C; Zanon, D
2004-01-01
In this paper we discuss the contribution of planar diagrams to gravitational F-terms for N=1 supersymmetric gauge theories admitting a large N description. We show how the planar diagrams lead to a universal contribution at the extremum of the glueball superpotential, leaving only the genus one contributions, as was previously conjectured. We also discuss the physical meaning of gravitational F-terms.
Entangled States and the Gravitational Quantum Well
Alves, Rui; Bertolami, Orfeu
2016-01-01
We study the continuous variable entanglement of a system of two particles under the influence of Earth's gravitational field. We determine a phase-space description of this bipartite system by calculating its Wigner function and verify its entanglement by applying a generalization of the PPT criterion for non-Gaussian states. We also examine the influence of gravity on an idealized entanglement protocol to be shared between stations at different potentials based on the correlation of states of the gravitational quantum well.
Measuring gravitational effects on antimatter in space
Piacentino, Giovanni Maria; Venanzoni, Graziano
2016-01-01
We propose an experimental test of the gravitational interaction with antimatter by measuring the branching fraction of the CP~violating decay $K_\\mathrm{L} \\to \\pi^{+} \\pi^{-}$ in space. We show that at the altitude of the International Space Station, gravitational effects may change the level of CP~violation such that a 5$\\sigma$ discrimination may be obtained by collecting the $K_\\mathrm{L}$ produced by the cosmic proton flux within a few years.
Neutrino oscillations in the gravitational field
Energy Technology Data Exchange (ETDEWEB)
Godunov, S. I., E-mail: sgodunov@itep.ru; Pastukhov, G. S., E-mail: grigoriypas@gmail.com [Moscow Institute of Physics and Technology (Russian Federation)
2011-02-15
We calculate the gravitational correction to the phase difference between neutrino mass eigenstates for the spherically symmetric gravitational field described by the Schwarzschild metric. This correction was calculated in a number of works, but the results of these works differ from each other. Our result does not coincide with the results ever published. In this work, we make calculations in the simplest way and verify our result by several tests.
Gravitational wave astronomy: the current status
Blair, David; Ju, Li; Zhao, ChunNong; Wen, LinQing; Chu, Qi; Fang, Qi; Cai, RongGen; Gao, JiangRui; Lin, XueChun; Liu, Dong; Wu, Ling-An; Zhu, ZongHong; Reitze, David H.; Arai, Koji; Zhang, Fan; Flaminio, Raffaele; Zhu, XingJiang; Hobbs, George; Manchester, Richard N.; Shannon, Ryan M.; Baccigalupi, Carlo; Gao, Wei; Xu, Peng; Bian, Xing; Cao, ZhouJian; Chang, ZiJing; Dong, Peng; Gong, XueFei; Huang, ShuangLin; Ju, Peng; Luo, ZiRen; Qiang, Li'E.; Tang, WenLin; Wan, XiaoYun; Wang, Yue; Xu, ShengNian; Zang, YunLong; Zhang, HaiPeng; Lau, Yun-Kau; Ni, Wei-Tou
2015-12-01
In the centenary year of Einstein's General Theory of Relativity, this paper reviews the current status of gravitational wave astronomy across a spectrum which stretches from attohertz to kilohertz frequencies. Sect. 1 of this paper reviews the historical development of gravitational wave astronomy from Einstein's first prediction to our current understanding the spectrum. It is shown that detection of signals in the audio frequency spectrum can be expected very soon, and that a north-south pair of next generation detectors would provide large scientific benefits. Sect. 2 reviews the theory of gravitational waves and the principles of detection using laser interferometry. The state of the art Advanced LIGO detectors are then described. These detectors have a high chance of detecting the first events in the near future. Sect. 3 reviews the KAGRA detector currently under development in Japan, which will be the first laser interferometer detector to use cryogenic test masses. Sect. 4 of this paper reviews gravitational wave detection in the nanohertz frequency band using the technique of pulsar timing. Sect. 5 reviews the status of gravitational wave detection in the attohertz frequency band, detectable in the polarisation of the cosmic microwave background, and discusses the prospects for detection of primordial waves from the big bang. The techniques described in sects. 1-5 have already placed significant limits on the strength of gravitational wave sources. Sects. 6 and 7 review ambitious plans for future space based gravitational wave detectors in the millihertz frequency band. Sect. 6 presents a roadmap for development of space based gravitational wave detectors by China while sect. 7 discusses a key enabling technology for space interferometry known as time delay interferometry.
Frequency shifts in gravitational resonance spectroscopy
Baeßler, S; Pignol, G; Protasov, K V; Rebreyend, D; Kupriyanova, E A; Voronin, A Yu
2015-01-01
Quantum states of ultracold neutrons in the gravitational field are to be characterized through gravitational resonance spectroscopy. This paper discusses systematic effects that appear in the spectroscopic measurements. The discussed frequency shifts, which we call Stern-Gerlach shift, interference shift, and spectator state shift, appear in conceivable measurement schemes and have general importance. These shifts have to be taken into account in precision experiments.
On the Possibility to Construct Gravitational Eye
Institute of Scientific and Technical Information of China (English)
CHEN Ying-Tian
2007-01-01
The possibility of modifying a conventional Cavendish torsion pendulum into a half-armed pendulum oscillator to measure the horizontal gravitational acceleration is discussed. A new kind of gravitational detector, gravieye,as we named, can be made by a proper combination of such oscillators to "see" remote objects and to be used, e.g. to detect the movement of huge mass at a long distance.
Exact plane gravitational waves and electromagnetic fields
Enrico MontanariUniversity of Ferrara and INFN sezione di Ferrara, Italy; Mirco Calura(University of Ferrara and INFN sezione di Ferrara, Italy)
2000-01-01
The behaviour of a "test" electromagnetic field in the background of an exact gravitational plane wave is investigated in the framework of Einstein's general relativity. We have expressed the general solution to the de Rham equations as a Fourier-like integral. In the general case we have reduced the problem to a set of ordinary differential equations and have explicitly written the solution in the case of linear polarization of the gravitational wave. We have expressed our ...
Relic Gravitational Waves and Their Detection
Grishchuk, L. P.
2000-01-01
The range of expected amplitudes and spectral slopes of relic (squeezed) gravitational waves, predicted by theory and partially supported by observations, is within the reach of sensitive gravity-wave detectors. In the most favorable case, the detection of relic gravitational waves can be achieved by the cross-correlation of outputs of the initial laser interferometers in LIGO, VIRGO, GEO600. In the more realistic case, the sensitivity of advanced ground-based and space-based laser interferom...
Gravitational wave astronomy: the current status
Blair, David; Ju, Li; Zhao, ChunNong; Wen, LinQing; Chu, Qi; Fang, Qi; Cai, RongGen; Gao, JiangRui; Lin, XueChun; Liu, Dong; Wu, Ling-An; Zhu, ZongHong; Reitze, David H.; Arai, Koji; Zhang, Fan; Flaminio, Raffaele; Zhu, XingJiang; Hobbs, George; Manchester, Richard N.; Shannon, Ryan M.; Baccigalupi, Carlo; Gao, Wei; Xu, Peng; Bian, Xing; Cao, ZhouJian; Chang, ZiJing; Dong, Peng; Gong, XueFei; Huang, ShuangLin; Ju, Peng; Luo, ZiRen; Qiang, Li'E.; Tang, WenLin; Wan, XiaoYun; Wang, Yue; Xu, ShengNian; Zang, YunLong; Zhang, HaiPeng; Lau, Yun-Kau; Ni, Wei-Tou
2015-12-01
In the centenary year of Einstein's General Theory of Relativity, this paper reviews the current status of gravitational wave astronomy across a spectrum which stretches from attohertz to kilohertz frequencies. Sect. 1 of this paper reviews the historical development of gravitational wave astronomy from Einstein's first prediction to our current understanding the spectrum. It is shown that detection of signals in the audio frequency spectrum can be expected very soon, and that a north-south pair of next generation detectors would provide large scientific benefits. Sect. 2 reviews the theory of gravitational waves and the principles of detection using laser interferometry. The state of the art Advanced LIGO detectors are then described. These detectors have a high chance of detecting the first events in the near future. Sect. 3 reviews the KAGRA detector currently under development in Japan, which will be the first laser interferometer detector to use cryogenic test masses. Sect. 4 of this paper reviews gravitational wave detection in the nanohertz frequency band using the technique of pulsar timing. Sect. 5 reviews the status of gravitational wave detection in the attohertz frequency band, detectable in the polarisation of the cosmic microwave background, and discusses the prospects for detection of primordial waves from the big bang. The techniques described in sects. 1-5 have already placed significant limits on the strength of gravitational wave sources. Sects. 6 and 7 review ambitious plans for future space based gravitational wave detectors in the millihertz frequency band. Sect. 6 presents a roadmap for development of space based gravitational wave detectors by China while sect. 7 discusses a key enabling technology for space interferometry known as time delay interferometry.
Physical optics in a uniform gravitational field
Hacyan, Shahen
2012-01-01
The motion of a (quasi-)plane wave in a uniform gravitational field is studied. It is shown that the energy of an elliptically polarized wave does not propagate along a geodesic, but in a direction that is rotated with respect to the gravitational force. The similarity with the walk-off effect in anisotropic crystals or the optical Magnus effect in inhomogeneous media is pointed out.
A Phase Space Approach to Gravitational Enropy
Rothman, T
2000-01-01
We examine the definition S = ln Omega as a candidate "gravitational entropy" function. We calculate its behavior for gravitationl and density perturbations in closed, open and flat cosmologies and find that in all cases it increases monotonically. Using the formalism to calculate the gravitational entropy produced during inflation gives the canonical answer. We compare the behavior of S with the behavior of the square of the Weyl tensor. Applying the formalism to black holes has proven more problematical.
Building Interstellar's black hole: the gravitational renderer
James, Oliver; Dieckmann, Sylvan; Pabst, Simon; Roberts, Paul-George H.; Thorne, Kip S.
2015-01-01
Interstellar is the first feature film to attempt depicting a black hole as it would actually be seen by somebody nearby. A close collaboration between the production's Scientific Advisor and the Visual Effects team led to the development of a new renderer, DNGR (Double Negative Gravitational Renderer) which uses novel techniques for rendering in curved space-time. Following the completion of the movie, the code was adapted for scientific research, leading to new insights into gravitational l...
Gravitational wave astronomy with radio galaxy surveys
Raccanelli, Alvise
2016-01-01
In the next decade, new astrophysical instruments will deliver the first large-scale maps of gravitational waves and radio sources. Therefore, it is timely to investigate the possibility to combine them to provide new and complementary ways to study the Universe. Using simulated catalogues appropriate to the planned surveys, it is possible to predict measurements of the cross-correlation between radio sources and GW maps and the effects of a stochastic gravitational wave background on galaxy ...
