Silva, P J; Dudal, D; Bicudo, P; Cardoso, N
2016-01-01
The gluon propagator is investigated at finite temperature via lattice simulations. In particular, we discuss its interpretation as a massive-type bosonic propagator. Moreover, we compute the corresponding spectral density and study the violation of spectral positivity. Finally, we explore the dependence of the gluon propagator on the phase of the Polyakov loop.
Confinement at Finite Temperature
Cardoso, Nuno; Bicudo, Pedro; Cardoso, Marco
2017-05-01
We show the flux tubes produced by static quark-antiquark, quark-quark and quark-gluon charges at finite temperature. The sources are placed on the lattice with fundamental and adjoint Polyakov loops. We compute the squared strengths of the chromomagnetic and chromoelectric fields above and below the critical temperature. Our results are for pure gauge SU(3) gauge theory, they are invariant and all computations are done with GPUs using CUDA.
Mallik, Samirnath
2016-01-01
High energy laboratories are performing experiments in heavy ion collisions to explore the structure of matter at high temperature and density. This elementary book explains the basic ideas involved in the theoretical analysis of these experimental data. It first develops two topics needed for this purpose, namely hadron interactions and thermal field theory. Chiral perturbation theory is developed to describe hadron interactions and thermal field theory is formulated in the real-time method. In particular, spectral form of thermal propagators is derived for fields of arbitrary spin and used to calculate loop integrals. These developments are then applied to find quark condensate and hadron parameters in medium, including dilepton production. Finally, the non-equilibrium method of statistical field theory to calculate transport coefficients is reviewed. With technical details explained in the text and appendices, this book should be accessible to researchers as well as graduate students interested in thermal ...
Finite Temperature Matrix Theory
Meana, M L; Peñalba, J P; Meana, Marco Laucelli; Peñalba, Jesús Puente
1998-01-01
We present the way the Lorentz invariant canonical partition function for Matrix Theory as a light-cone formulation of M-theory can be computed. We explicitly show how when the eleventh dimension is decompactified, the N=1 eleven dimensional SUGRA partition function appears. From this particular analysis we also clarify the question about the discernibility problem when making statistics with supergravitons (the N! problem) in Matrix black hole configurations. We also provide a high temperature expansion which captures some structure of the canonical partition function when interactions amongst D-particles are on. The connection with the semi-classical computations thermalizing the open superstrings attached to a D-particle is also clarified through a Born-Oppenheimer approximation. Some ideas about how Matrix Theory would describe the complementary degrees of freedom of the massless content of eleven dimensional SUGRA are also discussed.
Electroweak relaxation from finite temperature
Hardy, Edward
2015-01-01
We study theories which naturally select a vacuum with parametrically small Electroweak Scale due to finite temperature effects in the early universe. In particular, there is a scalar with an approximate shift symmetry broken by a technically natural small coupling to the Higgs, and a temperature dependent potential. As the temperature of the universe drops, the scalar follows the minimum of its potential altering the Higgs mass squared parameter. The scalar also has a periodic potential with amplitude proportional to the Higgs expectation value, which traps it in a vacuum with a small Electroweak Scale. The required temperature dependence of the potential can occur through strong coupling effects in a hidden sector that are suppressed at high temperatures. Alternatively, it can be generated perturbatively from a one-loop thermal potential. In both cases, for the scalar to be displaced, a hidden sector must be reheated to temperatures significantly higher than the visible sector. However this does not violate...
Flux tubes at Finite Temperature
Bicudo, Pedro; Cardoso, Marco
2016-01-01
We show the flux tubes produced by static quark-antiquark, quark-quark and quark-gluon charges at finite temperature. The sources are placed in the lattice with fundamental and adjoint Polyakov loops. We compute the square densities of the chromomagnetic and chromoelectric fields above and below the phase transition. Our results are gauge invariant and produced in pure gauge SU(3). The codes are written in CUDA and the computations are performed with GPUs.
Electroweak relaxation from finite temperature
Hardy, Edward
2015-11-01
We study theories which naturally select a vacuum with parametrically small Electroweak Scale due to finite temperature effects in the early universe. In particular, there is a scalar with an approximate shift symmetry broken by a technically natural small coupling to the Higgs, and a temperature dependent potential. As the temperature of the universe drops, the scalar follows the minimum of its potential altering the Higgs mass squared parameter. The scalar also has a periodic potential with amplitude proportional to the Higgs expectation value, which traps it in a vacuum with a small Electroweak Scale. The required temperature dependence of the potential can occur through strong coupling effects in a hidden sector that are suppressed at high temperatures. Alternatively, it can be generated perturbatively from a one-loop thermal potential. In both cases, for the scalar to be displaced, a hidden sector must be reheated to temperatures significantly higher than the visible sector. However this does not violate observational constraints provided the hidden sector energy density is transferred to the visible sector without disrupting big bang nucleosynthesis. We also study how the mechanism can be implemented when the visible sector is completed to the Minimal Supersymmetric Standard Model at a high scale. Models with a UV cutoff of 10 TeV and no fields taking values over a range greater than 1012 GeV are possible, although the scalar must have a range of order 108 times the effective decay constant in the periodic part of its potential.
Quantum memories at finite temperature
Brown, Benjamin J.; Loss, Daniel; Pachos, Jiannis K.; Self, Chris N.; Wootton, James R.
2016-10-01
To use quantum systems for technological applications one first needs to preserve their coherence for macroscopic time scales, even at finite temperature. Quantum error correction has made it possible to actively correct errors that affect a quantum memory. An attractive scenario is the construction of passive storage of quantum information with minimal active support. Indeed, passive protection is the basis of robust and scalable classical technology, physically realized in the form of the transistor and the ferromagnetic hard disk. The discovery of an analogous quantum system is a challenging open problem, plagued with a variety of no-go theorems. Several approaches have been devised to overcome these theorems by taking advantage of their loopholes. The state-of-the-art developments in this field are reviewed in an informative and pedagogical way. The main principles of self-correcting quantum memories are given and several milestone examples from the literature of two-, three- and higher-dimensional quantum memories are analyzed.
Dynamical CP violation at finite temperature
Institute of Scientific and Technical Information of China (English)
WANG Dian-Fu; SUN Xiao-Yu; LIANG Chao
2012-01-01
By using the generalized Yang-Mills model,CP violation behavior at finite temperature is investigated,and it is shown that dynamical CP violation of the generalized Yang-Mills model at zero temperature can be restored at finite temperature.
Quantized gravitoelectromagnetism theory at finite temperature
Santos, A F
2016-01-01
The Gravitoelectromagnetism (GEM) theory is considered in a lagrangian formulation using the Weyl tensor components. A perturbative approach to calculate processes at zero temperature has been used. Here the GEM at finite temperature is analyzed using Thermo Field Dynamics, real time finite temperature quantum field theory. Transition amplitudes involving gravitons, fermions and photons are calculated for various processes. These amplitudes are likely of interest in astrophysics.
Finite temperature reservoir engineering and entanglement dynamics
Fedortchenko, S.; Keller, A.; Coudreau, T.; Milman, P.
2014-01-01
We propose experimental methods to engineer reservoirs at arbitrary temperature which are feasible with current technology. Our results generalize to mixed states the possibility of quantum state engineering through controlled decoherence. Finite temperature engineered reservoirs can lead to the experimental observation of thermal entanglement --the appearance and increase of entanglement with temperature-- to the study of the dependence of finite time disentanglement and revival with tempera...
Finite Temperature Casimir Effect for Corrugated Plates
Institute of Scientific and Technical Information of China (English)
ZHAO Yan; SHAO Cheng-Gang; LUO Jun
2006-01-01
@@ Using the path-integral method, the corrections to the Casimir energy due to the combined effect of surface roughness and the finite temperature are calculated. For the specific case of two sinusoidally corrugated plates,the lateral Casimir force at finite temperature is obtained. The amplitude of the lateral Casimir force has a maximum at an optimal wavelength of λ≈ 2H with the mean plate distance H. This optimal parameter relation is almost independent of temperature.
Finite volume form factors and correlation functions at finite temperature
Pozsgay, Balázs
2009-01-01
In this thesis we investigate finite size effects in 1+1 dimensional integrable QFT. In particular we consider matrix elements of local operators (finite volume form factors) and vacuum expectation values and correlation functions at finite temperature. In the first part of the thesis we give a complete description of the finite volume form factors in terms of the infinite volume form factors (solutions of the bootstrap program) and the S-matrix of the theory. The calculations are correct to all orders in the inverse of the volume, only exponentially decaying (residual) finite size effects are neglected. We also consider matrix elements with disconnected pieces and determine the general rule for evaluating such contributions in a finite volume. The analytic results are tested against numerical data obtained by the truncated conformal space approach in the Lee-Yang model and the Ising model in a magnetic field. In a separate section we also evaluate the leading exponential correction (the $\\mu$-term) associate...
Holographic trace anomaly at finite temperature
Lee, Bum-Hoon; Nam, Siyoung; Park, Chanyong
2017-01-01
Using the holographic renormalization, we investigate the finite temperature and size effect to the energy-momentum tensor of the dual field theory and its renormalization group (RG) flow. Following the anti-de Sitter/conformal field theory correspondence, the dual field theory of the AdS space is well known to be a conformal field theory that has no nontrivial RG flow. Holographically, that theory can be lifted to a finite temperature version by considering a AdS black hole solution. Because the black hole horizon associated with temperature is dimensionful, it breaks the boundary conformal symmetry and leads to a nontrivial RG flow. In this work, we investigate the finite temperature and size correction to a strongly interacting conformal field theory along the Wisonian renormalization group flow.
Strange stars at finite temperature
Ray, Subharthi; Bagchi, Manjari; Dey, Jishnu; Dey, Mira
2006-03-01
We calculate strange star properties, using large Nc approximation with built-in chiral symmetry restoration (CSM). We used a relativistic Hartree Fock meanfield approximation method, using a modi.ed Richardson potential with two scale parameters Λ and Λ', to find a new set of equation of state (EOS) for strange quark matter. We take the effect of temperature (T) on gluon mass, in addition to the usual density dependence, and find that the transition T from hadronic matter to strange matter is 80 MeV. Therefore formation of strange stars may be the only signal for formation of QGP with asymptotic freedom (AF) and CSM.
Anguelova, Lilia
2007-01-01
We study whether finite temperature corrections decompactify the internal space in KKLT compactifications with an uplifting sector given by a system that exhibits metastable dynamical supersymmetry breaking. More precisely, we calculate the one-loop temperature corrections to the effective potential of the volume modulus in the KKLT model coupled to the quantum corrected O'Raifeartaigh model. We prove that for the original KKLT model, namely with one exponent in the non-perturbative superpotential, the finite temperature potential is runaway when at zero temperature there is a dS minimum at finite distance in field space. On the other hand, for a non-perturbative superpotential of the race-track type with two exponents, we demonstrate that the temperature-dependent part of the effective potential can have local minima at finite distance. However, rather unexpectedly, it turns out that these minima do not affect the structure of the full effective potential and so the volume modulus is stabilized at the local ...
Half-metals at finite temperature
Attema, J.J.
2008-01-01
The research presented in this thesis is aimed at achieving finite temperature spin injection. The first chapters are dedicated to the half-metallic half-heuslers, in particular NiMnSb. The problem of creating half-metallic interfaces between NiMnSb and a semiconductor is addressed. It is shown that
Emergent Kink Statistics at Finite Temperature
Lopez-Ruiz, Miguel Angel; Szczepaniak, Adam P; Liao, Jinfeng
2016-01-01
In this paper we use 1D quantum mechanical systems with Higgs-like interaction potential to study the emergence of topological objects at finite temperature. Two different model systems are studied, the standard double-well potential model and a newly introduced discrete kink model. Using Monte-Carlo simulations as well as analytic methods, we demonstrate how kinks become abundant at low temperatures. These results may shed useful insights on how topological phenomena may occur in QCD.
Thermal Operator Representation of Finite Temperature Graphs
Brandt, Fernando T.; Das, Ashok; Espinosa, Olivier; Frenkel, Josif; Perez, Silvana
2005-01-01
Using the mixed space representation (t,p) in the context of scalar field theories, we prove in a simple manner that the Feynman graphs at finite temperature are related to the corresponding zero temperature diagrams through a simple thermal operator, both in the imaginary time as well as in the real time formalisms. This result is generalized to the case when there is a nontrivial chemical potential present. Several interesting properties of the thermal operator are also discussed.
Gribov gap equation at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Canfora, Fabrizio; Pais, Pablo [Centro de Estudios Cientificos (CECS), Valdivia (Chile); Universidad Andres Bello, Santiago (Chile); Salgado-Rebolledo, Patricio [Centro de Estudios Cientificos (CECS), Valdivia (Chile); Universidad de Concepcion, Departamento de Fisica, Concepcion (Chile); Universite Libre de Bruxelles and International Solvay Insitutes, Physique Theorique et Mathematique, Bruxelles (Belgium)
2014-05-15
In this paper the Gribov gap equation at finite temperature is analyzed. The solutions of the gap equation (which depend explicitly on the temperature) determine the structure of the gluon propagator within the semi-classical Gribov approach. The present analysis is consistent with the standard confinement scenario for low temperatures, while for high enough temperatures, deconfinement takes place and a free gluon propagator is obtained. An intermediate regime in between the confined and free phases can be read off from the resulting gluon propagator, which appears to be closely related to partial deconfinement. (orig.)
G_2 gauge theory at finite temperature
Cossu, Guido; Di Giacomo, Adriano; Lucini, Biagio; Pica, Claudio
2007-01-01
The gauge group being centreless, $G_2$ gauge theory is a good laboratory for studying the role of the centre of the group for colour confinement in Yang-Mills gauge theories. In this paper, we investigate $G_2$ pure gauge theory at finite temperature on the lattice. By studying the finite size scaling of the plaquette, the Polyakov loop and their susceptibilities, we show that a deconfinement phase transition takes place. The analysis of the pseudocritical exponents give strong evidence of the deconfinement transition being first order. Implications of our findings for scenarios of colour confinement are discussed.
Finite Temperature QCD Sum Rules: A Review
Directory of Open Access Journals (Sweden)
Alejandro Ayala
2017-01-01
Full Text Available The method of QCD sum rules at finite temperature is reviewed, with emphasis on recent results. These include predictions for the survival of charmonium and bottonium states, at and beyond the critical temperature for deconfinement, as later confirmed by lattice QCD simulations. Also included are determinations in the light-quark vector and axial-vector channels, allowing analysing the Weinberg sum rules and predicting the dimuon spectrum in heavy-ion collisions in the region of the rho-meson. Also, in this sector, the determination of the temperature behaviour of the up-down quark mass, together with the pion decay constant, will be described. Finally, an extension of the QCD sum rule method to incorporate finite baryon chemical potential is reviewed.
Evidence for a Finite-Temperature Insulator.
Ovadia, M; Kalok, D; Tamir, I; Mitra, S; Sacépé, B; Shahar, D
2015-08-27
In superconductors the zero-resistance current-flow is protected from dissipation at finite temperatures (T) by virtue of the short-circuit condition maintained by the electrons that remain in the condensed state. The recently suggested finite-T insulator and the "superinsulating" phase are different because any residual mechanism of conduction will eventually become dominant as the finite-T insulator sets-in. If the residual conduction is small it may be possible to observe the transition to these intriguing states. We show that the conductivity of the high magnetic-field insulator terminating superconductivity in amorphous indium-oxide exhibits an abrupt drop, and seem to approach a zero conductance at T insulator.
Three-Point Functions at Finite Temperature
Carrington, M E
1996-01-01
We study 3-point functions at finite temperature in the closed time path formalism. We give a general decomposition of the eight component tensor in terms of seven vertex functions. We derive a spectral representation for these seven functions in terms of two independent spectral functions. We derive relationships between the seven functions and obtain a representation of the vertex tensor that greatly simplifies calculations in real time.
Assymptotic multipartite entanglement at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Sauer, Simeon; Mintert, Florian; Buchleitner, Andreas [Physikalisches Institut, Albert-Ludwigs-Universitaet Freiburg (Germany)
2010-07-01
When a many-body system is coupled to a noisy, thermal environment, it rapidly loses its coherences. Multipartite entanglement relies on such coherences, and therefore decays accordingly; and it does so, the faster, the larger the system and the hotter the environment is. However, external coherent driving is likely to slow down such decay, and it might even stabilize entanglement at a finite level. Here, we study the entanglement dynamics in a periodically driven many-body system, embedded in a thermal environment. With the help of the Floquet formalism, we identify steady states and characterize their entanglement properties. With this approach, we look for conditions (such as strength and frequency of the driving, and environmental temperature) that maintain a finite amount of multipartite entanglement for asymptotically large times.
Finite temperature Casimir effect for graphene
Fialkovsky, Ignat V; Vassilevich, Dmitri V
2011-01-01
We adopt the Dirac model for quasiparticles in graphene and calculate the finite temperature Casimir interaction between a suspended graphene layer and a parallel conducting surface. We find that at high temperature the Casimir interaction in such system is just one half of that for two ideal conductors separated by the same distance. In this limit single graphene layer behaves exactly as a Drude metal. In particular, the contribution of the TE mode is suppressed, while one of the TM mode saturates the ideal metal value. Behaviour of the Casimir interaction for intermediate temperatures and separations accessible for an experiment is studied in some detail. We also find an interesting interplay between two fundamental constants of graphene physics: the fine structure constant and the Fermi velocity.
Thermal geometry from CFT at finite temperature
Directory of Open Access Journals (Sweden)
Wen-Cong Gan
2016-09-01
Full Text Available We present how the thermal geometry emerges from CFT at finite temperature by using the truncated entanglement renormalization network, the cMERA. For the case of 2d CFT, the reduced geometry is the BTZ black hole or the thermal AdS as expectation. In order to determine which spacetimes prefer to form, we propose a cMERA description of the Hawking–Page phase transition. Our proposal is in agreement with the picture of the recent proposed surface/state correspondence.
Finite temperature effects on CP violating asymmetries
Covi, L; Roulet, Esteban; Vissani, F; Covi, Laura; Rius, Nuria; Roulet, Esteban; Vissani, Francesco
1998-01-01
We compute the CP violating decay asymmetries relevant for baryogenesis scenarios involving the out of equilibrium decays of heavy particles, including the finite temperature effects arising from the background of light thermal particles which are present during the decay epoch. Thermal effects can modify the size of CP violation by a sizeable fraction in the decay of scalar particles, but we find interesting cancellations in the thermal corrections affecting the asymmetries in the decays of fermions, as well as in the decay of scalars in supersymmetric theories. We also estimate the effects which arise from the motion of the decaying particles with respect to the background plasma.
Transition paths in molecules at finite temperature
Pinski, F. J.; Stuart, A. M.
2010-05-01
In the zero temperature limit, it is well known that in systems evolving via Brownian dynamics, the most likely transition path between reactant and product may be found as a minimizer of the Freidlin-Wentzell action functional. An analog for finite temperature transitions is given by the Onsager-Machlup functional. The purpose of this work is to investigate properties of Onsager-Machlup minimizers. We study transition paths for thermally activated molecules governed by the Langevin equation in the overdamped limit of Brownian dynamics. Using gradient descent in pathspace, we minimize the Onsager-Machlup functional for a range of model problems in one and two dimensions and then for some simple atomic models including Lennard-Jones seven-atom and 38-atom clusters, as well as for a model of vacancy diffusion in a planar crystal. Our results demonstrate interesting effects, which can occur at nonzero temperature, showing transition paths that could not be predicted on the basis of the zero temperature limit. However the results also demonstrate unphysical features associated with such Onsager-Machlup minimizers. As there is a growing literature that addresses transition path sampling by related techniques, these insights add a potentially useful perspective into the interpretation of this body of work.
Twisted mass QCD at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Ilgenfritz, E.M.; Mueller-Preussker, M.; Petschlies, M. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Jansen, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Lombardo, M.P. [Istituto Nazionale di Fisica Nucleare, LNF, Frascati (Italy); Philipsen, O.; Zeidlewicz, L. [Muenster Univ. (Germany). Inst. fuer Theoretische Physik 1; Sternbeck, A. [Adelaide Univ. (Australia). CSSM School of Chemistry and Physics
2007-10-15
We discuss the use of Wilson fermions with twisted mass for simulations of QCD thermodynamics. As a prerequisite for a future analysis of the finite-temperature transition making use of automatic {partial_derivative} (a) improvement, we investigate the phase structure in the space spanned by the hopping parameter {kappa}, the coupling {beta}, and the twisted mass parameter {mu}. We present results for N{sub f}=2 degenerate quarks on a 16{sup 3} x 8 lattice, for which we investigate the possibility of an Aoki phase existing at strong coupling and vanishing {mu}, as well as of a thermal phase transition at moderate gauge couplings and non-vanishing {mu}. (orig.)
Soliton Solution of SU(3) Gauge Fields at Finite Temperature
Institute of Scientific and Technical Information of China (English)
WANG Dian-Fu; SONG He-Shan
2005-01-01
@@ Starting from a soliton model of SU(3) gauge fields, we investigate the behaviour of the model at finite temperature. it is found that colour confinement at zero temperature can be melted away under high temperatures.
Two-dimensional finite-element temperature variance analysis
Heuser, J. S.
1972-01-01
The finite element method is extended to thermal analysis by forming a variance analysis of temperature results so that the sensitivity of predicted temperatures to uncertainties in input variables is determined. The temperature fields within a finite number of elements are described in terms of the temperatures of vertices and the variational principle is used to minimize the integral equation describing thermal potential energy. A computer calculation yields the desired solution matrix of predicted temperatures and provides information about initial thermal parameters and their associated errors. Sample calculations show that all predicted temperatures are most effected by temperature values along fixed boundaries; more accurate specifications of these temperatures reduce errors in thermal calculations.
Lorentz violation in Bhabha scattering at finite temperature
Santos, A. F.; Khanna, Faqir C.
2017-06-01
Corrections to the Bhabha scattering cross section, due to Lorentz violation, at finite temperature are calculated. The vertex interaction between fermions and photons is modified by introducing the Lorentz violation, for the Standard Model extension, from C P T odd nonminimal coupling. The finite temperature corrections are calculated using the thermo field dynamics formalism. The Lorentz violation corrections are presented for zero to high temperatures.
"Modified" BCS theory at finite temperature and its flaws
Ponomarev, V Yu
2003-01-01
Drawbacks of a recently suggested modified BCS theory at finite temperature in [Phys. Rev. C {\\bf 67}, 014304 (2003)] are discussed. We conclude that the thermal behavior of the pairing correlations is not under control within this model.
Mass-radius relations of white dwarfs at finite temperatures
Boshkayev, Kuantay; Rueda, Jorge A.; Ruffini, Remo; Zhami, Bakytzhan; Kalymova, Zhanerke; Balgimbekov, Galymdin
2016-01-01
We construct mass-radius relations of white dwarfs taking into account the effects of rotation and finite temperatures. We compare and contrast the theoretical mass-radius relations with observational data.
Finite Temperature Field Theory of "Extreme Black Holes"
Degura, Yoshitaka; Shiraishi, Kiyoshi
2000-01-01
We treat the model which describes "extreme black holes" moving slowly. We derive an effective lagrangian in the low energy for this model and then investigate a statistical behavior of "extreme black holes" in the finite temperature.
Symmetry restoration at finite temperature with weak magnetic fields
Navarro, Jorge; Tejeda-Yeomans, Maria Elena; Ayala, Alejandro; Piccinelli, Gabriella
2010-01-01
We study symmetry restoration at finite temperature in the standard model during the electroweak phase transition in the presence of a weak magnetic field. We compute the finite temperature effective potential up to the contribution of ring diagrams, using the broken phase degrees of freedom, and keep track of the gauge parameter dependence of the results. We show that under these conditions, the phase transition becomes stronger first order.
THE TWO-LEVEL MODEL AT FINITE-TEMPERATURE
Energy Technology Data Exchange (ETDEWEB)
Goodman, A.L.
1980-07-01
The finite-temperature HFB cranking equations are solved for the two-level model. The pair gap, moment of inertia and internal energy are determined as functions of spin and temperature. Thermal excitations and rotations collaborate to destroy the pair correlations. Raising the temperature eliminates the backbending effect and improves the HFB approximation.
Institute of Scientific and Technical Information of China (English)
刘嘉; 康忠波; 王恩科
2011-01-01
Using a reaction operator approach, we derive the multiple-scattering induced gluon number distribution function to all orders in powers of opacity at finite temperature. The detailed balance effect is analyzed by taking into account both gluon emission a
A Finite Temperature Phase Diagram in Rotating Bosonic Optical Lattices
Institute of Scientific and Technical Information of China (English)
HUANG Bei-Bing; WAN Shao-Long
2011-01-01
A finite temperature phase diagram of the rotating Bose-Hubbard model, including the crossover between Mott insulator and the normal state, is derived on the frame of the Gutzwiller mean-field theory. In addition, we calculate the critical temperature of superBuid-normal phase transition.%@@ A finite temperature phase diagram of the rotating Bose-Hubbard model, including the crossover between Mort insulator and the normal state, is derived on the frame of the Gutzwiller mean-field theory.In addition, we calculate the critical temperature of superfluid-normal phase transition.
On the fate of the Standard Model at finite temperature
Rose, Luigi Delle; Urbano, Alfredo
2015-01-01
In this paper we revisit and update the computation of thermal corrections to the stability of the electroweak vacuum in the Standard Model. At zero temperature, we make use of the full two-loop effective potential, improved by three-loop beta functions with two-loop matching conditions. At finite temperature, we include one-loop thermal corrections together with resummation of daisy diagrams. We solve numerically---both at zero and finite temperature---the bounce equation, thus providing an accurate description of the thermal tunneling. We find that at finite temperature the instability bound excludes values of the top mass $M_t \\gtrsim 173.6$ GeV, assuming $M_h \\simeq 125$ GeV and including uncertainties on the strong coupling. We discuss the validity and temperature-dependence of this bound in the early Universe, with a special focus on the reheating phase after inflation.
Inheritance principle and Non-renormalization theorems at finite temperature
Brigante, M; Liu, H; Brigante, Mauro; Festuccia, Guido; Liu, Hong
2006-01-01
We show that in the large $N$ limit, a weakly coupled SU(N) gauge theory with adjoint matter on a class of compact manifolds (like $S^3$) satisfies an ``inheritance principle'' in the low temperature phase. Finite temperature correlation functions of gauge invariant single-trace operators are related to those at zero temperature by summing over images of each operator in the Euclidean time direction. This implies that the corresponding finite temperature string theory dual can be formulated as a sigma model with Euclidean time direction periodically compactified. As a consequence, various non-renormalization theorems of $\\NN=4$ Super-Yang-Mills theory survive at finite temperature despite the fact that the conformal and supersymmetries are both broken.
Fluctuation of Mesoscopic RLC Circuit at Finite Temperature
Institute of Scientific and Technical Information of China (English)
ZHANG Xiao-Yan; WANG Ji-Suo; FAN Hong-Yi
2008-01-01
We consider the fluctuation of mesoscopic RLC circuit at finite temperature since a resistance always produces Joule heat when the circuit is working. By virtue of the thermo field dynamics and the coherent thermo state representation we show that the quantum mechanical zero-point fluctuations of both charge and current increase with the rising temperature and the resistance value.
Medley in finite temperature field theory
Pisarski, R D
1993-01-01
I discuss three subjects in thermal field theory: why in \\sun gauge theories the \\zn symmetry is broken at high (instead of low) temperature, the possible singularity structure of gauge variant propagators, and the problem of how to compute the viscosity from the Kubo formula.
QCD nature of dark energy at finite temperature: cosmological implications
Azizi, K
2015-01-01
The Veneziano ghost field has been proposed as an alternative source of dark energy whose energy density is consistent with the cosmological observations. In this model, the energy density of QCD ghost field is expressed in terms of QCD degrees of freedom at zero temperature. We extend this model to finite temperature to search the model predictions from the late time to the early universe. We depict the variations of QCD parameters entering the calculations, dark energy density, equation of state, Hubble and deceleration parameters on temperature from zero to a critical temperature. We compare our results with the observations and theoretical predictions existing at different eras.It is found that this model safely define the universe from quark condensation up to now and its predictions are not in tension with those of the standard cosmology. The finite temperature ghost dark energy predictions on the Hubble parameter slightly better fit to observations compared to those of zero temperature.
Operator product expansion at finite temperature
Mallik, S.
1997-01-01
We extend an earlier, configuration space method to find the Wilson coefficients of operators appearing in the short distance expansion of thermal correlation functions of different quark bilinears. Considering all the different correlation functions, there arise, up to dimension four, two new operators, in addition to the two appearing already in the vacuum correlation functions. They would contribute substantially to the QCD sum rules, when the temperature is not too low.
Thermophysical properties of iridium at finite temperature
Kumar, Priyank; Bhatt, N. K.; Vyas, P. R.; Gohel, V. B.
2016-11-01
The bulk properties of materials in an extreme environment such as high temperature and high pressure can be understood by studying anharmonic effects due to the vibration of lattice ions and thermally excited electrons. In this spirit, in the present paper, anharmonic effects are studied by using the recently proposed mean-field potential (MFP) approach and Mermin functional which arise due to the vibration of lattice ions and thermally excited electrons, respectively. The MFP experienced by a wanderer atom in the presence of surrounding atoms is constructed in terms of cold energy using the local form of the pseudopotential. We have calculated the temperature variation of several thermophysical properties in an extreme environment up to melting temperature. The results of our calculations are in excellent agreement with the experimental findings as well as the theoretical results obtained by using first principle methods. We conclude that presently used conjunction scheme (MFP+pseudopotential) is simple computationally, transparent physically, and accurate in the sense that the results generated are comparable and sometimes better than the results obtained by first principle methods. Local pseudopotential used is transferable to extreme environment without adjusting its parameters. Project supported by the Department of Science and Technology-Fund for Improvement of Science and Technology Infrastructure Project (DST-FIST) (Level 1) of Department of Sciences and Technology (DST), New Delhi (Grant No. SR/FST/PST-001/2006).
Gravitino dark matter production at finite temperature
Dalianis, Iannis
2013-01-01
The production and the final abundance of gravitino dark matter appear to depend crucially on the restoration of the global U(1) $R$-symmetry of GMSB sectors in a threefold way. An $R$-symmetric phase effectively suppresses the production of goldstinos from scatterings with the supersymmetric Standard Model particles and it generically initiates the goldstino production from the thermalized messenger particles. In addition, the GMSB spurion gets displaced from the zero temperature minimum and under certain conditions it dominates the energy density of the universe producing late entropy. We show that it is possible to have high enough reheating temperatures that thermal leptogenesis and thermal vacuum selection can be realized without gravitino overproduction. The gravitino dark matter can be produced either thermally or non-thermally. In the former case the messenger scale has to be less than about $10^6$ GeV with the gravitino relatively heavy, $m_{3/2}\\geq {\\cal O}(10)$ GeV. In the later case, the gravitin...
Optimized Perturbation Theory at Finite Temperature Two-Loop Analysis
Chiku, S
2000-01-01
We study the optimized perturbation theory (OPT) at finite temperature, which is a self-consistent resummation method. Firstly, we generalize the idea of the OPT to optimize the coupling constant in lambda phi^4 theory, and give a proof of the renormalizability of this generalized OPT. Secondly, the principle of minimal sensitivity and the criterion of the fastest apparent convergence, which are conditions to determine the optimal parameter values, are examined in lambda phi^4 theory. Both conditions exhibit a second-order transition at finite temperature with critical exponent beta = 0.5 in the two-loop approximation.
Chiral phase transition in QED$_3$ at finite temperature
Wei, Wei; Zong, Hong-Shi
2016-01-01
Chiral phase transition in (2+1)-dimensional quantum electrodynamics (QED$_3$) at finite temperature is investigated in the framework of truncated Dyson-Schwinger equations (DSEs). We go beyond the widely used instantaneous approximation and adopt a method that retains the full frequency dependence of the fermion self-energy. We also take further step to include the effects of wave-function renormalizations and introduce a minimal dressing of the bare vertex. Finally, with the more complete solutions of the truncated DSEs, we revisit the study of chiral phase transition in finite-temperature QED$_3$.
Gravitational Coleman–Weinberg potential and its finite temperature counterpart
Energy Technology Data Exchange (ETDEWEB)
Bhattacharjee, Srijit [Astroparticle Physics and Cosmology Division, Saha Institute of Nuclear Physics, Kolkata 700064 (India); Discipline of Physics, Indian Institute of Technology Gandhinagar, Ahmedabad, Gujarat 382424 (India); Majumdar, Parthasarathi [Department of Physics, Ramakrishna Mission Vivekananada University, Belur Math, Howrah 711202 (India)
2014-08-15
Coleman–Weinberg (CW) phenomena for the case of gravitons minimally coupled to massless scalar field is studied. The one-loop effect completely vanishes if there is no self-interaction term present in the matter sector. The one-loop effective potential is shown to develop an instability in the form of acquiring an imaginary part, which can be traced to the tachyonic pole in the graviton propagator. The finite temperature counterpart of this CW potential is computed to study the behaviour of the potential in the high and low temperature regimes with respect to the typical energy scale of the theory. Finite temperature contribution to the imaginary part of gravitational CW potential exhibits a damped oscillatory behaviour; all thermal effects are damped out as the temperature vanishes, consistent with the zero-temperature result.
Finite Temperature Maps in Vector/Higher Spin Duality
Jevicki, Antal; Suzuki, Kenta; Yoon, Junggi
We discuss the question of reconstructing higher spin bulk fields from finite temperature N-component vector models. This is done in the framework of thermofield quantum theory at Large N. A bi-local construction of connected dual space-times is accomplished, and issues related to the implementation of domain duality are discussed.
Finite Temperature Phase Diagramm of QCD with improved Wilson fermions
Karsch, Frithjof; Oevers, M; Schmidt, P
1998-01-01
We present first results of a study of two flavour QCD with Wilson fermions at finite temperature. We have used tree level Symanzik improvement in both the gauge and fermion part of the action. In a first step we explore the phase diagramm on an $8^3 \\times 4$ lattice, with particular emphasis on checking Aoki's conjecture with an improved action.
Analytic regularization of the Yukawa model at finite temperature
Malbouisson, A P C; Svaiter, N F
1996-01-01
We analyse the one-loop fermionic contribution for the scalar effective potential in the temperature dependent Yukawa model. In order to regularize the model a mix between dimensional and analytic regularization procedures is used. We find a general expression for the fermionic contribution in arbitrary spacetime dimension. It is found that in D=3 this contribution is finite.
Electromagnetic field at Finite Temperature: A new view
Casana, R; Valverde, J S
2005-01-01
In this work we study the electromagnetic field at Finite Temperature via the massless DKP formalism. The constraint analysis is performed and the partition function for the theory is constructed and computed. When it is specialized to the spin 1 sector we obtain the well-known result for the thermodynamic equilibrium of the electromagnetic field.
Electromagnetic field at finite temperature: A first order approach
Casana, R.; Pimentel, B. M.; Valverde, J. S.
2006-10-01
In this work we study the electromagnetic field at finite temperature via the massless DKP formalism. The constraint analysis is performed and the partition function for the theory is constructed and computed. When it is specialized to the spin 1 sector we obtain the well-known result for the thermodynamic equilibrium of the electromagnetic field.
Lattice QCD Results at Finite Temperature and Density
Fodor, Z
2003-01-01
Recent lattice results on QCD at finite temperatures and densities are reviewed. Two new and independent techniques give compatible results for physical quantities. The phase line separating the hadronic and quark-gluon plasma phases, the critical endpoint and the equation of state are discussed.
Finite temperature Casimir effect in the presence of nonlinear dielectrics
Kheirandish, Fardin; Soltani, Morteza
2010-01-01
Starting from a Lagrangian, electromagnetic field in the presence of a nonlinear dielectric medium is quantized using path-integral techniques and correlation functions of different fields are calculated. The susceptibilities of the nonlinear medium are obtained and their relation to coupling functions are determined. Finally, the Casimir energy and force in the presence of a nonlinear medium at finite temperature is calculated.
Meson properties at finite temperature and baryon density
Energy Technology Data Exchange (ETDEWEB)
Lutz, M.; Klimt, S.; Weise, W. (Inst. of Theoretical Physics, Univ. Regensburg (Germany))
1992-06-22
We use the generalized SU(3) version of the Nambu and Jona-Lasinio model to discuss properties of mesons, constituent quarks and vacuum structure as a function of density and temperature in compressed matter. Systematic low-density expansions are derived. In particular, we show that effects due to finite quasi-particle size are important in stabilizing the density and temperature dependence of the pion mass. (orig.).
Friedberg-Lee model at finite temperature and density
Mao, Hong; Yao, Minjie; Zhao, Wei-Qin
2008-06-01
The Friedberg-Lee model is studied at finite temperature and density. By using the finite temperature field theory, the effective potential of the Friedberg-Lee model and the bag constant B(T) and B(T,μ) have been calculated at different temperatures and densities. It is shown that there is a critical temperature TC≃106.6 MeV when μ=0 MeV and a critical chemical potential μ≃223.1 MeV for fixing the temperature at T=50 MeV. We also calculate the soliton solutions of the Friedberg-Lee model at finite temperature and density. It turns out that when T⩽TC (or μ⩽μC), there is a bag constant B(T) [or B(T,μ)] and the soliton solutions are stable. However, when T>TC (or μ>μC) the bag constant B(T)=0 MeV [or B(T,μ)=0 MeV] and there is no soliton solution anymore, therefore, the confinement of quarks disappears quickly.
The Friedberg-Lee model at finite temperature and density
Mao, Hong; Zhao, Wei-Qin
2007-01-01
The Friedberg-Lee model is studied at finite temperature and density. By using the finite temperature field theory, the effective potential of the Friedberg-Lee model and the bag constant $B(T)$ and $B(T,\\mu)$ have been calculated at different temperatures and densities. It is shown that there is a critical temperature $T_{C}\\simeq 106.6 \\mathrm{MeV}$ when $\\mu=0 \\mathrm{MeV}$ and a critical chemical potential $\\mu \\simeq 223.1 \\mathrm{MeV}$ for fixing the temperature at $T=50 \\mathrm{MeV}$. We also calculate the soliton solutions of the Friedberg-Lee model at finite temperature and density. It turns out that when $T\\leq T_{C}$ (or $\\mu \\leq \\mu_C$), there is a bag constant $B(T)$ (or $B(T,\\mu)$) and the soliton solutions are stable. However, when $T>T_{C}$ (or $\\mu>\\mu_C$) the bag constant $B(T)=0 \\mathrm{MeV}$ (or $B(T,\\mu)=0 \\mathrm{MeV}$) and there is no soliton solution anymore, therefore, the confinement of quarks disappears quickly.
Baryon number fluctuations at finite temperature and density
Fu, Wei-jie; Rennecke, Fabian; Schaefer, Bernd-Jochen
2016-01-01
We investigate baryon number fluctuations for finite temperature and density in two-flavor QCD. This is done within a QCD-improved low-energy effective theory in an extension of the approach put forward in [1,2]. In the present work we aim at improving the predictive power of this approach for large temperatures and density, that is, for small collision energies. This is achieved by taking into account the full frequency dependence of the quark dispersion. This ensures the necessary Silver Blaze property of finite density QCD for the first time, which so far was only implemented approximately. Moreover, we show that Polyakov loop fluctuations have a sizeable impact at large temperatures and density. The results for the kurtosis of baryon number fluctuations are compared to previous effective theory results, lattice results and recent experimental data from STAR.
A note on the pulay force at finite temperatures
Energy Technology Data Exchange (ETDEWEB)
Niklasson, Anders M N [Los Alamos National Laboratory
2008-01-01
Pulay's original expression for the basis-set dependent adjustment term to the Hellmann-Feynman force in electronic structure theory, which occurs for nonorthogonal local basis-set representations, is based on the idempotency condition of a pure ensemble. At finite electronic temperatures with a fractional occupation of the states, the conventional expression of the Pulay force is therefore no longer valid. Here we derive a simple and computationally efficient expression for a generalized Pulay force, which is suitable for large-scale ab initio simulations at finite electronic temperatures using local nonorthogonal basis-set representations. The generalized Pulay force expression is given in terms of the temperature-dependent density matrix. For the construction of the density matrix, we propose a recursive Fermi operator expansion algorithm that automatically converges to the correct chemical potential.
Analytic behavior of the QED polarizability function at finite temperature
Directory of Open Access Journals (Sweden)
A. Bernal
2012-03-01
Full Text Available We revisit the analytical properties of the static quasi-photon polarizability function for an electron gas at finite temperature, in connection with the existence of Friedel oscillations in the potential created by an impurity. In contrast with the zero temperature case, where the polarizability is an analytical function, except for the two branch cuts which are responsible for Friedel oscillations, at finite temperature the corresponding function is non analytical, in spite of becoming continuous everywhere on the complex plane. This effect produces, as a result, the survival of the oscillatory behavior of the potential. We calculate the potential at large distances, and relate the calculation to the non-analytical properties of the polarizability.
QCD Sum Rules at Finite Temperature: a Review
Ayala, Alejandro; Loewe, M
2016-01-01
The method of QCD sum rules at finite temperature is reviewed, with emphasis on recent results. These include predictions for the survival of charmonium and bottonium states, at and beyond the critical temperature for de-confinement, as later confirmed by lattice QCD simulations. Also included are determinations in the light-quark vector and axial-vector channels, allowing to analyse the Weinberg sum rules, and predict the dimuon spectrum in heavy ion collisions in the region of the rho-meson. Also in this sector, the determination of the temperature behaviour of the up-down quark mass, together with the pion decay constant, will be described. Finally, an extension of the QCD sum rule method to incorporate finite baryon chemical potential is reviewed.
Analytic behavior of the QED polarizability function at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Bernal, A. [Dept. de Matematica Aplicada i Analisi, Universitat de Barcelona. Av Joan XXIII s/n Edifici A, Escala A, Tercer pis, Matematiques 08028, Barcelona (Spain); Perez, A. [Departament de Fisica Teorica and IFIC, Universitat de Valencia-CSIC, Dr. Moliner 50, 46100-Burjassot (Spain)
2012-03-15
We revisit the analytical properties of the static quasi-photon polarizability function for an electron gas at finite temperature, in connection with the existence of Friedel oscillations in the potential created by an impurity. In contrast with the zero temperature case, where the polarizability is an analytical function, except for the two branch cuts which are responsible for Friedel oscillations, at finite temperature the corresponding function is non analytical, in spite of becoming continuous everywhere on the complex plane. This effect produces, as a result, the survival of the oscillatory behavior of the potential. We calculate the potential at large distances, and relate the calculation to the non-analytical properties of the polarizability.
Phase transition in finite density and temperature lattice QCD
Wang, Rui; Gong, Ming; Liu, Chuan; Liu, Yu-Bin; Liu, Zhao-Feng; Ma, Jian-Ping; Meng, Xiang-Fei; Zhang, Jian-Bo
2015-01-01
We investigate the behavior of the chiral condensate in lattice QCD at finite temperature and finite chemical potential. The study was done using two flavors of light quarks and with a series of $\\beta$ and $ma$ at the lattice size $24\\times12^{2}\\times6$. The calculation was done in the Taylar expansion formalism. We are able to calculate the first and second order derivatives of $\\langle\\bar{\\psi}\\psi\\rangle$ in both isoscalar and isovector channels. With the first derivatives being small, we find that the second derivatives are sizable close to the phase transition and the magnitude of $\\bar{\\psi}\\psi$ decreases under the influence of finite chemical potential in both channels.