Dynamical Space-Time and Gravitational Waves
van Holten, J W
2016-01-01
According to General Relativity gravity is the result of the interaction between matter and space-time geometry. In this interaction space-time geometry itself is dynamical: it can store and transport energy and momentum in the form of gravitational waves. We give an introductory account of this phenomenon and discuss how the observation of gravitational waves may open up a fundamentally new window on the universe.
Resonant speed meter for gravitational wave detection
Nishizawa, Atsushi; Sakagami, Masa-aki
2008-01-01
Gravitational-wave detectors have been well developed and operated with high sensitivity. However, they still suffer from mirror displacement noise. In this paper, we propose a resonant speed meter, as a displacement noise-canceled configuration based on a ring-shaped synchronous recycling interferometer. The remarkable feature of this interferometer is that, at certain frequencies, gravitational-wave signals are amplified, while displacement noises are not.
Global gravitational anomalies and transport
Chowdhury, Subham Dutta; David, Justin R.
2016-12-01
We investigate the constraints imposed by global gravitational anomalies on parity odd induced transport coefficients in even dimensions for theories with chiral fermions, gravitinos and self dual tensors. The η-invariant for the large diffeomorphism corresponding to the T transformation on a torus constraints the coefficients in the thermal effective action up to mod 2. We show that the result obtained for the parity odd transport for gravitinos using global anomaly matching is consistent with the direct perturbative calculation. In d = 6 we see that the second Pontryagin class in the anomaly polynomial does not contribute to the η-invariant which provides a topological explanation of this observation in the `replacement rule'. We then perform a direct perturbative calculation for the contribution of the self dual tensor in d = 6 to the parity odd transport coefficient using the Feynman rules proposed by Gaumé and Witten. The result for the transport coefficient agrees with that obtained using matching of global anomalies.
Gravitational action with null boundaries
Lehner, Luis; Myers, Robert C.; Poisson, Eric; Sorkin, Rafael D.
2016-10-01
We present a complete discussion of the boundary term in the action functional of general relativity when the boundary includes null segments in addition to the more usual timelike and spacelike segments. We confirm that ambiguities appear in the contribution from a null segment, because it depends on an arbitrary choice of parametrization for the generators. We also show that similar ambiguities appear in the contribution from a codimension-two surface at which a null segment is joined to another (spacelike, timelike, or null) segment. The parametrization ambiguity can be tamed by insisting that the null generators be affinely parametrized; this forces each null contribution to the boundary action to vanish, but leaves intact the fredom to rescale the affine parameter by a constant factor on each generator. Once a choice of parametrization is made, the ambiguity in the joint contributions can be eliminated by formulating well-motivated rules that ensure the additivity of the gravitational action. Enforcing these rules, we calculate the time rate of change of the action when it is evaluated for a so-called "Wheeler-DeWitt patch" of a black hole in asymptotically anti de Sitter space. We recover a number of results cited in the literature, obtained with a less complete analysis.
On aberration in gravitational lensing
Sereno, M
2008-01-01
It is known that a relative translational motion between the deflector and the observer affects gravitational lensing. In this paper, a lens equation is obtained to describe such effects on actual lensing observables. Results can be easily interpreted in terms of aberration of light-rays. Both radial and transverse motions with relativistic velocities are considered. The lens equation is derived by first considering geodesic motion of photons in the rest-frame Schwarzschild spacetime of the lens, and, then, light-ray detection in the moving observer's frame. Due to the transverse motion images are displaced and distorted in the observer's celestial sphere, whereas the radial velocity along the line of sight causes an effective re-scaling of the lens mass. The Einstein ring is distorted to an ellipse whereas the caustics in the source plane are still point-like. Either for null transverse motion or up to linear order in velocities, the critical curve is still a circle with its radius corrected by a factor (1+z...
Gravitational Waves from Axion Monodromy
Hebecker, Arthur; Rompineve, Fabrizio; Witkowski, Lukas T
2016-01-01
Large field inflation is arguably the simplest and most natural variant of slow-roll inflation. Axion monodromy may be the most promising framework for realising this scenario. As one of its defining features, the long-range polynomial potential possesses short-range, instantonic modulations. These can give rise to a series of local minima in the post-inflationary region of the potential. We show that for certain parameter choices the inflaton populates more than one of these vacua inside a single Hubble patch. This corresponds to a dynamical phase decomposition, analogously to what happens in the course of thermal first-order phase transitions. In the subsequent process of bubble wall collisions, the lowest-lying axionic minimum eventually takes over all space. Our main result is that this violent process sources gravitational waves, very much like in the case of a first-order phase transition. We compute the energy density and peak frequency of the signal, which can lie anywhere in the mHz-GHz range, possib...
Boyle's law and gravitational instability
Lombardi, M; Lombardi, Marco; Bertin, Giuseppe
2001-01-01
We have re-examined the classical problem of the macroscopic equation of state for a hydrostatic isothermal self-gravitating gas cloud bounded by an external medium at constant pressure. We have obtained analytical conditions for its equilibrium and stability without imposing any specific shape and symmetry to the cloud density distribution. The equilibrium condition can be stated in the form of an upper limit to the cloud mass; this is found to be inversely proportional to the power 3/2 of a form factor \\mu characterizing the shape of the cloud. In this respect, the spherical solution, associated with the maximum value of the form factor, \\mu = 1, turns out to correspond to the shape that is most difficult to realize. Surprisingly, the condition that defines the onset of the Bonnor instability (or gravothermal catastrophe) can be cast in the form of an upper limit to the density contrast within the cloud that is independent of the cloud shape. We have then carried out a similar analysis in the two-dimensiona...
CHAOTIC ZONES AROUND GRAVITATING BINARIES
Energy Technology Data Exchange (ETDEWEB)
Shevchenko, Ivan I., E-mail: iis@gao.spb.ru [Pulkovo Observatory of the Russian Academy of Sciences, Pulkovskoje ave. 65, St. Petersburg 196140 (Russian Federation)
2015-01-20
The extent of the continuous zone of chaotic orbits of a small-mass tertiary around a system of two gravitationally bound primaries of comparable masses (a binary star, a binary black hole, a binary asteroid, etc.) is estimated analytically, as a function of the tertiary's orbital eccentricity. The separatrix map theory is used to demonstrate that the central continuous chaos zone emerges (above a threshold in the primaries' mass ratio) due to overlapping of the orbital resonances corresponding to the integer ratios p:1 between the tertiary and the central binary periods. In this zone, the unlimited chaotic orbital diffusion of the tertiary takes place, up to its ejection from the system. The primaries' mass ratio, above which such a chaotic zone is universally present at all initial eccentricities of the tertiary, is estimated. The diversity of the observed orbital configurations of biplanetary and circumbinary exosystems is shown to be in accord with the existence of the primaries' mass parameter threshold.
Gravitational spectra from direct measurements
Wagner, C. A.; Colombo, O. L.
1978-01-01
A simple rapid method is described for determining the spectrum of a surface field from harmonic analysis of direct measurements along great circle arcs. The method is shown to give excellent overall trends to very high degree from even a few short arcs of satellite data. Three examples are taken with perfect measurements of satellite tracking over a planet made up of hundreds of point-masses using (1) altimetric heights from a low orbiting spacecraft, (2) velocity residuals between a low and a high satellite in circular orbits, and (3) range-rate data between a station at infinity and a satellite in highly eccentric orbit. In particular, the smoothed spectrum of the Earth's gravitational field is determined to about degree 400(50 km half wavelength) from 1 D x 1 D gravimetry and the equivalent of 11 revolutions of Geos 3 and Skylab altimetry. This measurement shows there is about 46 cm of geoid height remaining in the field beyond degree 180.
Gravitational wave detection in space
Ni, Wei-Tou
2016-01-01
Gravitational wave (GW) detection in space is aimed at low frequency band (100 nHz - 100 mHz) and middle frequency band (100 mHz - 10 Hz). The science goals are the detection of GWs from (i) Supermassive Black Holes; (ii) Extreme-Mass-Ratio Black Hole Inspirals; (iii) Intermediate-Mass Black Holes; (iv) Galactic Compact Binaries and (v) Relic GW Background. In this paper, we present an overview on the sensitivity, orbit design, basic orbit configuration, angular resolution, orbit optimization, deployment, time-delay interferometry and payload concept of the current proposed GW detectors in space under study. The detector proposals under study have arm length ranging from 1000 km to 1.3 x 109 km (8.6 AU) including (a) Solar orbiting detectors -- ASTROD-GW (ASTROD [Astrodynamical Space Test of Relativity using Optical Devices] optimized for GW detection), BBO (Big Bang Observer), DECIGO (DECi-hertz Interferometer GW Observatory), e-LISA (evolved LISA [Laser Interferometer Space Antenna]), LISA, other LISA-type ...
The Gravitational Wave Detector EXPLORER
2002-01-01
%RE5 EXPLORER is a cryogenic resonant-mass gravitational wave (GW) detector. It is in operation at CERN since 1984 and it has been the first cryogenic GW antenna to perform continuous observations (since 1990).\\\\ \\\\EXPLORER is actually part of the international network of resonant-mass detectors which includes ALLEGRO at the Louisiana State University, AURIGA at the INFN Legnaro Laboratories, NAUTILUS at the INFN Frascati Laboratories and NIOBE at the University of Western Australia. The EXPLORER sensitivity, at present of the same order of the other antennas, is 10$^{-20}$ Hz$^{-1/2}$ over a bandwidth of 20 Hz and 6 10$^{-22}$ Hz$^{-1/2}$ with a bandwidth of about 0.5 Hz, corresponding to a sensitivity to short GW bursts of \\textit{h} = 6 10$^{-19}$.\\\\ \\\\This sensitivity should allow the detection of the burst sources in our Galaxy and in the Local Group. No evidence of GW signals has been reported up to now.\\\\ \\\\The principle of operation is based on the assumption that any vibrational mode of a resonant bo...
An Imitation Game concerning gravitational wave physics
Collins, Harry
2016-01-01
The 'Imitation Game' is a Turing Test played with a human participant instead of a computer. Here the author, a sociologist, who has been immersed in the field of gravitational wave physics since 1972, tried to pass an Imitation Game as a gravitational wave physicist. He already passed such a test in mid-2000s but this test was more elaborate and compared his performance with that of other kinds of physicists and with other sociologists as well as gravitational wave physicists. The test was based on 8 technical questions about gravitational wave physics asked by Professor Sathyprakash of Cardiff University. Collins marks compared well with that of the other gravitational wave physicists and were markedly better than that of other classes of respondent. Collins also marked the test and it can be seen that the way he marked was also much closer to the gravitational wave physicists than other categories. Though Collins's expertise can be shown to have degraded a little in the last ten years it seems not to have ...
Particle production in a gravitational wave background
Jones, Preston; Singleton, Douglas
2016-01-01
We study the possibility that massless particles, such as photons, are produced by a gravitational wave. That such a process should occur is implied by tree-level, Feynman diagrams such as two gravitons turning into two photons {\\it i.e.} $g + g \\rightarrow \\gamma + \\gamma$. Here we calculate the rate at which a gravitational wave creates a massless, scalar field. This is done by placing the scalar field in the background of a plane gravitational wave and calculating the 4-current of the scalar field. Even in the vacuum limit of the scalar field it has a non-zero vacuum expectation value (similar to what occurs in the Higgs mechanism) and a non-zero current. We associate this with the production of scalar field quanta by the gravitational field. This effect has potential consequences for the attenuation of gravitational waves since the massless particles are being produced at the expense of the gravitational field. This is related to the (time-dependent) Schwinger effect but with the electric field replaced b...
Gravitational wave asteroseismology with protoneutron stars
Sotani, Hajime; Takiwaki, Tomoya
2016-08-01
We examine the time evolution of the frequencies of the gravitational wave after the bounce within the framework of relativistic linear perturbation theory using the results of one-dimensional numerical simulations of core-collapse supernovae. Protoneutron star models are constructed in such a way that the mass and the radius of the protoneutron star become equivalent to the results obtained from the numerical simulations. Then we find that the frequencies of gravitational waves radiating from protoneutron stars strongly depend on the mass and the radius of protoneutron stars, but almost independently of the profiles of the electron fraction and the entropy per baryon inside the star. Additionally, we find that the frequencies of gravitational waves can be characterized by the square root of the average density of the protoneutron star irrespective of the progenitor models, which are completely different from the empirical formula for cold neutron stars. The dependence of the spectra on the mass and the radius is different from that of the g -mode: the oscillations around the surface of protoneutron stars due to the convection and the standing accretion-shock instability. Careful observation of these modes of gravitational waves can determine the evolution of the mass and the radius of protoneutron stars after core bounce. Furthermore, the expected frequencies of gravitational waves are around a few hundred hertz in the early stages after bounce, which must be a good candidate for the ground-based gravitational wave detectors.
Gravitational Waves and Light Cosmic Strings
Depies, Matthew R
2009-01-01
Gravitational wave signatures from cosmic strings are analyzed numerically. Cosmic string networks form during phase transistions in the early universe and these networks of long cosmic strings break into loops that radiate energy in the form of gravitational waves until they decay. The gravitational waves come in the form of harmonic modes from individual string loops, a "confusion noise" from galactic loops, and a stochastic background of gravitational waves from a network of loops. In this study string loops of larger size $\\alpha$ and lower string tensions $G\\mu$ (where $\\mu$ is the mass per unit length of the string) are investigated than in previous studies. Several detectors are currently searching for gravitational waves and a space based satellite, the Laser Interferometer Space Antenna (LISA), is in the final stages of pre-flight. The results for large loop sizes ($\\alpha=0.1$) put an upper limit of about $G\\mu<10^{-9}$ and indicate that gravitational waves from string loops down to $G\\mu \\approx...
Development as adaptation: a paradigm for gravitational and space biology
Alberts, Jeffrey R.; Ronca, April E.
2005-01-01
Adaptation is a central precept of biology; it provides a framework for identifying functional significance. We equate mammalian development with adaptation, by viewing the developmental sequence as a series of adaptations to a stereotyped sequence of habitats. In this way development is adaptation. The Norway rat is used as a mammalian model, and the sequence of habitats that is used to define its adaptive-developmental sequence is (a) the uterus, (b) the mother's body, (c) the huddle, and (d) the coterie of pups as they gain independence. Then, within this framework and in relation to each of the habitats, we consider problems of organismal responses to altered gravitational forces (micro-g to hyper-g), especially those encountered during space flight and centrifugation. This approach enables a clearer identification of simple "effects" and active "responses" with respect to gravity. It focuses our attention on functional systems and brings to the fore the manner in which experience shapes somatic adaptation. We argue that this basic developmental approach is not only central to basic issues in gravitational biology, but that it provides a natural tool for understanding the underlying processes that are vital to astronaut health and well-being during long duration flights that will involve adaptation to space flight conditions and eventual re-adaptation to Earth's gravity.
Alterations in gut transport of minerals and in binding proteins during simulated weightlessness
Bikle, D. D.
1984-01-01
The structural components of the skeleton develop and are maintained in a 1 g environment, shaped by the mechanical load to which they are constantly exposed. Altering such a mechanical load by reducing the gravitational force imposed on the system, as in space flight, has profound effects on the skeleton and permits an exploration of the molecular events which regulate normal skeletal homeostasis. The objective was to determine whether simulated weightlessness reduced intestinal calcium transport, and if so, to determine the molecular mechanisms for such an effect. A nonstressful tail suspension in which the rats gained weight normally while suspended was used to simulate weightlessness. A significant change in intestinal calcium transport was not demonstrated. However, a cyclic change in bone formation with suspension was shown. Based on these observations, the objective changed to determination of the hormonal regulation of bone formation during simulated weightlessness.
Vector-averaged gravity does not alter acetylcholine receptor single channel properties
Reitstetter, R.; Gruener, R.
1994-01-01
To examine the physiological sensitivity of membrane receptors to altered gravity, we examined the single channel properties of the acetylcholine receptor (AChR), in co-cultures of Xenopus myocytes and neurons, to vector-averaged gravity in the clinostat. This experimental paradigm produces an environment in which, from the cell's perspective, the gravitational vector is "nulled" by continuous averaging. In that respect, the clinostat simulates one aspect of space microgravity where the gravity force is greatly reduced. After clinorotation, the AChR channel mean open-time and conductance were statistically not different from control values but showed a rotation-dependent trend that suggests a process of cellular adaptation to clinorotation. These findings therefore suggest that the ACHR channel function may not be affected in the microgravity of space despite changes in the receptor's cellular organization.
Mental imagery of gravitational motion.
Gravano, Silvio; Zago, Myrka; Lacquaniti, Francesco
2017-10-01
There is considerable evidence that gravitational acceleration is taken into account in the interaction with falling targets through an internal model of Earth gravity. Here we asked whether this internal model is accessed also when target motion is imagined rather than real. In the main experiments, naïve participants grasped an imaginary ball, threw it against the ceiling, and caught it on rebound. In different blocks of trials, they had to imagine that the ball moved under terrestrial gravity (1g condition) or under microgravity (0g) as during a space flight. We measured the speed and timing of the throwing and catching actions, and plotted ball flight duration versus throwing speed. Best-fitting duration-speed curves estimate the laws of ball motion implicit in the participant's performance. Surprisingly, we found duration-speed curves compatible with 0g for both the imaginary 0g condition and the imaginary 1g condition, despite the familiarity with Earth gravity effects and the added realism of performing the throwing and catching actions. In a control experiment, naïve participants were asked to throw the imaginary ball vertically upwards at different heights, without hitting the ceiling, and to catch it on its way down. All participants overestimated ball flight durations relative to the durations predicted by the effects of Earth gravity. Overall, the results indicate that mental imagery of motion does not have access to the internal model of Earth gravity, but resorts to a simulation of visual motion. Because visual processing of accelerating/decelerating motion is poor, visual imagery of motion at constant speed or slowly varying speed appears to be the preferred mode to perform the tasks. Copyright © 2017 Elsevier Ltd. All rights reserved.
Astrophysical applications of gravitational microlensing
Institute of Scientific and Technical Information of China (English)
Shude Mao
2012-01-01
Since the first discovery of microlensing events nearly two decades ago,gravitational microlensing has accumulated tens of TBytes of data and developed into a powerful astrophysical technique with diverse applications.The review starts with a theoretical overview of the field and then proceeds to discuss the scientific highlights.(1) Microlensing observations toward the Magellanic Clouds rule out the Milky Way halo being dominated by MAssive Compact Halo Objects (MACHOs).This confirms most dark matter is non-baryonic,consistent with other observations.(2) Microlensing has discovered about 20 extrasolar planets (16 published),including the first two Jupiter-Saturn like systems and the only five "cold Neptunes" yet detected.They probe a different part of the parameter space and will likely provide the most stringent test of core accretion theory of planet formation.(3) Microlensing provides a unique way to measure the mass of isolated stars,including brown dwarfs and normal stars.Half a dozen or so stellar mass black hole candidates have also been proposed.(4) High-resolution,target-of-opportunity spectra of highly-magnified dwarf stars provide intriguing "age" determinations which may either hint at enhanced helium enrichment or unusual bulge formation theories.(5) Microlensing also measured limb-darkening profiles for close to ten giant stars,which challenges stellar atmosphere models.(6) Data from surveys also provide strong constraints on the geometry and kinematics of the Milky Way bar (through proper motions); the latter indicates predictions from current models appear to be too anisotropic compared with observations.The future of microlensing is bright given the new capabilities of current surveys and forthcoming new telescope networks from the ground and from space.Some open issues in the field are identified and briefly discussed.
Gravitation Astrometric Measurement Experiment (GAME)
Gai, M.; Vecchiato, A.; Ligori, S.; Riva, A.; Lattanzi, M. G.; Busonero, D.; Fienga, A.; Loreggia, D.; Crosta, M. T.
2012-07-01
GAME is a recent concept for a small/medium class mission aimed at Fundamental Physics tests in the Solar system, by means of an optimised instrument in the visible, based on smart combination of coronagraphy and Fizeau interferometry. The targeted precision on the γ and β parameters of the Parametrised Post-Newtonian formulation of General Relativity are respectively in the 10-7-10-8 and 10-5-10-6 range, improving by one or two orders of magnitude with respect to the expectations on current or near future experiments. Such precision is suitable to detect possible deviations from the unity value, associated to generalised Einstein models for gravitation, with potentially huge impacts on the cosmological distribution of dark matter and dark energy from a Solar system scale experiment. The measurement principle is based on the differential astrometric signature on the stellar positions, i.e. based on the spatial component of the effect rather than the temporal component as in the most recent experiments using radio link delay timing variation (Cassini). The instrument concept is based on multiple field, multiple aperture Fizeau interferometry, observing simultaneously regions close to the Solar limb (requiring the adoption of coronagraphic techniques), and others in opposition to the Sun. The diluted optics approach is selected for achieving an efficient rejection of the scattered solar radiation, while retaining an acceptable angular resolution on the science targets. The multiple field observation is aimed at cost-effective control of systematic effects through simultaneous calibration. We describe the science motivation, the proposed mission profile, the instrument concept and the expected performance.