Convexity at finite temperature and non-extensive thermodynamics
Alexandre, J.
2016-09-01
Assuming that tunnel effect between two degenerate bare minima occurs, in a scalar field theory at finite volume, this article studies the consequences for the effective potential, to all loop orders. Convexity is achieved only if the two bare minima are taken into account in the path integral, and a new derivation of the effective potential is given, in the large volume limit. The effective potential then has a universal form, it is suppressed by the space time volume, and does not feature spontaneous symmetry breaking as long as the volume is finite. The finite temperature analysis leads to surprising thermal properties, following from the non-extensive expression for the free energy. Although the physical relevance of these results is not clear, the potential application to ultra-light scalar particles is discussed.
Kinetic Description of a Finite Temperature Meson Gas
Tan, Z G; Terranova, S; Bonasera, A; Tan, Zhi Guang; Zhou, Dai-Mei
2006-01-01
A transport model based on the mean free path approach for an interacting meson system at finite temperatures is discussed. A transition to a quark gluon plasma is included within the framework of the bag model. We discuss some calculations for a pure meson gas where the Hagedorn limiting temperature is reproduced when including the experimentally observed resonances. Next we include the possibility for a QGP formation based on the MIT bag model. The results obtained compare very well with Lattice QCD calculations. In particular the cross over to the QGP at about 175 MeV temperature is nicely reproduced.
A first-principles approach to finite temperature elastic constants
Energy Technology Data Exchange (ETDEWEB)
Wang, Y; Wang, J J; Zhang, H; Manga, V R; Shang, S L; Chen, L-Q; Liu, Z-K [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States)
2010-06-09
A first-principles approach to calculating the elastic stiffness coefficients at finite temperatures was proposed. It is based on the assumption that the temperature dependence of elastic stiffness coefficients mainly results from volume change as a function of temperature; it combines the first-principles calculations of elastic constants at 0 K and the first-principles phonon theory of thermal expansion. Its applications to elastic constants of Al, Cu, Ni, Mo, Ta, NiAl, and Ni{sub 3}Al from 0 K up to their respective melting points show excellent agreement between the predicted values and existing experimental measurements.
Finite Temperature Quasicontinuum: Molecular Dynamics without all the Atoms
Energy Technology Data Exchange (ETDEWEB)
Dupuy, L; Tadmor, E B; Miller, R E; Phillips, R
2005-02-02
Using a combination of statistical mechanics and finite-element interpolation, the authors develop a coarse-grained (CG) alternative to molecular dynamics (MD) for crystalline solids at constant temperature. The new approach is significantly more efficient than MD and generalizes earlier work on the quasi-continuum method. The method is validated by recovering equilibrium properties of single crystal Ni as a function of temperature. CG dynamical simulations of nanoindentation reveal a strong dependence on temperature of the critical stress to nucleate dislocations under the indenter.
Huge Casimir effect at finite temperature in electromagnetic Rindler space
Zhao, Tian-Ming
2011-01-01
We investigate the Casimir effect at finite temperature in electromagnetic Rindler space, and find the Casimir energy is proportional to $\\frac{T^4}{d^2}$ in the high temperature limit, where $T\\approx 27 ^\\circ\\mathrm{C}$ is the temperature and $d\\approx 100nm$ is a small cutoff. We propose to make metamaterials to mimic Rindler space and measure the predicted Casimir effect. Since the parameters of metamaterials we proposed are quite simple, this experiment would be easily implemented in laboratory.
Huge Casimir effect at finite temperature in electromagnetic Rindler space
Zhao, Tian-Ming; Miao, Rong-Xin
2011-12-01
We investigate the Casimir effect at finite temperature in electromagnetic Rindler space, and find the Casimir energy is proportional to $\\frac{T^4}{d^2}$ in the high temperature limit, where $T\\approx 27 ^\\circ\\mathrm{C}$ is the temperature and $d\\approx 100nm$ is a small cutoff. We propose to make metamaterials to mimic Rindler space and measure the predicted Casimir effect. Since the parameters of metamaterials we proposed are quite simple, this experiment would be easily implemented in laboratory.
Huge Casimir effect at finite temperature in electromagnetic Rindler space
Zhao, Tian-Ming; Miao, Rong-Xin
2011-01-01
We investigate the Casimir effect at finite temperature in electromagnetic Rindler space, and find the Casimir energy is proportional to $\\frac{T^4}{d^2}$ in the high temperature limit, where $T\\approx 27 ^\\circ\\mathrm{C}$ is the temperature and $d\\approx 100nm$ is a small cutoff. We propose to make metamaterials to mimic Rindler space and measure the predicted Casimir effect. Since the parameters of metamaterials we proposed are quite simple, this experiment would be easily implemented in la...
Quark mass dependence of quarkonium properties at finite temperature
Ohno, H; Kaczmarek, O
2014-01-01
Quarkonium properties at finite temperature have been studied with quark masses of the charm and bottom quarks. Our simulations have been performed in quenched QCD with the $O(a)$-improved Wilson quarks on large and fine isotropic lattices with the spatial lattice extents $N_\\sigma =$ 96, 192 and the corresponding lattice spacings $a =$ 0.0190, 0.00967 fm, respectively, at temperatures in a range between about 0.7$T_c$ and 1.4$T_c$. We show temperature and quark mass dependence of quarkonium correlation functions and related physical quantities: the quark number susceptibility and the heavy quark diffusion constant.
Test of modified BCS model at finite temperature
Ponomarev, V Yu
2005-01-01
A recently suggested modified BCS (MBCS) model has been studied at finite temperature. We show that this approach does not allow the existence of the normal (non-superfluid) phase at any finite temperature. Other MBCS predictions such as a negative pairing gap, pairing induced by heating in closed-shell nuclei, and ``superfluid -- super-superfluid'' phase transition are discussed also. The MBCS model is tested by comparing with exact solutions for the picket fence model. Here, severe violation of the internal symmetry of the problem is detected. The MBCS equations are found to be inconsistent. The limit of the MBCS applicability has been determined to be far below the ``superfluid -- normal'' phase transition of the conventional FT-BCS, where the model performs worse than the FT-BCS.
Intersecting D3-D3' system at finite temperature
Cottrell, William; Hashimoto, Akikazu; Loveridge, Andrew; Pettengill, Duncan
2015-01-01
We analyze the embedding of probe D3'-brane in the background of $N$ D3-branes at finite temperature, oriented such that they overlap in 1+1 dimensions. As the distance between the D3'-brane and the D3 brane is varied, we find solutions that appear to intersect the horizon. We find that this brane bends logarithmically, making the precise definition of the distance separating the D3 and the D3' brane scale dependent. We also consider the embedding of a probe M5-brane in the background of $N$ M2-branes at finite temperature, for which the logarithmic bending is absent. These systems appear to open a path to probe physics near and behind the black hole horizon in a strictly field theoretic framework.
Excitations of Bose-Einstein condensates at finite temperatures
Rusch, M
2000-01-01
in their frequency spectra. Where possible we derive energy shifts and lifetimes of excitations. For one particular mode, the breathing mode, the effects of the discreteness of the system are sufficiently pronounced that the simple picture of an energy shift and width fails. Experiments in spherical traps have recently become feasible and should be able to test our detailed quantitative predictions. Recent experimental observations of collective excitations of Bose condensed atomic vapours have stimulated interest in the microscopic description of the dynamics of a Bose-Einstein condensate confined in an external potential. We present a finite temperature field theory for collective excitations of trapped Bose-Einstein condensates and use a finite-temperature linear response formalism, which goes beyond the simple mean-field approximation of the Gross-Pitaevskii equation. The effect of the non-condensed thermal atoms we include using perturbation theory in a quasiparticle basis. This presents a simple scheme ...
Magnetic Elements at Finite Temperature and Large Deviation Theory
Kohn, R. V.; Reznikoff, M. G.; vanden-Eijnden, E.
2005-08-01
We investigate thermally activated phenomena in micromagnetics using large deviation theory and concepts from stochastic resonance. We give a natural mathematical definition of finite-temperature astroids, finite-temperature hysteresis loops, etc. Generically, these objects emerge when the (generalized) Arrhenius timescale governing the thermally activated barrier crossing event of magnetic switching matches the timescale at which the magnetic element is pulsed or ramped by an external field; in the special and physically relevant case of multiple-pulse experiments, on the other hand, short-time switching can lead to non-Arrhenius behavior. We show how large deviation theory can be used to explain some properties of the astroids, like their shrinking and sharpening as the number of applied pulses is increased. We also investigate the influence of the dynamics, in particular the relative importance of the gyromagnetic and the damping terms. Finally, we discuss some issues and open questions regarding spatially nonuniform magnetization.
Massive renormalization scheme and perturbation theory at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Blaizot, Jean-Paul, E-mail: jean-paul.blaizot@cea.fr [Institut de Physique Théorique, CNRS/URA2306, CEA-Saclay, 91191 Gif-sur-Yvette (France); Wschebor, Nicolás [Instituto de Fìsica, Faculdad de Ingeniería, Universidade de la República, 11000 Montevideo (Uruguay)
2015-02-04
We argue that the choice of an appropriate, massive, renormalization scheme can greatly improve the apparent convergence of perturbation theory at finite temperature. This is illustrated by the calculation of the pressure of a scalar field theory with quartic interactions, at 2-loop order. The result, almost identical to that obtained with more sophisticated resummation techniques, shows a remarkable stability as the coupling constant grows, in sharp contrast with standard perturbation theory.
Finite Temperature Casimir Effect in Randall-Sundrum Models
Rypestøl, Marianne
2009-01-01
The finite temperature Casimir effect for a scalar field in the bulk region of the two Randall-Sundrum models, RSI and RSII, is studied. We calculate the Casimir energy and the Casimir force for two parallel plates with separation $a$ on the visible brane in the RSI model. High-temperature and low-temperature cases are covered. Attractiveness versus repulsiveness of the temperature correction to the force is discussed in the typical special cases of Dirichlet-Dirichlet, Neumann-Neumann, and Dirichlet-Neumann boundary conditions at low temperature. The Abel-Plana summation formula is made use of, as this turns out to be most convenient. Some comments are made on the related contemporary literature.
Lipkin-Meshkov-Glick model at finite temperature
Storozhenko, A N; Vdovin, A I
1997-01-01
The Lipkin-Meshkov-Glick model is used to examine the validity of some approximate methods in a many-body theory at finite temperatures. Namely, the thermal random phase approximation (TRPA) and the thermal renormalized random phase approximation (TRRPA) are studied. An average energy of the system, an average quasispin projection and a particle number variance are calculated within these approximation and exactly with the grand canonical ensemble partition function. On the whole the results of TRRPA are found to be in better agreement with the exact ones. The validity of the both approximation becomes better with increasing temperature as well as particle number.
Anatomy of SU(3) flux tubes at finite temperature
Cea, Paolo; Cuteri, Francesca; Papa, Alessandro
2015-01-01
An attempt to adapt the study of color flux tubes to the case of finite temperature has been made. The field is measured both through the correlator of two Polyakov loops, one of which connected to a plaquette, and through a connected correlator of Wilson loop and plaquette in the spatial sublattice. Still the profile of the flux tube resembles the transverse field distribution around an isolated vortex in an ordinary superconductor. The temperature dependence of all the parameters characterizing the flux tube is investigated.
Finite temperature Casimir effect in spacetime with extra compactified dimensions
Energy Technology Data Exchange (ETDEWEB)
Teo, L.P. [Faculty of Information Technology, Multimedia University, Jalan Multimedia, Cyberjaya 63100, Selangor Darul Ehsan (Malaysia)], E-mail: lpteo@mmu.edu.my
2009-02-16
In this Letter, we derive the explicit exact formulas for the finite temperature Casimir force acting on a pair of parallel plates in the presence of extra compactified dimensions within the framework of Kaluza-Klein theory. Using the piston analysis, we show that at any temperature, the Casimir force due to massless scalar field with Dirichlet boundary conditions on the plates is always attractive and the effect of extra dimensions becomes stronger when the size or number of the extra dimensions increases. These properties are not affected by the explicit geometry and topology of the Kaluza-Klein space.
A Dyson-Schwinger approach to finite temperature QCD
Energy Technology Data Exchange (ETDEWEB)
Mueller, Jens Andreas
2011-10-26
The different phases of quantum chromodynamics at finite temperature are studied. To this end the nonperturbative quark propagator in Matsubara formalism is determined from its equation of motion, the Dyson-Schwinger equation. A novel truncation scheme is introduced including the nonperturbative, temperature dependent gluon propagator as extracted from lattice gauge theory. In the first part of the thesis a deconfinement order parameter, the dual condensate, and the critical temperature are determined from the dependence of the quark propagator on the temporal boundary conditions. The chiral transition is investigated by means of the quark condensate as order parameter. In addition differences in the chiral and deconfinement transition between gauge groups SU(2) and SU(3) are explored. In the following the quenched quark propagator is studied with respect to a possible spectral representation at finite temperature. In doing so, the quark propagator turns out to possess different analytic properties below and above the deconfinement transition. This result motivates the consideration of an alternative deconfinement order parameter signaling positivity violations of the spectral function. A criterion for positivity violations of the spectral function based on the curvature of the Schwinger function is derived. Using a variety of ansaetze for the spectral function, the possible quasi-particle spectrum is analyzed, in particular its quark mass and momentum dependence. The results motivate a more direct determination of the spectral function in the framework of Dyson-Schwinger equations. In the two subsequent chapters extensions of the truncation scheme are considered. The influence of dynamical quark degrees of freedom on the chiral and deconfinement transition is investigated. This serves as a first step towards a complete self-consistent consideration of dynamical quarks and the extension to finite chemical potential. The goodness of the truncation is verified first
On the fate of the Standard Model at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Rose, Luigi Delle; Marzo, Carlo [Università del Salento, Dipartimento di Matematica e Fisica “Ennio De Giorgi' ,Via Arnesano, 73100 Lecce (Italy); INFN - Sezione di Lecce,via Arnesano, 73100 Lecce (Italy); Urbano, Alfredo [SISSA - International School for Advanced Studies,via Bonomea 256, 34136 Trieste (Italy)
2016-05-10
In this paper we revisit and update the computation of thermal corrections to the stability of the electroweak vacuum in the Standard Model. At zero temperature, we make use of the full two-loop effective potential, improved by three-loop beta functions with two-loop matching conditions. At finite temperature, we include one-loop thermal corrections together with resummation of daisy diagrams. We solve numerically — both at zero and finite temperature — the bounce equation, thus providing an accurate description of the thermal tunneling. Assuming a maximum temperature in the early Universe of the order of 10{sup 18} GeV, we find that the instability bound excludes values of the top mass M{sub t}≳173.6 GeV, with M{sub h}≃125 GeV and including uncertainties on the strong coupling. We discuss the validity and temperature-dependence of this bound in the early Universe, with a special focus on the reheating phase after inflation.
Spectral Properties of Quarks at Finite Temperature in Lattice QCD
Kitazawa, Masakiyo
2009-01-01
We analyze the quark spectral function above and below the critical temperature for deconfinement and at finite momentum in quenched lattice QCD. It is found that the temporal quark correlation function in the deconfined phase near the critical temperature is well reproduced by a two-pole ansatz for the spectral function. The bare quark mass and momentum dependences of the spectral function are analyzed with this ansatz. In the chiral limit we find that even near the critical temperature the quark spectral function has two collective modes corresponding to the normal and plasmino excitations in the high temperature (T) limit. The pole mass of these modes at zero momentum, which should be identified to be the thermal mass of the quark, is approximately proportional to T in a rather wide range of T in the deconfined phase.
Repulsive Casimir force at zero and finite temperature
Energy Technology Data Exchange (ETDEWEB)
Lim, S C [Faculty of Engineering, Multimedia University, Jalan Multimedia, Cyberjaya, 63100 Selangor Darul Ehsan (Malaysia); Teo, L P [Faculty of Information Technology, Multimedia University, Jalan Multimedia, Cyberjaya, 63100 Selangor Darul Ehsan (Malaysia)], E-mail: sclim@mmu.edu.my, E-mail: lpteo@mmu.edu.my
2009-01-15
We study the zero and finite temperature Casimir force acting on a perfectly conducting piston with arbitrary cross section moving inside a closed cylinder with infinitely permeable walls. We show that at any temperature, the Casimir force always tends to move the piston away from the walls and toward its equilibrium position. In the case of a rectangular piston, exact expressions for the Casimir force are derived. In the high-temperature regime, we show that the leading term of the Casimir force is linear in temperature and therefore the Casimir force has a classical limit. Due to duality, all these results also hold for an infinitely permeable piston moving inside a closed cylinder with perfectly conducting walls.
PT Symmetry and QCD: Finite Temperature and Density
Directory of Open Access Journals (Sweden)
Michael C. Ogilvie
2009-04-01
Full Text Available The relevance of PT symmetry to quantum chromodynamics (QCD, the gauge theory of the strong interactions, is explored in the context of finite temperature and density. Two significant problems in QCD are studied: the sign problem of finite-density QCD, and the problem of confinement. It is proven that the effective action for heavy quarks at finite density is PT-symmetric. For the case of 1+1 dimensions, the PT-symmetric Hamiltonian, although not Hermitian, has real eigenvalues for a range of values of the chemical potential μ, solving the sign problem for this model. The effective action for heavy quarks is part of a potentially large class of generalized sine-Gordon models which are non-Hermitian but are PT-symmetric. Generalized sine-Gordon models also occur naturally in gauge theories in which magnetic monopoles lead to confinement. We explore gauge theories where monopoles cause confinement at arbitrarily high temperatures. Several different classes of monopole gases exist, with each class leading to different string tension scaling laws. For one class of monopole gas models, the PT-symmetric affine Toda field theory emerges naturally as the effective theory. This in turn leads to sine-law scaling for string tensions, a behavior consistent with lattice simulations.
Reduced density matrix functional theory at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Baldsiefen, Tim
2012-10-15
Density functional theory (DFT) is highly successful in many fields of research. There are, however, areas in which its performance is rather limited. An important example is the description of thermodynamical variables of a quantum system in thermodynamical equilibrium. Although the finite-temperature version of DFT (FT-DFT) rests on a firm theoretical basis and is only one year younger than its brother, groundstate DFT, it has been successfully applied to only a few problems. Because FT-DFT, like DFT, is in principle exact, these shortcomings can be attributed to the difficulties of deriving valuable functionals for FT-DFT. In this thesis, we are going to present an alternative theoretical description of quantum systems in thermal equilibrium. It is based on the 1-reduced density matrix (1RDM) of the system, rather than on its density and will rather cumbersomly be called finite-temperature reduced density matrix functional theory (FT-RDMFT). Its zero-temperature counterpart (RDMFT) proved to be successful in several fields, formerly difficult to address via DFT. These fields include, for example, the calculation of dissociation energies or the calculation of the fundamental gap, also for Mott insulators. This success is mainly due to the fact that the 1RDM carries more directly accessible ''manybody'' information than the density alone, leading for example to an exact description of the kinetic energy functional. This sparks the hope that a description of thermodynamical systems employing the 1RDM via FT-RDMFT can yield an improvement over FT-DFT. Giving a short review of RDMFT and pointing out difficulties when describing spin-polarized systems initiates our work. We then lay the theoretical framework for FT-RDMFT by proving the required Hohenberg-Kohn-like theorems, investigating and determining the domain of FT-RDMFT functionals and by deriving several properties of the exact functional. Subsequently, we present a perturbative method to
Quarkonium at finite temperature: towards realistic phenomenology from first principles
Energy Technology Data Exchange (ETDEWEB)
Burnier, Yannis [Institute of Theoretical Physics, EPFL,CH-1015 Lausanne (Switzerland); Kaczmarek, Olaf [Fakultät für Physik, Universität Bielefeld,D-33615 Bielefeld (Germany); Rothkopf, Alexander [Institute for Theoretical Physics, Heidelberg University,Philosophenweg 16, 69120 Heidelberg (Germany)
2015-12-16
We present the finite temperature spectra of both bottomonium and charmonium, obtained from a consistent lattice QCD based potential picture. Starting point is the complex in-medium potential extracted on full QCD lattices with dynamical u,d and s quarks, generated by the HotQCD collaboration. Using the generalized Gauss law approach, vetted in a previous study on quenched QCD, we fit Re[V] with a single temperature dependent parameter m{sub D}, the Debye screening mass, and confirm the up to now tentative values of Im[V]. The obtained analytic expression for the complex potential allows us to compute quarkonium spectral functions by solving an appropriate Schrödinger equation. These spectra exhibit thermal widths, which are free from the resolution artifacts that plague direct reconstructions from Euclidean correlators using Bayesian methods. In the present adiabatic setting, we find clear evidence for sequential melting and derive melting temperatures for the different bound states. Quarkonium is gradually weakened by both screening (Re[V]) and scattering (Im[V]) effects that in combination lead to a shift of their in-medium spectral features to smaller frequencies, contrary to the mass gain of elementary particles at finite temperature.
Finite size and finite temperature studies of the osp(1|2) spin chain
Tavares, T. S.; Ribeiro, G. A. P.
2017-08-01
We studied a quantum spin chain invariant by the superalgebra osp (1 | 2). We derived non-linear integral equations for the row-to-row transfer matrix eigenvalue in order to analyze its finite size scaling behavior and we determined its central charge. We also studied the thermodynamical properties of the spin chain via non-linear integral equations for the quantum transfer matrix eigenvalue. We numerically solved these NLIE and evaluated the specific heat and magnetic susceptibility. The analytical low temperature analysis was performed providing the effective central charge. The computed values are in agreement with the numerical predictions in the literature.
Nonperturbative Yukawa theory at finite density and temperature
Fraga, Eduardo S; Pinto, Marcus Benghi
2009-01-01
In-medium Yukawa theory is part of the thermodynamics of the Standard Model of particle physics and is one of the main building blocks of most effective field theories of fermionic systems. By computing its pressure we investigate the nonperturbative thermodynamics at finite temperature and density using the optimized perturbation theory (OPT) framework. Our calculations are valid for arbitrary fermion and scalar masses, temperature, chemical potential, and not restricted to weak coupling. The model is considered in the presence as well as in the absence of condensates. Comparison with nonperturbative results shows that second order perturbation theory (PT) fails in the first case but performs rather well when condensates are absent, even at high-temperature regimes.
Aspects of Holographic Entanglement at Finite Temperature and Chemical Potential
Kundu, Sandipan
2016-01-01
We investigate the behavior of entanglement entropy at finite temperature and chemical potential for strongly coupled large-N gauge theories in $d$-dimensions ($d\\ge 3$) that are dual to Anti-de Sitter-Reissner-Nordstrom geometries in $(d+1)-$dimensions, in the context of gauge-gravity duality. We develop systematic expansions based on the Ryu-Takayanagi prescription that enable us to derive analytic expressions for entanglement entropy and mutual information in different regimes of interest. Consequently, we identify the specific regions of the bulk geometry that contribute most significantly to the entanglement entropy of the boundary theory at different limits. We define a scale, dubbed as the effective temperature, which determines the behavior of entanglement in different regimes. At high effective temperature, entanglement entropy is dominated by the thermodynamic entropy, however, mutual information subtracts out this contribution and measures the actual quantum entanglement. Finally, we study the enta...
The Fading of Symmetry Non-Restoration at Finite Temperature
Gavela-Legazpi, Maria Belen; Rius, N; Vargas-Castrillon, S
1999-01-01
The fate of symmetries at high temperature determines the dynamics of the very early universe. It is conceivable that temperature effects favor symmetry breaking instead of restoration. Concerning global symmetries, the non-linear sigma model is analyzed in detail. For spontaneously broken gauge symmetries, we propose the gauge boson magnetic mass as a ``flag'' for symmetry (non)-restoration. We consider several cases: the standard model with one and two Higgs doublets in the perturbative regime, and the case of a strongly interacting Higgs sector. The latter is done in a model independent way with the tools provided by chiral Lagrangians. Our results clearly point towards restoration, a pattern consistent with recent lattice computations for global symmetries. In addition, we explicitly verify $BRST$ invariance for gauge theories at finite temperature.
Sideband Rabi spectroscopy of finite-temperature trapped Bose gases
Allard, Baptiste; Schmied, Roman; Treutlein, Philipp
2016-01-01
We use Rabi spectroscopy to explore the low-energy excitation spectrum of a finite-temperature Bose gas of rubidium atoms across the phase transition to a Bose-Einstein condensate (BEC). To record this spectrum, we coherently drive the atomic population between two spin states. A small relative displacement of the spin-specific trapping potentials enables sideband transitions between different motional states. The intrinsic non-linearity of the motional spectrum, mainly originating from two-body interactions, makes it possible to resolve and address individual excitation lines. Together with sensitive atom-counting, this constitutes a feasible technique to count single excited atoms of a BEC and to determine the temperature of nearly pure condensates. As an example, we show that for a nearly pure BEC of N = 800 atoms the first excited state has a population of less than 5 atoms, corresponding to an upper bound on the temperature of 30 nK.
Towards quantum turbulence in finite temperature Bose-Einstein condensates
Energy Technology Data Exchange (ETDEWEB)
Lan, Shanquan [Department of Physics, Beijing Normal University,Beijing, 100875 (China); Tian, Yu [School of Physics, University of Chinese Academy of Sciences,Beijing, 100049 (China); Shanghai Key Laboratory of High Temperature Superconductors,Shanghai, 200444 (China); Zhang, Hongbao [Department of Physics, Beijing Normal University,Beijing, 100875 (China); Theoretische Natuurkunde, Vrije Universiteit Brussel, andThe International Solvay Institutes,Pleinlaan 2, Brussels, B-1050 (Belgium)
2016-07-19
Motivated by the various indications that holographic superfluid is BCS like at the standard quantization but BEC like at the alternative quantization, we have implemented the alternative quantization in the dynamical holographic superfluid for the first time. With this accomplishment, we further initiate the detailed investigation of quantum turbulence in finite temperature BEC by a long time stable numerical simulation of bulk dynamics, which includes the two body decay of vortex number caused by vortex pair annihilation, the onset of superfluid turbulence signaled by Kolmogorov scaling law, and a direct energy cascade demonstrated by injecting energy to the turbulent superfluid. All of these results share the same patterns as the holographic superfluid at the standard quantization, thus suggest that these should be universal features for quantum turbulence at temperatures order of the critical temperature.
Decay Process of Quantum Open System at Finite Temperatures
Institute of Scientific and Technical Information of China (English)
肖骁; 高一波
2012-01-01
Starting from the formal solution to the Heisenberg equation, we revisit an universal model for a quantum open system with a harmonic oscillator linearly coupled to a boson bath. The analysis of the decay process for a Fock state and a coherent state demonstrate that this method is very useful in dealing with the problems in decay process of the open system. For finite temperatures, the calculations of the reduced density matrix and the mean excitation number for the open system show that an initiaJ coherent state will evolve into a temperature-dependant coherent state after tracing over the bath variables. Also in short-time limit, a temperature-dependant effective Hamiltonian for the open system characterizes the decay process of the open system.
Gravitational collapse of a magnetized fermion gas with finite temperature
Energy Technology Data Exchange (ETDEWEB)
Delgado Gaspar, I. [Instituto de Geofisica y Astronomia (IGA), La Habana (Cuba); Perez Martinez, A. [Instituto de Cibernetica, Matematica y Fisica (ICIMAF), La Habana (Cuba); Sussman, Roberto A. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico (ICN-UNAM), Mexico (Mexico); Ulacia Rey, A. [Instituto de Cibernetica, Matematica y Fisica (ICIMAF), La Habana (Cuba); Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico (ICN-UNAM), Mexico (Mexico)
2013-07-15
We examine the dynamics of a self-gravitating magnetized fermion gas at finite temperature near the collapsing singularity of a Bianchi-I spacetime. Considering a general set of appropriate and physically motivated initial conditions, we transform Einstein-Maxwell field equations into a complete and self-consistent dynamical system amenable for numerical work. The resulting numerical solutions reveal the gas collapsing into both, isotropic (''point-like'') and anisotropic (''cigar-like''), singularities, depending on the initial intensity of the magnetic field. We provide a thorough study of the near collapse behavior and interplay of all relevant state and kinematic variables: temperature, expansion scalar, shear scalar, magnetic field, magnetization, and energy density. A significant qualitative difference in the behavior of the gas emerges in the temperature range T/m{sub f} {proportional_to} 10{sup -6} and T/m{sub f} {proportional_to} 10{sup -3}. (orig.)
Towards quantum turbulence in finite temperature Bose-Einstein condensates
Lan, Shanquan; Tian, Yu; Zhang, Hongbao
2016-07-01
Motivated by the various indications that holographic superfluid is BCS like at the standard quantization but BEC like at the alternative quantization, we have implemented the alternative quantization in the dynamical holographic superfluid for the first time. With this accomplishment, we further initiate the detailed investigation of quantum turbulence in finite temperature BEC by a long time stable numerical simulation of bulk dynamics, which includes the two body decay of vortex number caused by vortex pair annihilation, the onset of superfluid turbulence signaled by Kolmogorov scaling law, and a direct energy cascade demonstrated by injecting energy to the turbulent superfluid. All of these results share the same patterns as the holographic superfluid at the standard quantization, thus suggest that these should be universal features for quantum turbulence at temperatures order of the critical temperature.
Towards Quantum Turbulence in Finite Temperature Bose-Einstein Condensates
Lan, Shanquan; Zhang, Hongbao
2016-01-01
Motivated by the various indications that holographic superfluid is BCS like at the standard quantization but BEC like at the alternative quantization, we have implemented the alternative quantization in the dynamical holographic superfluid for the first time. With this accomplishment, we further initiate the detailed investigation of quantum turbulence in finite temperature BEC by a long time stable numerical simulation of bulk dynamics, which includes the two body decay of vortex number caused by vortex pair annihilation, the onset of superfluid turbulence signaled by Kolmogorov scaling law, and a direct energy cascade demonstrated by injecting energy to the turbulent superfluid. All of these results share the same patterns as the holographic superfluid at the standard quantization, thus suggest that these should be universal features for quantum turbulence at temperatures order of the critical temperature.
Properties of the sigma meson at finite temperature
Ibarra, J. R. Morones; Aguirre, A. J. Garza; Flores-Baez, Francisco V.
2015-12-01
We study the changes of the mass and width of the sigma meson in the framework of the Linear Sigma Model at finite temperature, in the one-loop approximation. We have found that as the temperature increases, the mass of sigma shifts down. We have also analyzed the σ-spectral function and we observe an enhancement at the threshold which is a signature of partial restoration of chiral symmetry, also interpreted as a tendency to chiral phase transition. Additionally, we studied the width of the sigma, when the threshold enhancement takes place, for different values of the sigma mass. We found that there is a brief enlargement followed by an abrupt fall in the width as the temperature increases, which is also related with the restoration of chiral symmetry and an indication that the sigma is a bound state of two pions.
On the axial $U(1)$ symmetry at finite temperature
Cossu, Guido; Hashimoto, Shoji; Noaki, Jun-ichi; Tomiya, Akio
2015-01-01
We study the $U(1)_A$ anomaly in two-flavor lattice QCD at finite temperature with the M\\"obius domain-wall Dirac operator. We generate gauge configurations in the temperature range $(0.9, 1.2) T_c$ on different physical volumes, $L=$ 2--4 fm, and lattice spacings. We measure the difference of the susceptibilities of the flavor non-singlet scalar ($\\chi_\\delta$) and pseudoscalar ($\\chi_\\pi$) mesons. They are related by an axial $U(1)$ transformation and the difference vanishes if the axial $U(1)$ symmetry is respected. We identify the source of axial $U(1)$ symmetry breaking at finite temperature in the lowest eigenmodes, for the observable $\\chi_\\pi - \\chi_\\delta$. We then reweight the M\\"obius domain-wall fermion partition function to that of the overlap-Dirac operator to fully recover chiral symmetry. Our data show a significant discrepancy in the results coming from the M\\"obius domain-wall valence quarks, the overlap valence quarks on our DWF configurations and the reweighted ones that have full chiral s...
Engineering autonomous error correction in stabilizer codes at finite temperature
Freeman, C. Daniel; Herdman, C. M.; Whaley, K. B.
2017-07-01
We present an error-correcting protocol that enhances the lifetime of stabilizer code-based qubits which are susceptible to the creation of pairs of localized defects (due to stringlike error operators) at finite temperature, such as the toric code. The primary tool employed is periodic application of a local, unitary operator, which exchanges defects and thereby translates localized excitations. Crucially, the protocol does not require any measurements of stabilizer operators and therefore can be used to enhance the lifetime of a qubit in the absence of such experimental resources.
Comparison between microscopic methods for finite-temperature Bose gases
DEFF Research Database (Denmark)
Cockburn, S.P.; Negretti, Antonio; Proukakis, N.P.;
2011-01-01
We analyze the equilibrium properties of a weakly interacting, trapped quasi-one-dimensional Bose gas at finite temperatures and compare different theoretical approaches. We focus in particular on two stochastic theories: a number-conserving Bogoliubov (NCB) approach and a stochastic Gross...... on different thermodynamic ensembles (NCB, canonical; SGPE, grand-canonical), they yield the correct condensate statistics in a large Bose-Einstein condensate (BEC) (strong enough particle interactions). For smaller systems, the SGPE results are prone to anomalously large number fluctuations, well known...
Radial convection of finite ion temperature, high amplitude plasma blobs
DEFF Research Database (Denmark)
Wiesenberger, M.; Madsen, Jens; Kendl, Alexander
2014-01-01
We present results from simulations of seeded blob convection in the scrape-off-layer of magnetically confined fusion plasmas. We consistently incorporate high fluctuation amplitude levels and finite Larmor radius (FLR) effects using a fully nonlinear global gyrofluid model. This is in line...... with conditions found in tokamak scrape-off-layers (SOL) regions. Varying the ion temperature, the initial blob width, and the initial amplitude, we found an FLR dominated regime where the blob behavior is significantly different from what is predicted by cold-ion models. The transition to this regime is very...
Can sigma models describe finite temperature chiral transitions?
Kocic, Aleksandar; Aleksandar KOCIC; John KOGUT
1995-01-01
Large-N expansions and computer simulations indicate that the universality class of the finite temperature chiral symmetry restoration transition in the 3D Gross-Neveu model is mean field theory. This is a counterexample to the standard 'sigma model' scenario which predicts the 2D Ising model universality class. We trace the breakdown of the standard scenario (dimensional reduction and universality) to the absence of canonical scalar fields in the model. We point out that our results could be generic for theories with dynamical symmetry breaking, such as Quantum Chromodynamics.
Small velocity and finite temperature variations in kinetic relaxation models
Markowich, Peter
2010-01-01
A small Knuden number analysis of a kinetic equation in the diffusive scaling is performed. The collision kernel is of BGK type with a general local Gibbs state. Assuming that the flow velocity is of the order of the Knudsen number, a Hilbert expansion yields a macroscopic model with finite temperature variations, whose complexity lies in between the hydrodynamic and the energy-transport equations. Its mathematical structure is explored and macroscopic models for specific examples of the global Gibbs state are presented. © American Institute of Mathematical Sciences.
Charmonium correlation and spectral functions at finite temperature
Ding, H -T; Kaczmarek, O; Karsch, F; Satz, H; Soeldner, W
2010-01-01
We study the properties of charmonium states at finite temperature in quenched QCD on isotropic lattices. We measured charmonium correlators using non-perturbatively $\\cO(a)$ improved clover fermions on fine ($a=0.01$ fm) lattices with a relatively large size of $128^{3}\\times 96$, $128^3\\times48$, $128^3\\times32$ and $128^3\\times24$ at $0.73~T_c$, $1.46~T_c$, $2.20~T_c$ and $2.93~T_c$, respectively. Our analysis suggests that $\\Jpsi$ is melted already at $1.46~T_c$ and $\\eta_c$ starts to dissolve at $1.46~T_c$ and does not exist at higher temperatures. We also identify the heavy quark transport contribution at the spectral function level for the first time.
Equation of state and QCD transition at finite temperature
Bazavov, A; Cheng, M; Christ, N H; DeTar, C; Ejiri, S; Gottlieb, Steven; Gupta, R; Heller, U M; Huebner, K; Jung, C; Karsch, F; Laermann, E; Levkova, L; Miao, C; Mawhinney, R D; Petreczky, P; Schmidt, C; Soltz, R A; Söldner, W; Sugar, R; Toussaint, D; Vranas, P
2009-01-01
We calculate the equation of state in 2+1 flavor QCD at finite temperature with physical strange quark mass and almost physical light quark masses using lattices with temporal extent Nt=8. Calculations have been performed with two different improved staggered fermion actions, the asqtad and p4 actions. Overall, we find good agreement between results obtained with these two O(a^2) improved staggered fermion discretization schemes. A comparison with earlier calculations on coarser lattices is performed to quantify systematic errors in current studies of the equation of state. We also present results for observables that are sensitive to deconfining and chiral aspects of the QCD transition on Nt=6 and 8 lattices. We find that deconfinement and chiral symmetry restoration happen in the same narrow temperature interval. In an Appendix we present a simple parametrization of the equation of state that can easily be used in hydrodynamic model calculations. In this parametrization we also incorporated an estimate of c...
Isospin mixing at finite temperature in 80Zr
Corsi, A.; Bracco, A.; Camera, F.; Crespi, F. C. L.; Giaz, A.; Leoni, S.; Montanari, D.; Nicolini, R.; Vandone, V.; Wieland, O.; Benzoni, G.; Blasi, N.; Brambilla, S.; Million, B.; Kravchuk, V. L.; Cinausero, M.; Degerlier, M.; Gramegna, F.; Marchi, T.; Barlini, S.; Bardelli, L.; Bini, M.; Casini, G.; Nannini, A.; Pasquali, G.; Poggi, G.; Baiocco, G.; Bruno, M.; D'Agostino, M.; Morelli, L.; Vannini, G.; Ciemala, M.; Kmiecik, M.; Maj, A.; Mazurek, K.; Meczynski, W.; Myalski, S.
2012-09-01
The degree of isospin mixing in the hot compound nucleus 80Zr has been extracted by statistical-model analysis of the γ-decay spectrum emitted in fusion reactions 40Ca+40Ca at Ebeam = 200 MeV and 37Cl+44Ca at Ebeam = 153 MeV. In the case of 40Ca+40Ca reaction an hindrance of first-step γ-decay is expected because in self-conjugate nuclei the E1 selection rules forbid the decay between states with isospin I=0. The results obtained at finite temperature (T ~ 2 MeV) have been used to extrapolate the degree of mixing at zero temperature
Renormalization Group Optimized Perturbation Theory at Finite Temperatures
Kneur, J -L
2015-01-01
A recently developed variant of the so-called optimized perturbation theory (OPT), making it perturbatively consistent with renormalization group (RG) properties, RGOPT, was shown to drastically improve its convergence for zero temperature theories. Here the RGOPT adapted to finite temperature is illustrated with a detailed evaluation of the two-loop pressure for the thermal scalar $ \\lambda\\phi^4$ field theory. We show that already at the simple one-loop level this quantity is exactly scale-invariant by construction and turns out to qualitatively reproduce, with a rather simple procedure, results from more sophisticated resummation methods at two-loop order, such as the two-particle irreducible approach typically. This lowest order also reproduces the exact large-$N$ results of the $O(N)$ model. Although very close in spirit, our RGOPT method and corresponding results differ drastically from similar variational approaches, such as the screened perturbation theory or its QCD-version, the (resummed) hard therm...
Finite temperature Casimir effect in Kaluza-Klein spacetime
Energy Technology Data Exchange (ETDEWEB)
Teo, L.P. [Faculty of Information Technology, Multimedia University, Jalan Multimedia, Cyberjaya, 63100 Selangor Darul Ehsan (Malaysia)], E-mail: lpteo@mmu.edu.my
2009-10-01
In this article, we consider the finite temperature Casimir effect in Kaluza-Klein spacetime due the vacuum fluctuation of massless scalar field with Dirichlet boundary conditions. We consider the general case where the extra dimensions (internal space) can be any compact connected manifold or orbifold without boundaries. Using piston analysis, we show that the Casimir force is always attractive at any temperature, regardless of the geometry of the internal space. Moreover, the magnitude of the Casimir force increases as the size of the internal space increases and it reduces to the Casimir force in (3+1)-dimensional Minkowski spacetime when the size of the internal space shrinks to zero. In the other extreme where the internal space is large, the Casimir force can increase beyond all bound. Asymptotic behaviors of the Casimir force in the low and high temperature regimes are derived and it is observed that the magnitude of the Casimir force grows linearly with temperature in the high temperature regime.
Coarse-grained molecular dynamics: Nonlinear finite elements and finite temperature
Energy Technology Data Exchange (ETDEWEB)
Rudd, R E; Broughton, J Q
2005-05-30
Coarse-grained molecular dynamics (CGMD) is a technique developed as a concurrent multiscale model that couples conventional molecular dynamics (MD) to a more coarse-grained description of the periphery. The coarse-grained regions are modeled on a mesh in a formulation that generalizes conventional finite element modeling (FEM) of continuum elasticity. CGMD is derived solely from the MD model, however, and has no continuum parameters. As a result, it provides a coupling that is smooth and provides control of errors that arise at the coupling between the atomistic and coarse-grained regions. In this article, we elaborate on the formulation of CGMD, describing in detail how CGMD is applied to anharmonic solids and finite temperature simulations. As tests of CGMD, we present in detail the calculation of the phonon spectra for solid argon and tantalum in 3D, demonstrating how CGMD provides a better description of the elastic waves than that provided by FEM. We also present elastic wave scattering calculations that show the elastic wave scattering is more benign in CGMD than FEM. We also discuss the dependence of scattering on the properties of the mesh. We introduce a rigid approximation to CGMD that eliminates internal relaxation, similar to the Quasicontinuum technique, and compare it to the full CGMD.
Quantum gases finite temperature and non-equilibrium dynamics
Szymanska, Marzena; Davis, Matthew; Gardiner, Simon
2013-01-01
The 1995 observation of Bose-Einstein condensation in dilute atomic vapours spawned the field of ultracold, degenerate quantum gases. Unprecedented developments in experimental design and precision control have led to quantum gases becoming the preferred playground for designer quantum many-body systems. This self-contained volume provides a broad overview of the principal theoretical techniques applied to non-equilibrium and finite temperature quantum gases. Covering Bose-Einstein condensates, degenerate Fermi gases, and the more recently realised exciton-polariton condensates, it fills a gap by linking between different methods with origins in condensed matter physics, quantum field theory, quantum optics, atomic physics, and statistical mechanics. Thematically organised chapters on different methodologies, contributed by key researchers using a unified notation, provide the first integrated view of the relative merits of individual approaches, aided by pertinent introductory chapters and the guidance of ed...
Perturbative algebraic quantum field theory at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Lindner, Falk
2013-08-15
We present the algebraic approach to perturbative quantum field theory for the real scalar field in Minkowski spacetime. In this work we put a special emphasis on the inherent state-independence of the framework and provide a detailed analysis of the state space. The dynamics of the interacting system is constructed in a novel way by virtue of the time-slice axiom in causal perturbation theory. This method sheds new light in the connection between quantum statistical dynamics and perturbative quantum field theory. In particular it allows the explicit construction of the KMS and vacuum state for the interacting, massive Klein-Gordon field which implies the absence of infrared divergences of the interacting theory at finite temperature, in particular for the interacting Wightman and time-ordered functions.