Hąc-Wydro, Katarzyna; Sroka, Aleksandra; Jabłońska, Klaudia
2016-07-01
Auxins are successfully used to improve phytoextraction efficiency of metal ions from the contaminated environment, however, the mechanism of their activity in this field is not explained. Auxins are known to exert various biochemical alterations in the plant membranes and cells, but their activity involves also direct interactions with lipids leading to changes in membrane organization. Following the suggestion that the auxins-induced modifications in membrane properties alleviate toxic effect of metal ions in this paper we have undertaken the comparative studies on the effect of metal ions and metal ions/auxins mixtures on model membrane systems. The experiments were done on lipid monolayers differing in their composition spread on water subphase and on Pb(2+), Indole-3-acetic acid (IAA), 1-Naphthaleneacetic acid (NAA) and Pb(2+)/IAA and Pb(2+)/NAA water solutions. The analysis of the collected data suggests that metal ions and auxins can change fluidity of the lipid systems and weaken the interactions between monolayer components. This manifested in the increase of the mean area per molecule and the excess area per molecule values for the films on Pb(2+), auxins as well as Pb(2+)/auxin solutions as compared to the values on pure water subphase. However, the presence of auxin in the mixture with lead(II) ions makes the alterations induced by sole metal ions weaker. This effect was more pronounced for the membranes of a higher packing. Thus it was proposed that auxins may enhance phytoextraction of metal ions by weakening their destabilizing effect on membrane. Copyright © 2016 Elsevier B.V. All rights reserved.
Szulcek, R.; van Bezu, J.; Boonstra, J.; van Loon, J.J.W.A.; van Nieuw Amerongen, G.P.
2015-01-01
Background Endothelial cells (EC) guard vascular functions by forming a dynamic barrier throughout the vascular system that sensitively adapts to ‘classical’ biomechanical forces, such as fluid shear stress and hydrostatic pressure. Alterations in gravitational forces might similarly affect EC integ
Nearby Stars as Gravitational Wave Detectors
Lopes, Ilídio; Silk, Joseph
2015-07-01
Sun-like stellar oscillations are excited by turbulent convection and have been discovered in some 500 main-sequence and sub-giant stars and in more than 12,000 red giant stars. When such stars are near gravitational wave sources, low-order quadrupole acoustic modes are also excited above the experimental threshold of detectability, and they can be observed, in principle, in the acoustic spectra of these stars. Such stars form a set of natural detectors to search for gravitational waves over a large spectral frequency range, from {10}-7 to {10}-2 Hz. In particular, these stars can probe the {10}-6-{10}-4 Hz spectral window which cannot be probed by current conventional gravitational wave detectors, such as the Square Kilometre Array and Evolved Laser Interferometer Space Antenna. The Planetary Transits and Oscillations of State (PLATO) stellar seismic mission will achieve photospheric velocity amplitude accuracy of {cm} {{{s}}}-1. For a gravitational wave search, we will need to achieve accuracies of the order of {10}-2 {cm} {{{s}}}-1, i.e., at least one generation beyond PLATO. However, we have found that multi-body stellar systems have the ideal setup for this type of gravitational wave search. This is the case for triple stellar systems formed by a compact binary and an oscillating star. Continuous monitoring of the oscillation spectra of these stars to a distance of up to a kpc could lead to the discovery of gravitational waves originating in our galaxy or even elsewhere in the universe. Moreover, unlike experimental detectors, this observational network of stars will allow us to study the progression of gravitational waves throughout space.
Directory of Open Access Journals (Sweden)
Vikin B. P.
2006-04-01
Full Text Available The annihilation of positrons is measured in a wide range of studies in the field of physical chemistry [1, 2]. One of the problems in these studies is the instability of the results of measurements [3–5]. As shown in our research, instability may result from the change of nonregistering gravitational effects related to alteration of the tidal forces upon the change of moon phases and the seasonal changes of the distance between the Earth and the Sun.
Directory of Open Access Journals (Sweden)
Vikin B. P.
2006-04-01
Full Text Available The annihilation of positrons is measured in a wide range of studies in the field of physical chemistry. One of the problems in these studies is the instability of the results of measurements. As shown in our research, instability may result from the change of nonregistering gravitational effects related to alteration of the tidal forces upon the change of moon phases and the seasonal changes of the distance between the Earth and the Sun.
EDITORIAL: Focus on Gravitational Lensing
Jain, Bhuvnesh
2007-11-01
Gravitational lensing emerged as an observational field following the 1979 discovery of a doubly imaged quasar lensed by a foreground galaxy. In the 1980s and '90s dozens of other multiply imaged systems were observed, as well as time delay measurements, weak and strong lensing by galaxies and galaxy clusters, and the discovery of microlensing in our galaxy. The rapid pace of advances has continued into the new century. Lensing is currently one of best techniques for finding and mapping dark matter over a wide range of scales, and also addresses broader cosmological questions such as understanding the nature of dark energy. This focus issue of New Journal of Physics presents a snapshot of current research in some of the exciting areas of lensing. It provides an occasion to look back at the advances of the last decade and ahead to the potential of the coming years. Just about a decade ago, microlensing was discovered through the magnification of stars in our galaxy by invisible objects with masses between that of Jupiter and a tenth the mass of the Sun. Thus a new component of the mass of our galaxy, dubbed MACHOs, was established (though a diffuse, cold dark matter-like component is still needed to make up most of the galaxy mass). More recently, microlensing led to another exciting discovery—of extra-solar planets with masses ranging from about five times that of Earth to that of Neptune. We can expect many more planets to be discovered through ongoing surveys. Microlensing is the best technique for finding Earth mass planets, though it is not as productive overall as other methods and does not allow for follow up observations. Beyond planet hunting, microlensing has enabled us to observe previously inaccessible systems, ranging from the surfaces of other stars to the accretion disks around the black holes powering distant quasars. Galaxies and galaxy clusters at cosmological distances can produce dramatic lensing effects: multiple images of background galaxies
Gravitational waves from binary supermassive black holes missing in pulsar observations.
Shannon, R M; Ravi, V; Lentati, L T; Lasky, P D; Hobbs, G; Kerr, M; Manchester, R N; Coles, W A; Levin, Y; Bailes, M; Bhat, N D R; Burke-Spolaor, S; Dai, S; Keith, M J; Osłowski, S; Reardon, D J; van Straten, W; Toomey, L; Wang, J-B; Wen, L; Wyithe, J S B; Zhu, X-J
2015-09-25
Gravitational waves are expected to be radiated by supermassive black hole binaries formed during galaxy mergers. A stochastic superposition of gravitational waves from all such binary systems would modulate the arrival times of pulses from radio pulsars. Using observations of millisecond pulsars obtained with the Parkes radio telescope, we constrained the characteristic amplitude of this background, A(c,yr), to be <1.0 × 10(-15) with 95% confidence. This limit excludes predicted ranges for A(c,yr) from current models with 91 to 99.7% probability. We conclude that binary evolution is either stalled or dramatically accelerated by galactic-center environments and that higher-cadence and shorter-wavelength observations would be more sensitive to gravitational waves.
Gravitational waves from binary supermassive black holes missing in pulsar observations
Shannon, R M; Lentati, L T; Lasky, P D; Hobbs, G; Kerr, M; Manchester, R N; Coles, W A; Levin, Y; Bailes, M; Bhat, N D R; Burke-Spolaor, S; Dai, S; Keith, M J; Osłowski, S; Reardon, D J; van Straten, W; Toomey, L; Wang, J -B; Wen, L; Wyithe, J S B; Zhu, X -J
2015-01-01
Gravitational waves are expected to be radiated by supermassive black hole binaries formed during galaxy mergers. A stochastic superposition of gravitational waves from all such binary systems will modulate the arrival times of pulses from radio pulsars. Using observations of millisecond pulsars obtained with the Parkes radio telescope, we constrain the characteristic amplitude of this background, $A_{\\rm c,yr}$, to be < $1.0\\times10^{-15}$ with 95% confidence. This limit excludes predicted ranges for $A_{\\rm c,yr}$ from current models with 91-99.7% probability. We conclude that binary evolution is either stalled or dramatically accelerated by galactic-center environments, and that higher-cadence and shorter-wavelength observations would result in an increased sensitivity to gravitational waves.
Gravitational properties of light - The gravitational field of a laser pulse
Rätzel, Dennis; Menzel, Ralf
2015-01-01
The gravitational field of a laser pulse of finite lifetime, is investigated in the framework of linearized gravity. Although the effects are very small, they may be of fundamental physical interest. It is shown that the gravitational field of a linearly polarized light pulse is modulated as the norm of the corresponding electric field strength, while no modulations arise for circular polarization. In general, the gravitational field is independent of the polarization direction. It is shown that all physical effects are confined to spherical shells expanding with the speed of light, and that these shells are associated with the emission and absorption of the pulse. Nearby test particles at rest are attracted towards the pulse trajectory by the gravitational field due to the emission of the pulse, and they are repelled from the pulse trajectory by the gravitational field due to its absorption. Examples are given for the size of the attractive effect. It is recovered that massless test particles do not experien...
Basic Gravitational Reflexes in the Larval Frog
Cochran, Stephen L.
1996-01-01
This investigation was designed to determine how a primitive vertebrate, the bullfrog tadpole, is able to sense and process gravitational stimuli. Because of the phylogenetic similarities of the vestibular systems in all vertebrates, the understanding of the gravitational reflexes in this relatively simple vertebrate should elucidate a skeletal framework on a elementary level, upon which the more elaborate reflexes of higher vertebrates may be constructed. The purpose of this study was to understand how the nervous system of the larval amphibian processes gravitational information. This study involved predominantly electrophysiological investigations of the isolated, alert (forebrain removed) bullfrog tadpole head. The focus of these experiments is threefold: (1) to understand from whole extraocular nerve recordings the signals sent to the eye following static gravitational tilt of the head; (2) to localize neuronal centers responsible for generating these signals through reversible pharmacological ablation of these centers; and (3) to record intracellularly from neurons within these centers in order to determine the single neuron's role in the overall processing of the center. This study has provided information on the mechanisms by which a primitive vertebrate processes gravitational reflexes.
Gravitational waves from cosmic bubble collisions
Energy Technology Data Exchange (ETDEWEB)
Kim, Dong-Hoon [Ewha Womans University, Basic Science Research Institute, Seoul (Korea, Republic of); Ewha Womans University, Institute for the Early Universe, Seoul (Korea, Republic of); Lee, Bum-Hoon [Sogang University, Center for Quantum Spacetime, Seoul (Korea, Republic of); Sogang University, Department of Physics, Seoul (Korea, Republic of); Lee, Wonwoo [Sogang University, Center for Quantum Spacetime, Seoul (Korea, Republic of); Yang, Jongmann [Ewha Womans University, Basic Science Research Institute, Seoul (Korea, Republic of); Ewha Womans University, Institute for the Early Universe, Seoul (Korea, Republic of); Ewha Womans University, Department of Physics, Seoul (Korea, Republic of); Yeom, Dong-han [Sogang University, Center for Quantum Spacetime, Seoul (Korea, Republic of); Kyoto University, Yukawa Institute for Theoretical Physics, Kyoto (Japan); National Taiwan University, Leung Center for Cosmology and Particle Astrophysics, Taipei (China)
2015-03-01
Cosmic bubbles are nucleated through the quantum tunneling process. After nucleation they would expand and undergo collisions with each other. In this paper, we focus in particular on collisions of two equal-sized bubbles and compute gravitational waves emitted from the collisions. First, we study the mechanism of the collisions by means of a real scalar field and its quartic potential. Then, using this model, we compute gravitational waves from the collisions in a straightforward manner. In the quadrupole approximation, time-domain gravitational waveforms are directly obtained by integrating the energy-momentum tensors over the volume of the wave sources, where the energy-momentum tensors are expressed in terms of the scalar field, the local geometry and the potential. We present gravitational waveforms emitted during (i) the initial-to-intermediate stage of strong collisions and (ii) the final stage of weak collisions: the former is obtained numerically, in full General Relativity and the latter analytically, in the flat spacetime approximation. We gain qualitative insights into the time-domain gravitational waveforms from bubble collisions: during (i), the waveforms show the non-linearity of the collisions, characterized by a modulating frequency and cusp-like bumps, whereas during (ii), the waveforms exhibit the linearity of the collisions, featured by smooth monochromatic oscillations. (orig.)
Relic gravitational waves from quintessential inflation
Ahmad, Safia; Myrzakulov, R.; Sami, M.
2017-09-01
We study relic gravitational waves in the paradigm of quintessential inflation. In this framework, irrespective of the underlying model, inflation is followed by the kinetic regime. Thereafter, the field energy density remains subdominant before the onset of acceleration. We carry out model-independent analysis to obtain the temperature at the end of inflation and the estimate for the upper bound on the Hubble parameter to circumvent the problem due to relic gravitational waves. In this process, we use Planck 2015 data to constrain the inflationary phase. We demonstrate that the required temperature can be produced by the mechanism of instant preheating. The generic feature of the scenario includes the presence of the kinetic regime after inflation, which results in the blue spectrum of gravitational wave background at high frequencies. We discuss the prospects of detection of relic gravitational wave background in the advanced LIGO and LISA space-born gravitational wave missions. Finally, we consider a concrete model to realize the paradigm of quintessential inflation and show that inflationary as well as postinflationary evolution can be successfully described by the inflaton potential, V (ϕ )∝Exp (-λ ϕn/MPln)(n >1 ) , by suitably constraining the parameters of the model.
Testing Gravity with Gravitational Wave Source Counts
Calabrese, Erminia; Spergel, David N
2016-01-01
We show that the gravitational wave source counts distribution can test how gravitational radiation propagates on cosmological scales. This test does not require obtaining redshifts for the sources. If the signal-to-noise from a gravitational wave source is proportional to the strain then it falls as $R^{-1}$, thus we expect the source counts to follow $dN/dS \\propto S^{-4}$. However, if gravitational waves decay as they propagate or can propagate into other dimensions, then there can be deviations from this generic prediction. We consider the possibility that the signal-to-noise falls as $R^{-\\gamma}$, where $\\gamma=1$ recovers the expected predictions in a Euclidean uniformly-filled universe. We forecast the sensitivity of future observations in constraining gravitational wave physics using this method by simulating sources distributed over a finite range of signal-to-noise. We first consider the case of few objects, 7 sources, with a signal-to-noise from 8 to 24, and impose a lower limit on $\\gamma$, findi...
Metabolic adaptation of skeletal muscles to gravitational unloading
Ohira, Y.; Yasui, W.; Kariya, F.; Wakatsuki, T.; Nakamura, K.; Asakura, T.; Edgerton, V. R.
Responses of high-energy phosphates and metabolic properties to hindlimb suspension were studied in adult rats. The relative content of phosphocreatine (PCr) in the calf muscles was significantly higher in rats suspended for 10 days than in age-matched cage controls. The Pi/PCr ratio, where Pi is inorganic phosphate, in suspended muscles was less than controls. The absolute weights of soleus and medial gastrocnemius (MG) were approximately 40% less than controls. Although the % fiber distribution in MG was unchanged, the % slow fibers decreased and the % fibers which were classified as both slow and fast was increased in soleus. The activities (per unit weight or protein) of succinate dehydrogenase and lactate dehydrogenase in soleus were unchanged but those of cytochrome oxidase, β-hydroxyacyl CoA dehydrogenase, and citrate synthase were decreased following unloading. None of these enzyme activities in MG changed. However, the total levels of all enzymes in whole muscles decreased by suspension. It is suggested that shift of slow muscle toward fast type by unloading is associated with a decrease in mitochondrial biogenesis. Further, gravitational unloading affected the levels of muscle proteins differently even in the same mitochondrial enzymes. Unloading-related atrophy is prominent in red muscle or slow-twitch fiber 1, 2. Such atrophy is accompanied by a shift of contractile properties toward fast-twitch type 2-9. Further, inhibition of mitochondrial metabolism in these muscles is also reported by some studies 10-14 suggesting a lowered mitochondrial biogenesis, although results from some studies do not necessarily agree 1, 7, 15. However, the precise mechanism responsible for such alterations of muscle properties in response to gravitational unloading is unclear. On the contrary, mitochondrial biogenesis, suggested by mitochondrial enzyme activities and/or mass, is stimulated in muscles with depleted high-energy phosphates by cold exposure 16 and/or by feeding
Trapping light by mimicking gravitational lensing
Sheng, C; Wang, Y; Zhu, S N; Genov, D A
2013-01-01
One of the most fascinating predictions of the theory of general relativity is the effect of gravitational lensing, the bending of light in close proximity to massive stellar objects. Recently, artificial optical materials have been proposed to study the various aspects of curved spacetimes, including light trapping and Hawking's radiation. However, the development of experimental toy models that simulate gravitational lensing in curved spacetimes remains a challenge, especially for visible light. Here, by utilizing a microstructured optical waveguide around a microsphere, we propose to mimic curved spacetimes caused by gravity, with high precision. We experimentally demonstrate both far-field gravitational lensing effects and the critical phenomenon in close proximity to the photon sphere of astrophysical objects under hydrostatic equilibrium. The proposed microstructured waveguide can be used as an omnidirectional absorber, with potential light harvesting and microcavity applications.
Effective gravitational fields in transplackian scattering
Betti, Luca S G
2014-01-01
After a short introduction to the general Quantum Gravity problem, we compare a result from the S-matrix description of gravitational interaction due to Amati, Ciafaloni and Veneziano (ACV) with classical General Relativity results. In Chapter 1, we introduce the metric produced by a massless particle moving at the speed of light. In Chapter 2, we review ACV's semiclassical approach to gravitation and show some of its result. In Chapter 3, we detail the computation of gravitational field expectation values in a high-energy scattering process, following ACV's prescriptions. In Chapter 4, we analyze our results. The main feature is that the leading contributions to the metric computed in terms of the Feynman diagrams deriving from ACV's model perfectly reproduce classical results.
On the gravitational seesaw and light bending
Accioly, Antonio; Shapiro, Ilya L
2016-01-01
Local gravitational theories with more than four derivatives are superrenormalizable, and also may be unitary in the Lee-Wick sense. It makes sense to study low-energy properties of these theories, e.g., identify observables which might be useful for experimental detection of higher derivatives. Using an analogy with neutrino Physics, we explore the possibility of a gravitational seesaw mechanism, in which several dimensional parameters of the same order of magnitude produce a hierarchy in the masses of propagating particles and make a relatively light degree of freedom detectable by frequency dependence in the gravitational light bending. It turns out that such a seesaw mechanism in the six- and more-derivative theories is unable to reduce the lightest mass more than in the simplest four-derivative model. Adding more derivatives can only make heavier masses even larger. This fact may be favorable for protecting the theory from instabilities, but makes experimental detection of higher derivatives more difficu...
Gravitational and Inertial Mass of Casimir Energy
Milton, Kimball A; Parashar, Prachi; Romeo, August; Shajesh, K V; Wagner, Jeffrey A
2007-01-01
It has been demonstrated, using variational methods, that quantum vacuum energy gravitates according to the equivalence principle, at least for the finite Casimir energies associated with perfectly conducting parallel plates. This conclusion holds independently of the orientation of the plates. We review these arguments and add further support to this conclusion by considering parallel semitransparent plates, that is, $\\delta$-function potentials, acting on a massless scalar field, in a spacetime defined by Rindler coordinates. We calculate the force on systems consisting of one or two such plates undergoing acceleration perpendicular to the plates. In the limit of small acceleration we recover (via the equivalence principle) the situation of weak gravity, and find that the gravitational force on the system is just $M\\mathbf{g}$, where $\\mathbf{g}$ is the gravitational acceleration and $M$ is the total mass of the system, consisting of the mass of the plates renormalized by the Casimir energy of each plate se...
Tests of gravitational symmetries with radio pulsars
Shao, LiJing; Wex, Norbert
2016-09-01
Symmetries play important roles in modern theories of physical laws. In this paper, we review several experimental tests of important symmetries associated with the gravitational interaction, including the universality of free fall for self-gravitating bodies, time-shift symmetry in the gravitational constant, local position invariance and local Lorentz invariance of gravity, and spacetime translational symmetries. Recent experimental explorations for post-Newtonian gravity are discussed, of which, those from pulsar astronomy are highlighted. All of these tests, of very different aspects of gravity theories, at very different length scales, favor to very high precision the predictions of the strong equivalence principle (SEP) and, in particular, general relativity which embodies SEP completely. As the founding principles of gravity, these symmetries are motivated to be promoted to even stricter tests in future.
Spin in an arbitrary gravitational field
Obukhov, Yuri N; Teryaev, Oleg V
2013-01-01
We study the quantum mechanics of a Dirac fermion on a curved spacetime manifold. The metric of the spacetime is completely arbitrary, allowing for the discussion of all possible inertial and gravitational field configurations. In this framework, we find the Hermitian Dirac Hamiltonian for an arbitrary classical external field (including the gravitational and electromagnetic ones). In order to discuss the physical content of the quantum-mechanical model, we further apply the Foldy-Wouthuysen transformation, and derive the quantum equations of motion for the spin and position operators. We analyse the semiclassical limit of these equations and compare the results with the dynamics of a classical particle with spin in the framework of the standard Mathisson-Papapetrou theory and in the classical canonical theory. The comparison of the quantum mechanical and classical equations of motion of a spinning particle in an arbitrary gravitational field shows their complete agreement.