Lattice QCD at finite temperature and density from Taylor expansion
Steinbrecher, Patrick
2017-01-01
In the first part, I present an overview of recent Lattice QCD simulations at finite temperature and density. In particular, we discuss fluctuations of conserved charges: baryon number, electric charge and strangeness. These can be obtained from Taylor expanding the QCD pressure as a function of corresponding chemical potentials. Our simulations were performed using quark masses corresponding to physical pion mass of about 140 MeV and allow a direct comparison to experimental data from ultra-relativistic heavy ion beams at hadron colliders such as the Relativistic Heavy Ion Collider at Brookhaven National Laboratory and the Large Hadron Collider at CERN. In the second part, we discuss computational challenges for current and future exascale Lattice simulations with a focus on new silicon developments from Intel and NVIDIA.
A schematic model for QCD at finite temperature
Lerma, S; Hess, P O; Civitarese, O; Reboiro, M
2002-01-01
The simplest version of a class of toy models for QCD is presented. It is a Lipkin-type model, for the quark-antiquark sector, and, for the gluon sector, gluon pairs with spin zero are treated as elementary bosons. The model restricts to mesons with spin zero and to few baryonic states. The corresponding energy spectrum is discussed. We show that ground state correlations are essential to describe physical properties of the spectrum at low energies. Phase transitions are described in an effective manner, by using coherent states. The appearance of a Goldstone boson for large values of the interaction strength is discussed, as related to a collective state. The formalism is extended to consider finite temperatures. The partition function is calculated, in an approximate way, showing the convenience of the use of coherent states. The energy density, heat capacity and transitions from the hadronic phase to the quark-gluon plasma are calculated.
Dynamical renormalization group resummation of finite temperature infrared divergences
Boyanovsky, D; Holman, R; Simionato, M
1999-01-01
We introduce the method of dynamical renormalization group to study relaxation and damping out of equilibrium directly in real time and applied it to the study of infrared divergences in scalar QED. This method allows a consistent resummation of infrared effects associated with the exchange of quasistatic transverse photons and leads to anomalous logarithmic relaxation of the form $e^{-\\alpha T t \\ln[t/t_0]}$ which prevents a quasiparticle interpretation of charged collective excitations at finite temperature. The hard thermal loop resummation program is incorporated consistently into the dynamical renormalization group yielding a picture of relaxation and damping phenomena in a plasma in real time that trascends the conceptual limitations of the quasiparticle picture and other type of resummation schemes. We derive a simple criterion for establishing the validity of the quasiparticle picture to lowest order.
Effective Polyakov Loop Dynamics for Finite Temperature G(2) Gluodynamics
Wellegehausen, Bjoern H; Wozar, Christian
2009-01-01
Based on the strong coupling expansion we obtain effective 3-dimensional models for the Polyakov loop in finite-temperature G_2 gluodynamics. The Svetitsky-Jaffe conjecture relates the resulting continuous spin models with G_2 gluodynamics near phase transition points. In the present work we analyse the effective theory in leading order with the help of a generalised mean field approximation and with detailed Monte-Carlo simulations. In addition we derive a Potts-type discrete spin model by restricting the characters of the Polyakov loops to the three extremal points of the fundamental domain of G_2. Both the continuous and discrete effective models show a rich phase structure with a ferromagnetic, symmetric and several anti-ferromagnetic phases. The phase diagram contains first and second order transition lines and tricritical points. The modified mean field predictions compare very well with the results of our simulations.
Instanton dynamics in finite temperature QCD via holography
Directory of Open Access Journals (Sweden)
Masanori Hanada
2015-10-01
Full Text Available We investigate instantons in finite temperature QCD via Witten's holographic QCD. To study the deconfinement phase, we use the setup proposed in [1]. We find that the sizes of the instantons are stabilized at certain values both in the confinement and deconfinement phases. This agrees with the numerical result in the lattice gauge theory. Besides we find that the gravity duals of the large and small instantons in the deconfinement phase have different topologies. We also argue that the fluctuation of the topological charges is large in confinement phase while it is exponentially suppressed in deconfinement phase, and a continuous transition occurs at the Gross–Witten–Wadia (GWW point. It would be difficult to observe the counterpart of this transition in lattice QCD, since the GWW point in QCD may stay at an unstable branch.
Separation of finite electron temperature effect on plasma polarimetry
Energy Technology Data Exchange (ETDEWEB)
Imazawa, Ryota; Kawano, Yasunori; Kusama, Yoshinori [Japan Atomic Energy Agency, 801-1 Mukoyama, Naka, Ibaraki (Japan)
2012-12-15
This study demonstrates the separation of the finite electron temperature on the plasma polarimetry in the magnetic confined fusion plasma for the first time. Approximate solutions of the transformed Stokes equation, including the relativistic effect, suggest that the orientation angle, {theta}, and ellipticity angle, {epsilon}, of polarization state have different dependency on the electron density, n{sub e}, and the electron temperature, T{sub e}, and that the separation of n{sub e} and T{sub e} from {theta} and {epsilon} is possible in principle. We carry out the equilibrium and kinetic reconstruction of tokamak plasma when the central electron density was 10{sup 20} m{sup -3}, and the central electron temperatures were 5, 10, 20, and 30 keV. For both cases when a total plasma current, I{sub p}, is known and when I{sub p} is unknown, the profiles of plasma current density, j{sub {phi}}, n{sub e}, and T{sub e} are successfully reconstructed. The reconstruction of j{sub {phi}} without the information of I{sub p} indicates the new method of I{sub p} measurement applicable to steady state operation of tokamak.
Finite-Temperature Properties of Three-Dimensional Chiral Helimagnets
Shinozaki, Misako; Hoshino, Shintaro; Masaki, Yusuke; Kishine, Jun-ichiro; Kato, Yusuke
2016-07-01
We study a three-dimensional (3d) classical chiral helimagnet at finite temperatures through analysis of a spin Hamiltonian, which is defined on a simple cubic lattice and consists of the Heisenberg exchange, monoaxial Dzyaloshinskii-Moriya interactions, and the Zeeman energy due to a magnetic field applied in the plane perpendicular to the helical axis. We take account of the quasi-two-dimensionality of the known monoaxial chiral helimagnet CrNb3S6 and we adopt three methods: (i) a conventional mean-field (MF) analysis, which we call the 3dMF method, (ii) a hybrid method called the 2dMC-1dMF method, which is composed of a classical Monte Carlo (MC) simulation and a MF approximation applied respectively to the intra- and interlayer interactions, and (iii) a simple-MC simulation (3dMC) at zero field. The temperature dependence of the magnetization calculated by the 3dMF method shows a cusp-like structure similar to that observed in experiments. In the absence of a magnetic field, both 2dMC-1dMF and 3dMC yield similar values of the transition temperature. The 2dMC-1dMF method provides a quantitative description of the thermodynamic properties, even under an external field, at an accessible numerical cost.
Separation of finite electron temperature effect on plasma polarimetry.
Imazawa, Ryota; Kawano, Yasunori; Kusama, Yoshinori
2012-12-01
This study demonstrates the separation of the finite electron temperature on the plasma polarimetry in the magnetic confined fusion plasma for the first time. Approximate solutions of the transformed Stokes equation, including the relativistic effect, suggest that the orientation angle, θ, and ellipticity angle, ε, of polarization state have different dependency on the electron density, n(e), and the electron temperature, T(e), and that the separation of n(e) and T(e) from θ and ε is possible in principle. We carry out the equilibrium and kinetic reconstruction of tokamak plasma when the central electron density was 10(20) m(-3), and the central electron temperatures were 5, 10, 20, and 30 keV. For both cases when a total plasma current, I(p), is known and when I(p) is unknown, the profiles of plasma current density, j(φ), n(e), and T(e) are successfully reconstructed. The reconstruction of j(φ) without the information of I(p) indicates the new method of I(p) measurement applicable to steady state operation of tokamak.
Finite-temperature corrections in the dilated chiral quark model
Kim, Y; Rho, M; Kim, Youngman; Lee, Hyun Kyu; Rho, Mannque
1995-01-01
We calculate the finite-temperature corrections in the dilated chiral quark model using the effective potential formalism. Assuming that the dilaton limit is applicable at some short length scale, we interpret the results to represent the behavior of hadrons in dense {\\it and} hot matter. We obtain the scaling law, \\frac{f_{\\pi}(T)}{f_{\\pi}} = \\frac{m_Q (T)}{m_Q} \\simeq \\frac{m_{\\sigma}(T)}{m_{\\sigma}} while we argue, using PCAC, that pion mass does not scale within the temperature range involved in our Lagrangian. It is found that the hadron masses and the pion decay constant drop faster with temperature in the dilated chiral quark model than in the conventional linear sigma model that does not take into account the QCD scale anomaly. We attribute the difference in scaling in heat bath to the effect of baryonic medium on thermal properties of the hadrons. Our finding would imply that the AGS experiments (dense {\\it and} hot matter) and the RHIC experiments (hot and dilute matter) will ``see" different hadron...
Radial convection of finite ion temperature, high amplitude plasma blobs
Wiesenberger, M; Kendl, A
2014-01-01
We present results from simulations of seeded blob convection in the scrape-off-layer of magnetically confined fusion plasmas. We consistently incorporate high fluctuation amplitude levels and finite Larmor radius (FLR) effects using a fully nonlinear global gyrofluid model. This is in line with conditions found in tokamak scrape-off-layers (SOL) regions. Varying the ion temperature, the initial blob width and the initial amplitude, we found an FLR dominated regime where the blob behavior is significantly different from what is predicted by cold-ion models. The transition to this regime is very well described by the ratio of the ion gyroradius to the characteristic gradient scale length of the blob. We compare the global gyrofluid model with a partly linearized local model. For low ion temperatures we find that simulations of the global model show more coherent blobs with an increased cross-field transport compared to blobs simulated with the local model. The maximal blob amplitude is significantly higher in ...
PHD TUTORIAL: Finite-temperature models of Bose Einstein condensation
Proukakis, Nick P.; Jackson, Brian
2008-10-01
The theoretical description of trapped weakly interacting Bose-Einstein condensates is characterized by a large number of seemingly very different approaches which have been developed over the course of time by researchers with very distinct backgrounds. Newcomers to this field, experimentalists and young researchers all face a considerable challenge in navigating through the 'maze' of abundant theoretical models, and simple correspondences between existing approaches are not always very transparent. This tutorial provides a generic introduction to such theories, in an attempt to single out common features and deficiencies of certain 'classes of approaches' identified by their physical content, rather than their particular mathematical implementation. This tutorial is structured in a manner accessible to a non-specialist with a good working knowledge of quantum mechanics. Although some familiarity with concepts of quantum field theory would be an advantage, key notions, such as the occupation number representation of second quantization, are nonetheless briefly reviewed. Following a general introduction, the complexity of models is gradually built up, starting from the basic zero-temperature formalism of the Gross-Pitaevskii equation. This structure enables readers to probe different levels of theoretical developments (mean field, number conserving and stochastic) according to their particular needs. In addition to its 'training element', we hope that this tutorial will prove useful to active researchers in this field, both in terms of the correspondences made between different theoretical models, and as a source of reference for existing and developing finite-temperature theoretical models.
Institute of Scientific and Technical Information of China (English)
WANG Dian-Fu
2008-01-01
In terms of the Nambu-Jona-Lasinio mechanism, dynamical breaking of gauge symmetry for the maximally generalized Yang-Mills model is investigated. The gauge symmetry behavior at finite temperature is also investigated and it is shown that the gauge symmetry broken dynamically at zero temperature can be restored at finite temperatures.
Aguirre-Ramirez, G.; Oden, J. T.
1969-01-01
Finite element method applied to heat conduction in solids with temperature dependent thermal conductivity, using nonlinear constitutive equation for heat ABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGH
Finite Temperature Induced Fermion Number In The Nonlinear sigma Model In (2+1) Dimensions
Dunne, G V; Rao, K; Dunne, Gerald V.; Lopez-Sarrion, Justo; Rao, Kumar
2002-01-01
We compute the finite temperature induced fermion number for fermions coupled to a static nonlinear sigma model background in (2+1) dimensions, in the derivative expansion limit. While the zero temperature induced fermion number is well known to be topological (it is the winding number of the background), at finite temperature there is a temperature dependent correction that is nontopological -- this finite T correction is sensitive to the detailed shape of the background. At low temperature we resum the derivative expansion to all orders, and we consider explicit forms of the background as a CP^1 instanton or as a baby skyrmion.
Lorentz Invariance at Finite Temperature and Its Effect on Production Rate and Equation of State
Institute of Scientific and Technical Information of China (English)
HE Lian-Yi; ZHUANG Peng-Fei
2004-01-01
The effect of Lorentz invariance breaking on the production rate and the equation of state at finite temperature is investigated in the frame of φ3 theory. The invariance breaking significantly changes the off-shell degree at high temperatures.
Quantum Fluids of Self-Assembled Chains of Polar Molecules at Finite Temperature
Institute of Scientific and Technical Information of China (English)
ZHU Kun-Yan; TAN Lei; GAO Xiang; WANG Daw-Wei
2008-01-01
The finite temperature properties of self-assembled dipole chains of polar molecules in strongly confined pancake traps are investigated.The single-chain vibrations at finite temperature,which become important for long chains in a strongly interacting regime,are found to lower the transition temperature and to shift the chain distribution by less than 10%.We also propose experimental parameters to observe such quantum phase transition.
Finite-temperature study of eight-flavor SU(3) gauge theory
Schaich, David; Rinaldi, Enrico
2015-01-01
We present new lattice investigations of finite-temperature transitions for SU(3) gauge theory with Nf=8 light flavors. Using nHYP-smeared staggered fermions we are able to explore renormalized couplings $g^2 \\lesssim 20$ on lattice volumes as large as $48^3 \\times 24$. Finite-temperature transitions at non-zero fermion mass do not persist in the chiral limit, instead running into a strongly coupled lattice phase as the mass decreases. That is, finite-temperature studies with this lattice action require even larger $N_T > 24$ to directly confirm spontaneous chiral symmetry breaking.
Quantum Electrodynamics in Two-Dimensions at Finite Temperature. Thermofield Bosonization Approach
Belvedere, L V; Rothe, K D; Rodrigues, A F
2009-01-01
The Schwinger model at finite temperature is analyzed using the Thermofield Dynamics formalism. The operator solution due to Lowenstein and Swieca is generalized to the case of finite temperature within the thermofield bosonization approach. The general properties of the statistical-mechanical ensemble averages of observables in the Hilbert subspace of gauge invariant thermal states are discussed. The bare charge and chirality of the Fermi thermofields are screened, giving rise to an infinite number of mutually orthogonal thermal ground states. One consequence of the bare charge and chirality selection rule at finite temperature is that there are innumerably many thermal vacuum states with the same total charge and chirality of the doubled system. The fermion charge and chirality selection rules at finite temperature turn out to imply the existence of a family of thermal theta vacua states parametrized with the same number of parameters as in zero temperature case. We compute the thermal theta-vacuum expectat...
Parity-odd and CPT-even electrodynamics of the SME at Finite Temperature
Casana, Rodolfo; Silva, Madson R O
2009-01-01
This work examines the finite temperature properties of the CPT-even and parity-odd electrodynamics of the standard model extension. We start from the partition function written into the functional integral formalism in Ref. \\cite{Finite}. After specializing the Lorentz-violating tensor $ W_{\\alpha \
The calculation of quark number susceptibility at finite chemical potential and temperature
Energy Technology Data Exchange (ETDEWEB)
Jiang Yu; Li Ning [Department of Physics, Nanjing University, Nanjing 210093 (China); Sun Weimin [Department of Physics, Nanjing University, Nanjing 210093 (China); Joint Center for Particle, Nuclear Physics and Cosmology, Nanjing 210093 (China); Zong Hongshi, E-mail: zonghs@chenwang.nju.edu.c [Department of Physics, Nanjing University, Nanjing 210093 (China); Joint Center for Particle, Nuclear Physics and Cosmology, Nanjing 210093 (China)
2010-03-01
In this paper, we calculate the quark number susceptibility (QNS) at finite chemical potential mu and finite temperature T in the framework of the Dyson-Schwinger approach using the meromorphic quark propagator proposed in [Phys. Rev. D 70, 014014 (2004)]. Analysis and discussions of the calculated result of the QNS is given.
Revisiting strong coupling QCD at finite baryon density and temperature
Fromm, M
2008-01-01
The strong coupling limit ($\\beta_{gauge}=0$) of lattice QCD with staggered fermions enjoys the same non-perturbative properties as continuum QCD, namely confinement and chiral symmetry breaking. In contrast to the situation at weak coupling, the sign problem which appears at finite density can be brought under control for a determination of the full (mu,T) phase diagram by Monte Carlo simulations. Further difficulties with efficiency and ergodicity of the simulations, especially at the strongly first-order, low-T, finite-mu transition, are addressed respectively with a worm algorithm and multicanonical sampling. Our simulations reveal sizeable corrections to the old results of Karsch and Muetter. Comparison with analytic mean-field determinations of the phase diagram shows discrepancies of O(10) in the location of the QCD critical point.
Finite Temperature CPT-even Electrodynamics of the Standard Model Extension
Casana, Rodolfo; Rodrigues, Josberg S; Silva, Madson R O
2009-01-01
In this work, we examine the finite temperature properties of the non-birefringent coefficients of the CPT-even and Lorentz-invariance-violating (LIV) electrodynamics of the standard model extension, represented by the term $W_{\\alpha \
Quantum Fluctuation of a Mesoscopic Inductance Coupling Circuit at Finite Temperature
Institute of Scientific and Technical Information of China (English)
SONG Tong-Qiang; ZHU Yue-Jin
2003-01-01
We study the quantization of mesoscopic inductance coupling circuit and discuss its time evolution. Bymeans of the thermal field dynamics theory we study the quantum fluctuation of the system at finite temperature.
Institute of Scientific and Technical Information of China (English)
Zhan You-Bang
2004-01-01
We have investigated the reduced fluctuation properties in a mesoscopic Josephson junction with the squeezed state at a finite temperature. It is shown that the fluctuations increase with increasing temperature and the mesoscopic Josephson junction subsystem can exhibit squeezing behaviour at an appropriately low temperature.
Finite-temperature field theory and quantum noise in an electrical network
Energy Technology Data Exchange (ETDEWEB)
Garavaglia, T.
1988-10-15
Finite-temperature (0less than or equal toT
Nucleons and isobars at finite density ({rho}) and temperature (T)
Energy Technology Data Exchange (ETDEWEB)
Cenni, R. [Dipt. di Fisica, Univ. di Genova (Italy); Istituto Nazionale di Fisica Nucleare, Genoa (Italy); Dey, J. [Abdus Salam International Centre for Theoretical Physics, Trieste (Italy); Maulana Azad Coll., Calcutta (India); Dey, M. [Department of Physics, Presidency College, Calcutta 700 073 (India)
2001-09-01
The importance of studying matter at high {rho} increases as more astrophysical data becomes available from recently launched spacecrafts. The importance of high-T studies derives from heavy-ion data. In this paper we set up a formalism to study the nucleons and isobars with long- and short-range potentials non-pertubatively, bosonizing and expanding semi-classically the Feyman integrals up to one loop. We address the low-density, finite-T problem first, the case relevant to heavy-ion collisions, hoping to address the high-density case later. Interactions change the nucleon and isobar numbers at different {rho} and T non-trivially. (orig.)
Nucleons and Isobars at finite density ($\\rho$) and temperature (T)
Cenni, Rinaldo; Dey, Jishnu; Dey, Mira
2001-01-01
The importance of studying matter at high $\\rho$ increases as more astrophysical data becomes available from recently launched spacecrafts. The importance of high T studies derives from heavy ion data. In this paper we set up a formalism to study the nucleons and isobars with long and short range potentials non-pertubatively, bosonizing and expanding semi-classically the Feyman integrals up to one loop. We address the low density, finite T problem=A0 first, the case relevant to heavy ion coll...
Nucleons and Isobars at finite density ($\\rho$) and temperature (T)
Cenni, R; Dey, M; Cenni, Rinaldo; Dey, Jishnu; Dey, Mira
2001-01-01
The importance of studying matter at high $\\rho$ increases as more astrophysical data becomes available from recently launched spacecrafts. The importance of high T studies derives from heavy ion data. In this paper we set up a formalism to study the nucleons and isobars with long and short range potentials non-pertubatively, bosonizing and expanding semi-classically the Feyman integrals up to one loop. We address the low density, finite T problem=A0 first, the case relevant to heavy ion collisions, hoping to adresss the high density case later. Interactions change the nucleon and isobar numbers at different $\\rho$ and T non-trivially.
One-point functions in finite volume/temperature: a case study
Szécsényi, I M; Watts, G M T
2013-01-01
We consider finite volume (or equivalently, finite temperature) expectation values of local operators in integrable quantum field theories using a combination of numerical and analytical approaches. It is shown that the truncated conformal space approach, when supplemented with a recently proposed renormalization group, can be sufficiently extended to the low-energy regime that it can be matched with high precision by the low-temperature expansion proposed by Leclair and Mussardo. Besides verifying the consistency of the two descriptions, their combination leads to an evaluation of expectation values which is valid to a very high precision for all volume/temperature scales. As a side result of the investigation, we also discuss some unexpected singularities in the framework recently proposed by Pozsgay and Tak\\'acs for the description of matrix elements of local operators in finite volume, and show that while some of these singularities are resolved by the inclusion of the class of exponential finite size cor...
Three-loop HTLpt thermodynamics at finite temperature and isospin chemical potential
Andersen, Jens O; Mustafa, Munshi G; Strickland, Michael
2015-01-01
In a previous paper (JHEP {\\bf 05} (2014) 27), we calculated the three-loop thermodynamic potential of QCD at finite temperature $T$ and quark chemical potentials $\\mu_q$ using the hard-thermal-loop perturbation theory (HTLpt) reorganization of finite temperature and density QCD. The result allows us to study the thermodynamics of QCD at finite temperature and isospin chemical potential $\\mu_I$. We calculate the pressure, energy density, and entropy density, the trace anomaly, and the speed of sound at zero and nonzero $\\mu_I$. The second, fourth, and sixth-order isospin susceptibilities are calculated at zero $\\mu_I$. Our results can be directly compared to lattice QCD without Taylor expansions around $\\mu_q=0$ since QCD has no sign problem at finite isospin chemical potential.
QCD sum rule studies at finite density and temperature
Energy Technology Data Exchange (ETDEWEB)
Kwon, Youngshin
2010-01-21
In-medium modifications of hadronic properties have a strong connection to the restoration of chiral symmetry in hot and/or dense medium. The in-medium spectral functions for vector and axial-vector mesons are of particular interest in this context, considering the experimental dilepton production data which signal the in-medium meson properties. In this thesis, finite energy sum rules are employed to set constraints for the in-medium spectral functions of vector and axial-vector mesons. Finite energy sum rules for the first two moments of the spectral functions are investigated with emphasis on the role of a scale parameter related to the spontaneous chiral symmetry breaking in QCD. It is demonstrated that these lowest moments of vector current spectral functions do permit an accurate sum rule analysis with controlled inputs, such as the QCD condensates of lowest dimensions. In contrast, the higher moments contain uncertainties from the higher dimensional condensates. It turns out that the factorization approximation for the four-quark condensate is not applicable in any of the cases studied in this work. The accurate sum rules for the lowest two moments of the spectral functions are used to clarify and classify the properties of vector meson spectral functions in a nuclear medium. Possible connections with the Brown-Rho scaling hypothesis are also discussed. (orig.)
Optimal configuration for a finite low-temperature source refrigerator cycle with heat transfer law
Directory of Open Access Journals (Sweden)
Jun Li, Lingen Chen, Yanlin Ge, Fengrui Sun
2016-01-01
Full Text Available The optimal configuration of a refrigeration cycle operating between a finite low-temperature source and an infinite high-temperature sink are derived by using finite time thermodynamics based on a complex heat transfer law, including Newtonian heat transfer law, linear phenomenological heat transfer law, radiative heat transfer law, Dulong-Petit heat transfer law, generalized convective heat transfer law and generalized radiative heat transfer law. In the refrigeration cycle model the only irreversibility of finite rate heat transfer is considered. The optimal relation between cooling load and coefficient of performance (COP of the refrigeration cycle is also derived by using an equivalent temperature of low-temperature source. The obtained results include those with various heat transfer laws and infinite low-temperature source, and can provide some theoretical guidelines for the designs of practical refrigerators.
The topological susceptibility in finite temperature QCD and axion cosmology
Petreczky, Peter; Schadler, Hans-Peter; Sharma, Sayantan
2016-11-01
We study the topological susceptibility in 2 + 1 flavor QCD above the chiral crossover transition temperature using Highly Improved Staggered Quark action and several lattice spacings corresponding to temporal extent of the lattice, Nτ = 6 , 8 , 10 and 12. We observe very distinct temperature dependences of the topological susceptibility in the ranges above and below 250 MeV. While for temperatures above 250 MeV, the dependence is found to be consistent with dilute instanton gas approximation, at lower temperatures the fall-off of topological susceptibility is milder. We discuss the consequence of our results for cosmology wherein we estimate the bounds on the axion decay constant and the oscillation temperature if indeed the QCD axion is a possible dark matter candidate.
The topological susceptibility in finite temperature QCD and axion cosmology
Petreczky, Peter; Sharma, Sayantan
2016-01-01
We study the topological susceptibility in 2+1 flavor QCD above the chiral crossover transition temperature using Highly Improved Staggered Quark action and several lattice spacings, corresponding to temporal extent of the lattice, $N_\\tau=6,8,10$ and $12$. We observe very distinct temperature dependences of the topological susceptibility in the ranges above and below $250$ MeV. While for temperatures above $250$ MeV, the dependence is found to be consistent with dilute instanton gas approximation, at lower temperatures the fall-off of topological susceptibility is milder. We discuss the consequence of our results for cosmology wherein we estimate the bounds on the axion decay constant and the oscillation temperature if indeed the QCD axion is a possible dark matter candidate.
Quark propagator at finite temperature and finite momentum in quenched lattice QCD
Karsch, Frithjof
2009-01-01
We present an analysis of the quark spectral function above and below the critical temperature for deconfinement performed at zero and non-zero momentum in quenched lattice QCD using clover improved Wilson fermions in Landau gauge. It is found that the temporal quark correlation function in the deconfined phase near the critical temperature is well reproduced by a two-pole ansatz for the spectral function. This indicates that excitation modes of the quark field have small decay rates. The bare quark mass and momentum dependence of the spectral function is analyzed with this ansatz. In the chiral limit we find that the quark spectral function has two collective modes corresponding to the normal and plasmino excitations in the high temperature limit. Over a rather wide temperature range in the deconfined phase the pole mass of these modes at zero momentum, which corresponds to the thermal mass of the quark, is approximately proportional to temperature. With increasing bare quark masses the plasmino mode gradual...
Thermal effects on seeded finite ion temperature, high amplitude plasma blobs
Held, M; Madsen, J; Kendl, A
2016-01-01
Thermal effects on the perpendicular convection of seeded pressure blobs in the scrape-off layer of magnetised fusion plasmas are investigated. Our numerical study is based on a four field full-F gyrofluid model, which entails the consistent description of high fluctuation amplitudes and dynamic finite Larmor radius effects. We find that a temperature perturbation increases the maximal blob velocity and that a finite Larmor radius contributes to highly compact blob structures with finite poloidal motion. An extensive parameter study reveals that a smooth transition to this compact blob regime occurs when the finite Larmor radius effect strength, defined by the ratio of the ion diamagnetic to the perpendicular vorticity, exceeds unity. The maximal blob velocities excellently agree with the inertial velocity scaling law over more than an order of magnitude. We show that the finite Larmor radius effect strength affects the radial transport and verify the here presented empirical scaling law for the maximal radia...
[Dynamics of charge transfer along an oligonucleotide at finite temperature].
Lakhno, V D; Fialko, N S
2004-01-01
The quantum-statistical approach was used to describe the charge transfer in nucleotide sequences. The results of numerical modeling for hole transfer in the GTTGGG sequence with background temperature noise are given. It was shown that, since guanine has an oxidation potential lower than thymine, the hole created at the G donor in this sequence passes through the thymine barrier into the guanine triplet (acceptor) at a time of approximately 10 ps at a temperature of 37 degrees C.
Directory of Open Access Journals (Sweden)
M. Abu-Shady
2014-01-01
Full Text Available A baryonic chemical potential (μb is included in the linear sigma model at finite temperature. The effective mesonic potential is numerically calculated using the N-midpoint rule. The meson masses are investigated as functions of the temperature (T at fixed value of baryonic chemical potential. The pressure and energy density are investigated as functions of temperature at fi xed value of μb. The obtained results are in good agreement in comparison with other techniques. We conclude that the calculated effective potential successfully predicts the meson properties and thermodynamic properties at finite baryonic chemical potential.
Properties of Proton Transfer in Hydrogen-Bonded Systems at Finite Temperature
Institute of Scientific and Technical Information of China (English)
PANG Xiao-Feng
2002-01-01
The properties of proton transfer along hydrogen-bonded molecular systems are studied at finite temperature. The dynamic equations of the proton transport along the systems are obtained by using a completely quantummechanics method. From the dynamic equations and its soliton solutions we find out specific heat arising from the motionof solitons in the systems with finite temperature and the critical temperature of the soliton in the protein molecules,which is about 318 K. This shows that we can continuously study some biological phenomena in the living systems bythis model.
Institute of Scientific and Technical Information of China (English)
Chen Furong; Liu Jun; Xie Ruijun; Liu Fangjun; Hu Gang
2006-01-01
Based on thermal-elasto-plastic finite element theory, a two-dimensional finite element model for calculating electron beam brazing temperature and residual stress fields of stainless steel radiator are presented.The distributions of temperature and residual stress are studied.The results showed that temperature distribution on brazing surface is rather uniform, ranging from 1026 ℃ to 1090 ℃.The residual stresses are varied from initial compressive to tensile , and the variation of residual stress is very little in total zone of brazing surface.
Quantum electron-vibrational dynamics at finite temperature: Thermo field dynamics approach
Borrelli, Raffaele; Gelin, Maxim F.
2016-12-01
Quantum electron-vibrational dynamics in molecular systems at finite temperature is described using an approach based on the thermo field dynamics theory. This formulation treats temperature effects in the Hilbert space without introducing the Liouville space. A comparison with the theoretically equivalent density matrix formulation shows the key numerical advantages of the present approach. The solution of thermo field dynamics equations with a novel technique for the propagation of tensor trains (matrix product states) is discussed. Numerical applications to model spin-boson systems show that the present approach is a promising tool for the description of quantum dynamics of complex molecular systems at finite temperature.
Three-loop HTLpt thermodynamics at finite temperature and chemical potential
Energy Technology Data Exchange (ETDEWEB)
Haque, Najmul; Bandyopadhyay, Aritra [Theory Division, Saha Institute of Nuclear Physics,1/AF Bidhannagar, Kolkata-700107 (India); Andersen, Jens O. [Department of Physics, Norwegian University of Science and Technology,N-7491 Trondheim (Norway); Mustafa, Munshi G. [Theory Division, Saha Institute of Nuclear Physics,1/AF Bidhannagar, Kolkata-700107 (India); Strickland, Michael [Department of Physics, Kent State University,Kent, Ohio 44242 (United States); Su, Nan [Faculty of Physics, University of Bielefeld,D-33615 Bielefeld (Germany)
2014-05-07
We calculate the three-loop thermodynamic potential of QCD at finite temperature and chemical potential(s) using the hard-thermal-loop perturbation theory (HTLpt) reorganization of finite temperature and density QCD. The resulting analytic thermodynamic potential allows us to compute the pressure, energy density, and entropy density of the quark-gluon plasma. Using these we calculate the trace anomaly, speed of sound, and second-, fourth-, and sixth-order quark number susceptibilities. For all observables considered we find good agreement between our three-loop HTLpt calculations and available lattice data for temperatures above approximately 300 MeV.
Quarkonium correlation functions at finite temperature in the charm to bottom region
Ohno, Hiroshi
2013-01-01
Quarkonium correlation functions at finite temperature were studied in a region of the quark mass for charmonia to bottomonia in quenched lattice QCD with $O(a)$-improved Wilson quarks. Our simulations were performed on large isotropic lattices at temperatures in the range from about 0.80$T_c$ to 1.61$T_c$. We investigated quarkonium behavior in terms of temperature dependence as well as quark mass dependence of the quarkonium correlation functions and related quantities at both vanishing and finite momenta.
Supersymmetry and R-symmetry Breaking in Meta-stable Vacua at Finite Temperature and Density
Arai, Masato; Sasaki, Shin
2014-01-01
We study a meta-stable supersymmetry-breaking vacuum in a generalized O'Raifeartaigh model at finite temperature and chemical potentials. Fields in the generalized O'Raifeartaigh model possess different R-charges to realize R-symmetry breaking. Accordingly, at finite density and temperature, the chemical potentials have to be introduced in a non-uniform way. Based on the formulation elaborated in our previous work we study the one-loop thermal effective potential including the chemical potentials in the generalized O'Raifeartaigh model. We perform the numerical analysis and find that the R-symmetry breaking vacua, which exist at zero temperature and zero chemical potential, are destabilized for some parameter regions. In addition, we find that there are parameter regions where new R-symmetry breaking vacua are realized even at high temperature by the finite density effects.
Charmonium spectrum at finite temperature from a Bayesian analysis of QCD sum rules
Directory of Open Access Journals (Sweden)
Morita Kenji
2012-02-01
Full Text Available Making use of a recently developed method of analyzing QCD sum rules, we investigate charmonium spectral functions at finite temperature. This method employs the Maximum Entropy Method, which makes it possible to directly obtain the spectral function from the sum rules, without having to introduce any strong assumption about its functional form. Finite temperature effects are incorporated into the sum rules by the change of the various gluonic condensates that appear in the operator product expansion. These changes depend on the energy density and pressure at finite temperature, which are extracted from lattice QCD. As a result, J/ψ and ηc dissolve into the continuum already at temperatures around 1.0 ~ 1.1 Tc.
Finite temperature quantum correlations in su(2)(c) quark states and quantum spin models
Hamieh, S; Tawfik, A
2005-01-01
The entanglement at finite temperatures is analyzed by using thermal models for colored quarks making tip the hadron physical states. We have found that these quantum correlations entirely vanish at T-c >= m(q)/ln(1.5). For temperatures larger than T-c the correlations are classical. We have also wo
Quark-Number Susceptibility at Finite Chemical Potential and Zero Temperature
Institute of Scientific and Technical Information of China (English)
HE Deng-Ke; JIANG Yu; FENG Hong-Tao; SUN Wei-Min; ZONG Hong-Shi
2008-01-01
We give a direct method for calculating the quark-number susceptibility at finite chemical potential and zero temperature.In this approach the quark-number susceptibility is totally determined by G[μ](p)(the dressed quark propagator at finite chemical potential μ).By applying the general result in our previous study[Phys.Rev.C 71(2005)015205,034901,73 (2006) 016004] G[μ](p)is calculated from the model quark propagator proposed by Pagels and Stokar[Phys.Rev.D 20(1979)2947].The full analytic expression of the quark-number susceptibility at finite μ and zero T is obtained.
Finite-temperature magnetism of FeRh compounds
Polesya, S.; Mankovsky, S.; Ködderitzsch, D.; Minár, J.; Ebert, H.
2016-01-01
The temperature dependent stability of the magnetic phases of FeRh were investigated by means of total energy calculations with magnetic disorder treated within the uncompensated disordered local moment approach. In addition, Monte Carlo simulations based on the extended Heisenberg model have been performed, using exchange coupling parameters obtained from first principles. The crucial role and interplay of two factors in the metamagnetic transition in FeRh has been revealed, namely the dependence of the Fe-Fe exchange coupling parameters on the temperature-governed degree of magnetic disorder in the system and the stabilizing nature of the induced magnetic moment on Rh-sites. An important observation is the temperature dependence of these two competing factors.
Chemical relaxation times in a hadron gas at finite temperature
Goity, J L
1993-01-01
The relaxation times of particle numbers in hot hadronic matter with vanishing baryon number are estimated using the ideal gas approximation and taking into account resonance decays and annihilation processes as the only sources of particle number fluctuations. Near the QCD critical temperature the longest relaxation times turn out to be of the order of 10 fm and grow roughly exponentially to become of the order of $10^{3}$ fm at temperatures around 100 MeV. As a consequence of such long relaxation times, a clear departure from chemical equilibrium must be observed in the momentum distribution of secondary particles produced in high energy nuclear collisions.
Hamiltonian simulation of the Schwinger model at finite temperature
Buyens, Boye; Van Acoleyen, Karel
2016-01-01
Using Matrix Product Operators (MPO) the Schwinger model is simulated in thermal equilibrium. The variational manifold of gauge invariant MPO is constructed to represent Gibbs states. As a first application the chiral condensate in thermal equilibrium is computed and agreement with earlier studies is found. Furthermore, as a new application the Schwinger model is probed with a fractional charged static quark-antiquark pair separated infinitely far from each other. A critical temperature beyond which the string tension is exponentially suppressed is found, which is in qualitative agreement with analytical studies in the strong coupling limit. Finally, the CT symmetry breaking is investigated and our results strongly suggest that the symmetry is restored at any nonzero temperature.
Hamiltonian simulation of the Schwinger model at finite temperature
Buyens, Boye; Verstraete, Frank; Van Acoleyen, Karel
2016-10-01
Using matrix product operators, the Schwinger model is simulated in thermal equilibrium. The variational manifold of gauge-invariant matrix product operators is constructed to represent Gibbs states. As a first application, the chiral condensate in thermal equilibrium is computed, and agreement with earlier studies is found. Furthermore, as a new application, the Schwinger model is probed with a fractional charged static quark-antiquark pair separated infinitely far from each other. A critical temperature beyond which the string tension is exponentially suppressed is found and is in qualitative agreement with analytical studies in the strong coupling limit. Finally, the C T symmetry breaking is investigated, and our results strongly suggest that the symmetry is restored at any nonzero temperature.
Chiral phase transition in QED3 at finite temperature
Yin, Pei-Lin; Xiao, Hai-Xiao; Wei, Wei; Feng, Hong-Tao; Zong, Hong-Shi
2016-12-01
In the framework of Dyson-Schwinger equations, we employ two kinds of criteria (one kind is the chiral condensate, the other kind is thermodynamic quantities, such as the pressure, the entropy, and the specific heat) to investigate the nature of chiral phase transitions in QED3 for different fermion flavors. It is found that the chiral phase transitions in QED3 for different fermion flavors are all typical second-order phase transitions; the critical temperature and order of the chiral phase transition obtained from the chiral condensate and susceptibility are the same with that obtained by the thermodynamic quantities, which means that they are equivalent in describing the chiral phase transition; the critical temperature decreases as the number of fermion flavors increases and there is a boundary that separates the Tc-Nf plane into chiral symmetry breaking and restoration regions.
Universality in fermionic field theories at finite temperature
Strouthos, C G
2003-01-01
We discuss the critical properties of the three-dimensional NJL model at nonzero temperature. We show that the Z(2)-symmetric model undergoes a second order phase transition with 2d Ising exponents and its critical region is suppressed by a factor 1/N^{-0.5}. We also provide numerical evidence that the U(1)-symmetric model undergoes a BKT transition in accordance with the dimensional reduction scenario.
A SIMPLE DERIVATION OF FINITE-TEMPERATURE CFT CORRELATORS FROM THE BTZ BLACK HOLE
Directory of Open Access Journals (Sweden)
Satoshi Ohya
2014-04-01
Full Text Available We present a simple Lie-algebraic approach to momentum-space two-point functions of two-dimensional conformal field theory at finite temperature dual to the BTZ black hole. Making use of the real-time prescription of AdS/CFT correspondence and ladder equations of the Lie algebra so(2,2 ∼= sl(2,RL⊕sl(2,RR, we show that the finite-temperature two-point functions in momentum space satisfy linear recurrence relations with respect to the left and right momenta. These recurrence relations are exactly solvable and completely determine the momentum-dependence of retarded and advanced two-point functions of finite-temperature conformal field theory.
Finite-temperature effects on a triatomic Efimov resonance in ultracold cesium
Huang, B.; Sidorenkov, L. A.; Grimm, R.
2015-06-01
We report a thorough investigation of finite-temperature effects on three-body recombination near a triatomic Efimov resonance in an ultracold gas of cesium atoms. Our measurements cover a wide range from a near-ideal realization of the zero-temperature limit to a strongly temperature-dominated regime. The experimental results are analyzed within a recently introduced theoretical model based on a universal zero-range theory. The temperature-induced shift of the resonance reveals a contribution that points to an energy dependence of the three-body parameter. We interpret this contribution in terms of the finite range of the van der Waals interaction in real atomic systems and we quantify it in an empirical way based on length scale arguments. A universal character of the corresponding resonance shift is suggested by observations related to other Efimov resonances and the comparison with a theoretical finite-temperature approach that explicitly takes the van der Waals interaction into account. Our findings are of importance for the precise determination of Efimov resonance positions from experiments at finite temperatures.
Standard Model Extension and Casimir effect for fermions at finite temperature
Santos, A. F.; Khanna, Faqir C.
2016-11-01
Lorentz and CPT symmetries are foundations for important processes in particle physics. Recent studies in Standard Model Extension (SME) at high energy indicate that these symmetries may be violated. Modifications in the lagrangian are necessary to achieve a hermitian hamiltonian. The fermion sector of the standard model extension is used to calculate the effects of the Lorentz and CPT violation on the Casimir effect at zero and finite temperature. The Casimir effect and Stefan-Boltzmann law at finite temperature are calculated using the thermo field dynamics formalism.
Equation of state for QCD at finite temperature and density. Resummation versus lattice data
Energy Technology Data Exchange (ETDEWEB)
Andersen, Jens O. [Department of Physics, Norwegian University of Science and Technology, N-7491 Trondheim (Norway); Haque, Najmul; Mustafa, Munshi G. [Theory Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata-700064 (India); Strickland, Michael [Department of Physics, Kent State University, Kent, Ohio 44242 (United States); Su, Nan [Fakultät für Physik, Universität Bielefeld, 33615 Bielefeld (Germany)
2016-01-22
The perturbative series for finite-temperature field theories has very poor convergence properties and one needs a way to reorganize it. In this talk, I review two ways of reorganizing the perturbative series for field theories at finite temperature and chemical potential, namely hard-thermal-loop perturbation theory (HTLpt) and dimensional reduction (DR). I will present results for the pressure, trace anomaly, speed of sound, and the quark susceptibilities from a 3-loop HTLpt calculation and for the quark susceptibilities using DR at four loops. A careful comparison with available lattice data shows good agreement for a number of physical quantities.
Equation of State for QCD at finite temperature and density. Resummation versus lattice data
Andersen, Jens O; Mustafa, Munshi G; Strickland, Michael; Su, Nan
2016-01-01
The perturbative series for finite-temperature field theories has very poor convergence properties and one needs a way to reorganize it. In this talk, I review two ways of reorganizing the perturbative series for field theories at finite temperature and chemical potential, namely hard-thermal-loop perturbation theory (HTLpt) and dimensional reduction (DR). I will present results for the pressure, trace anomaly, speed of sound and the quark susceptibilities from a 3-loop HTLpt calculation and for the quark susceptibilities using DR at four loops. A careful comparison with available lattice data shows good agreement for a number of physical quantities.