Gravitational scaling in Beijing Subway Network
Leng, Biao; Wang, Jianyuan; Xiong, Zhang; Havlin, Shlomo; Li, Daqing
2016-01-01
Recently, with the availability of various traffic datasets, human mobility has been studied in different contexts. Researchers attempt to understand the collective behaviors of human movement with respect to the spatio-temporal distribution in traffic dynamics, from which a gravitational scaling law characterizing the relation between the traffic flow, population and distance has been found. However, most studies focus on the integrated properties of gravitational scaling, neglecting its dynamical evolution during different hours of a day. Investigating the hourly traffic flow data of Beijing subway network, based on the hop-count distance of passengers, we find that the scaling exponent of the gravitational law is smaller in Beijing subway system compared to that reported in Seoul subway system. This means that traffic demand in Beijing is much stronger and less sensitive to the travel distance. Furthermore, we analyzed the temporal evolution of the scaling exponents in weekdays and weekends. Our findings m...
Improving LLR Tests of Gravitational Theory
Williams, J G; Williams, James G.; Turyshev, Slava G.; Jr, Thomas W. Murphy
2003-01-01
Accurate analysis of precision ranges to the Moon has provided several tests of gravitational theory including the Equivalence Principle, geodetic precession, parameterized post-Newtonian (PPN) parameters $\\gamma$ and $\\beta$, and the constancy of the gravitational constant {\\it G}. Since the beginning of the experiment in 1969, the uncertainties of these tests have decreased considerably as data accuracies have improved and data time span has lengthened. We are exploring the modeling improvements necessary to proceed from cm to mm range accuracies enabled by the new Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) currently under development in New Mexico. This facility will be able to make a significant contribution to the solar system tests of fundamental and gravitational physics. In particular, the Weak and Strong Equivalence Principle tests would have a sensitivity approaching 10$^{-14}$, yielding sensitivity for the SEP violation parameter $\\eta$ of $\\sim 3\\times 10^{-5}$, $v^2/c^2$ gene...
Gravitational positive energy theorems from information inequalities
Lashkari, Nima; Lin, Jennifer; Ooguri, Hirosi; Stoica, Bogdan; Van Raamsdonk, Mark
2016-12-01
In this paper we argue that classical asymptotically anti-de Sitter spacetimes that arise as states in consistent ultraviolet completions of Einstein gravity coupled to matter must satisfy an infinite family of positive energy conditions. To each ball-shaped spatial region B of the boundary spacetime we can associate a bulk spatial region Σ between B and the bulk extremal surface \\Btilde with the same boundary as B. We show that there exists a natural notion of a gravitational energy for every such region that is non-negative, and non-increasing as one makes the region smaller. The results follow from identifying this gravitational energy with a quantum relative entropy in the associated dual conformal field theory state. The positivity and monotonicity properties of the gravitational energy are implied by the positivity and monotonicity of relative entropy, which holds universally in all quantum systems.
Gravitational Lensing Characteristics of the Transparent Sun
Patla, Bijunath
2007-01-01
The transparent Sun is modeled as a spherically symmetric and centrally condensed gravitational lens using recent Standard Solar Model (SSM) data. The Sun's minimum focal length is computed to a refined accuracy of 23.5 +/- 0.1 AU, just beyond the orbit of Uranus. The Sun creates a single image of a distant point source visible to observers inside this minimum focal length and to observers sufficiently removed from the line connecting the source through the Sun's center. Regions of space are mapped where three images of a distant point source are created, along with their associated magnifications. Solar caustics, critical curves, and Einstein rings are computed and discussed. Extremely high gravitational lens magnifications exist for observers situated so that an angularly small, unlensed source appears near a three-image caustic. Types of radiations that might undergo significant solar lens magnifications as they can traverse the core of the Sun, including neutrinos and gravitational radiation, are discusse...
General relativity and gravitation a centennial perspective
Berger, Beverly K; Isenberg, James; MacCallum, Malcolm
2015-01-01
Explore spectacular advances in cosmology, relativistic astrophysics, gravitational wave science, mathematics, computational science, and the interface of gravitation and quantum physics with this unique celebration of the centennial of Einstein's discovery of general relativity. Twelve comprehensive and in-depth reviews, written by a team of world-leading international experts, together present an up-to-date overview of key topics at the frontiers of these areas, with particular emphasis on the significant developments of the last three decades. Interconnections with other fields of research are also highlighted, making this an invaluable resource for both new and experienced researchers. Commissioned by the International Society on General Relativity and Gravitation, and including accessible introductions to cutting-edge topics, ample references to original research papers, and informative colour figures, this is a definitive reference for researchers and graduate students in cosmology, relativity, and grav...
Orbital Motion During Gravitational Lensing Events
Di Stefano, Rosanne
2014-01-01
Gravitational lensing events provide unique opportunities to discover and study planetary systems and binaries. Here we build on previous work to explore the role that orbital motion can play in both identifying and learning more about multiple-mass systems that serve as gravitational lenses. We find that a significant fraction of planet-lens and binary-lens light curves are influenced by orbital motion. Furthermore, the effects of orbital motion extend the range of binaries for which lens multiplicity can be discovered and studied. Orbital motion will play an increasingly important role as observations with sensitive photometry, such as those made by the space missions Kepler, Transiting Exoplanet Survey Satellite, (TESS), and WFIRST discover gravitational lensing events. Similarly, the excellent astrometric measurements made possible by GAIA will allow it to study the effects of orbital motion. Frequent observations, such as those made possible with the Korean Microlensing Telescope Network, KMTNet, will al...
Electromagnetic and Gravitational Waves: the Third Dimension
Marsh, Gerald E
2011-01-01
Plane electromagnetic and gravitational waves interact with particles in such a way as to cause them to oscillate not only in the transverse direction but also along the direction of propagation. The electromagnetic case is usually shown by use of the Hamilton-Jacobi equation and the gravitational by a transformation to a local inertial frame. Here, the covariant Lorentz force equation and the second order equation of geodesic deviation followed by the introduction of a local inertial frame are respectively used. It is often said that there is an analogy between the motion of charged particles in the field of an electromagnetic wave and the motion of test particles in the field of a gravitational wave. This analogy is examined and found to be rather limited. It is also shown that a simple special relativistic relation leads to an integral of the motion, characteristic of plane waves, that is satisfied in both cases.
Gravitational wave asteroseismology with protoneutron stars
Sotani, Hajime
2016-01-01
We examine the time evolution of the frequencies of the gravitational wave after the bounce within the framework of relativistic linear perturbation theory using the results of one dimensional numerical simulations of core-collapse supernovae. Protoneutron star models are constructed in such a way that the mass and radius of protoneutron star become equivalent to the results obtained from the numerical simulations. Then, we find that the frequencies of gravitational waves radiating from protoneutron stars strongly depend on the mass and radius of protoneutron stars, but almost independently of the profiles of electron fraction and entropy per baryon inside the star. Additionally, we find that the frequencies of gravitational waves can be characterized by the square root of the average density of protoneutron star irrespectively the progenitor models, which are completely different from the empirical formula for cold neutron stars. The dependence of the spectra on the mass and radius is different from that of ...
Do gravitational waves travel at light velocity?
Energy Technology Data Exchange (ETDEWEB)
Novello, M.; De Lorenci, V.A. [Laboratorio de Cosmologia e Fisica Experimental de Altas Energias, Centro Brasileiro de Pesquisas Fisicas, Rua Dr. Xavier Sigaud, 150, Urca, Rio de Janeiro CEP 22290-180-RJ (Brazil); de Freitas, L.R. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Ilha do Fundao-CT-Bloco A, Rio de Janeiro-RJ (Brazil)
1997-02-01
We extend the standard Feynman{endash}Deser approach of field theoretical derivation of Einstein{close_quote}s gravitational theory. We show that it is possible to obtain a theory that incorporates a great part of general relativity (GR) and can be interpreted in the standard geometrical way like GR, as far as the interaction of matter to gravity is concerned. The most important distinction of the new theory concerns the gravity-to-gravity interaction. This theory satisfies all standard tests of gravity and leads to new predictions about gravitational propagation. Since there is a strong expectation that the detection of gravitational waves will occur in the near future, the question of which theory describes nature better will probably be settled soon. {copyright} 1997 Academic Press, Inc.
Summary of session C9: experimental gravitation
Lämmerzahl, Claus; Müller, Jürgen
2014-05-01
General relativity (GR) is based on the Universality of Free Fall, the Universality of the Gravitational Redshift, and Local Lorentz Invariance, alltogether called the Einstein Equivalence principle. This implies that gravity has to be described by a metrical theory. Such theories in general give rise to the standard effects like perihelion shift, light deflection, gravitational time delay, Lense-Thirring effect, and the Schiff effect. Only if the underlying theory is Einstein's GR we have certain values for these effects. GR in turn predicts the existence, certain properties, and a particular dynamics of gravitational waves, black holes, binary systems, etc. which are also subject to experimental/observational proof. This includes practical applications in clock synchronization, positioning, navigation and geodesy.
Bigravitons as dark matter and gravitational waves
Aoki, Katsuki
2016-01-01
We consider the possibility that the massive graviton is a viable candidate of dark matter in the context of bimetric gravity. We first derive the energy-momentum tensor of the massive graviton and show that it indeed behaves as that of dark matter fluid. We then discuss a production mechanism and the present abundance of massive gravitons as dark matter. Since the metric to which ordinary matter fields couple is a linear combination of the two mass eigenstates of bigravity, production of massive gravitons, i.e. the dark matter particles, is inevitably accompanied by generation of massless gravitons, i.e. the gravitational waves. Therefore, in this scenario some information about dark matter in our universe is encoded in gravitational waves. For instance, if LIGO detects gravitational waves generated by the preheating after inflation then the massive graviton with the mass of $\\sim 0.01$ GeV is a candidate of the dark matter.
Tests of Gravitational Symmetries with Radio Pulsars
Shao, Lijing
2016-01-01
Symmetries play important roles in modern theories of physical laws. In this paper, we review several experimental tests of important symmetries associated with the gravitational interaction, including the universality of free fall for self-gravitating bodies, time-shift symmetry in the gravitational constant, local position invariance and local Lorentz invariance of gravity, and spacetime translational symmetries. Recent experimental explorations for post-Newtonian gravity are discussed, of which, those from pulsar astronomy are highlighted. All of these tests, of very different aspects of gravity theories, at very different length scales, favor to very high precision the predictions of the strong equivalence principle (SEP) and, in particular, general relativity which embodies SEP completely. As the founding principles of gravity, these symmetries are motivated to be promoted to even stricter tests in future.
Cosmic Time Variation of the Gravitational Constant
Tomaschitz, R
2000-01-01
A pre-relativistic cosmological approach to electromagnetism and gravitation is explored that leads to a cosmic time variation of the fundamental constants. Space itself is supposed to have physical substance, which manifests by its permeability. The scale factors of the permeability tensor induce a time variation of the fundamental constants. Atomic radii, periods, and energy levels scale in cosmic time, which results in dispersionless redshifts without invoking a space expansion. Hubble constant and deceleration parameter are reviewed in this context. The time variation of the gravitational constant at the present epoch can be expressed in terms of these quantities. This provides a completely new way to restrain the deceleration parameter from laboratory bounds on the time variation of the gravitational constant. This variation also affects the redshift dependence of angular diameters and the surface brightness, and we study in some detail the redshift scaling of the linear sizes of radio sources. The effec...