Single-bubble sonoluminescence as Dicke superradiance at finite temperature
Aparicio Alcalde, M.; Quevedo, H.; Svaiter, N. F.
2014-12-01
Sonoluminescence is a process in which a strong sound field is used to produce light in liquids. We explain sonoluminescence as a phase transition from ordinary fluorescence to a superradiant phase. We consider a spin-boson model composed of a single bosonic mode and an ensemble of N identical two-level atoms. We assume that the whole system is in thermal equilibrium with a reservoir at temperature β-1. We show that, in a ultrastrong-coupling regime, between the two-level atoms and the electromagnetic field it is possible to have a cooperative interaction of the molecules of the gas in the interior of the bubble with the field, generating sonoluminescence.
Institute of Scientific and Technical Information of China (English)
马鑫; 钱乙余
2001-01-01
Nonlinear finite element simulation for mechanical response of surface mounted solder joint under different temperature cycling was carried out. Seven sets of parameters were used in order to evaluate the influence of temperature cycling profile parameters. The results show that temperature cycling history has significant effect on the stress response of the solder joint. Based on the concept of relative damage stress proposed by the authors, it is found that enough high temperature holding time is necessary for designing the temperature cycling profile in accelerated thermal fatigue test.
Ambiguities of the CPT-even aether-like Lorentz-breaking term at the finite temperature
Mariz, T; Petrov, A Yu; Serafim, W
2014-01-01
In this paper, we consider the finite temperature behaviour of the CPT-even aether-like Lorentz-breaking term in the extended Lorentz-breaking QED and demonstrate that its ambiguities whose presence has been shown earlier in the zero temperature case stay also at the finite temperature.
Equation of State and the Finite Temperature Transition in QCD
Gupta, Rajan
2009-01-01
This talk provides a summary of the results obtained by the HotQCD collaboration on the equation of state and the crossover transition in 2+1 flavor QCD. We investigate bulk thermodynamic quantities - energy density, pressure, entropy density, and the speed of sound over the temperature range 140 < T < 540 MeV. These results have been obtained on lattices of temporal size N_tau = 6 and 8 and with two improved staggered fermion actions, asqtad and p4. Our most extensive results are with masses of the two degenerate light quarks set at m_l = 0.1 m_s corresponding to the Goldstone pion mass m_pi between 220-260 MeV. In these simulations, the strange quark mass is tuned to its physical value and constant values of m_l/m_s define lines of constant physics. We also summarize the current state of results on observables sensitive to the chiral and deconfining physics -- the light and strange quark number susceptibilities, the chiral condensate and its susceptibility, and the renormalized Polyakov loop. Our resu...
QCD Topology at Finite Temperature: Statistical Mechanics of Selfdual Dyons
Faccioli, Pietro
2013-01-01
Topological phenomena in gauge theories have long been recognized as the driving force for chiral symmetry breaking and confinement. These phenomena can be conveniently investigated in the semi-classical picture, in which the topological charge is entirely carried by (anti-)self-dual gauge configurations. In such an approach, it has been shown that near the critical temperature, the non-zero expectation value of the Polyakov loop (holonomy) triggers the "Higgsing" of the color group, generating the splitting of instantons into $N_c$ self-dual dyons. A number of lattice simulations have provided some evidence for such dyons, and traced their relation with specific observables, such as the Dirac eigenvalue spectrum. In this work, we formulate a model, based on one-loop partition function and including Coulomb interaction, screening and fermion zee modes. We then perform the first numerical Monte Carlo simulations of a statistical ensemble of self-dual dyons,as a function of their density, quark mass and the num...
Dissipative soliton protocols in semiconductor microcavities at finite temperatures
Karpov, D. V.; Savenko, I. G.; Flayac, H.; Rosanov, N. N.
2015-08-01
We consider exciton polaritons in a semiconductor microcavity with a saturable absorber in the growth direction of the heterostructure. This feature promotes additional nonlinear losses of the system with the emergence of bistability of the condensate particles number on the nonresonant (electrical or optical) excitation intensity. Furthermore, we demonstrate a new type of bright spatial dissipative exciton-polariton soliton which emerges in the equilibrium between the regions with different particle density. We develop protocols of soliton creation and destruction. The switch to a solitonlike behavior occurs if the cavity is exposed by a short strong laser pulse with certain energy and duration. We estimate the characteristic times of soliton switch on and off and the time of return to the initial cycle. In particular, we demonstrate surprising narrowing of the spatial profile of the soliton and its vanishing at certain temperature due to interaction of the system with the thermal bath of acoustic phonons. We also address the role of polariton-polariton interaction (Kerr-like nonlinearity) on formation of dissipative solitons and show that the soliton may exist both in its presence and its absence.
Constructing warm inflationary model in finite temperature BIon
Setare, M R
2014-01-01
We study warm inflationary universe model on the BIon in thermal background. The BIon is a configuration in flat space of a D-brane and a parallel anti-D-brane connected by a wormhole with F-string charge. When the branes and antibranes are well separated and the brane's spike is far from the antibrane's spike, wormhole isn't formed however when two branes are close to each other, they can be connected by a wormhole. In this condition, there exists many channels for flowing energy from extra dimensions into our universe and inflation may naturally occur in a warm region. We present a model that allows all cosmological parameters like the scale factor $a$, the Hubble parameter $H$ and universe energy density depend on the shape function and temperature of wormhole in transverse dimension between two branes. In our model, the expansion of 4D universe is controlled by the thermal wormhole between branes and ends up in Big-Rip singularity. We show that at this singularity, universe would be destroyed and one blac...
Three dimensional finite temperature SU(3) gauge theory near the phase transition
Bialas, Piotr; Morel, Andre; Petersson, Bengt
2012-01-01
We have measured the correlation function of Polyakov loops on the lattice in three dimensional SU(3) gauge theory near its finite temperature phase transition. Using a new and powerful application of finite size scaling, we furthermore extend the measurements of the critical couplings to considerably larger values of the lattice sizes, both in the temperature and space directions, than was investigated earlier in this theory. With the help of these measurements we perform a detailed finite size scaling analysis, showing that for the critical exponents of the two dimensional three state Potts model the mass and the susceptibility fall on unique scaling curves. This strongly supports the expectation that the gauge theory is in the same universality class. The Nambu-Goto string model on the other hand predicts that the exponent \
Electronic chemical response indexes at finite temperature in the canonical ensemble
Energy Technology Data Exchange (ETDEWEB)
Franco-Pérez, Marco, E-mail: qimfranco@hotmail.com, E-mail: jlgm@xanum.uam.mx, E-mail: avela@cinvestav.mx; Gázquez, José L., E-mail: qimfranco@hotmail.com, E-mail: jlgm@xanum.uam.mx, E-mail: avela@cinvestav.mx [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, México, D. F. 09340, México (Mexico); Departamento de Química, Centro de Investigación y de Estudios Avanzados, Av. Instituto Politécnico Nacional 2508, México, D. F. 07360, México (Mexico); Vela, Alberto, E-mail: qimfranco@hotmail.com, E-mail: jlgm@xanum.uam.mx, E-mail: avela@cinvestav.mx [Departamento de Química, Centro de Investigación y de Estudios Avanzados, Av. Instituto Politécnico Nacional 2508, México, D. F. 07360, México (Mexico)
2015-07-14
Assuming that the electronic energy is given by a smooth function of the number of electrons and within the extension of density functional theory to finite temperature, the first and second order chemical reactivity response functions of the Helmholtz free energy with respect to the temperature, the number of electrons, and the external potential are derived. It is found that in all cases related to the first or second derivatives with respect to the number of electrons or the external potential, there is a term given by the average of the corresponding derivative of the electronic energy of each state (ground and excited). For the second derivatives, including those related with the temperature, there is a thermal fluctuation contribution that is zero at zero temperature. Thus, all expressions reduce correctly to their corresponding chemical reactivity expressions at zero temperature and show that, at room temperature, the corrections are very small. When the assumption that the electronic energy is given by a smooth function of the number of electrons is replaced by the straight lines behavior connecting integer values, as required by the ensemble theorem, one needs to introduce directional derivatives in most cases, so that the temperature dependent expressions reduce correctly to their zero temperature counterparts. However, the main result holds, namely, at finite temperature the thermal corrections to the chemical reactivity response functions are very small. Consequently, the present work validates the usage of reactivity indexes calculated at zero temperature to infer chemical behavior at room and even higher temperatures.
Finite Temperature Properties of Mixed Diamond Chain with Spins 1 and 1/2
Hida, Kazuo; Takano, Ken'ichi; Suzuki, Hidenori
2009-08-01
We formulate statistical mechanics for a mixed diamond chain with spins 1 and 1/2. Owing to a series of conservation laws, any eigenstate of this system is decomposed into eigenstates of finite odd-length spin-1 chains. The ground state undergoes five quantum phase transitions with varying λ, a parameter that controls frustration. We evaluated the residual entropy and Curie constant which characterize each phase and phase boundary at low temperatures. We further find various characteristic finite-temperature properties such as the nonmonotonic temperature dependence of magnetic susceptibility, the multipeak structure in the λ-dependence of entropy, the plateau-like temperature dependence of entropy and the multipeak structure of specific heat.
Simulation of Temperature Distribution In a Rectangular Cavity using Finite Element Method
Naa, Christian
2013-01-01
This paper presents the study and implementation of finite element method to find the temperature distribution in a rectangular cavity which contains a fluid substance. The fluid motion is driven by a sudden temperature difference applied to two opposite side walls of the cavity. The remaining walls were considered adiabatic. Fluid properties were assumed incompressible. The problem has been approached by two-dimensional transient conduction which applied on the heated sidewall and one-dimensional steady state convection-diffusion equation which applied inside the cavity. The parameters which investigated are time and velocity. These parameters were computed together with boundary conditions which result in temperature distribution in the cavity. The implementation of finite element method was resulted in algebraic equation which is in vector and matrix form. Therefore, MATLAB programs used to solve this algebraic equation. The final temperature distribution results were presented in contour map within the re...
Stability of gold cages (Au16 and Au17) at finite temperature
Indian Academy of Sciences (India)
Prachi Chandrachud; Kavita Joshi; Sailaja Krishnamurty; D G Kanhere
2009-05-01
We have employed ab initio molecular dynamics to investigate the stability of the smallest gold cages, namely Au16 and Au17, at finite temperatures. First, we obtain the ground state structure along with at least 50 distinct isomers for both the clusters. This is followed by the finite temperature simulations of these clusters. Each cluster is maintained at 12 different temperatures for a time period of at least 150 ps. Thus, the total simulation time is of the order of 2.4 ns for each cluster. We observe that the cages are stable at least up to 850 K. Although both clusters melt around the same temperature, i.e. around 900 K, Au17 shows a peak in the heat capacity curve in contrast to the broad peak seen for Au16.
Comment on "Dual path integral representation for finite temperature quantum field theory"
Kazinski, P O
2008-01-01
I show that the novel dual path integral representation for finite temperature quantum field theory proposed in [Phys. Rev. D 77, 105030 (2008), arXiv:0803.1667 ] is a well-known representation of quantum mechanics in terms of symbols of operators.
Finite-temperature correlations in the Lieb-Liniger one-dimensional Bose gas
Panfil, M.; Caux, J.-S.
2014-01-01
We address the problem of calculating finite-temperature response functions of an experimentally relevant low-dimensional, strongly correlated system: the integrable one-dimensional Bose gas with a repulsive δ-function interaction (the Lieb-Liniger model). Focusing on the dynamical density-density f
Finite-Temperature Phase Structure in the Chiral σ-ω Model with Dilatons
Institute of Scientific and Technical Information of China (English)
ZHANG Xiao-Bing ZHANG Xiao-Bing; LI Xue-Qian; NING Ping-Zhi
2000-01-01
We investigate the finite-temperature phase structure in a scaled chiral model which includes the dilaton (glueball) field. It is shown that hot nuclear matter undergoes a discontinuous transition in the mean field of scalar mesons as well as the Lee-Wick abnormal transition. The corresponding behavior of the gluon condensate during the chiral phase transition is also studied.
Energy Technology Data Exchange (ETDEWEB)
Sato, K.; Koide, Tomoi; Maruyama, Masahiro [Tohoku Univ., Faculty of Science, Sendai, Miyagi (Japan)
1999-08-01
There are various approaches to nonequilibrium system. We use the projection operator method investigated by F. Shibata and N. Hashitsume on the linear sigma model at finite temperature and density. We derive a differential equation of the time evolution for the order parameter and pion number density in chiral phase transition. (author)
Quantum Fluctuation in Mesoscopic Coupled LC Electric Circuits at FiniteTemperature
Institute of Scientific and Technical Information of China (English)
LIANG Xian-Ting; FAN Hong-Yi
2001-01-01
We consider the quantization of two coupled LC circuits with mutual inductance at a finite temperature T. It is shown that the quantum mechanical zero-point fluctuations of currents in the two circuits both increase with upgoing T. Thermal field dynamics and Weyl-Wigner theorern are used in our calculation of ensemble average of the observables.
Renormalized Polyakov loops in various representations in finite temperature SU(2) gauge theory
Huebner, K
2008-01-01
We present results for the renormalized Polyakov loop in the three lowest irreducible representations of SU(2) gauge theory at finite temperature. We will discuss their scaling behavior near $T_c$ and test Casimir scaling in the deconfined phase. Moreover, we will compare these results to calculations for the renormalized Polyakov loops in several representations in the SU(3) gauge theory.
Energy Technology Data Exchange (ETDEWEB)
Niekerken, Ole
2009-06-15
In this diploma thesis the Casimir-Polder force at zero temperature and at finite temperatures is calculated by using a well-defined quantum field theory (formulated in position space) and the method of image charges. For the calculations at finite temperature KMS-states are used. The so defined temperature describes the temperature of the electromagnetic background. A one oscillator model for inhomogeneous dispersive absorbing dielectric material is introduced and canonically quantized to calculate the Casimir-Polder force at a dielectric interface at finite temperature. The model fulfils causal commutation relations and the dielectric function of the model fulfils the Kramer-Kronig relations. We then use the same methods to calculate the van der Waals force between two neutral atoms at zero temperature and at finite temperatures. It is shown that the high temperature behaviour of the Casimir-Polder force and the van der Waals force are independent of {Dirac_h}. This means that they have to be understood classically, what is then shown in an algebraic statistical theory by using classical KMS states. (orig.)
Low-temperature study of the magnetic properties of finite atomic chains
Kolesnikov, S. V.
2016-05-01
A simple method for the calculation of the spontaneous remagnetization time and magnetization curves of atomic finite-length ferromagnetic chains at a low temperature within the Heisenberg model has been proposed. The applicability limits of the method have been studied. It has been shown that the proposed method gives results being in good agreement with the kinetic Monte Carlo simulation results. Formulas obtained within our model can also be used to determine the lower bound for the Curie temperature.
Institute of Scientific and Technical Information of China (English)
LIANG XIAN-TING; FAN HONG-YI
2001-01-01
By using the charge and current in a quantization resistance-inductance-capacitance (RLC) electric circuit, we construct a pair of canonical variables. Using this pair of variables and the thermal field dynamics, we obtain the fluctuations of charge and current in the RLC electric circuit at finite temperatures. It is shown that the fluctuations increase with increasing temperature and decrease with prolonging of time.
Finite Temperature and Density Effects in Higher Dimensions with and without Compactifications
Shiraishi, Kiyoshi
2012-01-01
Expressions for the thermodynamic potential of a Dirac fermion gas are represented at finite temperature with the chemical potential in an ultrastatic space $R^d\\times S^N$. The high- and low- temperature expansions for the thermodynamic potential are obtained and, in particular, strongly degenerate fermi gas is investigated. For the Candelas-Weinberg model, sufficiently high "charge" density prevents the compactification of the extra space.
1999-01-01
In this paper we apply the renormalization-group (RG) inspired resummation method to the one-loop effective potential at finite temperature evaluated in the massive scalar 04 model renormalized at zero-temperature, and study whether ourresummation procedure a la RG uccessfully resum the dominant correction terms apperaed in the perturbative caluculation in the T = 0 renormalization scheme or not.Our findings are i) that if we start from the theory renormalized at T = 0, then the condition tha...
Finite-temperature electromagnetic-field quantization in a medium: The thermofield approach
Energy Technology Data Exchange (ETDEWEB)
Kheirandish, F.; Soltani, M.; Jafari, M. [Department of Physics, Faculty of Science, University of Isfahan, Hezar-Jarib Street, 81746-73441, Isfahan (Iran, Islamic Republic of)
2011-12-15
Starting from a Lagrangian, an electromagnetic field is quantized in the presence of a medium in thermal equilibrium and also in a medium with time-varying temperature. The vector potential for both equilibrium and nonequilibrium cases is obtained and vacuum fluctuations of the fields are calculated. As an illustrative example, the finite-temperature decay rate and level shift of an atom in a polarizable medium are calculated in this approach.
Molecular dynamics simulation for baryon-quark phase transition at finite temperature and density
Akimura, Y; Yoshinaga, N; Chiba, S; Akimura, Yuka; Maruyama, Toshiki; Yoshinaga, Naotaka; Chiba, Satoshi
2005-01-01
We study the baryon-quark phase transition in a molecular dynamics (MD) of quark degrees of freedom at finite temperature and density. The baryon state at low density and temperature, and the deconfined quark state at high density and temperature are reproduced. We investigate the equations of state of matters with different $u$-$d$-$s$ compositions. Then we draw phase diagrams in the temperature-density plane by this simulation. It is found that the baryon-quark transition is sensitive to the quark width.
Spin polarization and color superconductivity in the Nambu-Jona-Lasinio model at finite temperature
Matsuoka, Hiroaki; da Providencia, Joao; Providencia, Constancia; Yamamura, Masatoshi
2016-01-01
We investigate the possible existence of spin polarization and color superconductivity in the Nambu-Jona-Lasinio model with a tensor-type interaction at finite density and temperature. The thermodynamic potential is calculated by the functional integral method. Numerical results indicate that at low temperature and quark chemical potential the chiral condensed phase exists, and at intermediate chemical potential the color superconducting phase appears. In addition, depending on the magnitude of the tensor coupling, at large chemical potential and low temperature, a color superconducting phase and a spin polarized phase may coexist while at intermediate temperatures only the spin polarized phase occurs.
SU($4$) Polyakov linear-sigma model at finite temperature and density
Diab, Abdel Magied; Tawfik, Abdel Nasser; Dahab, Eiman Abou El
2016-01-01
In mean-field approximation, the SU($4$) Polyakov linear - sigma model (PLSM) is constructed in order to characterize the quark-hadron phase structure in a wide range of temperatures and densities. The chiral condensates $\\sigma_l$, $\\sigma_s$ and $\\sigma_c$ for light, strange and charm quarks, respectively, and the deconfinement order-parameters $\\phi$ and $\\phi^*$ shall be analyzed at finite temperatures and densities. We conclude that the critical temperatures corresponding to charm condensates are greater than that to strange and light ones, respectively. Thus, the charm condensates are likely not affected by the QCD phase transition. Furthermore, increasing the chemical potentials decreases the corresponding critical temperatures.
Hamiltonian finite-temperature quantum field theory from its vacuum on partially compactified space
Reinhardt, Hugo
2016-01-01
The partition function of a relativistic invariant quantum field theory is expressed by its vacuum energy calculated on a spatial manifold with one dimension compactified to a 1-sphere $S^1 (\\beta)$, whose circumference $\\beta$ represents the inverse temperature. Explicit expressions for the usual energy density and pressure in terms of the energy density on the partially compactified spatial manifold $\\mathbb{R}^2 \\times S^1 (\\beta)$ are derived. To make the resulting expressions mathematically well-defined a Poisson resummation of the Matsubara sums as well as an analytic continuation in the chemical potential are required. The new approach to finite-temperature quantum field theories is advantageous in a Hamilton formulation since it does not require the usual thermal averages with the density operator. Instead, the whole finite-temperature behaviour is encoded in the vacuum wave functional on the spatial manifold $\\mathbb{R}^2 \\times S^1 (\\beta)$. We illustrate this approach by calculating the pressure of...
Finite-temperature pairing re-entrance in the drip-line nucleus 48Ni
Belabbas, Mohamed; Li, Jia Jie; Margueron, Jérôme
2017-08-01
Finite-temperature Hartree-Fock-Bogoliubov theory using Skyrme interactions and relativistic Hartree-Fock effective Lagrangians predicts 48Ni as being a possible candidate for the finite-temperature pairing re-entrance phenomenon. For this proton-drip-line nucleus, proton resonant states are expected to contribute substantially to pairing correlations and the two predicted critical temperatures are Tc 1˜0.08 -0.2 MeV and Tc 2˜0.7 -0.9 MeV. It is also shown that pairing re-entrance modifies the proton single-particle energies around the Fermi level, as well as occupation numbers and quasiparticle levels. The understanding of pairing re-entrance in 48Ni presently challenges our understanding of exotic matter under extreme conditions.
Cabra, D C; Rossini, L; Schaposnik, F A; Fradkin, Eduardo
1995-01-01
We discuss the behavior of theories of fermions coupled to Chern-Simons gauge fields with a non-abelian gauge group in three dimensions and at finite temperature. Using non-perturbative arguments and gauge invariance, and in contradiction with perturbative results, we show that the coefficient of the Chern-Simons term of the effective actions for the gauge fields at finite temperature can be {\\it at most} an integer function of the temperature. This is in a sense a generalized no-renormalization theorem. We also discuss the case of abelian theories and give indications that a similar condition should hold there too. We discuss consequences of our results to the thermodynamics of anyon superfluids and fractional quantum Hall systems.
Topological susceptibility at zero and finite temperature in the Nambu-Jona-Lasinio model
Ohnishi, K; Ohta, K
2001-01-01
We consider the three flavor Nambu-Jona-Lasinio model with the 't Hooft interaction incorporating the U(1)_A anomaly. In order to set the coupling strength of the 't Hooft term, we employ the topological susceptibility $\\chi$ instead of the eta' meson mass. The value for $\\chi$ is taken from lattice simulations. We also calculate $\\chi$ at finite temperature within the model. Comparing it with the lattice data, we extract information about the behavior of the U(1)_A anomaly at finite temperature. We conclude that within the present framework, the effective restoration of the U(1)_A symmetry does not necessarily take place even at high temperature where the chiral symmetry is restored.
Finite-temperature twisted-untwisted transition of the kagome lattice
Bedi, Deshpreet; Rocklin, D. Zeb; Mao, Xiaoming
Mechanical instability governs many fascinating phenomena in nature, including jamming, glass transitions, and structural phase transitions. Although mechanical instability in athermal systems is well understood, how thermal fluctuations modify such transitions remains largely unexplored. Recent studies reveal that, due to the large number of floppy modes that emerge at mechanical instability, intriguing new phenomena occur, such as fluctuation-driven first-order transitions and order-by-disorder. In this talk, we present an analytic study of the finite-temperature rigidity transition for the kagome lattice. Our model exhibits a zero-temperature continuous twisted-untwisted transition as the sign of the next-nearest-neighbor spring constant changes. At finite temperature, we show that the divergent contribution of floppy modes to the vibrational entropy renormalizes this spring constant, resulting in a first-order transition. We also propose an experimental manifestation of this transition in the system of self-assembling triblock Janus particles.
Effects of interactions on dynamic correlations of hard-core bosons at finite temperatures
Fauseweh, Benedikt; Uhrig, Götz S.
2017-09-01
We investigate how dynamic correlations of hard-core bosonic excitation at finite temperature are affected by additional interactions besides the hard-core repulsion which prevents them from occupying the same site. We focus especially on dimerized spin systems, where these additional interactions between the elementary excitations, triplons, lead to the formation of bound states, relevant for the correct description of scattering processes. In order to include these effects quantitatively, we extend the previously developed Brückner approach to include also nearest-neighbor (NN) and next-nearest neighbor (NNN) interactions correctly in a low-temperature expansion. This leads to the extension of the scalar Bethe-Salpeter equation to a matrix-valued equation. As an example, we consider the Heisenberg spin ladder to illustrate the significance of the additional interactions on the spectral functions at finite temperature, which are proportional to inelastic neutron scattering rates.
Finite element simulation of three-dimensional temperature field in underwater welding
Institute of Scientific and Technical Information of China (English)
Liu Xiwen; Wang Guorong; Shi Yonghua; Zhong Jiguang
2007-01-01
Mathematical models of three-dimensional temperature fields in underwater welding with moving heat sources are built. Double ellipsoid Gauss model is proposed as heat sources models. Several factors which affect the temperature fields of underwater welding are analyzed. Water has little influence on thermal efficiency. Water convection coefficient varies with the temperature difference between the water and the workpiece, and water convection makes molten pool freeze quickly. With the increase of water depth, the dimensions of heat sources model should be reduced as arc shrinks. Finite element technology is used to solve mathematical models. ANSYS software is used as finite element tool, and ANSYS Parametric Design Language is used to develop subprograms for loading the moving heat sources and the various convection coefficients. Experiment results show that computational results by using double ellipsoid Gauss heat sources model accord well with the experimental results.
Toward a unified description of spin incoherent behavior at zero and finite temperatures
Soltanieh-Ha, Mohammad; Feiguin, Adrian
2013-03-01
While the basic theoretical understanding of spin-charge separation in one-dimension, known as ``Luttinger liquid theory'', has existed for some time, recently a previously unidentified regime of strongly interacting one-dimensional systems at finite temperature came to light: The ``spin-incoherent Luttinger liquid'' (SILL). This occurs when the temperature is larger than the characteristic spin energy scale. I will show that the spin-incoherent state can be written exactly as a generalization of Ogata and Shiba's factorized wave function in an enlarged Hilbert space, using the so-called ``thermo-field formalism.'' Interestingly, this wave-function can also describe the *ground-state* of other model Hamiltonians, such as t-J ladders, and the Kondo lattice. This allows us to develop a unified formalism to describe SILL physics both at zero, and finite temperatures.
Finite temperature effect on mechanical properties of graphene sheets with various grain boundaries
Yong, Ge; Hong-Xiang, Sun; Yi-Jun, Guan; Gan-He, Zeng
2016-06-01
The mechanical properties of graphene sheets with various grain boundaries are studied by molecular dynamics method at finite temperatures. The finite temperature reduces the ultimate strengths of the graphenes with different types of grain boundaries. More interestingly, at high temperatures, the ultimate strengths of the graphene with the zigzag-orientation grain boundaries at low tilt angles exhibit different behaviors from those at lower temperatures, which is determined by inner initial stress in grain boundaries. The results indicate that the finite temperature, especially the high one, has a significant effect on the ultimate strength of graphene with grain boundaries, which gives a more in-depth understanding of their mechanical properties and could be useful for potential graphene applications. Project supported by the Nation Natural Science Foundation of China (Grant Nos. 11347219 and 11404147), the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20140519), the Training Project of Young Backbone Teacher of Jiangsu University, the Advanced Talents of Jiangsu University, China (Grant No. 11JDG118), the Practice Innovation Training Program Projects for Industrial Center of Jiangsu University, China, and the State Key Laboratory of Acoustics, Chinese Academy of Sciences (Grant No. SKLOA201308).
Finite-temperature effects on a triatomic Efimov resonance in ultracold cesium
Huang, Bo; Grimm, Rudolf
2015-01-01
We report a thorough investigation of finite-temperature effects on three-body recombination near a triatomic Efimov resonance in an ultracold gas of cesium atoms. Our measurements cover a wide range from a near-ideal realization of the zero-temperature limit to a strongly temperature-dominated regime. The experimental results are analyzed within a recently introduced theoretical model based on a universal zero-range theory. The temperature-induced shift of the resonance reveals a contribution that points to an energy-dependence of the three-body parameter. We interpret this contribution in terms of the finite range of the van der Waals interaction in real atomic systems and we quantify it in an empirical way based on length scale arguments. A universal character of the corresponding resonance shift is suggested by observations related to other Efimov resonances and the comparison with a theoretical finite-temperature approach that explicitly takes the van der Waals interaction into account. Our findings are ...
Finite-temperature second-order many-body perturbation theory revisited
Santra, Robin
2016-01-01
We present an algebraic, nondiagrammatic derivation of finite-temperature second-order many-body perturbation theory [FT-MBPT(2)], using techniques and concepts accessible to theoretical chemical physicists. We give explicit expressions not just for the grand potential but particularly for the mean energy of an interacting many-electron system. The framework presented is suitable for computing the energy of a finite or infinite system in contact with a heat and particle bath at finite temperature and chemical potential. FT-MBPT(2) may be applied if the system, at zero temperature, may be described using standard (i.e., zero-temperature) second-order many-body perturbation theory [ZT-MBPT(2)] for the energy. We point out that in such a situation, FT-MBPT(2) reproduces, in the zero-temperature limit, the energy computed within ZT-MBPT(2). In other words, the difficulty that has been referred to as the Kohn--Luttinger conundrum, does not occur. We comment, in this context, on a "renormalization" scheme recently ...
Pairing phase transition: A Finite-Temperature Relativistic Hartree-Fock-Bogoliubov study
Li, Jia Jie; Long, Wen Hui; Van Giai, Nguyen
2015-01-01
Background: The relativistic Hartree-Fock-Bogoliubov (RHFB) theory has recently been developed and it provides a unified and highly predictive description of both nuclear mean field and pairing correlations. Ground state properties of finite nuclei can accurately be reproduced without neglecting exchange (Fock) contributions. Purpose: Finite-temperature RHFB (FT-RHFB) theory has not yet been developed, leaving yet unknown its predictions for phase transitions and thermal excitations in both stable and weakly bound nuclei. Method: FT-RHFB equations are solved in a Dirac Woods-Saxon (DWS) basis considering two kinds of pairing interactions: finite or zero range. Such a model is appropriate for describing stable as well as loosely bound nuclei since the basis states have correct asymptotic behaviour for large spatial distributions. Results: Systematic FT-RH(F)B calculations are performed for several semi-magic isotopic/isotonic chains comparing the predictions of a large number of Lagrangians, among which are PK...
Automatic control of finite element models for temperature-controlled radiofrequency ablation
Directory of Open Access Journals (Sweden)
Haemmerich Dieter
2005-07-01
Full Text Available Abstract Background The finite element method (FEM has been used to simulate cardiac and hepatic radiofrequency (RF ablation. The FEM allows modeling of complex geometries that cannot be solved by analytical methods or finite difference models. In both hepatic and cardiac RF ablation a common control mode is temperature-controlled mode. Commercial FEM packages don't support automating temperature control. Most researchers manually control the applied power by trial and error to keep the tip temperature of the electrodes constant. Methods We implemented a PI controller in a control program written in C++. The program checks the tip temperature after each step and controls the applied voltage to keep temperature constant. We created a closed loop system consisting of a FEM model and the software controlling the applied voltage. The control parameters for the controller were optimized using a closed loop system simulation. Results We present results of a temperature controlled 3-D FEM model of a RITA model 30 electrode. The control software effectively controlled applied voltage in the FEM model to obtain, and keep electrodes at target temperature of 100°C. The closed loop system simulation output closely correlated with the FEM model, and allowed us to optimize control parameters. Discussion The closed loop control of the FEM model allowed us to implement temperature controlled RF ablation with minimal user input.
Finite line-source model for borehole heat exchangers. Effect of vertical temperature variations
Energy Technology Data Exchange (ETDEWEB)
Bandos, Tatyana V.; Fernandez, Esther; Santander, Juan Luis G.; Isidro, Jose Maria; Perez, Jezabel; Cordoba, Pedro J. Fernandez de [Instituto Universitario de Matematica Pura y Aplicada, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Montero, Alvaro; Urchueguia, Javier F. [Instituto de Ingenieria Energetica, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain)
2009-06-15
A solution to the three-dimensional finite line-source (FLS) model for borehole heat exchangers (BHEs) that takes into account the prevailing geothermal gradient and allows arbitrary ground surface temperature changes is presented. Analytical expressions for the average ground temperature are derived by integrating the exact solution over the line-source depth. A self-consistent procedure to evaluate the in situ thermal response test (TRT) data is outlined. The effective thermal conductivity and the effective borehole thermal resistance can be determined by fitting the TRT data to the time-series expansion obtained for the average temperature. (author)
Wang, Ziyue; Zhuang, Pengfei
2017-07-01
The pion superfluid and the corresponding Goldstone and soft modes are investigated in a two-flavor quark-meson model with a functional renormalization group. By solving the flow equations for the effective potential and the meson two-point functions at finite temperature and isospin density, the critical temperature for the superfluid increases sizeably in comparison with solving the flow equation for the potential only. The spectral function for the soft mode shows clearly a transition from meson gas to quark gas with increasing temperature and a crossover from Bose-Einstein condensation to Bardeen-Cooper-Schrieffer pairing of quarks with increasing isospin density.
Fermionic spectral functions in backreacting p-wave superconductors at finite temperature
Giordano, G L; Lugo, A R
2016-01-01
We investigate the spectral function of fermions in a $p$-wave superconducting state, at finite both temperature and gravitational coupling, using the $AdS/CFT$ correspondence and extending previous research. We found that, for any coupling below a critical value, the system behaves as its zero temperature limit. By increasing the coupling, the "peak-dip-hump" structure that characterizes the spectral function at fixed momenta disappears. In the region where the normal/superconductor phase transition is first order, the presence of a non-zero order parameter is reflected in the absence of rotational symmetry in the fermionic spectral function at the critical temperature.
Dynamical Model of QCD Vacuum and Color Thaw at Finite Temperatures
Institute of Scientific and Technical Information of China (English)
WANG Dian-Fu; SONG He-Shan; MI Dong
2004-01-01
In terms of the Nambu-Jona-Lasinio (NJL) mechanism, the dynamical symmetry breaking of a simple localgauge model is investigated. An important relation between the vacuum expectation value of gauge fields and scalarfields is derived by solving the Euler equation for the gauge fields. Based on this relation the SU(3) gauge potential isgiven which can be used to explain the asymptotic freedom and confinement of quarks in a hadron. The confinementbehavior at finite temperatures is also investigated and it is shown that color confinement at zero temperature can bemelted away under high temperatures.
Dynamical Model of QCD Vacuum and Color Thaw at Finite Temperatures
Institute of Scientific and Technical Information of China (English)
WANGDian-Fu; SONGHe-Shan; MIDong
2004-01-01
In terms of the Nambu Jona-Lasinio (NJL) mechanism, the dynamical symmetry breaking of a simple local gauge model is investigated. An important relation between the vacuum expectation value of gauge fields and scalar fields is derived by solving the Euler equation for the gauge fields. Based on this relation the SU(3) gauge potential is given which can be used to explain the asymptotic freedom and confinement of quarks in a hadron. The confinement behavior at finite temperatures is also investigated and it is shown that color confinement at zero temperature can be melted away under high temperatures.
FDTD simulation of finite-amplitude pressure and temperature fields for biomedical ultrasound.
Hallaj, I M; Cleveland, R O
1999-05-01
Full wave simulations provide a valuable tool for studying the spatial and temporal nature of an acoustic field. One method for producing such simulations is the finite-difference time-domain (FDTD) method. This method uses discrete differences to approximate derivatives in the governing partial differential equations. We used the FDTD method to model the propagation of finite-amplitude sound in a homogeneous thermoviscous fluid. The calculated acoustic pressure field was then used to compute the transient temperature rise in the fluid; the heating results from absorption of acoustic energy by the fluid. As an example, the transient temperature field was calculated in biological tissue in response to a pulse of focused ultrasound. Enhanced heating of the tissue from finite-amplitude effects was observed. The excess heating was attributed to the nonlinear generation of higher-frequency harmonics which are absorbed more readily than the fundamental. The effect of nonlinear distortion on temperature rise in tissue was observed to range from negligible at 1 MPa source pressure to an 80% increase in temperature elevation at 10 MPa source pressure.
Magnetospheric Whistler Mode Ray Tracing with the Inclusion of Finite Electron and Ion Temperature
Maxworth, A. S.; Golkowski, M.
2015-12-01
Ray tracing is an important technique for the study of whistler mode wave propagation in the Earth's magnetosphere. In numerical ray tracing the trajectory of a wave packet is calculated at each point in space by solving the Haselgrove equations, assuming a smooth, loss-less medium with no mode coupling. Previous work on ray tracing has assumed a cold plasma environment with negligible electron and ion temperatures. In this work we present magnetospheric whistler mode wave ray tracing results with the inclusion of finite ion and electron temperature. The inclusion of finite temperature effects makes the fourth order dispersion relation become sixth order. We compare our results with the work done by previous researchers for cold plasma environments, using two near earth space models (NGO and GCPM). Inclusion of finite temperature closes the otherwise open refractive index surface near the lower hybrid resonance frequency and affects the magnetospheric reflection of whistler waves. We also asses the main changes in the ray trajectory and implications for cyclotron resonance wave particle interactions including energetic particle precipitation.
Quantum dynamics at finite temperature: Time-dependent quantum Monte Carlo study
Energy Technology Data Exchange (ETDEWEB)
Christov, Ivan P., E-mail: ivan.christov@phys.uni-sofia.bg
2016-08-15
In this work we investigate the ground state and the dissipative quantum dynamics of interacting charged particles in an external potential at finite temperature. The recently devised time-dependent quantum Monte Carlo (TDQMC) method allows a self-consistent treatment of the system of particles together with bath oscillators first for imaginary-time propagation of Schrödinger type of equations where both the system and the bath converge to their finite temperature ground state, and next for real time calculation where the dissipative dynamics is demonstrated. In that context the application of TDQMC appears as promising alternative to the path-integral related techniques where the real time propagation can be a challenge.
Finite Temperature Corrections to Tachyon Mass in Intersecting D-Branes
Sethi, Varun; Sarkar, Swarnendu
2016-01-01
We continue with the analysis of finite temperature corrections to the Tachyon mass in intersecting branes which was initiated in arxiv:1403.0389. In this paper we extend the computation to the case of intersecting D3-branes by considering a setup of two intersecting branes in flat-space background. A holographic model dual to BCS superconductor consisting of intersecting D8-branes in D4-brane background was proposed in arxiv:1104.2843. The background considered here is a simplified configuration of this dual model. We compute the one-loop Tachyon amplitude in the Yang-Mills approximation and show that the result is finite. Analyzing the amplitudes further we numerically compute the transition temperature at which the Tachyon becomes massless. The analytic expressions for the one-loop amplitudes obtained here reduce to those for intersecting D1-branes obtained in arxiv:1403.0389 as well as those for intersecting D2-branes.
Measurements of Finite Dust Temperature Effects in the Dispersion Relation of the Dust Acoustic Wave
Snipes, Erica; Williams, Jeremiah
2009-04-01
A dusty plasma is a four-component system composed of ions, electrons, neutral particles and charged microparticles. The presence of these charged microparticles gives rise to new plasma wave modes, including the dust acoustic wave. Recent measurements [1, 2] of the dispersion relationship for the dust acoustic wave in a glow discharge have shown that finite temperature effects are observed at higher values of neutral pressure. Other work [3] has shown that these effects are not observed at lower values of neutral pressure. We present the results of ongoing work examining finite temperature effects in the dispersion relation as a function of neutral pressure. [4pt] [1] E. Thomas, Jr., R. Fisher, and R. L. Merlino, Phys. Plasmas 14, 123701 (2007). [0pt] [2] J. D. Williams, E. Thomas Jr., and L. Marcus, Phys. Plasmas 15, 043704 (2008). [0pt] [3] T. Trottenberg, D. Block, and A. Piel, Phys. Plasmas 13, 042105 (2006).
Continuum extrapolation of finite temperature meson correlation functions in quenched lattice QCD
Francis, Anthony
2010-01-01
We explore the continuum limit $a\\rightarrow 0$ of meson correlation functions at finite temperature. In detail we analyze finite volume and lattice cut-off effects in view of possible consequences for continuum physics. We perform calculations on quenched gauge configurations using the clover improved Wilson fermion action. We present and discuss simulations on isotropic $N_\\sigma^3\\times 16$ lattices with $N_\\sigma=32,48,64,128$ and $128^3 \\times N_\\tau$ lattices with $N_\\tau=16,24,32,48$ corresponding to lattice spacings in the range of $0.01 fm \\lsim a \\lsim\\ 0.031 fm$ at $T\\simeq1.45T_c$. Continuum limit extrapolations of vector meson and pseudo scalar correlators are performed and their large distance expansion in terms of thermal moments is introduced. We discuss consequences of this analysis for the calculation of the electrical conductivity of the QGP at this temperature.
Proposal for measuring the finite-temperature Drude weight of integrable systems
Karrasch, C.; Prosen, T.; Heidrich-Meisner, F.
2017-02-01
Integrable models such as the spin-1/2 Heisenberg chain, the Lieb-Liniger, or the one-dimensional Hubbard model are known to avoid thermalization, which was also demonstrated in several quantum-quench experiments. Another dramatic consequence of integrability is the zero-frequency anomaly in transport coefficients, which results in ballistic finite-temperature transport, despite the presence of strong interactions. While this aspect of nonergodic dynamics has been known for a long time, there has so far not been any unambiguous experimental realization thereof. We make a concrete proposal for the observation of ballistic transport via local quantum-quench experiments in fermionic quantum-gas microscopes. Such an experiment would also unveil the coexistence of ballistic and diffusive transport channels in one and the same system and provide a means of measuring finite-temperature Drude weights. The connection between local quenches and linear-response functions is established via time-dependent Einstein relations.
Niu, YiFei; Vretenar, Dario; Meng, Jie
2011-01-01
We introduce a self-consistent microscopic theoretical framework for modelling the process of electron capture on nuclei in stellar environment, based on relativistic energy density functionals. The finite-temperature relativistic mean-field model is used to calculate the single-nucleon basis and the occupation factors in a target nucleus, and $J^{\\pi} = 0^{\\pm}$, $1^{\\pm}$, $2^{\\pm}$ charge-exchange transitions are described by the self-consistent finite-temperature relativistic random-phase approximation. Cross sections and rates are calculated for electron capture on 54,56Fe and 76,78Ge in stellar environment, and results compared with predictions of similar and complementary model calculations.
Czarnik, Piotr; Rams, Marek M.; Dziarmaga, Jacek
2016-12-01
A Gibbs operator e-β H for a two-dimensional (2D) lattice system with a Hamiltonian H can be represented by a 3D tensor network, with the third dimension being the imaginary time (inverse temperature) β . Coarse graining the network along β results in a 2D projected entangled-pair operator (PEPO) with a finite bond dimension. The coarse graining is performed by a tree tensor network of isometries. They are optimized variationally to maximize the accuracy of the PEPO as a representation of the 2D thermal state e-β H. The algorithm is applied to the two-dimensional Hubbard model on an infinite square lattice. Benchmark results at finite temperature are obtained that are consistent with the best cluster dynamical mean-field theory and power-series expansion in the regime of parameters where they yield mutually consistent results.
Finite Element Analysis of Temperature Field in Automotive Dry Friction Clutch
O.I. Abdullah; J. Schlattmann
2012-01-01
The friction clutch design is strongly dependent upon the frictional heat generated between contact surfaces during the slipping at beginning of engagement. Because of that the frictional heat generated firstly will reduce the performance of clutch system and then will lead to premature failure in some cases. Finite element method was used to investigate aneffect of thermal load type on the temperature field of the clutch system. Two-dimensional axisymmetric model was used to study the tempe...
Brownian motion of the electron and the Lamb shift at finite temperature
Kolomeisky, Eugene B
2012-01-01
By enhancing electron position fluctuations, equilibrium electromagnetic radiation modifies the potential for an electron in a Hydrogen atom. This can have significant effects for weakly bound states and especially at finite temperature. This implies a 2% correction to Bethe's value for 2S-2P Lamb shift for weak fluctuations, but the effect is an order of magnitude larger for strong fluctuations where it provides direct measure of the proton diameter.
A renormalization-group approach to finite-temperature mass corrections
Marini, A; Marini, A; Burgess, C P
1994-01-01
We illustrate how the reorganization of perturbation theory at finite temperature can be economically cast in terms of the Wilson-Polchinski renormalization methods. We take as an example the old saw of the induced thermal mass of a hot scalar field with a quartic coupling, which we compute to second order in the coupling constant. We show that the form of the result can be largely determined by renormalization-group arguments without the explicit evaluation of Feynman graphs.
Multiple Scattering Expansion of the Self-Energy at Finite Temperature
Jeon, S; Jeon, Sangyong; Ellis, Paul J.
1998-01-01
An often used rule that the thermal correction to the self-energy is the thermal phase-space times the forward scattering amplitude from target particles is shown to be the leading term in an exact multiple scattering expansion. Starting from imaginary-time finite-temperature field theory, a rigorous expansion for the retarded self-energy is derived. The relationship to the thermodynamic potential is briefly discussed.
Three loop HTL perturbation theory at finite temperature and chemical potential
Energy Technology Data Exchange (ETDEWEB)
Strickland, Michael [Department of Physics, Kent State University, Kent, OH 44242 (United States); Andersen, Jens O. [Department of Physics, Norwegian University of Science and Technology, N-7491 Trondheim (Norway); Bandyopadhyay, Aritra; Haque, Najmul; Mustafa, Munshi G. [Theory Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Su, Nan [Faculty of Physics, University of Bielefeld, D-33615 Bielefeld (Germany)
2014-11-15
In this proceedings contribution we present a recent three-loop hard-thermal-loop perturbation theory (HTLpt) calculation of the thermodynamic potential for a finite temperature and chemical potential system of quarks and gluons. We compare the resulting pressure, trace anomaly, and diagonal/off-diagonal quark susceptibilities with lattice data. We show that there is good agreement between the three-loop HTLpt analytic result and available lattice data.
Three loop HTL perturbation theory at finite temperature and chemical potential
Strickland, Michael; Bandyopadhyay, Aritra; Haque, Najmul; Mustafa, Munshi G; Su, Nan
2014-01-01
In this proceedings contribution we present a recent three-loop hard-thermal-loop perturbation theory (HTLpt) calculation of the thermodynamic potential for a finite temperature and chemical potential system of quarks and gluons. We compare the resulting pressure, trace anomaly, and diagonal/off-diagonal quark susceptibilities with lattice data. We show that there is good agreement between the three-loop HTLpt analytic result and available lattice data.
Simulation on Temperature Field of Radiofrequency Lesions System Based on Finite Element Method
Xiao, D.; Qian, L.; Qian, Z.; Li, W.
2011-01-01
This paper mainly describes the way to get the volume model of damaged region according to the simulation on temperature field of radiofrequency ablation lesion system in curing Parkinson's disease based on finite element method. This volume model reflects, to some degree, the shape and size of the damaged tissue during the treatment with all tendencies in different time or core temperature. By using Pennes equation as heat conduction equation of radiofrequency ablation of biological tissue, the author obtains the temperature distribution field of biological tissue in the method of finite element for solving equations. In order to establish damage models at temperature points of 60°C, 65°C, 70°C, 75°C, 80°C, 85°C and 90 °C while the time points are 30s, 60s, 90s and 120s, Parkinson's disease model of nuclei is reduced to uniform, infinite model with RF pin at the origin. Theoretical simulations of these models are displayed, focusing on a variety of conditions about the effective lesion size on horizontal and vertical. The results show the binary complete quadratic non-linear joint temperature-time models of the maximum damage diameter and maximum height. The models can comprehensively reflect the degeneration of target tissue caused by radio frequency temperature and duration. This lay the foundation for accurately monitor of clinical RF treatment of Parkinson's disease in the future.
Entanglement and topological entropy of the toric code at finite temperature
Castelnovo, Claudio
2007-01-01
We calculate exactly the von Neumann and topological entropies of the toric code as a function of system size and temperature. We do so for systems with infinite energy scale separation between magnetic and electric excitations, so that the magnetic closed loop structure is fully preserved while the electric loop structure is tampered with by thermally excited electric charges. We find that the entanglement entropy is a singular function of temperature and system size, and that the limit of zero temperature and the limit of infinite system size do not commute. From the entanglement entropy we obtain the topological entropy, which is shown to drop to half its zero-temperature value for any infinitesimal temperature in the thermodynamic limit, and remains constant as the temperature is further increased. Such discontinuous behavior is replaced by a smooth decreasing function in finite-size systems. If the separation of energy scales in the system is large but finite, we argue that our results hold at small enou...
Chen, Roland K; Chastagner, Matthew W; Dodde, Robert E; Shih, Albert J
2013-02-01
The temporal and spatial tissue temperature profile in electrosurgical vessel sealing was experimentally measured and modeled using finite element modeling (FEM). Vessel sealing procedures are often performed near the neurovascular bundle and may cause collateral neural thermal damage. Therefore, the heat generated during electrosurgical vessel sealing is of concern among surgeons. Tissue temperature in an in vivo porcine femoral artery sealed using a bipolar electrosurgical device was studied. Three FEM techniques were incorporated to model the tissue evaporation, water loss, and fusion by manipulating the specific heat, electrical conductivity, and electrical contact resistance, respectively. These three techniques enable the FEM to accurately predict the vessel sealing tissue temperature profile. The averaged discrepancy between the experimentally measured temperature and the FEM predicted temperature at three thermistor locations is less than 7%. The maximum error is 23.9%. Effects of the three FEM techniques are also quantified.
Campo, V. L.; Ricco, L. S.; Seridonio, A. C.
2017-07-01
The zero-bias peak (ZBP) is understood as the definite signature of a Majorana bound state (MBS) when attached to a semi-infinite Kitaev nanowire (KNW) nearby zero temperature. However, such characteristics concerning the realization of the KNW constitute a profound experimental challenge. We explore theoretically a QD connected to a topological KNW of finite size at nonzero temperatures and show that overlapped MBSs of the wire edges can become effectively decoupled from each other and the characteristic ZBP can be fully recovered if one tunes the system into the leaked Majorana fermion fixed point. At very low temperatures, the MBSs become strongly coupled. We derive universal features of the conductance as a function of the temperature and the relevant crossover temperatures. Our findings offer additional guides to identify signatures of MBSs in solid state setups.
Real-time finite-temperature correlators from AdS/CFT
Barnes, Edwin; Wu, Chaolun; Arnold, Peter
2010-01-01
In this paper we use AdS/CFT ideas in conjunction with insights from finite temperature real-time field theory formalism to compute 3-point correlators of ${\\cal N}{=}4$ super Yang-Mills operators, in real time and at finite temperature. To this end, we propose that the gravity field action is integrated only over the right and left quadrants of the Penrose diagram of the Anti de Sitter-Schwarzschild background, with a relative sign between the two terms. For concreteness we consider the case of a scalar field in the black hole background. Using the scalar field Schwinger-Keldysh bulk-to-boundary propagators, we give the general expression of a 3-point real-time Green's correlator. We then note that this particular prescription amounts to adapting the finite-temperature analog of Veltman's circling rules to tree-level Witten diagrams, and comment on the retarded and Feynman scalar bulk-to-boundary propagators. We subject our prescription to several checks: KMS identities, the largest time equation and the zer...
Hamiltonian approach to QCD in Coulomb gauge at zero and finite temperature
Directory of Open Access Journals (Sweden)
Reinhardt H.
2017-01-01
Full Text Available I report on recent results obtained within the Hamiltonian approach to QCD in Coulomb gauge. By relating the Gribov confinement scenario to the center vortex picture of confinement it is shown that the Coulomb string tension is tied to the spatial string tension. For the quark sector a vacuum wave functional is used which results in variational equations which are free of ultraviolet divergences. The variational approach is extended to finite temperatures by compactifying a spatial dimension. For the chiral and deconfinement phase transition pseudo-critical temperatures of 170MeV and 198 MeV, respectively, are obtained.
Wang, Chong; Qiu, Zhi-Ping
2014-04-01
A new numerical technique named interval finite difference method is proposed for the steady-state temperature field prediction with uncertainties in both physical parameters and boundary conditions. Interval variables are used to quantitatively describe the uncertain parameters with limited information. Based on different Taylor and Neumann series, two kinds of parameter perturbation methods are presented to approximately yield the ranges of the uncertain temperature field. By comparing the results with traditional Monte Carlo simulation, a numerical example is given to demonstrate the feasibility and effectiveness of the proposed method for solving steady-state heat conduction problem with uncertain-but-bounded parameters. [Figure not available: see fulltext.
O(N) linear sigma model beyond the Hartree approximation at finite temperature
Baacke, J; Michalski, Stefan
2003-01-01
We study the O(N) linear sigma model with spontaneous symmetry breaking at finite temperature in the framework of the two-particle point-irreducible (2PPI) effective action. We go beyond the Hartree approximation by including the two-loop contribution, i.e., the sunset diagram. A phase transition of second order is found, whereas it is of first order in the one-loop Hartree approximation. Furthermore, we show the temperature-dependence of the variational mass parameters and comment on their relation to the physical sigma and pion masses.
$\\Delta$ self-energy at finite temperature and density and the $\\pi N$ cross-section
Ghosh, Snigdha; Sarkar, Sourav
2016-01-01
The self energy of $\\Delta$-baryon is evaluated at finite temperature and density using the real time formalism of thermal field theory. The Dyson-Schwinger equation is used to get the exact thermal propagator followed by the spectral function of $\\Delta$. The $\\pi N$ scattering cross section obtained using explicit $\\Delta$ exchange is normalized to the experimental data in vacuum and its medium modification is implemented by means of the exact thermal propagator. A significant suppression of the peak is observed at higher temperature and baryon density.
Temperature dependence of coulomb drag between finite-length quantum wires.
Peguiron, J; Bruder, C; Trauzettel, B
2007-08-24
We evaluate the Coulomb drag current in two finite-length Tomonaga-Luttinger-liquid wires coupled by an electrostatic backscattering interaction. The drag current in one wire shows oscillations as a function of the bias voltage applied to the other wire, reflecting interferences of the plasmon standing waves in the interacting wires. In agreement with this picture, the amplitude of the current oscillations is reduced with increasing temperature. This is a clear signature of non-Fermi-liquid physics because for coupled Fermi liquids the drag resistance is always expected to increase as the temperature is raised.
Study of the finite temperature transition in 3-flavor QCD using the R and RHMC algorithms
Cheng, M; Clark, M A; Jung, C; Kaczmarek, O; Karsch, Frithjof; Laermann, E; Mawhinney, R D; Miao, C; Petreczky, P; Petrov, K V; Schmidt, C; Söldner, W; Umeda, T; Van der Heide, J
2006-01-01
We study the finite temperature transition in QCD with three flavors of equal masses using the R and RHMC algorithm on lattices with temporal extent N_{\\tau}=4 and 6. For the transition temperature in the continuum limit we find r_0 T_c=0.429(8) for the light pseudo-scalar mass corresponding to the end point of the 1st order transition region. When comparing the results obtained with the R and RHMC algorithms for p4fat3 action we see no significant step-size errors down to a lightest pseudo-scalar mass of m_{ps} r_0=0.4.
A study of symmetry restoration at finite temperature in the O(4) model using anisotropic lattices
Gavai, R. V.; Heller, U. M.; Karsch, F.; Plache, B.; Neuhaus, T.
Results of investigations of the O(4) spin model at finite temperature using anisotropic lattices are presented. In both the large N approximation and the numerical simulations using the Wolff cluster algorithm we find that the ratio of the symmetry restoration temperature TSR to the Higgs mass mH is independent of the anisotropy. We obtain a lower bound of 0.59 ± 0.04 for the ratio, T SR/m H, at m H ⋍ 0.5 , which is lowered furhter by about 10% at m Ha ⋍ 1 .
A study of symmetry restoration at finite temperature in the O(4) model using anisotropic lattices
Gavai, R V; Karsch, Frithjof; Plache, B; Neuhaus, T
1992-01-01
Results of investigations of the $O(4)$ spin model at finite temperature using anisotropic lattices are presented. In both the large $N$ approximation and the numerical simulations using the Wolff cluster algorithm we find that the ratio of the symmetry restoration temperature $T_{\\rm SR}$ to the Higgs mass $m_{\\rm H}$ is independent of the anisotropy. We obtain a lower bound of $0.59 \\pm 0.04$ for the ratio, $T_{\\rm SR}/m_{\\rm H}$, at $m_{\\rm H}a \\simeq 0.5$, which is lowered further by about $10 \\%$ at $m_{\\rm H}a \\simeq 1.$
Hamiltonian approach to QCD in Coulomb gauge at zero and finite temperature
Reinhardt, H; Campagnari, D; Ebadati, E; Heffner, J; Quandt, M; Vastag, P; Vogt, H
2016-01-01
I report on recent results obtained within the Hamiltonian approach to QCD in Coulomb gauge. By relating the Gribov confinement scenario to the center vortex picture of confinement it is shown that the Coulomb string tension is tied to the spatial string tension. For the quark sector a vacuum wave functional is used which results in variational equations which are free of ultraviolet divergences. The variational approach is extended to finite temperatures by compactifying a spatial dimension. For the chiral and deconfinement phase transition pseudo-critical temperatures of 170 MeV and 198 MeV, respectively, are obtained.
Symmetry breaking in noncommutative finite temperature λphi4 theory with a nonuniform ground state
Hernández, J. M.; Ramírez, C.; Sánchez, M.
2014-05-01
We consider the CJT effective action at finite temperature for a noncommutative real scalar field theory, with noncommutativity among space and time variables. We study the solutions of a stripe type nonuniform background, which depends on space and time. The analysis in the first approximation shows that such solutions appear in the planar limit, but also under normal anisotropic noncommutativity. Further we show that the transition from the uniform ordered phase to the non uniform one is first order and that the critical temperature depends on the nonuniformity of the ground state.
Finite temperature Casimir effect for massive scalars in a magnetic field
Erdas, Andrea
2013-01-01
The finite temperature Casimir effect for a charged, massive scalar field confined between very large, perfectly conducting parallel plates is studied using the zeta function regularization technique. The scalar field satisfies Dirichlet boundary conditions at the plates and a magnetic field perpendicular to the plates is present. Four equivalent expressions for the zeta function are obtained, which are exact to all orders in the magnetic field strength, temperature, scalar field mass, and plate distance. The zeta function is used to calculate the Helmholtz free energy of the scalar field and the Casimir pressure on the plates, in the case of high temperature, small plate distance, strong magnetic field and large scalar mass. In all cases, simple analytic expressions of the zeta function, free energy and pressure are obtained, which are very accurate and valid for practically all values of temperature, plate distance, magnetic field and mass.
Finite temperature Casimir effect for charged massless scalars in a magnetic field
Erdas, Andrea
2013-01-01
The zeta function regularization technique is used to study the finite temperature Casimir effect for a charged and massless scalar field confined between parallel plates and satisfying Dirichlet boundary conditions at the plates. A magnetic field perpendicular to the plates is included. Three equivalent expressions for the zeta function are obtained, which are exact to all orders in the magnetic field strength, temperature and plate distance. These expressions of the zeta function are used to calculate the Helmholtz free energy of the scalar field and the pressure on the plates, in the case of high temperature, small plate distance and strong magnetic field. In all cases, simple analytic expressions are obtained for the free energy and pressure which are accurate and valid for practically all values of temperature, plate distance and magnetic field.
Application of Wavelet Finite Element Method to Simulation of the Temperature Field of Copier Paper
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
Simulation of the temperature field of copier paper in copier fusing is very important for improving the fusing property of reprography. The temperature field of copier paper varies with a high gradient when the copier paper is moving through the fusing rollers. By means of conventional shaft elements, the high gradient temperature variety causes the oscillation of the numerical solution. Based on the Daubechies scaling functions, a kind of wavelet-based element is constructed for the above problem. The temperature field of the copier paper moving through the fusing rollers is simulated using the two methods. Comparison of the results shows the advantages of the wavelet finite element method,which provides a new method for improving the copier properties.
Finite temperature and the Polyakov loop in the covariant variational approach to Yang-Mills Theory
Quandt, Markus; Reinhardt, Hugo
2017-03-01
We extend the covariant variational approach for Yang-Mills theory in Landau gauge to non-zero temperatures. Numerical solutions for the thermal propagators are presented and compared to high-precision lattice data. To study the deconfinement phase transition, we adapt the formalism to background gauge and compute the effective action of the Polyakov loop for the colour groups SU(2) and SU(3). Using the zero-temperature propagators as input, all parameters are fixed at T = 0 and we find a clear signal for a deconfinement phase transition at finite temperatures, which is second order for SU(2) and first order for SU(3). The critical temperatures obtained are in reasonable agreement with lattice data.
A finite-temperature Hartree-Fock code for shell-model Hamiltonians
Bertsch, G. F.; Mehlhaff, J. M.
2016-10-01
The codes HFgradZ.py and HFgradT.py find axially symmetric minima of a Hartree-Fock energy functional for a Hamiltonian supplied in a shell model basis. The functional to be minimized is the Hartree-Fock energy for zero-temperature properties or the Hartree-Fock grand potential for finite-temperature properties (thermal energy, entropy). The minimization may be subjected to additional constraints besides axial symmetry and nucleon numbers. A single-particle operator can be used to constrain the minimization by adding it to the single-particle Hamiltonian with a Lagrange multiplier. One can also constrain its expectation value in the zero-temperature code. Also the orbital filling can be constrained in the zero-temperature code, fixing the number of nucleons having given Kπ quantum numbers. This is particularly useful to resolve near-degeneracies among distinct minima.
Dȩbski, Lech
2016-03-01
This paper announces a possibility of detection of finite-temperature stripe ordering in the two-dimensional Falicov-Kimball model at half-filling by extensive Monte Carlo simulations. Moreover, the tools to study orderings and to detect phase transition temperatures are presented. The use of Binder's cumulant is supplemented by finite-size magnetization profiles not analyzed previously in this context. Continuous character of phase transitions is announced. Analyses proving the existence of more complicated phases of finite-temperature stripe ordering than the checkerboard one conclude the paper.
Finite Element Modeling of Transient Temperatures in a Small-Caliber Projectile
Directory of Open Access Journals (Sweden)
M. B. Thomas
2010-01-01
Full Text Available Problem statement: Future generations of intelligent munitions will use Microelectromechanical Systems (MEMS for guidance, fuzing logic and assessment of the battlefield environment. The temperatures fund in a gun system, however, are sufficient to damage some materials used in the fabrication of MEMS. The motivation of this study is to model the dynamic temperature distribution in a typical small-caliber projectile. Approach: An axisymmetric finite-element model of a projectile is developed to simulate temperatures through internal ballistics (the projectile is in the gun barrel and external ballistics (the projectile travels in a free trajectory towards the target. Accuracy of the simulation is confirmed through comparison to analytical models and to payloads attached to experimental projectiles. In the simulation, the exact values for some boundary conditions are unknown and/or unknowable. A sensitivity analysis determines the effect of these uncertain parameters. Results: The simulation shows that friction at the projectile-gun barrel interface is primarily responsible for elevated temperatures in a gun system. Other factors have much smaller effects. The short duration of the internal ballistics prevents the frictional heat from diffusing into the bulk of the projectile. As a result, the projectile has a shallow, high-temperature zone at its bearing surface as it leaves the gun barrel. During external ballistics, this heat will diffuse through the projectile, but most of the projectile experiences temperatures of 56°C or lower. Simulation shows that the polymer package around a MEMS device will further attenuate heat flow, limiting temperatures in the device to less than 30°C. Conclusion: The finite element model demonstrates that a MEMS device may be engineered to survive temperatures expected in the ballistic environment.
BCS Instability and Finite Temperature Corrections to Tachyon Mass in Intersecting D1-Branes
Chowdhury, Sudipto Paul; Sathiapalan, B
2014-01-01
A holographic description of BCS superconductivity is given in arxiv:1104.2843. This model was constructed by insertion of a pair of D8-branes on a D4-background. The spectrum of intersecting D8-branes has tachyonic modes indicating an instability which is identified with the BCS instability in superconductors. Our aim is to study the stability of the intersecting branes under finite temperature effects. Many of the technical aspects of this problem are captured by a simpler problem of two intersecting D1-branes on flat background. In the simplified set-up we compute the one-loop finite temperature corrections to the tree-level tachyon mass using the frame-work of SU(2) Yang-Mills theory in (1 + 1)-dimensions. We show that the one-loop two-point functions are ultraviolet finite due to cancellation of ultraviolet divergence between the amplitudes containing bosons and fermions in the loop. The amplitudes are found to be infrared divergent due to the presence of massless fields in the loops. We compute the fini...
Temperature control of transfer roller's bearing based on finite element analysis
Institute of Scientific and Technical Information of China (English)
Peng ZHANG; Yourong LI; Han XIAO
2009-01-01
After a heat preservation cover is installed on the main rolling line, the heat dissipation environment of the transfer roller working on the heat preservation cover is changed. To ensure the normal production, a reasonable working jet capacity of the roller neck is derived. First, a globe model of the transfer roller is built for finite element analysis. Second, the sub-model of the fixed end bearing is built and the boundary condition of the sub-model is supplied by the results of the globe model. The analysis result of the sub-model shows that the temperature of the transfer roller bearing exceeds 85℃ a rolling periodicity later. With finite element analysis, the heat flux is obtained and the minimum working jet capacity is derived.
Ejiri, Shinji; Yamada, Norikazu
2016-01-01
Aiming to understand the phase structure of lattice QCD at nonzero temperature and density, we study the phase transitions of QCD in an extended parameter space, where the number of flavor and quark masses are considered as parameters. Performing simulations of 2 flavor QCD and using the reweighting method, we investigate (2+Nf) flavor QCD at finite density, where two light flavors and Nf massive flavors exist. Calculating probability distribution functions, we determine the critical surface terminating first order phase transitions in the parameter space of the light quark mass, the heavy quark mass and the chemical potential. Through the study of the many flavor system, we discuss the phase structure of QCD at finite density.
Histograms in heavy-quark QCD at finite temperature and density
Saito, H; Aoki, S; Kanaya, K; Nakagawa, Y; Ohno, H; Okuno, K; Umeda, T
2013-01-01
We study the phase structure of lattice QCD with heavy quarks at finite temperature and density by a histogram method. We determine the location of the critical point at which the first-order deconfining transition in the heavy-quark limit turns into a crossover at intermediate quark masses through a change of the shape of the histogram under variation of coupling parameters. We estimate the effect of the complex phase factor which causes the sign problem at finite density, and show that, in heavy-quark QCD, the effect is small around the critical point. We determine the critical surface in 2+1 flavor QCD in the heavy-quark region at all values of the chemical potential mu including mu=infty.
QCD effective potential with strong magnetic fields at zero and finite temperatures
Ozaki, Sho; Arai, Takashi; Hattori, Koichi; Itakura, Kazunori
2014-09-01
In this contribution, we will discuss QCD vacuum in strong magnetic fields. As a first step towards understanding the effects of magnetic fields on QCD vacuum properties, we analytically derive the Euler-Heisenberg action for QCD + QED at zero and finite temperatures. From the action, at zero temperature, we found that the chromo-magnetic field prefers to be parallel to the external magnetic field, and thus the QCD vacuum with strong magnetic fields is spatially anisotropic. This result is consistent with recent lattice data. Furthermore, the chromo-magnetic condensate increases with an increasing magnetic field, which supports the ``gluonic magnetic catalysis'' as observed in current lattice data. Next, we will discuss the effective potential with strong magnetic fields at finite temperatures. In particular, we focus on the influence of the magnetic field on the center symmetry in QCD. The pure Yang-Mills theory has the center symmetry (being spontaneously broken at high temperature), but dynamical quarks explicitly break it. We will show how the magnetic fields affect the explicit symmetry breaking, by using the effective potential for the Polyakov loop. We will also discuss the confinement-deconfinement phase transition in strong magnetic fields in terms of nonperturbative approaches such as functional renormalization group.
Neutrino Dispersion Relations at Finite Temperature and Density in the Left-Right Symmetric Model
Villalba-Pardo, F D
2010-01-01
In the framework of the Left-Right Symmetric Model, where left-handed neutrinos are massive via the see-saw mechanism, we determine the effects of temperature and density in the dispersion relations for neutrinos, considering that there exists an excess of leptons over antileptons in the plasma. To achieve this we first calculate the dispersion relations at finite temperature and density, computing the neutrino self-energy at one loop order in perturbation theory, obtaining a fully analytic expression for this self-energy even in the fully broken symmetry case by using the Mellin summation technique. From the dispersion relation found from the self energy we obtain the thermal effective mass for neutrinos at high temperature limit. This result allow us to establish the effect of finite temperature and density for neutrino oscillations in thermal and dense media for this framework. We can do it if we take into account that the oscillation patterns depend explicitly on neutrino masses. As a result, a generaliza...
Nucleon Properties at Finite Temperature in the Extended Quark-Sigma Model
Abu-Shady, M
2014-01-01
Hadron properties are studied at hot medium using the quark sigma model. The quark sigma model is extended to include eighth-order of mesonic interactions based on some aspects of quantum chromodynamic (QCD) theory. The extended effective potential tends to the original effective potential when the coupling between the higher order mesonic interactions equal to zero. The field equations have been solved in the mean-field approximation by using the extended iteration method. We found that the nucleon mass increases with increasing temperature and the magnetic moments of proton and neutron increase with increasing temperature. A comparison is presented with recent previous works and other models. We conclude that higher-order mesonic interactions play an important role in changing the behavior of nucleon properties at finite temperature. In addition, the deconfinement phase transition is satisfied in the present model.
Holographic zero sound at finite temperature in the Sakai-Sugimoto model
DiNunno, Brandon S; Jokela, Niko; Pedraza, Juan F
2014-01-01
In this paper, we study the fate of the holographic zero sound mode at finite temperature and non-zero baryon density in the deconfined phase of the Sakai-Sugimoto model of holographic QCD. We establish the existence of such a mode for a wide range of temperatures and investigate the dispersion relation, quasi-normal modes, and spectral functions of the collective excitations in four different regimes, namely, the collisionless quantum, collisionless thermal, and hydrodynamic regimes, as well as an intermediate crossover between the latter two. For sufficiently high temperatures, the zero sound completely disappears, and the physics is dominated by an emergent diffusive mode. We compare our findings to Landau-Fermi liquid theory and to other holographic models.
A Calculation Approach to Elastic Constants of Crystallines at High Pressure and Finite Temperature
Institute of Scientific and Technical Information of China (English)
向士凯; 蔡灵仓; 张林; 经福谦
2002-01-01
Elastic constants of Na and Li metals are calculated successfully for temperatures up to 350K and pressures up to 30 GPa using a scheme without involving any adjustable parameter. Elastic constants are assumed to depend only on an effective pair potential that is only determined by the average interatomic distance. Temperature has an effect on elastic constants by way of charging the equilibrium. The elastic constants can be obtained by fitting the relationship between total energy and strain tensor using the new set of lattice parameters obtained by calculating displacement of atoms at the finite temperature and at a fixed pressure. The relationship between the effective pair potential and the interatomic distance is fitted by using a series of data of cohesive energy corresponding to lattice parameters.
Heavy quark free energies for three quark systems at finite temperature
Hübner, K; Kaczmarek, O; Vogt, O
2007-01-01
We study the free energy of static three quark systems in singlet, octet, decuplet and average color channels in the quenched approximation and in 2-flavor QCD at finite temperature. We show that in the high temperature phase singlet and decuplet free energies of three quark systems are well described by the sum of the free energies of three diquark systems plus self energy contributions of the three quarks. In the confining low temperature phase we find evidence for a Y-shaped flux tube in SU(3) pure gauge theory, which is less evident in 2-flavor QCD due to the onset of string breaking. We also compare the short distance behavior of octet and decuplet free energies to the free energies of single static quarks in the corresponding color representations.
Emergence of a Fermionic Finite-Temperature Critical Point in a Kondo Lattice.
Chou, Po-Hao; Zhai, Liang-Jun; Chung, Chung-Hou; Mou, Chung-Yu; Lee, Ting-Kuo
2016-04-29
The underlying Dirac point is central to the profound physics manifested in a wide class of materials. However, it is often difficult to drive a system with Dirac points across the massless fermionic critical point. Here by exploiting screening of local moments under spin-orbit interactions in a Kondo lattice, we show that below the Kondo temperature, the Kondo lattice undergoes a topological transition from a strong topological insulator to a weak topological insulator at a finite temperature T_{D}. At T_{D}, massless Dirac points emerge and the Kondo lattice becomes a Dirac semimetal. Our analysis indicates that the emergent relativistic symmetry dictates nontrivial thermal responses over large parameter and temperature regimes. In particular, it yields critical scaling behaviors both in magnetic and transport responses near T_{D}.
Finite-temperature behavior of an impurity in the spin-1/2 XXZ chain
Yahagi, Ryoko; Sato, Jun; Deguchi, Tetsuo
2014-11-01
We study the zero- and the finite-temperature behavior of the integrable spin-1/2 XXZ periodic chain with an impurity by the algebraic and thermal Bethe ansatz methods. We evaluate the local magnetization on the impurity site at zero temperature analytically and derive the impurity susceptibility exactly from it. In the graphs of the impurity specific heat versus temperature, we show how the impurity spin becomes more liberated from the bulk many-body effect as the exchange coupling between the impurity spin and other spins decreases and that at low temperature it couples strongly to them such as in the Kondo effect. Thus, we observe not only the crossover behavior from the high- to the low-temperature regime, but another from the N-site chain to the (N - 1)-site chain with a free impurity spin. We also show that the estimate of the Wilson ratio at a given low temperature is independent of the impurity parameter if its absolute value is small enough with respect to the temperature and the universality class is described by the XXZ anisotropy in terms of the dressed charge.
Wang, Wei; Qiao, Qingli; Gao, Weiping; Wu, Jun
2014-12-01
We studied the influence of electrode array parameters on temperature distribution to the retina during the use of retinal prosthesis in order to avoid thermal damage to retina caused by long-term electrical stimulation. Based on real epiretinal prosthesis, a three-dimensional model of electrical stimulation for retina with 4 X 4 microelectrode array had been established using the finite element software (COMSOL Multiphysics). The steady-state temperature field of electrical stimulation of the retina was calculated, and the effects of the electrode parameters such as the distance between the electrode contacts, the materials and area of the electrode contact on temperature field were considered. The maximum increase in the retina steady temperature was about 0. 004 degrees C with practical stimulation current. When the distance between the electrode contacts was changed from 130 microm to 520 microm, the temperature was reduced by about 0.006 microC. When the contact radius was doubled from 130 microm to 260 microm, the temperature decrease was about 0.005 degrees C. It was shown that there were little temperature changes in the retina with a 4 x 4 epiretinal microelectrode array, reflecting the safety of electrical stimulation. It was also shown that the maximum temperature in the retina decreased with increasing the distance between the electrode contacts, as well as increasing the area of electrode contact. However, the change of the maximum temperature was very small when the distance became larger than the diameter of electrode contact. There was no significant difference in the effects of temperature increase among the different electrode materials. Rational selection of the distance between the electrode contacts and their area in electrode design can reduce the temperature rise induced by electrical stimulation.
Magnetic susceptibility of QCD at zero and at finite temperature from the lattice
Bali, G S; Constantinou, M; Costa, M; Endrodi, G; Katz, S D; Panagopoulos, H; Schaefer, A
2012-01-01
The response of the QCD vacuum to a constant external (electro)magnetic field is studied through the tensor polarization of the chiral condensate and the magnetic susceptibility at zero and at finite temperature. We determine these quantities using lattice configurations generated with the tree-level Symanzik improved gauge action and N_f=1+1+1 flavors of stout smeared staggered quarks with physical masses. We carry out the renormalization of the observables under study and perform the continuum limit both at T>0 and at T=0, using different lattice spacings. Finite size effects are studied by using various spatial lattice volumes. The magnetic susceptibilities \\chi_f reveal a diamagnetic behavior; we obtain at zero temperature \\chi_u=-(2.08 +/- 0.08) 1/GeV^2, \\chi_d=-(2.02 +/- 0.09) 1/GeV^2 and \\chi_s=-(3.4 +/- 1.4) 1/GeV^2 for the up, down and strange quarks, respectively, in the MSBar scheme at a renormalization scale of 2 GeV. We also find the polarization to change smoothly with the temperature in the con...
A holographic model for QCD in the Veneziano limit at finite temperature and density
Energy Technology Data Exchange (ETDEWEB)
Alho, T. [Department of Physics, University of Jyväskylä,P.O. Box 35, FI-40014 Jyväskylä (Finland); Helsinki Institute of Physics, University of Helsinki,P.O. Box 64, FI-00014 Helsinki (Finland); Järvinen, M. [Physics Department, University of Crete,P.O. Box 2208, 71003 Heraklion, Crete (Greece); Kajantie, K. [Helsinki Institute of Physics, University of Helsinki,P.O. Box 64, FI-00014 Helsinki (Finland); Kiritsis, E. [Physics Department, University of Crete,P.O. Box 2208, 71003 Heraklion, Crete (Greece); APC, Université Paris 7,Bâtiment Condorcet, 75205, Paris Cedex 13 (France); Theory Group, Physics Department, CERN,CH-1211, Geneva 23 (Switzerland); Rosen, C. [Physics Department, University of Crete,P.O. Box 2208, 71003 Heraklion, Crete (Greece); Tuominen, K. [Department of Physics, University of Helsinki,P.O. Box 64, FI-00014 Helsinki (Finland); Helsinki Institute of Physics, University of Helsinki,P.O. Box 64, FI-00014 Helsinki (Finland)
2014-04-22
A holographic model of QCD in the limit of large number of colors, N{sub c}, and massless fermion flavors, N{sub f}, but constant ratio x{sub f}=N{sub f}/N{sub c} is analyzed at finite temperature and chemical potential. The five dimensional gravity model contains three bulk fields: a scalar dilaton sourcing TrF{sup 2}, a scalar tachyon dual to q-macron q and a 4-vector dual to the baryon current q-macron γ{sup μ}q. The main result is the μ,T phase diagram of the holographic theory. A first order deconfining transition along T{sub h}(μ) and a chiral transition at T{sub χ}(μ)>T{sub h}(μ) are found. The chiral transition is of second order for small μ and becomes of first order at larger μ. The two regimes are separated by a tricritical point. The dependence of thermodynamical quantities including the speed of sound and susceptibilities on the chemical potential and temperature is computed. A new quantum critical regime is found at zero temperature and finite chemical potential. It is controlled by an AdS{sub 2}×R{sup 3} geometry and displays semi-local criticality.
Czarnik, Piotr; Dziarmaga, Jacek; Oleś, Andrzej M.
2016-05-01
Progress in describing thermodynamic phase transitions in quantum systems is obtained by noticing that the Gibbs operator e-β H for a two-dimensional (2D) lattice system with a Hamiltonian H can be represented by a three-dimensional tensor network, the third dimension being the imaginary time (inverse temperature) β . Coarse graining the network along β results in a 2D projected entangled-pair operator (PEPO) with a finite bond dimension D . The coarse graining is performed by a tree tensor network of isometries. The isometries are optimized variationally, taking into account full tensor environment, to maximize the accuracy of the PEPO. The algorithm is applied to the isotropic quantum compass model on an infinite square lattice near a symmetry-breaking phase transition at finite temperature. From the linear susceptibility in the symmetric phase and the order parameter in the symmetry-broken phase, the critical temperature is estimated at Tc=0.0606 (4 ) J , where J is the isotropic coupling constant between S =1/2 pseudospins.
Light-front Nambu--Jona-Lasinio model at finite temperature and density
Strauss, S; Beyer, M
2009-01-01
In recent years light-front quantisation has been extended to allow for a consistent treatment of systems at finite temperature and density. This is in particular interesting for an investigation of the processes in nuclear matter under extreme condition as occurring, e.g., during a heavy ion collision. Utilising a Dyson expansion to the N-point Green functions at finite temperature and density we focus on the occurrence of pionic and scalar diquark dynamics in quark matter and compute the masses and the Mott dissociation using a separable t-matrix approach. For the scalar quark-quark correlation we determine the critical temperature of colour superconductivity using the Thouless criterion. On the same footing the properties of the nucleon in a medium of quark matter are computed within a Faddeev approach. Critical lines for nucleon breakup are given. Presently, we use a light-front Nambu--Jona-Lasinio model that allows us to compare these results of this novel approach to the more traditional instant form ap...
Finite Temperature Closed Superstring Theory Infrared Stability and a Minimum Temperature
Chaudhuri, S
2001-01-01
We show that flat spacetime is an unstable background of all of the weakly coupled ten-dimensional superstrings under infinitesimal thermal fluctuations in the absence of gauge or antisymmetric tensor field background. We demonstrate this principle in both type II and heterotic closed strings obtaining thermal duality invariant expressions for the normalized generating functional of connected one-loop vacuum graphs and exhibiting a continuous phase transition of the Kosterlitz-Thouless type at the self-dual temperature in the thermodynamic potentials. We find that the type II theory displays the unusual phenomenon of a minimum temperature below which the free string ensemble is unstable. We show that in the presence of a temperature dependent Wilson line the heterotic string theory has a stable and tachyon-free ground state at all temperatures starting from zero with gauge group SO(16)xSO(16). The one-loop contribution to the Helmholtz free energy of free SO(16)xSO(16) heterotic strings vanishes at the self-d...
Noninteracting fermions at finite temperature in a d -dimensional trap: Universal correlations
Dean, David S.; Le Doussal, Pierre; Majumdar, Satya N.; Schehr, Grégory
2016-12-01
We study a system of N noninteracting spinless fermions trapped in a confining potential, in arbitrary dimensions d and arbitrary temperature T . The presence of the confining trap breaks the translational invariance and introduces an edge where the average density of fermions vanishes. Far from the edge, near the center of the trap (the so-called "bulk regime"), where the fermions do not feel the curvature of the trap, physical properties of the fermions have traditionally been understood using the local density (or Thomas-Fermi) approximation. However, these approximations drastically fail near the edge where the density vanishes and thermal and quantum fluctuations are thus enhanced. The main goal of this paper is to show that, even near the edge, novel universal properties emerge, independently of the details of the shape of the confining potential. We present a unified framework to investigate both the bulk and the edge properties of the fermions. We show that for large N , these fermions in a confining trap, in arbitrary dimensions and at finite temperature, form a determinantal point process. As a result, any n -point correlation function, including the average density profile, can be expressed as an n ×n determinant whose entry is called the kernel, a central object for such processes. Near the edge, we derive the large-N scaling form of the kernels, parametrized by d and T . In d =1 and T =0 , this reduces to the so-called Airy kernel, that appears in the Gaussian unitary ensemble (GUE) of random matrix theory. In d =1 and T >0 we show a remarkable connection between our kernel and the one appearing in the (1 +1 )-dimensional Kardar-Parisi-Zhang equation at finite time. Consequently, our result provides a finite-T generalization of the Tracy-Widom distribution, that describes the fluctuations of the position of the rightmost fermion at T =0 , or those of the largest single-fermion momentum. In d >1 and T ≥0 , while the connection to GUE no longer holds
The O(N) linear sigma model at finite temperature beyond the Hartree approximation
Baacke, J
2003-01-01
We study the O(N) linear sigma model with spontaneous symmetry breaking, using a Hartree-like ansatz with a classical field and variational masses. We go beyond the Hartree approximation by including the two-loop contribution, the sunset diagram, using the 2PPI expansion. We have computed numerically the effective potential at finite temperature. We find a phase transition of second order, while it is first order in the one-loop Hartree approximation. We also discuss some implications of the fact that in this order, the decay of the sigma into two pions affects the thermal diagrams.
Multiscale coupling based on quasicontinuum method in nanowires at finite temperatures
DEFF Research Database (Denmark)
Esahani, Mohammad Nasr; Sonne, Mads Rostgaard; Hattel, Jesper Henri;
2015-01-01
Nanoelectromechanical systems have been developed for ultra-high frequency oscillators because of their small sizeand excellent material properties. Using flexural modes and electrothermal features in nanowires for frequency tuning necessitates a sound modeling approach. The quasicontinuum method...... was developed to link atomistic models with the continuum finite element method in order to study the material behavior across multiple length scales. These significant efforts to develop a continuum theory based on atomistic models have so far been limited to zero temperature. The purpose of this work...
Aether field in extra dimensions: Stefan-Boltzmann law and Casimir effect at finite temperature
Santos, A. F.; Khanna, Faqir C.
2017-01-01
The Lorentz and C P T symmetries are not violated at the highest laboratory energies available. However these symmetries may be violated at Planck scale. A particular development is to investigate the breakdown of Lorentz and C P T symmetries by introducing an aether field that exhibits nonzero vacuum expectation value along the fifth dimension. The interactions of the aether field with scalar, electromagnetic, and fermions fields are analyzed. The Stefan-Boltzmann law and Casimir effect at finite temperature are calculated using the Thermo Field Dynamics formalism.
Casimir effect at finite temperature for pure-photon sector of the minimal Standard Model Extension
Energy Technology Data Exchange (ETDEWEB)
Santos, A.F., E-mail: alesandroferreira@fisica.ufmt.br [Instituto de Física, Universidade Federal de Mato Grosso, 78060-900, Cuiabá, Mato Grosso (Brazil); Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road Victoria, BC (Canada); Khanna, Faqir C., E-mail: khannaf@uvic.ca [Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road Victoria, BC (Canada)
2016-12-15
Dynamics between particles is governed by Lorentz and CPT symmetry. There is a violation of Parity (P) and CP symmetry at low levels. The unified theory, that includes particle physics and quantum gravity, may be expected to be covariant with Lorentz and CPT symmetry. At high enough energies, will the unified theory display violation of any symmetry? The Standard Model Extension (SME), with Lorentz and CPT violating terms, has been suggested to include particle dynamics. The minimal SME in the pure photon sector is considered in order to calculate the Casimir effect at finite temperature.
LEVEL DENSITY AND FINITE-TEMPERATURE SPECIFIC HEATOF NUCLEUS 104pd UNDER MICROSCOPIC IBM
Institute of Scientific and Technical Information of China (English)
石筑一; 刘庸; 桑建平
2001-01-01
By using the microscopic sdgIBM-Fmax approach, the procedure of canonical ensemble average and the saddle point approximation, the thermodynamics of the nucleus is established under microscopic IBM. Calculations of spectrum, level density and finite-temperature specific heat for the nucleus 104pd are carried out. The calculated values are coincident with the experimental data reported recently. The results predict that the shape phase transition in the groundstate band appears at about T ≈0.230MeV and the phase transition of the thermal excitation mode takes place at T ≈0.630 MeV for the nucleus 104pd.
Finite-temperature Gutzwiller approximation from the time-dependent variational principle
Lanatà, Nicola; Deng, Xiaoyu; Kotliar, Gabriel
2015-08-01
We develop an extension of the Gutzwiller approximation to finite temperatures based on the Dirac-Frenkel variational principle. Our method does not rely on any entropy inequality, and is substantially more accurate than the approaches proposed in previous works. We apply our theory to the single-band Hubbard model at different fillings, and show that our results compare quantitatively well with dynamical mean field theory in the metallic phase. We discuss potential applications of our technique within the framework of first-principle calculations.