Gravitational perturbations of the Higgs field
Albareti, Franco D; Prada, Francisco
2016-01-01
We study the possible effects of classical gravitational fields on the Higgs vacuum expectation value through the modifications induced in the one-loop effective potential. We concentrate our study on the Higgs self-interactions contribution in a perturbed FRW background. For weak and slowly-varying gravitational fields, a complete set of mode solutions for the Klein-Gordon equation is obtained to leading order in the adiabatic approximation. The mode integrations are calculated using standard dimensional regularization techniques. As expected, the regularized effective potential contains the same divergences as in flat space-time, which can be renormalized without the need of additional counterterms. However, we find new finite non-local contributions which depend on the gravitational potentials, and introduce an explicit space-time dependence on the Higgs potential coefficients. Being finite, the new terms are free of renormalization ambiguities. Inhomogeneities in the effective potential translate into per...
Gravitational Waves- a new window to Cosmos
Prasanna, A R
2016-01-01
With the detection of Gravitational waves just about an year ago Einstein`s general theory of relativity- a space-time theory of gravity, got established on a firmer footing than any other theory in physics. Gravitational waves are just propagating disturbances in the gravitational field of extremely strong sources caused by some catastrophic event associated with cosmic bodies, like binary black hole coalescence, or neutron star mergers. As these events happen very far away in cosmos, and the signal strength would be extremely weak, it requires extraordinary detection and analysis technology to observe an event on earth. Luckily the joint collaboration LIGO-VIRGO, have so far detected two events in September and December of 2015 during their analysis of observations made with the laser interferometers over the last few observing sessions. The talk will give a brief theoretical sketch of the analysis required for describing the waves resulting from mass motion in the realm of general relativity, and point out...
On Gravitational Entropy of de Sitter Universe
Directory of Open Access Journals (Sweden)
S. C. Ulhoa
2016-01-01
Full Text Available The paper deals with the calculation of the gravitational entropy in the context of teleparallel gravity for de Sitter space-time. In such a theory it is possible to define gravitational energy and pressure; thus we use those expressions to construct the gravitational entropy. We use the temperature as a function of the cosmological constant and write the first law of thermodynamics from which we obtain the entropy. In the limit Λ≪1 we find that the entropy is proportional to volume, for a specific temperature’s choice; we find that ΔS≥0 as well. We also identify a phase transition in de Sitter space-time by analyzing the specific heat.
Gravitational analogue of the Witten effect
Energy Technology Data Exchange (ETDEWEB)
Foda, O. (International Centre for Theoretical Physics, Trieste (Italy))
1985-07-22
In the presence of massive fermions, and assuming a non-vanishing theta-parameter as the only source of CP violation, the Witten effect (a shift in the electric charge of a magnetic monopole due to CP non-conservation) is shown to follow from an anomalous chiral commutator. Next, given the gravitational contribution to the chiral anomaly, the corresponding anomalous commutator for Dirac fermion currents in a gravitational background is derived. From that, we infer the equivalence of a thetaR tildeR term in the lagrangian to a shift in the mass parameter of the NUT metric, in proportion to theta. This is interpreted as the gravitational analogue of the Witten effect. Its relevance to certain Kaluza-Klein monopoles is briefly discussed.
Gravitational Radiation from Massless Particle Collisions
Gruzinov, Andrei
2016-05-17
We compute classical gravitational bremsstrahlung from the gravitational scattering of two massless particles at leading order in the (center of mass) deflection angle $\\theta\\sim 8 G E/b \\ll 1$. The calculation, although non-perturbative in the gravitational constant, is surprisingly simple and yields explicit formulae --in terms of multidimensional integrals-- for the frequency and angular distribution of the radiation. In the range $ b^{-1} (GE)^{-1}$ the radiation is confined to cones of angular size of order $\\theta (GE\\omega)^{-1/2}$ resulting in a scale-invariant ($d\\omega/\\omega$) spectrum. The total efficiency in GW production is dominated by this "high frequency" region and is formally logarithmically divergent in the UV. If the spectrum is cutoff at the limit of validity of our approximations ($ GE \\omega \\sim \\theta^{-2}$), the fraction of incoming energy radiated away turns out to be $\\frac{1}{\\pi} \\theta ^2 \\log \\theta^{-2}$ at leading logarithmic accuracy.
Space Based Gravitational Wave Observatories (SGOs)
Livas, Jeff
2014-01-01
Space-based Gravitational-wave Observatories (SGOs) will enable the systematic study of the frequency band from 0.0001 - 1 Hz of gravitational waves, where a rich array of astrophysical sources is expected. ESA has selected The Gravitational Universe as the science theme for the L3 mission opportunity with a nominal launch date in 2034. This will be at a minimum 15 years after ground-based detectors and pulsar timing arrays announce their first detections and at least 18 years after the LISA Pathfinder Mission will have demonstrated key technologies in a dedicated space mission. It is therefore important to develop mission concepts that can take advantage of the momentum in the field and the investment in both technology development and a precision measurement community on a more near-term timescale than the L3 opportunity. This talk will discuss a mission concept based on the LISA baseline that resulted from a recent mission architecture study.
Summary of workshop on gravitational radiation
Energy Technology Data Exchange (ETDEWEB)
Amaldi, E.
1980-01-01
The detection of medium frequency gravitational radiation (GR) using resonant antennas and broadband laser interferometers is discussed. The separation of the signal from the total noise is considered along with the first-order predictive algorithm and the importance of high Q. A prototype interferometer showed laser beam lateral displacements in the kHz region. Scattered light was found disturbing, most critically in connection with the frequency jitter in the case of long effective baselines. Also discussed are the use of Doppler tracking of interplanetary spacecraft to reveal very low frequency GR, the noise in the spacecraft tracking network itself, an electromagnetic detector for gravitational waves, and the influence of a weak gravitational wave on a bound system of two point masses.
Self-gravitating Interferometry and Intrinsic Decoherence
Gooding, Cisco
2014-01-01
To investigate the possibility that intrinsic gravitational decoherence can be theoretically demonstrated within canonical quantum gravity, we develop a model of a self-gravitating interferometer. We search for evidence in the resulting interference pattern that would indicate coherence is fundamentally limited due to general relativistic effects. To eliminate the occurence of gravitational waves, we work in spherical symmetry, and construct the "beam" of the interferometer out of WKB states for an infinitesimally thin shell of matter. For internal consistency, we encode information about the beam optics within the dynamics of the shell itself, by arranging an ideal fluid on the surface of the shell with an equation of state that enforces beam-splitting and reflections. We then determine sufficient conditions for (interferometric) coherence to be fully present even after general relativistic corrections are introduced, test whether or not they can be satisfied, and remark on the implications of the results.
The dawn of gravitational wave astronomy
CERN. Geneva
2016-01-01
On Sep 14 2015, gravitational waves were for the first time detected directly. This observation by the LIGO interferometric detectors marks the dawn of a new era in our observational study of the cosmos as a qualitatively new window to its exploration has been opened. This talk reviews some of the fundamental concepts of gravitational waves and the methodology employed for their observation. The first event, dubbed GW150914, and the properties of its source, as inferred from the observation, will be discussed. The talk concludes with a selected set of the most important topics where we expect gravitational-wave observations to deepen and either challenge or confirm our present understanding of the laws and the history of our universe.
Gravitationally bound BCS state as dark matter
Alexander, Stephon
2016-01-01
We explore the possibility that fermionic dark matter undergoes a BCS transition to form a superfluid. This requires an attractive interaction between fermions and we describe a possible source of this interaction induced by torsion. We describe the gravitating fermion system with the Bogoliubov-de Gennes formalism in the local density approximation. We solve the Poisson equation along with the equations for the density and gap energy of the fermions to find a self-gravitating, superfluid solution for dark matter halos. In order to produce halos the size of dwarf galaxies, we require a particle mass of $\\sim 200\\mathrm{eV}$. We find a maximum attractive coupling strength before the halo becomes unstable. If dark matter halos do have a superfluid component, this raises the possibility that they contain vortex lines which may be detectable via gravitational lensing.
Generalized Gravitational Entropy from Fermion Fields
Huang, Wung-Hong
2016-01-01
The generalized gravitational entropy proposed in recent by Lewkowycz and Maldacena [1] is extended to the system of Fermion fields. We first find the regular wave solution of Fermion field which has arbitrary frequency and mode number on the BTZ spacetime, and then use it to calculate the exact gravitational entropy. The results show that there is a threshold frequency below which the Fermion fields could not contribute the generalized gravitational entropy. Also, the static and zero-mode solutions have not entropy, contrast to that in scalar field. We also found that the entropy of the static scalar fields and non-static fermions is an increasing function of mode number and, after arriving the maximum entropy it becomes a deceasing function and is derived to the asymptotic value.
Legreneur, Pierre; Bels, Vincent; Monteil, Karine; Laurin, Michel
2013-05-01
In this paper, we demonstrated that interarticular coordination of terrestrial tetrapods emerges from an environment highly constrained by friction and the gravitational field. We briefly review recent works on the jumping behavior in squamates, lemurs and amphibians. We then explore previously published work as well as some unpublished experimental data on human jumping. Finally, we end by inferring locomotion in some of the first limbed vertebrates using a simulation procedure. All these data show that despite changes in shape, structure, and motor controls of taxa, the same spatio-temporal sequence of joint displacements always occurs when the movement is executed in a terrestrial environment. Comparison with aquatic locomotion argues for the hypothesis that this pattern emerged in early terrestrial tetrapods as a response to the gravitational constraint and the terrestrial frictional environment.
Gravity's shadow the search for gravitational waves
Collins, Harry
2004-01-01
According to the theory of relativity, we are constantly bathed in gravitational radiation. When stars explode or collide, a portion of their mass becomes energy that disturbs the very fabric of the space-time continuum like ripples in a pond. But proving the existence of these waves has been difficult; the cosmic shudders are so weak that only the most sensitive instruments can be expected to observe them directly. Fifteen times during the last thirty years scientists have claimed to have detected gravitational waves, but so far none of those claims have survived the scrutiny of the scie
Self-gravitating systems in Extended Gravity
Stabile, A
2014-01-01
Starting from the weak field limit, we discuss astrophysical applications of Extended Theories of Gravity where higher order curvature invariants and scalar fields are considered by generalizing the Hilbert-Einstein action linear in the Ricci curvature scalar $R$. Results are compared to General Relativity in the hypothesis that Dark Matter contributions to the dynamics can be neglected thanks to modified gravity. In particular, we consider stellar hydrostatic equilibrium, galactic rotation curves, and gravitational lensing. Finally, we discuss the weak field limit in the Jordan and Einstein frames pointing out how effective quantities, as gravitational potentials, transform from one frame to the other and the interpretation of results can completely change accordingly.