Weak Coupling Phase Structureof the Abelian Higgs Model at Finite Temperature
Jakovác, A
1993-01-01
Using the 1-loop reduced 3D action of the Abelian Higgs-model we discuss the order of its finite temperature phase transition. A two-variable saddle point approximation is proposed for the evaluation of the effective potential. The strength of the first order case scales like \\sim e^{3-6}. Analytic asymptotic weak coupling and numerical small coupling solutions are compared with special emphasis on the cancellation of divergences. (Figures are not included, can be sent upon request from jako@hercules.elte.hu .)
Casimir Effect at finite temperature for the CPT-even extension of QED
Silva, L M; Helayël-Neto, J A
2016-01-01
By the thermofield dynamics (TFD) formalism we obtain the energy-momentum tensor for the Electromagnetism with Lorentz Breaking Even term of the Standard Model Extended (SME) Sector in a topology $S^{1}\\times S^{1}\\times R^{2}$. We carry out the compactification by a generalized TFD-Bogoliubov transformation that is used to define a renormalized energy-momentum tensor, and the Casimir energy and pressure at finite temperature are then derived. A comparative analysis with the electromagnetic case is developed, and we remark the influence of the background in the traditional Casimir effect.
Casimir effect at finite temperature for pure-photon sector of the minimal Standard Model Extension
Santos, A. F.; Khanna, Faqir C.
2016-12-01
Dynamics between particles is governed by Lorentz and CPT symmetry. There is a violation of Parity (P) and CP symmetry at low levels. The unified theory, that includes particle physics and quantum gravity, may be expected to be covariant with Lorentz and CPT symmetry. At high enough energies, will the unified theory display violation of any symmetry? The Standard Model Extension (SME), with Lorentz and CPT violating terms, has been suggested to include particle dynamics. The minimal SME in the pure photon sector is considered in order to calculate the Casimir effect at finite temperature.
BKT phase transitions in strongly coupled 3D Z(N) LGT at finite temperature
Borisenko, O.; V. Chelnokov; Cortese, G.; Fiore, R.; Gravina, M.; Papa, A.; Surzhikov, I.
2012-01-01
We investigate, both analytically and numerically, the phase diagram of three-dimensional Z(N) lattice gauge theories at finite temperature for N > 4. These models, in the strong coupling limit, are equivalent to a generalized version of vector Potts models in two dimension, with Polyakov loops playing the role of Z(N) spins. It is argued that the effective spin models have two phase transitions of infinite order (i.e. BKT). Using a cluster algorithm we confirm this conjecture, locate the pos...
BKT phase transitions in strongly coupled 3D Z(N) LGT at finite temperature
Borisenko, O; Cortese, G; Fiore, R; Gravina, M; Papa, A; Surzhikov, I
2012-01-01
We investigate, both analytically and numerically, the phase diagram of three-dimensional Z(N) lattice gauge theories at finite temperature for N > 4. These models, in the strong coupling limit, are equivalent to a generalized version of vector Potts models in two dimension, with Polyakov loops playing the role of Z(N) spins. It is argued that the effective spin models have two phase transitions of infinite order (i.e. BKT). Using a cluster algorithm we confirm this conjecture, locate the position of the critical points and extract various critical indices.
Unusual finite size effects on critical temperature in fcc Ising antiferromagnets
Pommier, J.; Diep, H. T.; Ghazali, A.; Lallemand, P.
1988-04-01
A new multispin coding technique is presented for Monte Carlo simulation of antiferromagnetic Ising spin systems on an fcc lattice. The nearest- and next-nearest-neighbor interactions J1 and J2 are included. This technique allows a considerable gain in CPU time and computer memory. As a first application, we have studied samples of 4L3 spins with L up to 48. An unusual behavior of the critical temperature with increasing L is found in the case of nearest-neighbor interaction in zero field. Finite size effects on the locations of tricrical points in the (T,J2/J1) plane are discussed.
Bialas, P; Morel, A; Petersson, B
2009-01-01
We determine the correlation between Polyakov loops in three dimensional SU(3) gauge theory in the confined region at finite temperature. For this purpose we perform lattice calculations for the number of steps in the temperature direction equal to six. This is expected to be in the scaling region of the lattice theory. We compare the results to the bosonic string model. The agreement is very good for temperatures T<0.7T_c, where T_c is the critical temperature. In the region 0.7T_c
Kawamoto, N; Ohnishi, A; Ohnuma, T
2005-01-01
We study the phase diagram of quark matter at finite temperature (T) and finite chemical potential (mu) in the strong coupling limit of lattice QCD for color SU(3). We derive an analytical expression of the effective free energy as a function of T and mu, including baryon effects. The finite temperature effects are evaluated by integrating over the temporal link variable exactly in the Polyakov gauge with anti-periodic boundary condition for fermions. The obtained phase diagram shows the first order phase transition at low temperatures and the second order phase transition at high temperatures separated by the tri-critical point in the chiral limit. Baryon has effects to reduce the effective free energy and to extend the hadron phase to a larger mu direction at low temperatures.
Finite-temperature scaling close to Ising-nematic quantum critical points in two-dimensional metals
Punk, Matthias
2016-11-01
We study finite-temperature properties of metals close to an Ising-nematic quantum critical point in two spatial dimensions. In particular we show that at any finite temperature there is a regime where order parameter fluctuations are characterized by a dynamical critical exponent z =2 , in contrast to z =3 found at zero temperature. Our results are based on a simple Eliashberg-type approach, which gives rise to a boson self-energy proportional to Ω /γ (T ) at small momenta, where γ (T ) is the temperature dependent fermion scattering rate. These findings might shed some light on recent Monte Carlo simulations at finite temperature, where results consistent with z =2 were found.
Finite Element Analysis of Temperature Field in Automotive Dry Friction Clutch
Directory of Open Access Journals (Sweden)
O.I. Abdullah
2012-12-01
Full Text Available The friction clutch design is strongly dependent upon the frictional heat generated between contact surfaces during the slipping at beginning of engagement. Because of that the frictional heat generated firstly will reduce the performance of clutch system and then will lead to premature failure in some cases. Finite element method was used to investigate aneffect of thermal load type on the temperature field of the clutch system. Two-dimensional axisymmetric model was used to study the temperature distribution for the clutch system (pressure plate, clutch disc and flywheel during heating phase (slipping period and in the cooling phase (full engagement period. Depending on basic friction clutch design two types of thermal loads were applied; load type A (uniform pressure and load type B (uniform wear. Repeated engagements made at regular interval wereconsidered in this work. ANSYS13 has been used to perform the numerical calculation in this paper.
Dzhioev, Alan A; Ponomarev, V Yu; Wambach, J; Langanke, K; Martínez-Pinedo, G
2009-01-01
We propose a new method to calculate stellar weak-interaction rates. It is based on the Thermo-Field-Dynamics formalism and allows the calculation of the weak-interaction response of nuclei at finite temperatures. The thermal evolution of the GT$_+$ distributions is presented for the sample nuclei $^{54, 56}$Fe and ~$^{76,78,80}$Ge. For Ge we also calculate the strength distribution of first-forbidden transitions. We show that thermal effects shift the GT$_+$ centroid to lower excitation energies and make possible negative- and low-energy transitions. In our model we demonstrate that the unblocking effect for GT$_+$ transitions in neutron-rich nuclei is sensitive to increasing temperature. The results are used to calculate electron capture rates and are compared to those obtained from the shell model.
Gubler, Philipp; Satow, Daisuke
2016-11-01
We derive three exact sum rules for the spectral function of the electromagnetic current with zero spatial momentum at finite temperature. Two of them are derived in this paper for the first time. We explicitly check that these sum rules are satisfied in the weak coupling regime and examine which sum rule is sensitive to the transport peak in the spectral function at low energy or the continuum at high energy. Possible applications of the three sum rules to lattice computations of the spectral function and transport coefficients are also discussed: we propose an Ansatz for the spectral function that can be applied to all three sum rules and fit it to available lattice data of the Euclidean vector correlator above the critical temperature. As a result, we obtain estimates for both the electrical conductivity σ and the second-order transport coefficient τJ .
Finite element analysis of spot laser of steel welding temperature history
Directory of Open Access Journals (Sweden)
Shibib Khalid S.
2009-01-01
Full Text Available Laser welding process reduces the heat input to the work-piece which is the main goal in aerospace and electronics industries. A finite element model for axi-symmetric transient heat conduction has been used to predict temperature distribution through a steel cylinder subjected to CW laser beam of rectangular beam profile. Many numerical improvements had been used to reduce time of calculation and size of the program so as to achieve the task with minimum time required. An experimental determined absorptivity has been used to determine heat induced when laser interact with material. The heat affected zone and welding zone have been estimated to determine the effect of welding on material. The ratio of depth to width of the welding zone can be changed by proper selection of beam power to meet the specific production requirement. The temperature history obtained numerically has been compared with experimental data indicating good agreement.
Non-compact QED3 at finite temperature the confinement-deconfinement transition
Fiore, Roberto; Papa, Alessandro
2008-01-01
The confinement-deconfinement phase transition is explored by lattice numerical simulations in non-compact (2+1)-dimensional quantum electrodynamics with massive fermions at finite temperature. The existence of two phases, one with and the other without confinement of fractional charges, is related to the realization of the Z symmetry. The order parameter of this transition can be clearly identified. We show that it is possible to detect the critical temperature for a given value of the fermion mass, by exploiting suitable lattice operators as probes of the Z symmetry. Moreover, the large-distance behavior of the correlation of these operators permits to distinguish the phase with Coulomb-confinement from the Debye-screened phase. The resulting scenario is compatible with the existence of a Berezinsky-Kosterlitz-Thouless transition. Some investigations are presented on the possible relation between chiral and deconfinement transitions and on the role of ``monopoles''.
Structure of chiral phase transitions at finite temperature in abelian gauge theories
Energy Technology Data Exchange (ETDEWEB)
Fukazawa, Kenji [Kure National College of Technology, Kure (Japan); Inagaki, Tomohiro [Information Media Center, Hiroshima Univ., Hiroshima (Japan); Mukaigawa, Seiji [Department of Electrical and Electronic Engineering, Faculty of Engineering, Iwate Univ., Iwate (Japan); Muta, Taizo [Department of Physics, Hiroshima Univ., Hiroshima (Japan)
2001-06-01
The mechanism of chiral symmetry breaking is investigated in strong-coupling Abelian gauge theories at finite temperature. The Schwinger-Dyson equation in the Landau gauge is employed in the real time formalism and is solved numerically within the framework of the instantaneous exchange approximation, including the effect of the thermal mass for the photon propagator. It is found that the chiral symmetry is broken below the critical temperature T for sufficiently large coupling {alpha}. The chiral phase transition is found to be of second order, and the phase diagram in the T-{alpha} plane is obtained. It is investigated how the structure of the chiral phase transition is affected by the thermal mass in the photon propagator. (author)
Structure of chiral phase transitions at finite temperature in Abelian gauge theories
Fukazawa, K; Mukaigawa, S; Muta, T; Fukazawa, Kenji; Inagaki, Tomohiro; Mukaigawa, Seiji; Muta, Taizo
1999-01-01
The mechanism of the chiral symmetry breaking is investigated in the strong-coupling Abelian gauge theories at finite temperature. The Schwinger-Dyson equation in Landau gauge is employed in the real time formalism and is solved numerically within the framework of the instantaneous exchange approximation including the effect of the hard thermal loop for the photon propagator. It is found that the chiral symmetry is broken below the critical temperature T for sufficiently large coupling. The chiral phase transition is found to be of the 2nd order and the phase diagram on the $T-\\alpha$ plane is obtained. It is investigated how the structure of the chiral phase transition is affected by the hard thermal loops in the photon propagator.
Exact vector channel sum rules at finite temperature and their applications to lattice QCD
Gubler, Philipp
2016-01-01
We derive three exact sum rules for the spectral function of the electromagnetic current with zero spatial momentum at finite temperature. Two of them are derived in this paper for the first time. We explicitly check that these sum rules are satisfied in the weak coupling regime and examine which sum rule is sensitive to the transport peak in the spectral function at low energy or the continuum at high energy. Possible applications of the three sum rules to lattice computations of the spectral function and transport coefficients are also discussed: We propose an ansatz for the spectral function that can be applied to all three sum rules and fit it to available lattice data of the Euclidean vector correlator above the critical temperature. As a result, we obtain estimates for both the electrical conductivity $\\sigma$ and the second order transport coefficient $\\tau_J$.
Fluctuation-dissipation theorem and quantum tunneling with dissipation at finite temperature
Fujikawa, K; Fujikawa, Kazuo; Terashima, Hiroaki
1998-01-01
A reformulation of the fluctuation-dissipation theorem of Callen and Welton is presented in such a manner that the basic idea of Feynman-Vernon and Caldeira -Leggett of using an infinite number of oscillators to simulate the dissipative medium is realized manifestly without actually introducing oscillators. If one assumes the existence of a well defined dissipative coefficient $R(\\omega)$ which little depends on the temperature in the energy region we are interested in, the spontanous and induced emissions as well as induced absorption of these effective oscillators with correct Bose distribution automatically appears. Combined with a dispersion relation, we reproduce the tunneling formula in the presence of dissipation at finite temperature without referring to an explicit model Lagrangian. The fluctuation-dissipation theorem of Callen-Welton is also generalized to the fermionic dissipation (or fluctuation) which allows a transparent physical interpretation in terms of second quantized fermionic oscillators....
Equivalence between a bosonic theory and a massive non-local Thirring model at Finite Temperature
Manias, M V
1998-01-01
Using the path-integral bosonization procedure at Finite Temperature we study the equivalence between a massive Thirring model with non-local interaction between currents (NLMT) and a non-local extension of the sine-Gordon theory (NLSG). To this end we make a perturbative expansion in the mass parameter of the NLMT model and in the cosine term of the NLSG theory in order to obtain explicit expressions for the corresponding partition functions. We conclude that for certain relationship between NLMT and NLSG potentials both the fermionic and bosonic expansions are equal term by term. This result constitutes a generalization of Coleman's equivalence at T=0, when considering a Thirring model with bilocal potentials in the interaction term at Finite Temperature. The study of this model is relevant in connection with the physics of strongly correlated systems in one spatial dimension. Indeed, in the language of many-body non-relativistic systems, the relativistic mass term can be shown to represent the introduction...
Particle-number projection in the finite-temperature mean-field approximation
Fanto, P; Bertsch, G F
2016-01-01
Calculation of statistical properties of nuclei in a finite-temperature mean-field theory requires projection onto good particle number, since the theory is formulated in the grand canonical ensemble. This projection is usually carried out in a saddle-point approximation. Here we derive formulas for an exact particle-number projection of the finite-temperature mean-field solution. We consider both deformed nuclei, in which the pairing condensate is weak and the Hartree-Fock (HF) approximation is the appropriate mean-field theory, and nuclei with strong pairing condensates, in which the appropriate theory is the Hartree-Fock-Bogoliubov (HFB) approximation, a method that explicitly violates particle-number conservation. For the HFB approximation, we present a general projection formula for a condensate that is time-reversal invariant and a simpler formula for the Bardeen-Cooper-Schrieffer (BCS) limit, which is realized in nuclei with spherical condensates. We apply the method to three heavy nuclei: a typical de...
Lectures On AdS-CFT At Weak 't Hooft Coupling At Finite Temperature
Furuuchi, K
2006-01-01
This is an introductory lecture note aiming at providing an overview of the AdS-CFT correspondence at weak 't Hooft coupling at finite temperature. The first aim of this note is to describe the equivalence of three interesting thermodynamical phenomena in theoretical physics, namely, Hawking-Page transition to black hole geometry, deconfinement transition in gauge theories, and vortex condensation on string worldsheets. The Hawking-Page transition and the deconfinement transition in weakly coupled gauge theories are briefly reviewed. Emphasis is on the study of 't Hooft-Feynman diagrams in the large $N$ gauge theories, which are supposed to describe closed string worldsheets and probe the above equivalence. Nature of the 't Hooft-Feynman diagrams at finite temperature is analyzed, both in the Euclidean signature (the imaginary time formalism) and in the Lorentzian signature (the real time formalism). The second aim of this note is to give an introduction to the real time formalism applied to AdS-CFT.
Finite-temperature effective boundary theory of the quantized thermal Hall effect
Nakai, Ryota; Ryu, Shinsei; Nomura, Kentaro
2016-02-01
A finite-temperature effective free energy of the boundary of a quantized thermal Hall system is derived microscopically from the bulk two-dimensional Dirac fermion coupled with a gravitational field. In two spatial dimensions, the thermal Hall conductivity of fully gapped insulators and superconductors is quantized and given by the bulk Chern number, in analogy to the quantized electric Hall conductivity in quantum Hall systems. From the perspective of effective action functionals, two distinct types of the field theory have been proposed to describe the quantized thermal Hall effect. One of these, known as the gravitational Chern-Simons action, is a kind of topological field theory, and the other is a phenomenological theory relevant to the Strěda formula. In order to solve this problem, we derive microscopically an effective theory that accounts for the quantized thermal Hall effect. In this paper, the two-dimensional Dirac fermion under a static background gravitational field is considered in equilibrium at a finite temperature, from which an effective boundary free energy functional of the gravitational field is derived. This boundary theory is shown to explain the quantized thermal Hall conductivity and thermal Hall current in the bulk by assuming the Lorentz symmetry. The bulk effective theory is consistently determined via the boundary effective theory.
Charmonium spectral functions with the variational method in zero and finite temperature lattice QCD
Ohno, H; Ejiri, S; Kanaya, K; Maezawa, Y; Saito, H; Umeda, T
2011-01-01
We propose a method to evaluate spectral functions (SPFs) on the lattice based on a variational method. On a lattice with a finite spatial extent, SPFs consist of discrete spectra only. Adopting a variational method, we calculate the locations and the heights of SPFs at low-lying discrete spectra. We first test the method in the case of analytically solvable free Wilson quarks at zero and finite temperatures and confirm that the method well reproduces the analytic results for low-lying spectra. We find that we can systematically improve the results by increasing the number of trial states. We then apply the method to calculate the charmonium SPFs for S and P-wave states at zero temperature in quenched QCD and compare the results with those obtained using the conventional maximum entropy method (MEM). The results for the ground state are consistent with the location and the area of the first peak in SPFs from the MEM, while the variational method leads to a mass which is closer to the experimental value for th...
Topological susceptibility in finite temperature (2+1)-flavor QCD using gradient flow
Taniguchi, Yusuke; Suzuki, Hiroshi; Umeda, Takashi
2016-01-01
We compute the topological charge and its susceptibility in finite temperature (2+1)-flavor QCD on the lattice applying a gradient flow method. With the Iwasaki gauge action and non-perturbatively $O(a)$-improved Wilson quarks, we perform simulations on a fine lattice with~$a\\simeq0.07\\,\\mathrm{fm}$ at a heavy $u$, $d$ quark mass with $m_\\pi/m_\\rho\\simeq0.63$ but approximately physical $s$ quark mass of $m_{\\eta_{ss}}/m_\\phi\\simeq0.74$. In a temperature range from~$T\\simeq174\\,\\mathrm{MeV}$ ($N_t=16$) to $697\\,\\mathrm{MeV}$ ($N_t=4$), we study two topics on the topological susceptibility. One is a comparison of gluonic and fermionic definitions of the topological susceptibility. Because the two definitions are related by chiral Ward-Takahashi identities, their equivalence is not trivial for lattice quarks which violate the chiral symmetry explicitly at finite lattice spacings. The gradient flow method enables us to compute them without being bothered by the chiral violation. We find a good agreement between t...
Spectral functions in finite temperature SU(3) gauge theory and applications to transport phenomena
Energy Technology Data Exchange (ETDEWEB)
Haas, Michael
2014-12-10
In this thesis, gluon spectral functions in SU(3) gauge theory are calculated at finite temperature. The temperature range covers the confining regime below T{sub c} to the high temperature regime, where perturbation theory is applicable. The numerical tool is the Maximum Entropy Method (MEM) employing euclidean, non-perturbative, Landau gauge gluon propagators, obtained with the Functional Renormalisation Group and Lattice QCD, as input. The spectral function is related to the propagators by an integral equation. MEM is a complex multidimensional optimisation algorithm to invert such integral equations, corresponding to an analytic continuation of the numerical data. A continuation of a discreet set of data cannot be unambiguous. The occuring ambiguities are resolved by introducing a priori knowledge of the asymptotic shape of the spectral function, in the form of a model function. Thereby, MEM simultaneously optimizes the spectral function to the input propagators and the model, leading to a unique model-dependent solution. Standard-MEM assumes positive definite spectral functions, whereas gluons show a violation of positivity in the spectral function, due to confinement. Therefore, an extended-MEM algorithm is proposed. The main application of this thesis is the calculation of the shear viscosity in units of the entropy density. A Kubo relation connects shear viscosity to the low frequency limit of a certain energy-momentum tensor correlation function. For this correlation function a loop representation of finite order in terms of gluon spectral functions is derived. That allows to calculate (η)/(s) from first principles in SU(3) for the first time for arbitrary temperatures. Further, a mapping of the SU(3) results for (η)/(s) to QCD is proposed.
Meirovitch, H.; Lim, H. A.
1989-04-01
We study by the scanning simulation method trails on a square lattice at finite temperatures. This method constitutes a very efficient tool since it enables one to obtain results at many temperatures from a single sample generated at any given temperature. The tricritical temperature at which the collapse transition occurs is -ɛ/kBTt=1.086+/-0.002. The tricritical exponents of the trail shape and its free energy are, respectively, νt=0.569+/-0.008 and γt=1.133+/-0.024 (95% confidence limits). They are equal within the error bars to the exact values of self-attracting self-avoiding walks (SAW's). However, the crossover exponent φt=0.807+/-0.005 is significantly larger than the exact value 0.423 of SAW's. We also carry out a detailed scaling analysis near Tt and demonstrate that the various properties scale as predicted by theory. At sufficiently low temperatures (Tappears to be ~1.
Energy Technology Data Exchange (ETDEWEB)
Franco-Pérez, Marco, E-mail: qimfranco@hotmail.com, E-mail: jlgm@xanum.uam.mx [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, México D. F. 09340 (Mexico); Department of Chemistry, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Gázquez, José L., E-mail: qimfranco@hotmail.com, E-mail: jlgm@xanum.uam.mx [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, México D. F. 09340 (Mexico); Ayers, Paul W. [Department of Chemistry, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Vela, Alberto [Departamento de Química, Centro de Investigación y de Estudios Avanzados (Cinvestav), Av. Instituto Politécnico Nacional 2508, México D. F. 07360 (Mexico)
2015-10-21
We extend the definition of the electronic chemical potential (μ{sub e}) and chemical hardness (η{sub e}) to finite temperatures by considering a reactive chemical species as a true open system to the exchange of electrons, working exclusively within the framework of the grand canonical ensemble. As in the zero temperature derivation of these descriptors, the response of a chemical reagent to electron-transfer is determined by the response of the (average) electronic energy of the system, and not by intrinsic thermodynamic properties like the chemical potential of the electron-reservoir which is, in general, different from the electronic chemical potential, μ{sub e}. Although the dependence of the electronic energy on electron number qualitatively resembles the piecewise-continuous straight-line profile for low electronic temperatures (up to ca. 5000 K), the introduction of the temperature as a free variable smoothens this profile, so that derivatives (of all orders) of the average electronic energy with respect to the average electron number exist and can be evaluated analytically. Assuming a three-state ensemble, well-known results for the electronic chemical potential at negative (−I), positive (−A), and zero values of the fractional charge (−(I + A)/2) are recovered. Similarly, in the zero temperature limit, the chemical hardness is formally expressed as a Dirac delta function in the particle number and satisfies the well-known reciprocity relation with the global softness.
Finite-temperature time-dependent variation with multiple Davydov states.
Wang, Lu; Fujihashi, Yuta; Chen, Lipeng; Zhao, Yang
2017-03-28
The Dirac-Frenkel time-dependent variational approach with Davydov Ansätze is a sophisticated, yet efficient technique to obtain an accurate solution to many-body Schrödinger equations for energy and charge transfer dynamics in molecular aggregates and light-harvesting complexes. We extend this variational approach to finite temperature dynamics of the spin-boson model by adopting a Monte Carlo importance sampling method. In order to demonstrate the applicability of this approach, we compare calculated real-time quantum dynamics of the spin-boson model with that from numerically exact iterative quasiadiabatic propagator path integral (QUAPI) technique. The comparison shows that our variational approach with the single Davydov Ansätze is in excellent agreement with the QUAPI method at high temperatures, while the two differ at low temperatures. Accuracy in dynamics calculations employing a multitude of Davydov trial states is found to improve substantially over the single Davydov Ansatz, especially at low temperatures. At a moderate computational cost, our variational approach with the multiple Davydov Ansatz is shown to provide accurate spin-boson dynamics over a wide range of temperatures and bath spectral densities.
Nussinov, Zohar; Johnson, Patrick; Graf, Matthias J.; Balatsky, Alexander V.
2013-05-01
Many electronic systems (e.g., the cuprate superconductors and heavy fermions) exhibit striking features in their dynamical response over a prominent range of experimental parameters. While there are some empirical suggestions of particular increasing length scales that accompany such transitions in some cases, this identification is not universal and in numerous instances no large correlation length is evident. To better understand, as a matter of principle, such behavior in quantum systems, we extend a known mapping (earlier studied in stochastic or supersymmetric quantum mechanics) between finite temperature classical Fokker-Planck systems and related quantum systems at zero temperature to include general nonequilibrium dynamics. Unlike Feynman mappings or stochastic quantization methods in field theories (as well as more recent holographic type dualities), the classical systems that we consider and their quantum duals reside in the same number of space-time dimensions. The upshot of our very broad and rigorous result is that a Wick rotation exactly relates (i) the dynamics in general finite temperature classical dissipative systems to (ii) zero temperature dynamics in the corresponding dual many-body quantum systems. Using this correspondence, we illustrate that, even in the absence of imposed disorder, many continuum quantum fluid systems (and possible lattice counterparts) may exhibit a zero-point “quantum dynamical heterogeneity” wherein the dynamics, at a given instant, is spatially nonuniform. While the static length scales accompanying this phenomenon do not seem to exhibit a clear divergence in standard correlation functions, the length scale of the dynamical heterogeneities can increase dramatically. We further study “quantum jamming” and illustrate how a hard-core bosonic system can undergo a zero temperature quantum critical metal-to-insulator-type transition with an extremely large effective dynamical exponent z>4 that is consistent with
Bouchoule, I.; Szigeti, S. S.; Davis, M. J.; Kheruntsyan, K. V.
2016-11-01
We develop a finite-temperature hydrodynamic approach for a harmonically trapped one-dimensional quasicondensate and apply it to describe the phenomenon of frequency doubling in the breathing-mode oscillations of the quasicondensate momentum distribution. The doubling here refers to the oscillation frequency relative to the oscillations of the real-space density distribution, invoked by a sudden confinement quench. By constructing a nonequilibrium phase diagram that characterizes the regime of frequency doubling and its gradual disappearance, we find that this crossover is governed by the quench strength and the initial temperature rather than by the equilibrium-state crossover from the quasicondensate to the ideal Bose gas regime. The hydrodynamic predictions are supported by the results of numerical simulations based on a finite-temperature c -field approach and extend the utility of the hydrodynamic theory for low-dimensional quantum gases to the description of finite-temperature systems and their dynamics in momentum space.
Monte Carlo analysis for finite-temperature magnetism of Nd2Fe14B permanent magnet
Toga, Yuta; Matsumoto, Munehisa; Miyashita, Seiji; Akai, Hisazumi; Doi, Shotaro; Miyake, Takashi; Sakuma, Akimasa
2016-11-01
We investigate the effects of magnetic inhomogeneities and thermal fluctuations on the magnetic properties of a rare-earth intermetallic compound, Nd2Fe14B . The constrained Monte Carlo method is applied to a Nd2Fe14B bulk system to realize the experimentally observed spin reorientation and magnetic anisotropy constants KmA(m =1 ,2 ,4 ) at finite temperatures. Subsequently, it is found that the temperature dependence of K1A deviates from the Callen-Callen law, K1A(T ) ∝M (T) 3 , even above room temperature, TR˜300 K , when the Fe (Nd) anisotropy terms are removed to leave only the Nd (Fe) anisotropy terms. This is because the exchange couplings between Nd moments and Fe spins are much smaller than those between Fe spins. It is also found that the exponent n in the external magnetic field Hext response of barrier height FB=FB0(1-Hext/H0) n is less than 2 in the low-temperature region below TR, whereas n approaches 2 when T >TR , indicating the presence of Stoner-Wohlfarth-type magnetization rotation. This reflects the fact that the magnetic anisotropy is mainly governed by the K1A term in the T >TR region.
Length and temperature dependence of the mechanical properties of finite-size carbyne
Yang, Xueming; Huang, Yanhui; Cao, Bingyang; To, Albert C.
2017-09-01
Carbyne is an ideal one-dimensional conductor and the thinnest interconnection in an ultimate nano-device and it requires an understanding of the mechanical properties that affect device performance and reliability. Here, we report the mechanical properties of finite-size carbyne, obtained by a molecular dynamics simulation study based on the adaptive intermolecular reactive empirical bond order potential. To avoid confusion in assigning the effective cross-sectional area of carbyne, the value of the effective cross-sectional area of carbyne (4.148 Å2) was deduced via experiment and adopted in our study. Ends-constraints effects on the ultimate stress (maximum force) of the carbyne chains are investigated, revealing that the molecular dynamics simulation results agree very well with the experimental results. The ultimate strength, Young's Modulus and maximum strain of carbyne are rather sensitive to the temperature and all decrease with the temperature. Opposite tendencies of the length dependence of the overall ultimate strength and maximum strain of carbyne at room temperature and very low temperature have been found, and analyses show that this originates in the ends effect of carbyne.
Institute of Scientific and Technical Information of China (English)
Monan Wang∗; Lei Sun
2015-01-01
A 3D femoral model was built to obtain the three⁃dimensional temperature distribution of femur and its surrounding tissues and provide references for clinical applications. According to the relationship between gray⁃value and material properties, the model was assigned with various materials to make sure that it is more similar to the real femur in geometry and physical properties. 3D temperature distribution is obtained by using finite element analysis software ANSYS 11�0 on the basis of heat conduction theory, Laplace equation, Pennes bio⁃heat transfer equation, thermo physical parameters of bone tissues, the boundary condition, and initial conditions. Taken the asymmetry of the 3D distribution of temperature into account, it is necessary to adopt the heating method with multiple heat sources. This method can ensure that the temperature fields match well with the tumor tissues and kill the tumor cells efficiently under the condition of protecting the normal tissues from damage. The analysis results supply important guidance for determining the needle position and the needle number and controlling the intensity of heating.
Casimir force on a piston at finite temperature in Randall-Sundrum models
Institute of Scientific and Technical Information of China (English)
CHENG Hong-Bo
2011-01-01
The Casimir effect for a three-parallel-plate system at finite temperature within the framework of five-dimensional Randall-Sundrum models is studied.In the case of the Randall-Sundrum model involving two branes we find that the Casimir force depends on the plate distance and temperature after one outer plate has been moved to a distant place.Further we discover that the sign of the reduced force is negative if the plate and piston are located close together,but the nature of reduced force becomes repulsive when the plate distance is not very small and finally the repulsive force vanishes with extremely large plate separation.A higher temperature causes a greater repulsive Casimir force.Within the framework of a one-brane scenario the reduced Casimir force between the piston and one plate remains attractive no matter how high the temperature is.It is interesting that a stronger thermal effect leads to a greater attractive Casimir force instead of changing the nature of the force.
The effects of strong magnetic fields and rotation on soliton stars at finite temperature
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
We study the effects of strong magnetic fields and uniform rotation on the properties of soliton stars in Lee-Wick model when a temperature dependence is introduced into this model. We first recall the properties of the Lee-Wick model and study the properties of soliton solutions, in particular, the stability condition, in terms of the parameters of the model and in terms of the number of fermions N inside the soliton (for very large N) in the presence of strong magnetic fields and uniform rotation. We also calculate the effects of gravity on the stability properties of the soliton stars in the simple approximation of coupling the Newtonian gravitational field to the energy density inside the soliton, treating this as constant throughout. Following Cottingham and Vinh Mau, we also make an analysis at finite temperature and show the possibility of a phase transition which leads to a model with parameters similar to those considered by Lee and his colleagues but in the presence of magnetic fields and rotation. More specifically, the effects of magnetic fields and rotation on the soliton mass and transition temperature are computed explicitly. We finally study the evolution on these magnetized and rotating soliton stars with the temperature from the early universe to the present time.
Low-energy effective field theory for finite-temperature relativistic superfluids
Nicolis, Alberto
2011-01-01
We derive the low-energy effective action governing the infrared dynamics of relativistic superfluids at finite temperature. We organize our derivation in an effective field theory fashion-purely in terms of infrared degrees of freedom and symmetries. Our degrees of freedom are the superfluid phase \\psi, and the comoving coordinates for the volume elements of the normal fluid component. The presence of two sound modes follows straightforwardly from Taylor-expanding the action at second order in small perturbations. We match our description to more conventional hydrodynamical ones, thus linking the functional form of our Lagrangian to the equation of state, which we assume as an input. We re-derive in our language some standard properties of relativistic superfluids in the high-temperature and low-temperature limits. As an illustration of the efficiency of our methods, we compute the cross-section for a sound wave (of either type) scattering off a superfluid vortex at temperatures right beneath the critical on...
Zhao, Bin
2015-02-01
Temperature-pressure coupled field analysis of liquefied petroleum gas (LPG) tank under jet fire can offer theoretical guidance for preventing the fire accidents of LPG tank, the application of super wavelet finite element on it is studied in depth. First, review of related researches on heat transfer analysis of LPG tank under fire and super wavelet are carried out. Second, basic theory of super wavelet transform is studied. Third, the temperature-pressure coupled model of gas phase and liquid LPG under jet fire is established based on the equation of state, the VOF model and the RNG k-ɛ model. Then the super wavelet finite element formulation is constructed using the super wavelet scale function as interpolating function. Finally, the simulation is carried out, and results show that the super wavelet finite element method has higher computing precision than wavelet finite element method.
Comment on the finite-temperature behavior of lambda(phi-arrow-right/sup 2/)/sup 2/ /sub 4/ theory
Energy Technology Data Exchange (ETDEWEB)
Bardeen, W.A.; Moshe, M.
1986-08-15
We examine the phase structure and stability of self-interacting scalar field theories at finite temperature. In the large-N-italic limit, the renormalized theory exhibits an intrinsic instability which becomes manifest at high temperature contrary to recent claims in the literature.
Caldas, H C G
2001-01-01
Feynman's functional formulation of statistical mechanics is used to study the renormalizability of the well known Linear Chiral Sigma Model in the presence of fermionic fields at finite temperature in an alternative way. It is shown that the renormalization conditions coincide with those of the zero temperature model.
Calculation of Equation of State of QCD at Finite Chemical Potential and Temperature
Institute of Scientific and Technical Information of China (English)
QIAO Qing-Peng; ZONG Hong-Shi; TANG Jian; HOU Feng-Yao; LI Xue-Qian; SUN Wei-Min; L(U) Xiao-Fu
2008-01-01
In this paper, using path integral techniques we derive a model-independent formula for the pressure density (μ, T) (or equivalently the partition function) of Quantum Chromodynamics (QCD), which gives the equation of state (EOS) of QCD at finite chemical potential and temperature. In this formula the pressure density (μ, T) consists of two terms: the first term (μ,T) T=0) is a #-independent (but T-dependent) constant; the second term is totally determined by G[μ, T] (p ωn) (the dressed quark propagator at finite μ and finite T), which contains all the nontrivial μ-dependence. Then, in the framework of the rainbow-ladder approximation of the Dyson-Schwinger (DS) approach and under the approximation of neglecting the μ-dependence of the dressed gluon propagator, we show that G[μ, T] (p, ωn) can be obtained from G[T] (p, ωn) (the dressed quark propagator at μ = 0) by the substitution ωn →ωn + iμ. This result facilitates numerical calculations considerably. By this result, once G[T](p, ωn) is known, one can determine the EOS of QCD under the above approximations (up to the additive term (μ, T)[T=0). Finally, a comparison of the present EOS of QCD and the EOS obtained in the previous literatures in the framework of the rainbow-ladder approximation of the DS approach is given. It is found that the EOS given in the previous literatures does not satisfy the thermodynamic relation p(μ, T) = T.
Finite-temperature perturbation theory for the random directed polymer problem
Energy Technology Data Exchange (ETDEWEB)
Korshunov, S. E., E-mail: dimagesh@phys.ethz.ch [Russian Academy of Sciences, Landau Institute for Theoretical Physics (Russian Federation); Geshkenbein, V. B.; Blatter, G. [Theoretische Physik (Switzerland)
2013-09-15
We study the random directed polymer problem-the short-scale behavior of an elastic string (or polymer) in one transverse dimension subject to a disorder potential and finite temperature fluctuations. We are interested in the polymer short-scale wandering expressed through the displacement correlator Left-Pointing-Angle-Bracket [{delta}u(X)]{sup 2} Right-Pointing-Angle-Bracket , with {delta}u(X) being the difference in the displacements at two points separated by a distance X. While this object can be calculated at short scales using the perturbation theory in higher dimensions d > 2, this approach becomes ill-defined and the problem turns out to be nonperturbative in the lower dimensions and for an infinite-length polymer. In order to make progress, we redefine the task and analyze the wandering of a string of a finite length L. At zero temperature, we find that the displacement fluctuations Left-Pointing-Angle-Bracket [{delta}u(X)]{sup 2} Right-Pointing-Angle-Bracket {proportional_to} LX{sup 2} depend on L and scale with the square of the segment length X, which differs from a straightforward Larkin-type scaling. The result is best understood in terms of a typical squared angle Left-Pointing-Angle-Bracket {alpha}{sup 2} Right-Pointing-Angle-Bracket {proportional_to} L, where {alpha} = {partial_derivative}{sub x}u, from which the displacement scaling for the segment X follows naturally, Left-Pointing-Angle-Bracket [{delta}u(X)]{sup 2} Right-Pointing-Angle-Bracket {proportional_to} Left-Pointing-Angle-Bracket {alpha}{sup 2} Right-Pointing-Angle-Bracket X{sup 2}. At high temperatures, thermal fluctuations smear the disorder potential and the lowest-order results for disorder-induced fluctuations in both the displacement field and the angle vanish in the thermodynamic limit L {yields} {infinity}. The calculation up to the second order allows us to identify the regime of validity of the perturbative approach and provides a finite expression for the displacement
Quark-gluon mixed condensate for the SU(2) light-flavor sector at finite temperature
Nam, Seung-il
2013-01-01
We investigate the quark-gluon mixed condensate m^2_0 = for the SU(2) light-flavor sector at finite temperature (T). Relevant model parameters, such as the average (anti)instanton size, inter-(anti)instanton distance, and constituent-quark mass at zero virtuality, are modified as functions of T, employing the trivial-holonomy caloron solution. By doing that, we observe correct chiral restoration patterns depending on the current-quark mass m. We also perform the two-loop renormalization-group (RG) evolution for the both condensates by increasing the renormalization scale mu=(0.6~2.0) GeV. It turns out that the mixed condensate is insensitive to the RG evolution, whereas the quark condensate become larger considerably by the evolution. Numerically, we obtain -^1/5 = (0.45 ~ 0.46) GeV at T=0 within the present theoretical framework, and the mixed condensate plays the role of the chiral order parameter for finite T. The ratio of the two condensates m^2_0 is almost flat below the chiral transition T (T_0), and ...
Finite-temperature dynamics and thermal intraband magnon scattering in Haldane spin-one chains
Becker, J.; Köhler, T.; Tiegel, A. C.; Manmana, S. R.; Wessel, S.; Honecker, A.
2017-08-01
The antiferromagnetic spin-one chain is considerably one of the most fundamental quantum many-body systems, with symmetry-protected topological order in the ground state. Here, we present results for its dynamical spin structure factor at finite temperatures, based on a combination of exact numerical diagonalization, matrix-product-state calculations, and quantum Monte Carlo simulations. Open finite chains exhibit a subgap band in the thermal spectral functions, indicative of localized edge states. Moreover, we observe the thermal activation of a distinct low-energy continuum contribution to the spin spectral function with an enhanced spectral weight at low momenta and its upper threshold. This emerging thermal spectral feature of the Haldane spin-one chain is shown to result from intraband magnon scattering due to the thermal population of the single-magnon branch, which features a large bandwidth-to-gap ratio. These findings are discussed with respect to possible future studies on spin-one chain compounds based on inelastic neutron scattering.
Formation of Vortex Lattices in Superfluid Bose Gases at Finite Temperatures
Arahata, E.; Nikuni, T.
2016-05-01
We study the dynamics of a rotating trapped Bose-Einstein condensate (BEC) at finite temperatures. Using the Zaremba-Nikuni-Griffin formalism, based on a generalized Gross-Pitaevskii equation for the condensate coupled to a semiclassical kinetic equation for a thermal cloud, we numerically simulate vortex lattice formation in the presence of a time-dependent rotating trap potential. At low rotation frequency, the thermal cloud undergoes rigid body rotation, while the condensate exhibits irrotational flow. Above a certain threshold rotation frequency, vortices penetrate into the condensate and form a vortex lattice. Our simulation result clearly indicates a crucial role for the thermal cloud, which triggers vortex lattice formation in the rotating BEC.
Albright, M
2016-01-01
We develop a flexible quasiparticle theory of transport coefficients of hot hadronic matter at finite baryon density. We begin with a hadronic quasiparticle model which includes a scalar and a vector mean field. Quasiparticle energies and the mean fields depend on temperature and baryon chemical potential. Starting with the quasiparticle dispersion relation, we derive the Boltzmann equation and use the Chapman-Enskog expansion to derive formulas for the shear and bulk viscosities and thermal conductivity. We obtain both relaxation time approximation formulas and more general integral equations. Throughout the work, we explicitly enforce the Landau-Lifshitz conditions of fit and ensure the theory is thermodynamically self-consistent. The derived formulas should be useful for predicting the transport coefficients of the hadronic phase of matter produced in heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC) and at other accelerators.
The scaling region of the lattice O(N) sigma model at finite temperature
Strouthos, C G; Strouthos, Costas G.; Tziligakis, Ioannis N.
2003-01-01
We present results from numerical studies of the finite temperature phase transition of the $(3+1)d$ O(N)-symmetric non-linear sigma model for $N=1,2$ and 3. We study the dependence of the width of the 3d critical region on $N$ and we show that the broken phase scaling region is much wider for N=1 and 2 than for N=1. We compare the widths of the critical region in the low $T$ and high $T$ phases of the O(2) model and we show that the scaling region in the broken phase is much wider than in the symmetric phase. We also report results for the width of the scaling region in the low $T$ phase $(2+1)d$ Ising model and we show that the spatial correlation length has to be approximately twice the lattice temporal extent before the 2d scaling region is reached.
Dispersion relations at finite temperature and density for nucleons and pions
Hurtado, R; Quimbay, C; Hurtado, Rafael; Morales, John; Quimbay, Carlos
2000-01-01
We calculate the nucleonic and pionic dispersion relations at finite temperature T and non-vanishing chemical potentials $(\\mu_f)$ in the context of an effective chiral theory that describes the strong and electromagnetic interactions for nucleons and pions. The dispersion relations are calculated in the broken chiral symmetry phase, where the nucleons are massive and pions are taken as massless. The calculation is performed at lowest order in the energy expansion, working in the framework of the real time formalism of thermal field theory in the Feynman gauge. These one-loop dispersion relations are obtained at leading order with respect to T and $\\mu_f$. We also evaluate the effective masses of the quasi-nucleon and quasi-pion excitations in thermal and chemical conditions as the ones of a neutron star.
Avancini, S S; Chiapparini, M; Peres-Menezes, D
2004-01-01
In this work we study in a formal way the density dependent hadron field theory at finite temperature for nuclear matter. The thermodynamical potential and related quantities, as energy density and pressure are derived in two different ways. We first obtain the thermodynamical potential from the grand partition function, where the Hamiltonian depends on the density operator and is truncated at first order. We then reobtain the thermodynamical potential by calculating explicitly the energy density in a Thomas-Fermi approximation and considering the entropy of a fermi gas. The distribution functions for particles and antiparticles are the output of the minimization of the thermodynamical potential. It is shown that in the mean field theory the thermodynamical consistency is achieved. The connection with effective chiral lagrangians with Brown-Rho scaling is discussed.
Full C P T -even photon sector of the standard model extension at finite temperature
Escobar, Carlos A.; Garcia, Marcos A. G.
2015-07-01
We study the finite temperature behavior of the C P T -even pure-photon sector of the standard model extension, which is defined by the standard Maxwell Lagrangian plus the term (kF)μν α βFμ νFα β. The Hamiltonian analysis is performed, from which the degrees of freedom and constraints of the theory are derived. We have explicitly calculated the partition function for an arbitrary configuration of the (kF)μν α β coefficients, to second order, and we have used it to obtain the thermodynamic properties of the modified photon sector. We find the correction to the frequency dependence in Planck's radiation law, and we identify that the total energy density is adjusted, relative to the standard scenario, by a global proportionality constant containing the Lorentz-violating contributions. Nevertheless, the equation of state is not affected by these modifications.
Finite-Temperature Phase Diagram of the d=3 tJ Model with Quenched Disorder
Berker, A. Nihat; Hinczewski, Michael
2008-03-01
We study a quenched disordered d=3 tJ Hamiltonian with static vacancies as a model of nonmagnetic impurities in high-Tc materials.[1,2] Using a position-space renormalization-group approach, we calculate the evolution of the finite-temperature phase diagram with impurity concentration p, and find several features with close experimental parallels: away from half-filling we see the rapid destruction of a spin-singlet liquid phase (analogous to the superconducting phase in cuprates) which is eliminated for p >=0.05; in the same region for these dilute impurity concentrations we observe an enhancement of antiferromagnetism. The antiferromagnetic phase near half-filling is robust against impurity addition, and disappears only for p >=0.40. [1] M. Hinczewski and A.N. Berker, Eur. Phys. J. B 51, 461 (2006). [2] M. Hinczewski and A.N. Berker, arXiv:cond-mat/0607171v1 [cond-mat.str-el].
Heavy Quark Potential at Finite Temperature in a Dual Gravity Closer to Large N QCD
Patra, Binoy Krishna
2014-01-01
In gauge-gravity duality, heavy quark potential at finite temperature is usually calculated with the pure AdS background, which does not capture the renormalisation group (RG) running in the gauge theory part and the potential also does not contain any confining term in the deconfined phase. Following the developments in \\cite{KS}, a geometry was contructed recently in \\cite{ Mia:NPB2010, Mia:PRD2010}, which captures the RG flow similar to QCD and we employ their geometry to obtain the heavy quark potential by analytically continuing the string configurations into the complex plane. In addition to the attractive terms, the obtained potential has confining terms both at $T=0$ and $T \
Phase transitions in strongly coupled 3d Z(N) lattice gauge theories at finite temperature
Borisenko, O; Cortese, G; Fiore, R; Gravina, M; Papa, A; Surzhikov, I
2012-01-01
We perform an analytical and numerical study of the phase transitions in three-dimensional Z(N) lattice gauge theories at finite temperature for N>4. In the strong coupling limit these models are equivalent to a generalized version of the vector Potts models in two dimensions, where Polyakov loops play the role of Z(N) spins. The effective couplings of these two-dimensional spin models are calculated explicitly. It is argued that the effective spin models have two phase transitions of BKT type. This is confirmed by large-scale Monte Carlo simulations. Using a cluster algorithm we locate the position of the critical points and study the critical behavior across both phase transitions in details. In particular, we determine various critical indices, compute the helicity modulus, the average action and the specific heat. A scaling formula for the critical points with N is proposed.
Phase structure of finite temperature QCD in the heavy quark region
Saito, H; Aoki, S; Hatsuda, T; Kanaya, K; Maezawa, Y; Ohno, H; Umeda, T
2011-01-01
We study the quark mass dependence of the finite temperature QCD phase transition in the heavy quark region using an effective potential defined through the probability distribution function of the average plaquette. Performing a simulation of SU(3) pure gauge theory, we first confirm that the distribution function has two peaks indicating that the phase transition is of first order in the heavy quark limit, while the first order transition turns into a crossover as the quark mass decreases from infinity, where the mass dependence of the distribution function is evaluated by the reweighting method combined with the hopping parameter expansion. We determine the endpoint of the first order transition region for N_f=1, 2, 3 and 2+1 cases. The quark mass dependence of the latent heat is also evaluated in the first order transition region.
Critical behaviour of the compact 3d U(1) gauge theory at finite temperature
Borisenko, Oleg; Gravina, Mario; Papa, Alessandro
2010-01-01
Critical properties of the compact three-dimensional U(1) lattice gauge theory are explored at finite temperatures. The critical point of the deconfinement phase transition, critical indices and the string tension are studied numerically on lattices with temporal extension N_t = 8 and spatial extension ranging from L = 32 to L = 256. The critical indices, which govern the behaviour across the deconfinement phase transition, are generally expected to coincide with the critical indices of the two-dimensional XY model. It is found that the determination of the infinite volume critical point differs from the pseudo-critical coupling at L = 32, found earlier in the literature and implicitly assumed as the onset value of the deconfined phase. The critical index $\
Nonanalyticity of the induced Carroll-Field-Jackiw term at finite temperature
Assuncao, J F; Petrov, A Yu
2016-01-01
In this paper, we discuss the behavior of the Carroll-Field-Jackiw (CFJ) coefficient $k^{\\mu}$ arising due to integration over massive fermions, and the modification suffered by its topological structure in the finite temperature case. Our study is based on the imaginary time formalism and summation over the Matsubara frequencies. We demonstrate that the self-energy of photon is non-analytic for the small $k^{\\mu}$ limit, i.e., the static limit $(k_0=0,\\vec k\\rightarrow 0)$ and the long wavelength limit $(k_0\\rightarrow 0,\\vec k= 0)$ do not commute, while the tensorial structure of the CFJ term holds in both limits.
Holographic geometry of cMERA for quantum quenches and finite temperature
Mollabashi, Ali; Naozaki, Masahiro; Ryu, Shinsei; Takayanagi, Tadashi
2014-03-01
We study the time evolution of cMERA (continuous MERA) under quantum quenches in free field theories. We calculate the corresponding holographic metric using the proposal in arXiv:1208.3469 and confirm that it qualitatively agrees with its gravity dual given by a half of the AdS black hole spacetime, argued by Hartman and Maldacena in arXiv:1303.1080. By doubling the cMERA for the quantum quench, we give an explicit construction of finite temperature cMERA. We also study cMERA in the presence of chemical potential and show that there is an enhancement of metric in the infrared region corresponding to the Fermi energy.
Holographic geometry of cMERA for quantum quenches and finite temperature
Energy Technology Data Exchange (ETDEWEB)
Mollabashi, Ali [School of physics, Institute for Research in Fundamental Sciences (IPM),Tehran (Iran, Islamic Republic of); Yukawa Institute for Theoretical Physics, Kyoto University,Kyoto 606-8502 (Japan); Naozaki, Masahiro [Yukawa Institute for Theoretical Physics, Kyoto University,Kyoto 606-8502 (Japan); Ryu, Shinsei [Department of Physics, University of Illinois at Urbana-Champaign,1110 West Green St, Urbana IL 61801 (United States); Takayanagi, Tadashi [Yukawa Institute for Theoretical Physics, Kyoto University,Kyoto 606-8502 (Japan); Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo,Kashiwa, Chiba 277-8582 (Japan)
2014-03-21
We study the time evolution of cMERA (continuous MERA) under quantum quenches in free field theories. We calculate the corresponding holographic metric using the proposal in http://arxiv.org/abs/1208.3469 and confirm that it qualitatively agrees with its gravity dual given by a half of the AdS black hole spacetime, argued by Hartman and Maldacena in http://arxiv.org/abs/1303.1080. By doubling the cMERA for the quantum quench, we give an explicit construction of finite temperature cMERA. We also study cMERA in the presence of chemical potential and show that there is an enhancement of metric in the infrared region corresponding to the Fermi energy.
Heit, Yonaton N; Beran, Gregory J O
2016-08-01
Molecular crystals expand appreciably upon heating due to both zero-point and thermal vibrational motion, yet this expansion is often neglected in molecular crystal modeling studies. Here, a quasi-harmonic approximation is coupled with fragment-based hybrid many-body interaction calculations to predict thermal expansion and finite-temperature thermochemical properties in crystalline carbon dioxide, ice Ih, acetic acid and imidazole. Fragment-based second-order Möller-Plesset perturbation theory (MP2) and coupled cluster theory with singles, doubles and perturbative triples [CCSD(T)] predict the thermal expansion and the temperature dependence of the enthalpies, entropies and Gibbs free energies of sublimation in good agreement with experiment. The errors introduced by neglecting thermal expansion in the enthalpy and entropy cancel somewhat in the Gibbs free energy. The resulting ∼ 1-2 kJ mol(-1) errors in the free energy near room temperature are comparable to or smaller than the errors expected from the electronic structure treatment, but they may be sufficiently large to affect free-energy rankings among energetically close polymorphs.
Effects of near-zero Dirac eigenmodes on axial U(1) symmetry at finite temperature
Tomiya, Akio; Fukaya, Hidenori; Hashimoto, Shoji; Noaki, Junichi
2014-01-01
We study the axial U(1)A symmetry of Nf = 2 QCD at finite temperature using the Dirac eigenvalue spectrum. The gauge configurations are generated employing the Mobius domain-wall fermion action on 16^3x8 and 32^3x8 lattices. The physical spatial size of these lattices is around 2 fm and 4 fm, respectively, and the simulated temperature is around 200 MeV, which is slightly above the critical temperature of the chiral phase transition. Although the Mobius domain-wall Dirac operator is expected to have a good chiral symmetry and our data actually show small values of the residual mass, we observe significant violation of the Ginsparg-Wilson relation for the low- lying eigenmodes of the Mobius domain-wall Dirac operator. Using the reweighting technique, we compute the overlap-Dirac operator spectrum on the same set of configurations and find a significant difference of the spectrum between the two Dirac operators for the low-lying eigenvalues. The overlap-Dirac spectrum shows a gap from zero, which is insensitive...
Finite element modal formulation for panel flutter at hypersonic speeds and elevated temperatures
Cheng, Guanfeng
A finite element time domain modal formulation for analyzing flutter behavior of aircraft surface panels in hypersonic airflow has been developed and presented for the first time. Von Karman large deflection plate theory is used for description of the structural nonlinearity and third order piston theory is employed to account for the aerodynamic nonlinearity. The thermal loadings of uniformly distributed temperature and temperature gradients across the panel thickness are incorporated into the finite element formulation. By applying the modal reduction technique, the number of governing equations of motion is reduced dramatically so that the computational time of direct numerical integration is dropped significantly. All possible types of panel behavior, including flat, buckled but dynamically stable, limit cycle oscillation (LCO), periodic motion, and chaotic motion can be observed and analyzed. As examples of the applications of the proposed methodology, flutter responses of isotropic, specially orthotropic and laminated composite panels are investigated. Special emphasis is put on the boundary between LCO and chaos, as well as the routes to chaos. A systematic mode filtering procedure that helps mode selection without specific knowledge of the complex mode shapes is presented and illustrated. Influences of aerodynamic parameters, including aerodynamic damping and Mach number, on the panel flutter responses are studied. The importance of nonlinear aerodynamic terms is examined in detail. The supporting conditions and panel aspect ratio on the onset condition of chaos are also investigated as an illustration of optimization among different design options. Several mathematical tools, including the time history, phase plane plot, Poincare map, and bifurcation diagram are employed in the chaos study. The largest Lyapunov exponent is also evaluated to assist in detection of chaos. It is found that at low or moderately high nondimensional dynamic pressures, the
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
The optimal configuration of a heat engine operating between a finite high-temperature source and an infinite low-temperature reservoir is derived by using finite time thermodynamics based on a complex heat transfer law,including Newtonian heat transfer law,linear phenomenological heat transfer law,radiative heat transfer law,Dulong-Petit heat transfer law,generalized convective heat transfer law and generalized radiative heat transfer law,q ∝(△T n). In the engine model the only irreversibility of finite rate heat transfer is considered. The optimal relation between the power output and efficiency of the heat engine is also derived by using an equivalent temperature of the hot reservoir. The obtained results include those obtained in recent literature and can provide some theoretical guidance for the designs of practical engines.
Institute of Scientific and Technical Information of China (English)
LI Jun; CHEN LinGen; SUN FengRui
2009-01-01
The optimal configuration of a heat engine operating between a finite high-temperature source and an infinite low-temperature reservoir is derived by using finite time thermodynamics based on a complex heat transfer law, including Newtonian heat transfer law, linear phenomenological heat transfer law, radiative heat transfer law, Dulong-Petit heat transfer law, generalized convective heat transfer law and generalized radiative heat transfer law, q∝ (△Tn). In the engine model the only irreversibility of finite rate heat transfer is considered. The optimal relation between the power output and efficiency of the heat engine is also derived by using an equivalent temperature of the hot reservoir. The obtained re-sults include those obtained in recent literature and can provide some theoretical guidance for the de-signs of practical engines.
SU(2 color NJL model and EOS of quark-hadron matter at finite temperature and density
Directory of Open Access Journals (Sweden)
Weise Wolfram
2012-02-01
Full Text Available We study the NJL model with the Polyakov loop in the SU(2-color case for the EOS of quark-hadron matter at finite temperature and density. We consider the spontaneous chiral symmetry breaking and the diquark condensation together with the behavior of the Polyakov loop for the phase diagram of quark-hadron matter. We discuss the spectrum of mesons and diquark baryons (boson at finite temperature and density.We derive also the linear sigma model Lagrangian for diquark baryon and mesons.
Importance of finite-temperature exchange correlation for warm dense matter calculations
Karasiev, Valentin V.; Calderín, Lázaro; Trickey, S. B.
2016-06-01
The effects of an explicit temperature dependence in the exchange correlation (XC) free-energy functional upon calculated properties of matter in the warm dense regime are investigated. The comparison is between the Karasiev-Sjostrom-Dufty-Trickey (KSDT) finite-temperature local-density approximation (TLDA) XC functional [Karasiev et al., Phys. Rev. Lett. 112, 076403 (2014), 10.1103/PhysRevLett.112.076403] parametrized from restricted path-integral Monte Carlo data on the homogeneous electron gas (HEG) and the conventional Monte Carlo parametrization ground-state LDA XC [Perdew-Zunger (PZ)] functional evaluated with T -dependent densities. Both Kohn-Sham (KS) and orbital-free density-functional theories are used, depending upon computational resource demands. Compared to the PZ functional, the KSDT functional generally lowers the dc electrical conductivity of low-density Al, yielding improved agreement with experiment. The greatest lowering is about 15% for T =15 kK. Correspondingly, the KS band structure of low-density fcc Al from the KSDT functional exhibits a clear increase in interband separation above the Fermi level compared to the PZ bands. In some density-temperature regimes, the deuterium equations of state obtained from the two XC functionals exhibit pressure differences as large as 4% and a 6% range of differences. However, the hydrogen principal Hugoniot is insensitive to the explicit XC T dependence because of cancellation between the energy and pressure-volume work difference terms in the Rankine-Hugoniot equation. Finally, the temperature at which the HEG becomes unstable is T ≥7200 K for the T -dependent XC, a result that the ground-state XC underestimates by about 1000 K.
Effective theory for heavy quark QCD at finite temperature and density with stochastic quantization
Energy Technology Data Exchange (ETDEWEB)
Neuman, Mathias
2015-07-01
In this thesis we presented the derivation as well as the numerical and analytical treatment of an effective theory for lattice Quantum Chromodynamics (LQCD). We derived the effective theory directly from LQCD, which allows us to systematically introduce further improvements. The derivation was performed by means of an expansion around the limit of infinite quark masses and infinite gauge coupling. Using this theory we were able to derive results in the region of large densities. This region is, due to the sign problem, inaccessible to standard LQCD approaches. Although LQCD simulations at large densities have been performed recently by applying stochastic quantization, those are still limited to lattice with low numbers of timeslices and therefor can not reach the low temperature region. Furthermore, they can not be crosschecked with Monte-Carlo simulations. Since the equivalence between stochastic quantization and Monte-Carlo is unproven for the case of finite density systems, new approaches to access the cold dense region of the QCD phase diagram are desirable. The effective theory presented in this thesis provides such an approach. We introduced continuum QCD in chapter 2. In chapter 3 we presented how LQCD, i.e. QCD in a discretized space-time, can be formulated and used as a tool to explore the non-perturbative regions of the QCD phase diagram. Special emphasis was placed on simulations at finite baryon densities and the numerical problems that arise in this region. These problems are caused by the complexification of the action and are known as the sign problem. We gave a detailed presentation of the derivation of our effective theory in chapter 4. For this we performed expansions around the limit of strong coupling and static quarks, κ=β=0, introducing corrections order by order in the expansion parameters κ and β. Truncating the theory at different orders allowed us to determine the parameter region where the convergence to full LQCD is good. The gauge
Albrecht, Joachim; Brück, Sebastian; Stahl, Claudia; Ruoß, Stephen
2016-11-01
We use quantitative magneto-optical microscopy to investigate the influence of finite temperatures on the critical state of thin YBCO films. In particular, temperature and time dependence of supercurrents in inhomogeneous and anisotropic films are analyzed to extract the role of temperature on the supercurrents themselves and the influence of thermally activated relaxation. We find that inhomogeneities and anisotropies of the current density distribution correspond to a different temperature dependence of local supercurrents. In addition, the thermally activated decay of supercurrents can be used to extract local vortex pinning energies. With these results the modification of vortex pinning introduced by substrate structures is studied. In summary the local investigation of supercurrent densities allows the full description of the vortex pinning landscape with respect to pinning forces and energies in superconducting films with complex properties under the influence of finite temperatures.
Tanaka, Shigenori
2016-12-01
Correlational and thermodynamic properties of homogeneous electron liquids at finite temperatures are theoretically analyzed in terms of dielectric response formalism with the hypernetted-chain (HNC) approximation and its modified version. The static structure factor and the local-field correction to describe the strong Coulomb-coupling effects beyond the random-phase approximation are self-consistently calculated through solution to integral equations in the paramagnetic (spin unpolarized) and ferromagnetic (spin polarized) states. In the ground state with the normalized temperature θ =0 , the present HNC scheme well reproduces the exchange-correlation energies obtained by quantum Monte Carlo (QMC) simulations over the whole fluid phase (the coupling constant rs≤100 ), i.e., within 1% and 2% deviations from putative best QMC values in the paramagnetic and ferromagnetic states, respectively. As compared with earlier studies based on the Singwi-Tosi-Land-Sjölander and modified convolution approximations, some improvements on the correlation energies and the correlation functions including the compressibility sum rule are found in the intermediate to strong coupling regimes. When applied to the electron fluids at intermediate Fermi degeneracies (θ ≈1 ), the static structure factors calculated in the HNC scheme show good agreements with the results obtained by the path integral Monte Carlo (PIMC) simulation, while a small negative region in the radial distribution function is observed near the origin, which may be associated with a slight overestimation for the exchange-correlation hole in the HNC approximation. The interaction energies are calculated for various combinations of density and temperature parameters ranging from strong to weak degeneracy and from weak to strong coupling, and the HNC values are then parametrized as functions of rs and θ. The HNC exchange-correlation free energies obtained through the coupling-constant integration show reasonable
The Master Equation for Two-Level Accelerated Systems at Finite Temperature
Tomazelli, J. L.; Cunha, R. O.
2016-10-01
In this work, we study the behaviour of two weakly coupled quantum systems, described by a separable density operator; one of them is a single oscillator, representing a microscopic system, while the other is a set of oscillators which perform the role of a reservoir in thermal equilibrium. From the Liouville-Von Neumann equation for the reduced density operator, we devise the master equation that governs the evolution of the microscopic system, incorporating the effects of temperature via Thermofield Dynamics formalism by suitably redefining the vacuum of the macroscopic system. As applications, we initially investigate the behaviour of a Fermi oscillator in the presence of a heat bath consisting of a set of Fermi oscillators and that of an atomic two-level system interacting with a scalar radiation field, considered as a reservoir, by constructing the corresponding master equation which governs the time evolution of both sub-systems at finite temperature. Finally, we calculate the energy variation rates for the atom and the field, as well as the atomic population levels, both in the inertial case and at constant proper acceleration, considering the two-level system as a prototype of an Unruh detector, for admissible couplings of the radiation field.
Moduli stabilization in type II Calabi-Yau compactifications at finite temperature
Liu, Lihui
2011-01-01
We consider the type II superstring compactified on Calabi-Yau threefolds at finite temperature. The latter is implemented at the string level by a free action on the Euclidean time circle. We show that all Kahler and complex structure moduli involved in the gauge theories geometrically engineered in the vicinity of singular loci are lifted by the stringy thermal effective potential. The analysis is based on the effective gauged supergravity at low energy, without integrating out the BPS states becoming massless at the singular loci. The universal form of the action in the weak coupling regime at low enough temperature is determined in two cases. Namely the conifold locus, as well as a locus where the internal space develops a genus-g curve of A{N-1} singularities, realizing an SU(N) gauge theory coupled to g hypermultiplets in the adjoint. In general, the favored points of stabilization sit at the intersection of several singular loci. Thus the entire vector multiplet moduli space can be lifted, together wit...
Magnetic hyperfine field at a Cd impurity diluted in RCo{sub 2} at finite temperatures
Energy Technology Data Exchange (ETDEWEB)
Oliveira, A.L. de, E-mail: alexandre.oliveira@ifrj.edu.br [Instituto Federal de Educação, Ciência e Tecnologia do Rio de Janeiro, Campus Nilópolis – RJ (Brazil); Chaves, C.M., E-mail: cmch@cbpf.br [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro (Brazil); Oliveira, N.A. de [Instituto de Física Armando Dias Tavares, Universidade do Estado do Rio de Janeiro, Rio de Janeiro (Brazil); Troper, A. [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro (Brazil)
2015-06-15
The local magnetic moments and the magnetic hyperfine fields at an s–p Cd impurity diluted in inter-metallic Laves phase compounds RCo{sub 2} (R=Gd, Tb) at finite temperatures are calculated. For other rare earth elements (light or heavy) the pure compounds display a magnetic first order transition and are not describable by our formalism. The host has two coupled lattices (R and Co) both having itinerant d electrons but only the rare earth lattice has localized f electrons. They all contribute to the magnetization of the host and also to the local moment and to the magnetic hyperfine field at the impurity. The investigation of magnetic hyperfine field in these materials then provides valuable information on the d-itinerant electrons and also on the localized (4f) magnetic moments. For the d–d electronic interaction we use the Hubbard–Stratonovich identity thus allowing the employment of functional integral in the static saddle point approximation. Our model reproduces quite well the experimental data. - Highlights: • A functional integral method in the static limit, producing site disorder, is used. • The site disorder is treated with the coherent potential approximation (CPA) • A Friedel sum rule gives a self-consistency condition for the impurity energy. • The experimental curve of hyperfine fields×temperature is very well reproduced.
Schunck, N; Carr, H
2013-01-01
Understanding the mechanisms of induced nuclear fission for a broad range of neutron energies could help resolve fundamental science issues, such as the formation of elements in the universe, but could have also a large impact on societal applications in energy production of nuclear waste management. The goal of this paper is to set up the foundations of a microscopic model to study the static aspects of induced fission as a function of the excitation energy of the incident neutron, from thermal to fast neutrons. To account for the high excitation energy of the compound nucleus, we employ a statistical approach based on finite temperature nuclear density functional theory with Skyrme energy densities, which we benchmark on the fission of 239Pu(n,f). We compute the evolution of the least-energy fission pathway across multidimensional potential energy surfaces with up to five collective variables as a function of the nuclear temperature, and predict the evolution of both the inner and outer fission barriers as ...
Sheng, Shiqi; Tu, Z C
2014-01-01
The concepts of weighted reciprocal of temperature and weighted thermal flux are proposed for a heat engine operating between two heat baths and outputting mechanical work. With the aid of these two concepts, the generalized thermodynamic fluxes and forces can be expressed in a consistent way within the framework of irreversible thermodynamics. Then the efficiency at maximum power output for a heat engine, one of key topics in finite-time thermodynamics, is investigated on the basis of a generic model under the tight-coupling condition. The corresponding results have the same forms as those of low-dissipation heat engines [ M. Esposito, R. Kawai, K. Lindenberg and C. Van den Broeck Phys. Rev. Lett. 105 150603 (2010)]. The mappings from two kinds of typical heat engines, such as the low-dissipation heat engine and the Feynman ratchet, into the present generic model are constructed. The universal efficiency at maximum power output up to the quadratic order is found to be valid for a heat engine coupled symmetrically and tightly with two baths. The concepts of weighted reciprocal of temperature and weighted thermal flux are also transplanted to the optimization of refrigerators.
Directory of Open Access Journals (Sweden)
Nikolić Radovan H.
2014-01-01
Full Text Available This paper is the result of research and operation modeling of the new systems for cooling of cutting tools based on thermoelectric module. A copper inlay with thermoelectric module on the back side was added to a standard turning tool for metal processing. For modeling and simulating the operation of thermoelectric module, finite element method was used as a method for successful solving the problems of inhomogeneous transient temperature field on the cutting tip of lathe knives. Developed mathematical model is implemented in the software package PAK-T through which numerical results are obtained. Experimental research was done in different conditions of thermoelectric module operation. Cooling of the hot module side was done by a heat exchanger based on fluid using automatic temperature regulator. After the calculation is done, numerical results are in good agreement with experimental. It can be concluded that developed mathematical model can be used successfully for modeling of cooling of cutting tools. [Projekat Ministarstva nauke Republike Srbije, br. TR32036
Temperature Distribution of Three-Dimensional Photovoltaic Panel by Using Finite Element Simulation
Directory of Open Access Journals (Sweden)
Leow Wai Zhe
2016-10-01
Full Text Available The low electricity performance of a photovoltaic (PV panel has been concerned in the PV application system. The effect of environmental and operating condition was affected the performance of the PV panel. In this research work, the main objective is to perform a three-dimensional geometry model of monocrystalline silicon PV panel with and without cooling system by using finite element method. In the case of a cooling system, the effect of the Direct Current (DC fan flow rate on the temperature distribution of PV panel was investigated. The electrical behaviour of this PV panel is obtained based on the average temperature of the PV panel obtained and average solar irradiance from site location. According to the experimental results, PV panel with cooling system can be significant to provide better performance than the PV panel without cooling system in the same environmental condition. For the effect of flow rate of DC fan in the PV panel with cooling system, the performance of this PV panel has been improved as increasing in flow rate of DC fan.
The Gross-Neveu model at finite temperature at next to leading order in the 1/N expansion
Blaizot, J P; Wschebor, N
2003-01-01
We present new results on the Gross-Neveu model at finite temperature and at next-to-leading order in the 1/N expansion. In particular, a new expression is obtained for the effective potential which is explicitly invariant under renormalization group transformations. The model is used as a playground to investigate various features of field theory at finite temperature. For example we verify that, as expected from general arguments, the cancellation of ultraviolet divergences takes place at finite temperature without the need for introducing counterterms beyond those of zero-temperature. As well known, the discrete chiral symmetry of the 1+1 dimensional model is spontaneously broken at zero temperature and restored, in leading order, at some temperature T_c; we find that the 1/N approximation breaks down for temperatures below T_c: As the temperature increases, the fluctuations become eventually too large to be treated as corrections, and a Landau pole invalidates the calculation of the effective potential in...
Effective theory for heavy quark QCD at finite temperature and density with stochastic quantization
Energy Technology Data Exchange (ETDEWEB)
Neuman, Mathias
2015-07-01
In this thesis we presented the derivation as well as the numerical and analytical treatment of an effective theory for lattice Quantum Chromodynamics (LQCD). We derived the effective theory directly from LQCD, which allows us to systematically introduce further improvements. The derivation was performed by means of an expansion around the limit of infinite quark masses and infinite gauge coupling. Using this theory we were able to derive results in the region of large densities. This region is, due to the sign problem, inaccessible to standard LQCD approaches. Although LQCD simulations at large densities have been performed recently by applying stochastic quantization, those are still limited to lattice with low numbers of timeslices and therefor can not reach the low temperature region. Furthermore, they can not be crosschecked with Monte-Carlo simulations. Since the equivalence between stochastic quantization and Monte-Carlo is unproven for the case of finite density systems, new approaches to access the cold dense region of the QCD phase diagram are desirable. The effective theory presented in this thesis provides such an approach. We introduced continuum QCD in chapter 2. In chapter 3 we presented how LQCD, i.e. QCD in a discretized space-time, can be formulated and used as a tool to explore the non-perturbative regions of the QCD phase diagram. Special emphasis was placed on simulations at finite baryon densities and the numerical problems that arise in this region. These problems are caused by the complexification of the action and are known as the sign problem. We gave a detailed presentation of the derivation of our effective theory in chapter 4. For this we performed expansions around the limit of strong coupling and static quarks, κ=β=0, introducing corrections order by order in the expansion parameters κ and β. Truncating the theory at different orders allowed us to determine the parameter region where the convergence to full LQCD is good. The gauge
Predictive Finite Rate Model for Oxygen-Carbon Interactions at High Temperature
Poovathingal, Savio
reaction products because the reaction probabilities were in the diffusion dominant regime. The molecular beam data at different surface temperatures was then used to build a finite rate model. Each reaction mechanism and all rate parameters of the new model were determined individually based on the molecular beam data. Despite the experiments being performed at near vacuum conditions, the finite rate model developed using the data could be used at pressures and temperatures relevant to hypersonic conditions. The new model was implemented in a computational fluid dynamics (CFD) solver and flow over a hypersonic vehicle was simulated. The new model predicted similar overall mass loss rates compared to existing models, however, the individual species production rates were completely different. The most notable difference was that the new model (based on molecular beam data) predicts CO as the oxidation reaction product with virtually no CO2 production, whereas existing models predict the exact opposite trend. CO being the dominant oxidation product is consistent with recent high enthalpy wind tunnel experiments. The discovery that measurements taken in molecular beam facilities are able to determine individual reaction mechanisms, including dependence on surface coverage, opens up an entirely new way of constructing ablation models.
Directory of Open Access Journals (Sweden)
Shivakumara I S,
2011-05-01
Full Text Available The linear stability analysis of Marangoni convection in a fluid layer with a boundary slab of finite conductivity is considered. The effects of various non uniform temperature gradients are investigated. The lower boundary is a considered to be a thin slab of finite conductivity instead of a regular rigid surface. At the contact surface between the thin slab and the fluid layer the thermalboundary conditions are used and the upper surface is considered to be free and insulating to temperature perturbation and also surface tension effects are allowed. The resulting eigen value problem is solved exactly. The critical values of the Marangoni numbers for the onset of Marangoni convection are calculated for different temperature profile and the latter is found to be critically dependent on the depth ratio and conductivity ratio. The effects of the thermal conductivity and the thickness of the solid plate on the onset of convective instability with different temperature profile arestudied in detail.
Chen, Yung-Chuan; Tu, Yuan-Kun; Zhuang, Jun-Yan; Tsai, Yi-Jung; Yen, Cheng-Yo; Hsiao, Chih-Kun
2017-03-28
A three-dimensional dynamic elastoplastic finite element model was constructed and experimentally validated and was used to investigate the parameters which influence bone temperature during drilling, including the drill speed, feeding force, drill bit diameter, and bone density. Results showed the proposed three-dimensional dynamic elastoplastic finite element model can effectively simulate the temperature elevation during bone drilling. The bone temperature rise decreased with an increase in feeding force and drill speed, however, increased with the diameter of drill bit or bone density. The temperature distribution is significantly affected by the drilling duration; a lower drilling speed reduced the exposure duration, decreases the region of the thermally affected zone. The constructed model could be applied for analyzing the influence parameters during bone drilling to reduce the risk of thermal necrosis. It may provide important information for the design of drill bits and surgical drilling powers.
Figueroa, Daniel G.
We discuss the non-conservation of fermion number (or chirality breaking, depending on the fermionic charge assignment) in Abelian gauge theories at finite temperature. We study different mechanisms of fermionic charge disappearance in the high temperature plasma, with the use of both analytical estimates and real-time classical numerical simulations. We investigate the random walk of the Chern-Simons number $N_{\\rm CS} \\propto \\int d^4x F_{\\mu\
Institute of Scientific and Technical Information of China (English)
Huaisheng WANG; Mingxiang WANG; Zhenyu YANG
2009-01-01
The temperature distribution of typical n-type polycrystalline silicon thin film transistors under selfheating (SH) stress is studied by finite element analysis.From both steady-state and transient thermal simulation,the influence of device power density, substrate material,and channel width on device temperature distribution is analyzed. This study is helpful to understand the mechanism of SH degradation, and to effectively alleviate the SH effect in device operation.
Finite-Temperature Atomic Structure of 180^o Ferroelectric Domain Walls in PbTiO3
Angoshtari, Arzhang; Yavari, Arash
2010-01-01
In this letter we obtain the finite-temperature structure of 180^o domain walls in PbTiO3 using a quasi-harmonic lattice dynamics approach. We obtain the temperature dependence of the atomic structure of domain walls from 0K up to room temperature. We also show that both Pb-centered and Ti-centered 180^o domain walls are thicker at room temperature; domain wall thickness at T=300K is about three times larger than that of T=0K. Our calculations show that Ti-centered domain walls have a lower f...
Finite temperature effective action, AdS_5 black holes, and 1/N expansion
Alvarez-Gaumé, Luís; Liu, H; Wadia, S; Alvarez-Gaume, Luis; Gomez, Cesar; Liu, Hong; Wadia, Spenta
2005-01-01
We propose a phenomenological matrix model to study string theory in AdS_5 \\times S_5 in the canonical ensemble. The model reproduces all the known qualitative features of the theory. In particular, it gives a simple effective potential description of Euclidean black hole nucleation and the tunnelling between thermal AdS and the big black hole. It also has some interesting predictions. We find that there exists a critical temperature at which the Euclidean small black hole undergoes a Gross-Witten phase transition. We identify the phase transition with the Horowitz-Polchinski point where the black hole horizon size becomes comparable to the string scale. The appearance of the Hagedorn divergence of thermal AdS is due to the merger of saddle points corresponding to the Euclidean small black hole and thermal AdS. The merger can be described in terms of a cusp (A_3) catastrophe and divergences at the perturbative string level are smoothed out at finite string coupling using standard techniques of catastrophe the...
Magnetic field effects on the static quark potential at zero and finite temperature
Bonati, Claudio; D'Elia, Massimo; Mariti, Marco; Mesiti, Michele; Negro, Francesco; Rucci, Andrea; Sanfilippo, Francesco
2016-11-01
We investigate the static Q Q ¯ potential at zero and finite temperature in the presence of a constant and uniform external magnetic field B →, for several values of the lattice spacing and for different orientations with respect to B →. As a byproduct, we provide continuum limit extrapolated results for the string tension, the Coulomb coupling and the Sommer parameter at T =0 and B =0 . We confirm the presence in the continuum of a B -induced anisotropy, regarding essentially the string tension, for which it is of the order of 15% at |e |B ˜1 GeV2 and would suggest, if extrapolated to larger fields, a vanishing string tension along the magnetic field for |e |B ≳4 GeV2. The angular dependence for |e |B ≲1 GeV2 can be nicely parametrized by the first allowed term in an angular Fourier expansion, corresponding to a quadrupole deformation. Finally, for T ≠0 , the main effect of the magnetic field is a general suppression of the string tension, leading to a early loss of the confining properties: this happens even before the appearance of inverse magnetic catalysis in the chiral condensate, supporting the idea that the influence of the magnetic field on the confining properties is the leading effect originating the decrease of Tc as a function of B .
Parity-odd and CPT-even electrodynamics of the standard model extension at finite temperature
Casana, Rodolfo; Ferreira, Manoel M., Jr.; Silva, Madson R. O.
2010-05-01
This work examines the finite temperature properties of the CPT-even and parity-odd electrodynamics of the standard model extension. The starting point is the partition function computed for an arbitrary and sufficiently small tensor (kF)ανρφ [see R. Casana, M. M. Ferreira, Jr., J. S. Rodrigues, and M. R. O. Silva, Phys. Rev. DPRVDAQ1550-7998 80, 085026 (2009).10.1103/PhysRevD.80.085026]. After specializing the Lorentz-violating tensor (kF)ανρφ for the leading-order-nonbirefringent and parity-odd coefficients, the partition function is explicitly carried out, showing that it is a power of the Maxwell partition function. Also, it is observed that the Lorentz invariance violation coefficients induce an anisotropy in the black-body angular energy density distribution. Planck’s radiation law retains its usual frequency dependence and the Stefan-Boltzmann law keeps the same form, except for a global proportionality constant.
Magnetic field effects on the static quark potential at zero and finite temperature
Bonati, Claudio; Mariti, Marco; Mesiti, Michele; Negro, Francesco; Rucci, Andrea; Sanfilippo, Francesco
2016-01-01
We investigate the static $Q\\bar{Q}$ potential at zero and finite temperature in the presence of a constant and uniform external magnetic field $\\vec{B}$, for several values of the lattice spacing and for different orientations with respect to $\\vec{B}$. As a byproduct, we provide continuum limit extrapolated results for the string tension, the Coulomb coupling and the Sommer parameter at $T = 0$ and $B = 0$. We confirm the presence in the continuum of a $B$-induced anisotropy, regarding essentially the string tension, for which it is of the order of 15\\% at $|e| B \\sim 1~{\\rm GeV}^2$ and would suggest, if extrapolated to larger fields, a vanishing string tension along the magnetic field for $|e| B \\gtrsim 4$ GeV$^2$. The angular dependence for $|e| B \\lesssim 1$ GeV$^2$ can be nicely parametrized by the first allowed term in an angular Fourier expansion, corresponding to a quadrupole deformation. Finally, for $T \
Institute of Scientific and Technical Information of China (English)
Hamidreza Emamipour; M.R. Abolhassani
2011-01-01
In this study, we investigate the tunneling conductance at a finite temperature in a normal metal/ferromagnetic superconductor nano-junction where the ferromagnetic superconductor (FS) is in three different cooper pairing states: spin singlet s-wave pairing (SWP), spin triplet opposite spin pairing (OSP), and spin triplet equal spin pairing (ESP) while including Fermi wave mismatch (FWM) and effective mass mismatch (EMM) in two sides of the nano-junction. We find that the conductance shows clearly different behaviors all depending on the symmetries of cooper pairing in a manner that the conductance spectra shows a gap-like structure, two interior dips structure and zero bias peak for SWP, OSP, and ESP, respectively. Also, the effective FS gap (Δeff) is a linear and decreasing function of exchange field. The slope of (Δeff) versus exchange field for OSP is twice the SWP. Thus, we can determine the spin polarization of N/FS nano-junction based on the dependence of (Δeff) to exchange field.
Phase transitions at finite temperature and dimensional reduction for fermions and bosons
Kocic, Aleksandar
1995-01-01
In a recent Letter we discussed the fact that large-N expansions and computer simulations indicate that the universality class of the finite temperature chiral symmetry restoration transition in the 3D Gross-Neveu model is mean field theory. This was seen to be a counterexample to the standard 'sigma model' scenario which predicts the 2D Ising model universality class. In this article we present more evidence, both theoretical and numerical, that this result is correct. We develop a physical picture for our results and discuss the width of the scaling region (Ginzburg criterion), 1/N corrections, and differences between the dynamics of BCS superconductors and Gross-Neveu models. Lattices as large as 12 \\times 72^2 are simulated for both the N=12 and N=4 cases and the numerical evidence for mean field scaling is quite compelling. We point out that the amplitude ratio for the model's susceptibility is a particulartly good observable for distinguishing between the dimensional reduction and the mean field sceneri...
Relevance of the axial anomaly at the finite-temperature chiral transition in QCD
Pelissetto, Andrea
2013-01-01
We address the issue of the relevance of the suppression of the U(1)_A symmetry breaking, induced by the axial anomaly, at the finite-temperature chiral QCD transition with two light flavors. If the U(1)_A breaking is substantially suppressed at the transition, the effective symmetry breaking that determines the universality class is U(2)_L X U(2)_R -> U(2)_V. We perform a high-order perturbative study of the renormalization-group (RG) flow of the corresponding three-dimensional (3D) multiparameter Phi theory that has the same order parameter and symmetry-breaking pattern. We confirm the existence of a stable fixed point (FP), and determine its attraction domain in the space of the bare quartic parameters. Therefore, the chiral QCD transition might be continuous also if the U(1)_A symmetry is effectively restored at Tc. However, the corresponding universality class differs from the O(4) vector universality class which would describe a continuous transition in the presence of a substantial U(1)_A symmetry brea...
Coherent tunneling of atoms from Bose-condensed gases at finite temperatures
Luxat, David L.; Griffin, Allan
2002-04-01
Tunneling of atoms between two trapped Bose-condensed gases at finite temperatures is explored using a many-body linear-response tunneling formalism similar to that used in superconductors. To lowest order, the tunneling currents can be expressed quite generally in terms of the single-particle Green's functions of isolated Bose gases. A coherent first-order tunneling Josephson current between two atomic Bose-Einstein condensates is found, in addition to coherent and dissipative contributions from second-order condensate-noncondensate and noncondensate-noncondensate tunneling. Our work is a generalization of Meier and Zwerger, who recently treated tunneling between uniform atomic Bose gases. We apply our formalism to the analysis of an out-coupling experiment induced by light wave fields, using a simple Bogoliubov-Popov quasiparticle approximation for the trapped Bose gas. For tunneling into the vacuum, we recover the results of Japha, Choi, Burnett, and Band, who recently pointed out the usefulness of studying the spectrum of out-coupled atoms. In particular, we show that the small tunneling current of noncondensate atoms from a trapped Bose gas has a broad spectrum of energies, with a characteristic structure associated with the Bogoliubov quasiparticle u2 and v2 amplitudes.
Nishimura, Kohji; Nishimori, Hidetoshi; Ochoa, Andrew J.; Katzgraber, Helmut G.