Gravitational Waves and Multi-Messenger Astronomy
Centrella, Joan M.
2010-01-01
Gravitational waves are produced by a wide variety of sources throughout the cosmos, including the mergers of black hole and neutron star binaries/compact objects spiraling into central black holes in galactic nuclei, close compact binaries/and phase transitions and quantum fluctuations in the early universe. Observing these signals can bring new, and often very precise, information about their sources across vast stretches of cosmic time. In this talk we will focus on thee opening of this gravitational-wave window on the universe, highlighting new opportunities for discovery and multi-messenger astronomy.
Gravitational waves in a de Sitter universe
Bishop, Nigel T
2015-01-01
The construction of exact linearized solutions to the Einstein equations within the Bondi-Sachs formalism is extended to the case of linearization about de Sitter spacetime. The gravitational wave field measured by distant observers is constructed, leading to a determination of the energy measured by such observers. It is found that gravitational wave energy conservation does not normally apply to inertial observers, but that it can be formulated for a class of accelerated observers, i.e. with worldlines that are timelike but not geodesic.
Photon gravitational defection in Lorentz violating scenarios
Accioly, Antonio; Helayël-Neto, José
2016-01-01
The effect of Lorentz symmetry violation in the phenomenon of photon gravitational bending, is investigated. Using a semiclassical approach, where the photon is described by the Carrol-Field-Jackiw (CFJ) electrodynamics which is responsible for implementing the Lorentz symmetry violation, the gravitational deflection angle related to the CFJ photon is computed. As expected, this bending angle experiences a deviation from the usual Einstein result and the latter is recovered in the appropriate limit. A comparison between the theoretical prediction and the experimental results allows to conclude that no trace of Lorentz symmetry breaking is found provided the components of the background vector field are $\\lesssim 10^{-8}$ eV.
The response of interferometric gravitational wave detectors
Finn, Lee Samuel
2008-01-01
The standard derivation of the response of interferometric gravitational wave detectors makes a series of erroneous approximations regarding the coordinate trajectory of the light and the parameterization of the null geodesic it travels along. These errors appear to have remained unrecognized for at least thirty five years. We provide, in full detail, a correct derivation of the response of a single-bounce Michelson interferometer to gravitational waves, compare it to the "standard", but incorrect, derivation, and show where the earlier mistakes were made. By a fortuitous set of circumstances, not generally so, the final result is the same.
Gravitational biology on the space station
Keefe, J. R.; Krikorian, A. D.
1983-01-01
The current status of gravitational biology is summarized, future areas of required basic research in earth-based and spaceflight projects are presented, and potential applications of gravitational biology on a space station are demonstrated. Topics covered include vertebrate reproduction, prenatal/postnatal development, a review of plant space experiments, the facilities needed for growing plants, gravimorphogenesis, thigmomorphogenesis, centrifuges, maintaining a vivarium, tissue culture, and artificial human organ generation. It is proposed that space stations carrying out these types of long-term research be called the National Space Research Facility.
Gravitational waves induced by spinor fields
Feng, Kaixi
2015-01-01
In realistic model-building, spinor fields with various masses are present. During inflation, spinor field may induce gravitational waves as a second order effect. In this paper, we calculate the contribution of single massive spinor field to the power spectrum of primordial gravitational wave by using retarded Green propagator. We find that the correction is scale-invariant and of order $H^4/M_P^4$ for arbitrary spinor mass $m_{\\psi}$. Additionally, we also observe that when $m_\\psi \\gtrsim H$, the dependence of correction on $m_\\psi/H$ is nontrivial.
Energy-Momentum Distribution of Gravitational Waves
Institute of Scientific and Technical Information of China (English)
M. Sharif; Kanwal Nazir
2008-01-01
This paper has been addressed to the well-known problem of energy in gravitational waves.We have investigated the energy of cylindrical gravitational waves in the context of General Relativity and teleparallel theory of gravity.For this purpose,the prescriptions of Einstein,Landau-Lifshitz,Bergmann-Thomson,and Moller are used in both the theories.It is shown that these energy-momentum complexes do not provide equivalent results in the two theories.However,these turn out to be constant for all the prescriptions except Moller in both the theories at large distances.
Gravitational Baryogenesis in Running Vacuum models
Oikonomou, V K; Nunes, Rafael C
2016-01-01
We study the gravitational baryogenesis mechanism for generating baryon asymmetry in the context of running vacuum models. Regardless if these models can produce a viable cosmological evolution, we demonstrate that they produce a non-zero baryon-to-entropy ratio even if the Universe is filled with conformal matter. This is a sound difference between the running vacuum gravitational baryogenesis and the Einstein-Hilbert one, since in the latter case, the predicted baryon-to-entropy ratio is zero. We consider two running vacuum models and show that the resulting baryon-to-entropy ratio is compatible with the observational data.
Leading gravitational corrections and a unified universe
DEFF Research Database (Denmark)
Codello, Alessandro; Jain, Rajeev Kumar
2016-01-01
Leading order gravitational corrections to the Einstein-Hilbert action can lead to a consistent picture of the universe by unifying the epochs of inflation and dark energy in a single framework. While the leading local correction induces an inflationary phase in the early universe, the leading...... nonlocal term leads to an accelerated expansion of the universe at the present epoch. We argue that both the leading UV and IR terms can be obtained within the framework of a covariant effective field theory of gravity. The perturbative gravitational corrections therefore provide a fundamental basis...
Gravitational self-localization in quantum measurement
Geszti, T
2004-01-01
Within Newton-Schr\\"odinger quantum mechanics which allows gravitational self-interaction, it is shown that a no-split no-collapse measurement scenario is possible. A macroscopic pointer moves at low acceleration, controlled by the Ehrenfest-averaged force acting on it. That makes classicality self-sustaining, resolves Everett's paradox, and outlines a way to spontaneous emergence of quantum randomness. Numerical estimates indicate that enhanced short-range gravitational forces are needed for the scenario to work. The scheme fails to explain quantum nonlocality, including two-detector anticorrelations, which points towards the need of a nonlocal modification of the Newton-Schr\\"odinger coupling scheme.
Matter and gravitons in the gravitational collapse
Casadio, Roberto; Giusti, Andrea
2016-01-01
We consider the effects of gravitons in the collapse of baryonic matter that forms a black hole. We first note that the effective number of (soft off-shell) gravitons that account for the (negative) Newtonian potential energy generated by the baryons is conserved and always in agreement with the area law of black holes. Moreover, their (positive) interaction energy reproduces the expected post-Newtonian correction and becomes of the order of the total ADM mass of the system when the size of the collapsing object approaches its gravitational radius. This supports a scenario in which the gravitational collapse of regular baryonic matter produces a corpuscular black hole without singularity.
Light clocks in strong gravitational fields
Punzi, Raffaele; Wohlfarth, Mattias N R
2009-01-01
We argue that the time measured by a light clock operating with photons rather than classical light requires a refinement of the standard clock postulate in general relativity. In the presence of a gravitational field, already the one-loop quantum corrections to classical Maxwell theory affect light propagation and the construction of observers' frames of reference. Carefully taking into account these kinematic effects, a concise geometric expression for the time shown by a light clock is obtained. This result has far-reaching implications for physics in strong gravitational fields.
Quantum metrology for gravitational wave astronomy.
Schnabel, Roman; Mavalvala, Nergis; McClelland, David E; Lam, Ping K
2010-11-16
Einstein's general theory of relativity predicts that accelerating mass distributions produce gravitational radiation, analogous to electromagnetic radiation from accelerating charges. These gravitational waves (GWs) have not been directly detected to date, but are expected to open a new window to the Universe once the detectors, kilometre-scale laser interferometers measuring the distance between quasi-free-falling mirrors, have achieved adequate sensitivity. Recent advances in quantum metrology may now contribute to provide the required sensitivity boost. The so-called squeezed light is able to quantum entangle the high-power laser fields in the interferometer arms, and could have a key role in the realization of GW astronomy.
The memory effect for plane gravitational waves
Zhang, P.-M.; Duval, C.; Gibbons, G. W.; Horvathy, P. A.
2017-09-01
We give an account of the gravitational memory effect in the presence of the exact plane wave solution of Einstein's vacuum equations. This allows an elementary but exact description of the soft gravitons and how their presence may be detected by observing the motion of freely falling particles. The theorem of Bondi and Pirani on caustics (for which we present a new proof) implies that the asymptotic relative velocity is constant but not zero, in contradiction with the permanent displacement claimed by Zel'dovich and Polnarev. A non-vanishing asymptotic relative velocity might be used to detect gravitational waves through the ;velocity memory effect;, considered by Braginsky, Thorne, Grishchuk, and Polnarev.
On the quantum corrected gravitational collapse
Energy Technology Data Exchange (ETDEWEB)
Torres, Ramón, E-mail: ramon.torres-herrera@upc.edu; Fayos, Francesc, E-mail: f.fayos@upc.edu
2015-07-30
Based on a previously found general class of quantum improved exact solutions composed of non-interacting (dust) particles, we model the gravitational collapse of stars. As the modeled star collapses a closed apparent 3-horizon is generated due to the consideration of quantum effects. The effect of the subsequent emission of Hawking radiation related to this horizon is taken into consideration. Our computations lead us to argue that a total evaporation could be reached. The inferred global picture of the spacetime corresponding to gravitational collapse is devoid of both event horizons and shell-focusing singularities. As a consequence, there is no information paradox and no need of firewalls.
On the quantum corrected gravitational collapse
Directory of Open Access Journals (Sweden)
Ramón Torres
2015-07-01
Full Text Available Based on a previously found general class of quantum improved exact solutions composed of non-interacting (dust particles, we model the gravitational collapse of stars. As the modeled star collapses a closed apparent 3-horizon is generated due to the consideration of quantum effects. The effect of the subsequent emission of Hawking radiation related to this horizon is taken into consideration. Our computations lead us to argue that a total evaporation could be reached. The inferred global picture of the spacetime corresponding to gravitational collapse is devoid of both event horizons and shell-focusing singularities. As a consequence, there is no information paradox and no need of firewalls.
SL(2,C) Gauge Theory of Gravitation and the Quantization of the Gravitational Field
Carmeli, M; Carmeli, Moshe; Malin, Shimon
1998-01-01
A new approach to quantize the gravitational field is presented. It is based on the observation that the quantum character of matter becomes more significant as one gets closer to the big bang. As the metric loses its meaning, it makes sense to consider Schrodinger's three generic types of manifolds - unconnected differentiable, affinely connected, and metrically connected - as a temporal sequence following the big bang. Hence one should quantize the gravitational field on general differentiable manifolds or on affinely connected manifolds. The SL(2,C) gauge theory of gravitation is employed to explore this possibility. Within this framework, the quantization itself may well be canonical.