2016-09-01
We study the problem to infer the ground state of a spin-glass Hamiltonian using data from another Hamiltonian with interactions disturbed by noise from the original Hamiltonian, motivated by the ground-state inference in quantum annealing on a noisy device. It is shown that the average Hamming distance between the inferred spin configuration and the true ground state is minimized when the temperature of the noisy system is kept at a finite value, and not at zero temperature. We present a spin-glass generalization of a well-established result that the ground state of a purely ferromagnetic Hamiltonian is best inferred at a finite temperature in the sense of smallest Hamming distance when the original ferromagnetic interactions are disturbed by noise. We use the numerical transfer-matrix method to establish the existence of an optimal finite temperature in one- and two-dimensional systems. Our numerical results are supported by mean-field calculations, which give an explicit expression of the optimal temperature to infer the spin-glass ground state as a function of variances of the distributions of the original interactions and the noise. The mean-field prediction is in qualitative agreement with numerical data. Implications on postprocessing of quantum annealing on a noisy device are discussed.
Effective field theories of QCD for heavy quarkonia at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Ghiglieri, Jacopo
2011-07-27
Quarkonia, i.e. heavy quark-antiquark bound states, represent one of the most important probes in the experimental investigation, through heavy-ion collisions, of the high-temperature region of the phase diagram of QCD, where the onset of a deconfined medium, the quark-gluon plasma, is expected. Such bound states were hypothesized to dissociate in this plasma due to the screening of the colour charges and experimental data from SPS, RHIC and very recently also LHC indeed show a suppression pattern. In this thesis we extend the well-established and successful zero temperature framework of Non-Relativistic (NR) Effective Field Theories (EFTs) (NRQCD, pNRQCD) for the study of heavy quarkonia (production, spectroscopy, decays,..) to finite temperatures. This is achieved by integrating out in sequence the scales that characterize a NR bound state and those that are typical of a thermal medium, in the possible hierarchies that are relevant for quarkonia in the quark-gluon plasma. Within this framework we show how the potential that governs the evolution of the quark-antiquark pair is derived from QCD in a modern and rigorous way, thereby bridging the gap between phenomenological potential models and QCD. We show how the EFTs can be systematically improved and how effects that cannot be encoded in a potential arise naturally in the EFT, giving rise to new mechanisms of dissociation. We use this EFT framework to compute the spectrum and width of quarkonia in a particular setting that is relevant for the phenomenology of the ground states of bottomonium at the LHC. We also analyze within this framework the correlator of Polyakov loops, which is related to the thermodynamical free energy of heavy quark-antiquark pairs in the medium. As such, lattice computations thereof were frequently used as input for potential models. With our approach we are able to clarify the relation between these free energies and the real-time potential describing the dynamics of quarkonia, finding
Khanday, M A; Hussain, Fida
2015-02-01
During cold exposure, peripheral tissues undergo vasoconstriction to minimize heat loss to preserve the maintenance of a normal core temperature. However, vasoconstricted tissues exposed to cold temperatures are susceptible to freezing and frostbite-related tissue damage. Therefore, it is imperative to establish a mathematical model for the estimation of tissue necrosis due to cold stress. To this end, an explicit formula of finite difference method has been used to obtain the solution of Pennes' bio-heat equation with appropriate boundary conditions to estimate the temperature profiles of dermal and subdermal layers when exposed to severe cold temperatures. The discrete values of nodal temperature were calculated at the interfaces of skin and subcutaneous tissues with respect to the atmospheric temperatures of 25 °C, 20 °C, 15 °C, 5 °C, -5 °C and -10 °C. The results obtained were used to identify the scenarios under which various degrees of frostbite occur on the surface of skin as well as the dermal and subdermal areas. The explicit formula of finite difference method proposed in this model provides more accurate predictions as compared to other numerical methods. This model of predicting tissue temperatures provides researchers with a more accurate prediction of peripheral tissue temperature and, hence, the susceptibility to frostbite during severe cold exposure.
Turner, Travis L.; Zhong, Z. W.; Mei, Chuh
1994-01-01
A feasibility study on the use of shape memory alloys (SMA) for suppression of the random response of composite panels due to acoustic loads at elevated temperatures is presented. The constitutive relations for a composite lamina with embedded SMA fibers are developed. The finite element governing equations and the solution procedures for a composite plate subjected to combined acoustic and thermal loads are presented. Solutions include: 1) Critical buckling temperature; 2) Flat panel random response; 3) Thermal postbuckling deflection; 4) Random response of a thermally buckled panel. The preliminary results demonstrate that the SMA fibers can completely eliminate the thermal postbuckling deflection and significantly reduce the random response at elevated temperatures.
Finite temperature CPT-even electrodynamics of the standard model extension
Energy Technology Data Exchange (ETDEWEB)
Casana, Rodolfo; Ferreira Junior, Manoel M.; Rodrigues, Josberg S.; Silva, Madson R.O. [Universidade Federal do Maranhao (UFMA), Sao Luiz, MA (Brazil)
2009-07-01
Full text. In this work, we examine the finite temperature properties of the non-birefringent coefficients of the CPT- even and Lorentz-invariance-violating (LIV) electrodynamics of the standard model extension, represented by the term W{sub {mu}}{sub {nu}}{sub {alpha}}{sub {beta}}F{sub {mu}}{sub {nu}}F{sub {alpha}}{sub {beta}}. We begin analyzing the Hamiltonian structure following the Diracs procedure for constrained systems. The partition function for this model in the functional integral formalism is properly written and explicitly carried out both for the parity-odd and parity-even sectors of the tensor WW{sub {mu}}{sub {nu}}{sub {alpha}}{sub {beta}}i. The modified partition function is a power of the Maxwell partition function. It is observed that the LIV coefficients induce an anisotropy in the black body energy density angular distribution in two cases of interest. The Planck radiation law, however, retains its frequency dependence and the Stefan-Boltzmann law keeps the usual form, except for a change in the Stefan-Boltzmann constant by a factor containing the LIV contributions. Since the LIV coefficients are constrained by very stringent upper bounds, the lower order non-null LIV contribution for the Maxwell thermodynamics would give a good information about the thermodynamical properties of the non birefringent sector the model. It is clearly observed for the parity-odd sector, where the lower correction is quadratic in the LIV parameter {kappa}. On the other hand, in the parity-even sector, the isotropic contribution gives a linear correction in n, whereas the anisotropic contribution coming from the matrix {kappa}{sub e-} only is manifest at fourth order. Hence, the pure anisotropic contribution is irrelevant when compared with the isotropic one. (author)
Nuclear Many-Body Problem at Finite Temperature A TFD Approach
Kosov, D S; Wambach, J
1997-01-01
Based on the formalism of thermo-field dynamics a new approach for studying collective excitations in hot finite Fermi systems is presented. Two approximations going beyond the thermal RPA namely renormalized thermal RPA and thermal second RPA are formulated.
Jin, Xiao-Yong; Kuramashi, Yoshinobu; Nakamura, Yoshifumi; Takeda, Shinji; Ukawa, Akira
2017-08-01
We study the finite temperature phase structure for three-flavor QCD with a focus on locating the critical point, which separates the crossover and the first order phase transition region in the chiral regime of the Columbia plot. In this study, we employ the Iwasaki gauge action and the nonperturvatively O (a ) improved Wilson-Clover fermion action. We discuss the finite size scaling analysis, including the mixing of magnetizationlike and energylike observables. We carry out the continuum extrapolation of the critical point using newly generated data at the Nt=8 , 10 and estimate the upper bound of the critical pseudoscalar meson mass mPS ,E≲170 MeV and the critical temperature TE=134 (3 ) MeV . Our estimate of the upper bound is derived from the existence of the critical point as an edge of the first order phase transition while that of the staggered-type fermions with smearing is based on its absence.
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He, Pei-Song, E-mail: hepeisong@th.btbu.edu.cn; Zhao, Jia; Geng, Ai-Cong; Xu, Deng-Hui; Hu, Rong
2013-11-01
We prove that in a two-dimensional homogeneous boson system with Rashba spin–orbit coupling, Bose–Einstein condensate with plane-wave order is unstable at finite temperature. The calculations are based on a nonlinear sigma model scheme. The density wave contributions to the thermal deletions are divergent in the infrared limit. The behavior of the divergence is different from that without spin–orbit coupling.
Directory of Open Access Journals (Sweden)
Huawei Zhou
2016-10-01
Full Text Available Achieving an effective combination of various temperature control measures is critical for temperature control and crack prevention of concrete dams. This paper presents a procedure for optimizing the temperature control scheme of roller compacted concrete (RCC dams that couples the finite element method (FEM with a sensitivity analysis method. In this study, seven temperature control schemes are defined according to variations in three temperature control measures: concrete placement temperature, water-pipe cooling time, and thermal insulation layer thickness. FEM is employed to simulate the equivalent temperature field and temperature stress field obtained under each of the seven designed temperature control schemes for a typical overflow dam monolith based on the actual characteristics of a RCC dam located in southwestern China. A sensitivity analysis is subsequently conducted to investigate the degree of influence each of the three temperature control measures has on the temperature field and temperature tensile stress field of the dam. Results show that the placement temperature has a substantial influence on the maximum temperature and tensile stress of the dam, and that the placement temperature cannot exceed 15 °C. The water-pipe cooling time and thermal insulation layer thickness have little influence on the maximum temperature, but both demonstrate a substantial influence on the maximum tensile stress of the dam. The thermal insulation thickness is significant for reducing the probability of cracking as a result of high thermal stress, and the maximum tensile stress can be controlled under the specification limit with a thermal insulation layer thickness of 10 cm. Finally, an optimized temperature control scheme for crack prevention is obtained based on the analysis results.
Strečka, Jozef; Verkholyak, Taras
2016-10-01
Magnetic properties of the ferrimagnetic mixed spin-(1/2,S) Heisenberg chains are examined using quantum Monte Carlo simulations for two different quantum spin numbers S=1 and 3/2. The calculated magnetization curves at finite temperatures are confronted with zero-temperature magnetization data obtained within the density matrix renormalization group method, which imply an existence of two quantum critical points determining a breakdown of the gapped Lieb-Mattis ferrimagnetic phase and Tomonaga-Luttinger spin-liquid phase, respectively. While a square root behavior of the magnetization accompanying each quantum critical point is gradually smoothed upon rising temperature, the susceptibility and isothermal entropy change data at low temperatures provide a stronger evidence of the zero-temperature quantum critical points through marked local maxima and minima, respectively.
Huang, Chen
2016-03-01
A key element in the density functional embedding theory (DFET) is the embedding potential. We discuss two major issues related to the embedding potential: (1) its non-uniqueness and (2) the numerical difficulty for solving for it, especially for the spin-polarized systems. To resolve the first issue, we extend DFET to finite temperature: all quantities, such as the subsystem densities and the total system's density, are calculated at a finite temperature. This is a physical extension since materials work at finite temperatures. We show that the embedding potential is strictly unique at T > 0. To resolve the second issue, we introduce an efficient iterative embedding potential solver. We discuss how to relax the magnetic moments in subsystems and how to equilibrate the chemical potentials across subsystems. The solver is robust and efficient for several non-trivial examples, in all of which good quality spin-polarized embedding potentials were obtained. We also demonstrate the solver on an extended periodic system: iron body-centered cubic (110) surface, which is related to the modeling of the heterogeneous catalysis involving iron, such as the Fischer-Tropsch and the Haber processes. This work would make it efficient and accurate to perform embedding simulations of some challenging material problems, such as the heterogeneous catalysis and the defects of complicated spin configurations in electronic materials.
Morales, J; Fonseca, F; Morales, John; Quimbay, Carlos; Fonseca, Frank
1999-01-01
We calculate the fermionic dispersion relations in the minimal standard model at finite temperature in presence of non-vanishing chemical potentials due to the CP-asymmetric fermionic background. The dispersion relations are calculated for a vacuum expectation value of the Higgs field equal to zero (unbroken electroweak symmetry). The calculation is performed in the real time formalism of the thermal field theory at one-loop order in a general $\\xi$ gauge. The fermionic self-energy is calculated at leading order in temperature and chemical potential and this fact permits us to obtain gauge invariant analytical expressions for the dispersion relations.
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Wadsworth, M.; Kyaw, S.T., E-mail: si.kyaw@nottingham.ac.uk; Sun, W.
2014-12-15
Highlights: • Effects of irradiation on fracture behaviours of graphite bricks are analysed. • Two irradiation conditions chosen are irradiation temperature and neutron dose. • The crack initiates around the keyway fillet of the brick for every study. • Higher temperature and higher neutron dose accelerate crack initiation time. • Turnaround point of hoop strain indicates the crack initiation time. - Abstract: Graphite moderator bricks used within many UK gas-cooled nuclear reactors undergo harsh temperature and radiation gradients. They cause changes in material properties of graphite over extended periods of time. Consequently, models have been developed in order to understand and predict the complex stresses formed within the brick by these processes. In this paper the effect of irradiation temperature and neutron dose on the fracture characteristics, crack initiation and crack growth are investigated. A finite element (FE) mechanical constitutive model is implemented in combination with the damage model to simulate crack growth within the graphite brick. The damage model is based on a linear traction–separation cohesive model in conjunction with the extended finite element method for arbitrary crack initiation and propagation. Results obtained have showed that cracks initiate in the vicinity of the keyway fillet of the graphite brick and initiation time accelerates with higher temperatures and doses.
Agarwal, Sumit; Briant, Clyde L.; Krajewski, Paul E.; Bower, Allan F.; Taleff, Eric M.
2007-04-01
A finite element method was recently designed to model the mechanisms that cause superplastic deformation (A.F. Bower and E. Wininger, A Two-Dimensional Finite Element Method for Simulating the Constitutive Response and Microstructure of Polycrystals during High-Temperature Plastic Deformation, J. Mech. Phys. Solids, 2004, 52, p 1289-1317). The computations idealize the solid as a collection of two-dimensional grains, separated by sharp grain boundaries. The grains may deform plastically by thermally activated dislocation motion, which is modeled using a conventional crystal plasticity law. The solid may also deform by sliding on the grain boundaries, or by stress-driven diffusion of atoms along grain boundaries. The governing equations are solved using a finite element method, which includes a front-tracking procedure to monitor the evolution of the grain boundaries and surfaces in the solid. The goal of this article is to validate these computations by systematically comparing numerical predictions to experimental measurements of the elevated-temperature response of aluminum alloy AA5083 (M.-A. Kulas, W.P. Green, E.M. Taleff, P.E. Krajewski, and T.R. McNelley, Deformation Mechanisms in Superplastic AA5083 materials. Metall. Mater. Trans. A, 2005, 36(5), p 1249-1261). The experimental work revealed that a transition occurs from grain-boundary sliding to dislocation (solute-drag) creep at approximately 0.001/s for temperatures between 425 and 500 °C. In addition, increasing the grain size from 7 to 10 μm decreased the transition to significantly lower strain rates. Predictions from the finite element method accurately predict the effect of grain size on the transition in deformation mechanisms.
Beran, Gregory J O; Hartman, Joshua D; Heit, Yonaton N
2016-11-15
Molecular crystals occur widely in pharmaceuticals, foods, explosives, organic semiconductors, and many other applications. Thanks to substantial progress in electronic structure modeling of molecular crystals, attention is now shifting from basic crystal structure prediction and lattice energy modeling toward the accurate prediction of experimentally observable properties at finite temperatures and pressures. This Account discusses how fragment-based electronic structure methods can be used to model a variety of experimentally relevant molecular crystal properties. First, it describes the coupling of fragment electronic structure models with quasi-harmonic techniques for modeling the thermal expansion of molecular crystals, and what effects this expansion has on thermochemical and mechanical properties. Excellent agreement with experiment is demonstrated for the molar volume, sublimation enthalpy, entropy, and free energy, and the bulk modulus of phase I carbon dioxide when large basis second-order Møller-Plesset perturbation theory (MP2) or coupled cluster theories (CCSD(T)) are used. In addition, physical insight is offered into how neglect of thermal expansion affects these properties. Zero-point vibrational motion leads to an appreciable expansion in the molar volume; in carbon dioxide, it accounts for around 30% of the overall volume expansion between the electronic structure energy minimum and the molar volume at the sublimation point. In addition, because thermal expansion typically weakens the intermolecular interactions, neglecting thermal expansion artificially stabilizes the solid and causes the sublimation enthalpy to be too large at higher temperatures. Thermal expansion also frequently weakens the lower-frequency lattice phonon modes; neglecting thermal expansion causes the entropy of sublimation to be overestimated. Interestingly, the sublimation free energy is less significantly affected by neglecting thermal expansion because the systematic
Patel, Niravkumar D.; Mukherjee, Anamitra; Kaushal, Nitin; Moreo, Adriana; Dagotto, Elbio
2017-08-01
We employ a recently developed computational many-body technique to study for the first time the half-filled Anderson-Hubbard model at finite temperature and arbitrary correlation U and disorder V strengths. Interestingly, the narrow zero temperature metallic range induced by disorder from the Mott insulator expands with increasing temperature in a manner resembling a quantum critical point. Our study of the resistivity temperature scaling Tα for this metal reveals non-Fermi liquid characteristics. Moreover, a continuous dependence of α on U and V from linear to nearly quadratic is observed. We argue that these exotic results arise from a systematic change with U and V of the "effective" disorder, a combination of quenched disorder and intrinsic localized spins.
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Teo, L P [Faculty of Information Technology, Multimedia University, Jalan Multimedia, Cyberjaya, 63100, Selangor Darul Ehsan (Malaysia)], E-mail: lpteo@mmu.edu.my
2009-03-13
In this paper, the finite-temperature Casimir force acting on a two-dimensional Casimir piston due to an electromagnetic field is computed. It was found that if mixed boundary conditions are assumed on the piston and its opposite wall, then the Casimir force always tends to restore the piston toward the equilibrium position, regardless of the boundary conditions assumed on the walls transverse to the piston. In contrast, if pure boundary conditions are assumed on the piston and the opposite wall, then the Casimir force always tends to pull the piston toward the closer wall and away from the equilibrium position. The nature of the force is not affected by temperature. However, in the high-temperature regime, the magnitude of the Casimir force grows linearly with respect to temperature. This shows that the Casimir effect has a classical limit as has been observed in other literature.
Dai, Yan-Wei; Shi, Qian-Qian; Cho, Sam Young; Batchelor, Murray T.; Zhou, Huan-Qiang
2017-06-01
The finite-temperature phase diagram is obtained for an infinite honeycomb lattice with spin-1 /2 Ising interaction J by using thermal-state fidelity and the von Neumann entropy based on the infinite projected entangled pair state algorithm with ancillas. The tensor network representation of the fidelity, which is defined as an overlap measurement between two thermal states, is presented for thermal states on the honeycomb lattice. We show that the fidelity per lattice site and the von Neumann entropy can capture the phase transition temperatures for an applied magnetic field, consistent with the transition temperatures obtained via the transverse magnetizations, which indicates that a continuous phase transition occurs in the system. In the temperature-magnetic field plane, the phase boundary for finite temperature is found to be well approximated by the functional form (kBTc) 2+hc2/2 =a J2 with a single numerical fitting coefficient a =2.298 (7 ) , where Tc and hc are the critical temperature and field with Boltzmann constant kB. The critical temperature in the absence of magnetic field is estimated as kBTc/J =√{a }≃1.516 (2 ) , compared with the exact result kBTc/J =1.51865 ⋯ . For the quantum state at zero temperature, this phase boundary function gives the critical field estimate hc/J =√{2 a }≃2.144 (3 ) , compared to the known value hc/J =2.13250 (4 ) calculated from a cluster Monte Carlo approach.
Directory of Open Access Journals (Sweden)
Huijun Feng, Lingen Chen, Fengrui Sun
2010-11-01
Full Text Available An irreversible universal steady flow heat pump cycle model with variable-temperature heat reservoirs and the losses of heat-resistance and internal irreversibility is established by using the theory of finite time thermodynamics. The universal heat pump cycle model consists of two heat-absorbing branches, two heat-releasing branches and two adiabatic branches. Expressions of heating load, coefficient of performance (COP and profit rate of the universal heat pump cycle model are derived, respectively. By means of numerical calculations, heat conductance distributions between hot- and cold-side heat exchangers are optimized by taking the maximum profit rate as objective. There exist an optimal heat conductance distribution and an optimal thermal capacity rate matching between the working fluid and heat reservoirs which lead to a double maximum profit rate. The effects of internal irreversibility, total heat exchanger inventory, thermal capacity rate of the working fluid and heat capacity ratio of the heat reservoirs on the optimal finite time exergoeconomic performance of the cycle are discussed in detail. The results obtained herein include the optimal finite time exergoeconomic performances of endoreversible and irreversible, constant- and variable-temperature heat reservoir Brayton, Otto, Diesel, Atkinson, Dual, Miller and Carnot heat pump cycles.
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Kulkarni, Y; Knap, J; Ortiz, M
2007-04-26
The aim of this paper is the development of equilibrium and non-equilibrium extensions of the quasicontinuum (QC) method. We first use variational mean-field theory and the maximum-entropy formalism for deriving approximate probability distribution and partition functions for the system. The resulting probability distribution depends locally on atomic temperatures defined for every atom and the corresponding thermodynamic potentials are explicit and local in nature. The method requires an interatomic potential as the sole empirical input. Numerical validation is performed by simulating thermal equilibrium properties of selected materials using the Lennard-Jones pair potential and the EAM potential and comparing with molecular dynamics results as well as experimental data. The max-ent variational approach is then taken as a basis for developing a three-dimensional non-equilibrium finite temperature extension of the quasicontinuum method. This extension is accomplished by coupling the local temperature-dependent free energy furnished by the max-ent approximation scheme to the heat equation in a joint thermo-mechanical variational setting. Results for finite-temperature nanoindentation tests demonstrate the ability of the method to capture non-equilibrium transport properties and differentiate between slow and fast indentation.
Palma, G; Niedermayer, F; Rácz, Z; Riveros, A; Zambrano, D
2016-08-01
The zero-temperature, classical XY model on an L×L square lattice is studied by exploring the distribution Φ_{L}(y) of its centered and normalized magnetization y in the large-L limit. An integral representation of the cumulant generating function, known from earlier works, is used for the numerical evaluation of Φ_{L}(y), and the limit distribution Φ_{L→∞}(y)=Φ_{0}(y) is obtained with high precision. The two leading finite-size corrections Φ_{L}(y)-Φ_{0}(y)≈a_{1}(L)Φ_{1}(y)+a_{2}(L)Φ_{2}(y) are also extracted both from numerics and from analytic calculations. We find that the amplitude a_{1}(L) scales as ln(L/L_{0})/L^{2} and the shape correction function Φ_{1}(y) can be expressed through the low-order derivatives of the limit distribution, Φ_{1}(y)=[yΦ_{0}(y)+Φ_{0}^{'}(y)]^{'}. Thus, Φ_{1}(y) carries the same universal features as the limit distribution and can be used for consistency checks of universality claims based on finite-size systems. The second finite-size correction has an amplitude a_{2}(L)∝1/L^{2} and one finds that a_{2}Φ_{2}(y)≪a_{1}Φ_{1}(y) already for small system size (L>10). We illustrate the feasibility of observing the calculated finite-size corrections by performing simulations of the XY model at low temperatures, including T=0.
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Farias, Ricardo Luciano Sonego; Teixeira Junior, Daniel Lombelo [Universidade Federal de Sao Joao del Rey (UFSJ), MG (Brazil); Ramos, Rudnei de Oliveira [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil)
2012-07-01
Full text: Many efforts have been dedicated to understand the behavior of relativistic field theories under extreme conditions. Phase transition phenomena in quantum field theories are typically of non-perturbative nature and thus naive perturbation theory based on an expansion in the coupling constant cannot be employed. This is clearly the case of phase changes at high temperatures, where perturbation theory becomes unreliable because powers of the coupling constant become surmounted by powers of the temperature. We know that a symmetry broken in low temperature is restored as the temperature is increased. However, in a work made in 1974, Weinberg showed that was possible, in a multi-field model, the existence of cases in that a symmetry broken in low temperature is not restored in high temperature or that the symmetry is broken in high temperature. It is possible when the coupling constant between the fields receive a negative value. This phenomenon was called SNR, Symmetry Non-restoration or ISB, Inverse symmetry breaking. Many studies were made to investigate the existence of ISB/SNR using different approaches like resummation, Monte Carlo approach etc, obtain contradictories results. Our purpose in this work is investigate the appearance of ISB/SNR in a scalar field theory at finite temperature in the presence of external magnetic field. We used the method known like OPT(Optimized Perturbation Theory) to show how ISB/SNR is present in a multi-scalar field theory. (author)
Chiral restoration of strong coupling QCD at finite temperature and baryon density
Fromm, Michael
2009-04-01
The strong coupling limit (β=0) of lattice QCD with staggered fermions enjoys the same non-perturbative properties as continuum QCD, namely confinement and chiral symmetry breaking. In contrast to the situation at weak coupling, the sign problem which appears at finite density can be brought under control for a determination of the full (μ,T) phase diagram by Monte Carlo simulations. Further difficulties with efficiency and ergodicity of the simulations, especially at the strongly first-order, low-T, finite-μ transition, are addressed respectively with a worm algorithm and multicanonical sampling. Our simulations reveal sizeable corrections to the old results of Karsch and Mütter. Comparison with analytic mean-field determinations of the phase diagram shows discrepancies of O(10) in the location of the QCD critical point.
A new method to study lattice QCD at finite temperature and chemical potential
Fodor, Z
2002-01-01
Due to the sign problem, it is exponentially difficult to study QCD on the lattice at finite chemical potential. In this letter we propose a method --an overlap ensuring multi-parameter reweighting technique-- to solve the problem. We apply this method and give the phase diagram of four-flavor QCD obtained on lattices 4^4 and 4\\cdot6^3. Our results are based on {\\cal{O}}(10^3-10^4) configurations.
Ghonge, Tanmay; Chakraborty, Jeevanjyoti; Chakraborty, Suman
2012-01-01
A wide spectrum of electrokinetic studies is modelled as isothermal ones to expedite analysis even when such conditions may be extremely difficult to realize in practice. As a clear and novel departure from this trend, we address the case of flow-induced electrohydrodynamics, commonly referred to as streaming potential, in a situation where finite temperature gradients do indeed exit. By way of analysing a model problem of flow through a narrow parallel plate channel, we show that the temperature gradients have a significant effect on the streaming potential, and, consequently, on the flow itself. We incorporate thermoelectic effects in our model by a full-fledged coupling among the electric potential, the ionic species distribution, the fluid velocity and the local fluid temperature fields without resorting to ad hoc simplifications. We expect this expository study to contribute towards more sophisticated future inquiries into practical micro-/nano-fluidic applications coupling thermal field focusing with el...
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Lim, S C [Faculty of Engineering, Multimedia University, Jalan Multimedia, Cyberjaya, 63100, Selangor Darul Ehsan (Malaysia); Teo, L P [Faculty of Information Technology, Multimedia University, Jalan Multimedia, Cyberjaya, 63100, Selangor Darul Ehsan (Malaysia)
2007-09-21
We derive rigorously explicit formulae of the Casimir free energy at finite temperature for massless scalar field and electromagnetic field confined in a closed rectangular cavity with different boundary conditions by a zeta regularization method. We study both the low and high temperature expansions of the free energy. In each case, we write the free energy as a sum of a polynomial in temperature plus exponentially decay terms. We show that the free energy is always a decreasing function of temperature. In the cases of massless scalar field with the Dirichlet boundary condition and electromagnetic field, the zero temperature Casimir free energy might be positive. In each of these cases, there is a unique transition temperature (as a function of the side lengths of the cavity) where the Casimir energy changes from positive to negative. When the space dimension is equal to two and three, we show graphically the dependence of this transition temperature on the side lengths of the cavity. Finally we also show that we can obtain the results for a non-closed rectangular cavity by letting the size of some directions of a closed cavity go to infinity, and we find that these results agree with the usual integration prescription adopted by other authors.
Simulation of Temperature Distribution in TIG Spot Welds of(Al-Mg Alloy Using Finite Element Method
Directory of Open Access Journals (Sweden)
Ahlam Abid Ameer Alkhafajy
2008-01-01
Full Text Available This research concern to analyse and simulate the temperature distribution in the spot welding joints using tungsten arc welding shielded with inert gas (TIG Spot for the aluminum-magnesium alloy type (5052-O. The effect of and the quantity of the heat input that enter the weld zone has been investigated welding current, welding time and arc length on temperature distribution. The finite element method (by utilizing programme ANSYS 5.4 is presented the temperature distribution in a circular weld pool and the weld pool penetration (depth of welding through the top sheet ,across the interface into the lower sheet forming a weld spot. A three dimensional (3-D model has been constructed to study the temperature distribution and the depth or penetration of the weld spot. The results showed that the weld zone and heat affected zone (HAZ suffer from high temperature variation caused by severe thermal cycle. The temperature reaches the highest value of the melt metal at the weld spot 698°C at weld current 130 Amp, weld time 6 sec and arc length 1.6 mm, then drops further away from the weld spot in the direction the base metal. Figuers were plotted to explain the results and to show the temperature distribution and its value in the weld spot and heat effected zone.
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Mohanty, Subhasish, E-mail: smohanty@anl.gov [Argonne National Laboratory, South Cass Avenue, Argonne, IL 60439 (United States); Majumdar, Saurindranath [Argonne National Laboratory, South Cass Avenue, Argonne, IL 60439 (United States); Srinivasan, Makuteswara [U.S. Nuclear Regulatory Commission, Washington, DC 20555 (United States)
2013-07-15
Highlights: • Finite element procedure developed for stress analysis of HTGR graphite component. • Realistic fluence profile and reflector brick shape considered for the simulation. • Also realistic H-451 grade material properties considered for simulation. • Typical outer reflector of a GT-MHR type reactor considered for numerical study. • Based on the simulation results replacement of graphite bricks can be scheduled. -- Abstract: High temperature gas cooled reactors, such as prismatic and pebble bed reactors, are increasingly becoming popular because of their inherent safety, high temperature process heat output, and high efficiency in nuclear power generation. In prismatic reactors, hexagonal graphite bricks are used as reflectors and fuel bricks. In the reactor environment, graphite bricks experience high temperature and neutron dose. This leads to dimensional changes (swelling and or shrinkage) of these bricks. Irradiation dimensional changes may affect the structural integrity of the individual bricks as well as of the overall core. The present paper presents a generic procedure for stress analysis of prismatic core graphite components using graphite reflector as an example. The procedure is demonstrated through commercially available ABAQUS finite element software using the option of user material subroutine (UMAT). This paper considers General Atomics Gas Turbine-Modular Helium Reactor (GT-MHR) as a bench mark design to perform the time integrated stress analysis of a typical reflector brick considering realistic geometry, flux distribution and realistic irradiation material properties of transversely isotropic H-451 grade graphite.
Quantum-Shell Corrections to the Finite-Temperature Thomas-Fermi-Dirac Statistical Model of the Atom
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Ritchie, A B
2003-07-22
Quantum-shell corrections are made directly to the finite-temperature Thomas-Fermi-Dirac statistical model of the atom by a partition of the electronic density into bound and free components. The bound component is calculated using analytic basis functions whose parameters are chosen to minimize the energy. Poisson's equation is solved for the modified density, thereby avoiding the need to solve Schroedinger's equation for a self-consistent field. The shock Hugoniot is calculated for aluminum: shell effects characteristic of quantum self-consistent field models are fully captures by the present model.
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Arora, H.S. [School of Mechanical, Material and Energy Engineering, Indian Institute of Technology Ropar, Rupnagar, Punjab 140001 (India); Singh, H., E-mail: harpreetsingh@iitrpr.ac.in [School of Mechanical, Material and Energy Engineering, Indian Institute of Technology Ropar, Rupnagar, Punjab 140001 (India); Dhindaw, B.K. [School of Materials and Mineral Resources, Universiti Sains Malaysia, Engineering Campus, Nibong Tebal, Pulau Penang 14300 (Malaysia)
2012-05-01
Highlights: Black-Right-Pointing-Pointer Magnesium alloy AE42 was friction stir processed under different cooling conditions. Black-Right-Pointing-Pointer Heat flow model was developed using finite difference heat equations. Black-Right-Pointing-Pointer Generalized MATLAB code was developed for solving heat flow model. Black-Right-Pointing-Pointer Regression equation for estimation of grain size was developed. - Abstract: The present investigation is aimed at developing a heat flow model to simulate temperature history during friction stir processing (FSP). A new approach of developing implicit form of finite difference heat equations solved using MATLAB code was used. A magnesium based alloy AE42 was friction stir processed (FSPed) at different FSP parameters and cooling conditions. Temperature history was continuously recorded in the nugget zone during FSP using data acquisition system and k type thermocouples. The developed code was validated at different FSP parameters and cooling conditions during FSP experimentation. The temperature history at different locations in the nugget zone at different instants of time was further utilized for the estimation of grain growth rate and final average grain size of the FSPed specimen. A regression equation relating the final grain size, maximum temperature during FSP and the cooling rate was developed. The metallurgical characterization was done using optical microscopy, SEM, and FIB-SIM analysis. The simulated temperature profiles and final average grain size were found to be in good agreement with the experimental results. The presence of fine precipitate particles generated in situ in the investigated magnesium alloy also contributed in the evolution of fine grain structure through Zener pining effect at the grain boundaries.
Correlation functions of the energy-momentum tensor in SU(2) gauge theory at finite temperature
DEFF Research Database (Denmark)
Huebner, K.; Karsch, F.; Pica, Claudio
2008-01-01
We calculate correlation functions of the energy-momentum tensor in the vicinity of the deconfinement phase transition of (3+1)-dimensional SU(2) gauge theory and discuss their critical behavior in the vicinity of the second order deconfinement transition. We show that correlation functions...... of the trace of the energy momentum tensor diverge uniformly at the critical point in proportion to the specific heat singularity. Correlation functions of the pressure, on the other hand, stay finite at the critical point. We discuss the consequences of these findings for the analysis of transport...... coefficients, in particular the bulk viscosity, in the vicinity of a second order phase transition point....
Correlation functions of the energy-momentum tensor in SU(2) gauge theory at finite temperature
Huebner, K; Pica, C
2008-01-01
We calculate correlation functions of the energy-momentum tensor in the vicinity of the deconfinement phase transition of (3+1)-dimensional SU(2) gauge theory and discuss their critical behavior in the vicinity of the second order deconfinement transition. We show that correlation functions of the trace of the energy momentum tensor diverge uniformly at the critical point in proportion to the specific heat singularity. Correlation functions of the pressure, on the other hand, stay finite at the critical point. We discuss the consequences of these findings for the analysis of transport coefficients, in particular the bulk viscosity, in the vicinity of a second order phase transition point.
Institute of Scientific and Technical Information of China (English)
刘龙权; 姚振强; 袁光杰
2004-01-01
In order to analyze the influences of the different tool's shape and surface conditions (such as different coated and material) and their interaction on the cutting temperature, a coupled thermo-mechanical finite element analysis (FEA)model of plane-strain orthogonal metal cutting process is constructed, and 16 simulation cases with 16 different types of tools, which cover 4 rake angles, - 10°, 0°, 10°, 20°,and 4 friction coefficient values, 0, 0.1, 0.2, 0.3 in the same cutting condition (cutting depth and cutting speed)have been performed. Finally the simulation results are analyzed according to the variance analysis method (VAM)of orthogonal array designs (OADs), the relationships between the rake angle, tool-workpiece interface's friction coefficient and their interact effect to the maximum temperature value and the temperature field of the chip are obtained. This result has some instructive meaning to analyze the causes of the cutting temperature and to control the maximum temperature value and the overall temperature field in the metal cutting process.
Peery, Jeffrey T; Klute, Glenn K; Blevins, Joanna J; Ledoux, William R
2006-09-01
Amputees who wear prosthetic limbs often experience discomfort from blisters and sores due to mechanical insult; these skin conditions are exacerbated by elevated skin temperatures and excessive perspiration within the prosthetic socket. The goal of this study was to create a tool for developing new prostheses that accommodate varying thermal loads arising from everyday activities. A three-dimensional thermal model of a transtibial residual limb and prosthesis was constructed using the finite element (FE) method. Transverse computerized tomography (CT) scans were used to specify the geometry of the residual limb and socket. Thermal properties from the literature were assigned to both biological tissue and prosthetic socket elements. The purpose of this work was to create a model that would aid in testing the effect of new prosthesis designs on skin temperature. To validate its output, the model was used to predict the skin temperature distribution in a common prosthetic socket system (silicone liner, wool sock, and carbon fiber socket) at rest with no mechanical loading. Skin temperatures were generally elevated near muscle and decreased anteriorly and at the distal end. Experimental temperature measurements taken at the skin-prosthesis interface of five human subjects were used to validate the model. Data extracted from the thermal model at anterior, posterior, lateral, and medial locations were typically within one standard deviation of experimental results; the mean temperatures were within 0.3 degree C for each section and were within 0.1 degree C overall.
Laurent, P.; Fagnard, J.-F.; Babu, N. Hari; Cardwell, D. A.; Vanderheyden, B.; Vanderbemden, P.
2010-12-01
In this work we study, both experimentally and numerically, the self-heating of a bulk, large YBCO pellet of aspect ratio (thickness/diameter) ~ 0.4 subjected to a large AC magnetic field. To ensure accurate temperature measurements, the sample was placed in an experimental vacuum chamber to achieve a small and reproducible heat transfer coefficient between the superconductor and the cryogenic fluid. The temperature was measured at several locations on the sample surface during the self-heating process. The experimentally determined temperature gradients are found to be very small in this arrangement (Bean model, assuming a uniform temperature in the sample. A 2D magneto-thermal model was also used to determine the space and time-dependent temperature distribution T(r, z, t) during the application of the AC field. The losses in the bulk pellet were determined using an algorithm based on the numerical method of Brandt, which was combined with a heat diffusion algorithm implemented using a finite-difference method. The model is shown to be able to reproduce the main trends of the observed temperature evolution of the bulk sample during a self-heating process. Finally, the 2D model is used to study the effect of a non-uniform distribution of critical current density Jc(r, z) on the losses within the bulk superconductor.
On the dynamics of a polaron in a classical chain with finite temperature
Energy Technology Data Exchange (ETDEWEB)
Lakhno, V. D., E-mail: lak@impb.psn.ru; Fialko, N. S., E-mail: fialka@impb.psn.ru [Russian Academy of Sciences, Institute of Mathematical Problems of Biology (Russian Federation)
2015-01-15
In today’s literature, polaron states in classical molecular chains are mostly calculated at zero temperature. It is assumed that the properties of these states change little if the temperature is different from zero but is much less than the characteristic energy equal to the depth of the polaron level. By numerical experiments, we demonstrate that the temperature decay of a polaron depends on the chain length. The longer the chain, the lower the critical temperature above which the charge is in a delocalized state, and, conversely, the shorter the chain, the higher the decay temperature of a polaron. The results of numerical experiments lead to a conclusion that, in an indefinitely long chain, polaron states decay at temperatures differing arbitrarily little from zero.
N=4 Supersymmetric Yang-Mills on S^3 in Plane Wave Matrix Model at Finite Temperature
Kitazawa, Yoshihisa
2008-01-01
We investigate the large N reduced model of gauge theory on a curved spacetime through the plane wave matrix model. We formally derive the action of the N=4 supersymmetric Yang-Mills theory on R \\times S^3 from the plane wave matrix model in the large N limit. Furthermore, we evaluate the effective action of the plane wave matrix model up to the two-loop level at finite temperature. We find that the effective action is consistent with the free energy of the N=4 supersymmetric Yang-Mills theory on S^3 at high temperature limit where the planar contributions dominate. We conclude that the plane wave matrix model can be used as a large N reduced model to investigate nonperturbative aspects of the N=4 supersymmetric Yang-Mills theory on R \\times S^3.
Matos, T
2011-01-01
Starting with a scalar field in a thermal bath and using the one loop quantum correction potential, we rewrite the Klein-Gordon equation in its thermodynamical representation and study the behavior of this scalar field due to temperature variations in the equations of motion. We find the generalization of a Gross-Pitaevskii like equation for a relativistic Bose gas with finite temperature, the corresponding thermodynamic and viscosity expressions, and an expression for the postulate of the first law of the thermodynamics for this BECs. We also propose that the equations obtained might help to explain at some level the phase transition of a Bose-Einstein Condensate in terms of quantum field theory in a simple way.
Sukhanov, A D
2010-01-01
We suggest a more general than quantum statistical mechanics ($QSM$) microdescription of objects in a heat bath taken into account a vacuum as an object environment - modification of quantum mechanics at finite temperatures; we call it $(\\hbar, k)$-dynamics ($ \\hbar kD$). This approach allows us in a new manner to calculate some important macroparameters and to modify standard thermodynamics. We create an effective apparatus for features description of nearly perfect fluids in various mediums. As an essentially new model of an object environment we suppose a quantum heat bath and its properties, including cases of cold and warm vacuums, are studied. We describe the thermal equilibrium state in place of the traditional density operator in term of a wave function the amplitude and phase of which have temperature dependence. We introduce a new generative operator, Schroedingerian, or stochastic action operator, and show its fundamental role in the microdescription. We demonstrate that a new macroparameter, namel...
Distilling momentum-space entanglement in Luttinger liquids at finite temperature
Dóra, Balázs; Lovas, Izabella; Pollmann, Frank
2017-08-01
While much is known about the entanglement characteristics of ground states, the properties of reduced thermal density matrices have received significantly less attention. Here we investigate the total correlations in reduced thermal density matrices for momentum-space bipartitioning in Luttinger liquids using analytical and numerical methods. The low-lying part of its spectrum contains an "entanglement gap", which persists up to temperatures comparable to the level spacing. With increasing temperature, the low-energy modes acquire dispersion and resemble those in the physical Hamiltonian with an enhanced effective temperature. The momentum-space entanglement is carried by high-energy modes (compared to temperature), featuring a completely flat spectrum. The von Neumann entropy increases with temperature with a universal Sommerfeld coefficient. The effective Hamiltonian of the right-moving excitations turns out to be as universal as the physical Hamiltonian.
Ruderman-Kittel-Kasuya-Yosida interaction at finite temperature: Graphene and bilayer graphene
Klier, N.; Shallcross, S.; Sharma, S.; Pankratov, O.
2015-11-01
We investigate the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between magnetic impurities in both single layer and Bernal stacked bilayer graphene, finding a number of striking anomalies in the temperature dependence of this interaction. In undoped single layer graphene the strength of the RKKY interaction for substitutional impurities anomalously increases upon increasing temperature, an effect that persists up to and beyond room temperature. For impurities intercalated in the Bernal stacked bilayer and a doping that places the chemical potential near the antibonding band edge, a qualitative change of the RKKY interaction with temperature occurs: a low-temperature oscillatory interaction develops into a high-temperature antiferromagnetic coupling, accompanied by an overall increase of the interaction strength. The origin of the temperature anomalies can be traced back to specific features of the density of states: the vanishing density of states at the apex of the Dirac cone in single layer graphene, and the "kink" in the density of states at the antibonding band edge in the case of the Bernal bilayer.
Finite-temperature dynamics of the spin- (1)/(2) bond alternating Heisenberg antiferromagnetic chain
Mikeska, H. J.; Luckmann, C.
2006-05-01
We present results for the dynamic structure factor of the S=1/2 bond alternating Heisenberg chain over a large range of frequencies and temperatures. Data are obtained from a numerical evaluation of thermal averages based on the calculation of all eigenvalues and eigenfunctions for chains of up to 20 spins. Interpretation is guided by the exact temperature dependence in the noninteracting dimer limit which remains qualitatively valid up to an interdimer exchange λ≈0.5 . The temperature induced central peak around zero frequency is clearly identified and aspects of the crossover to spin diffusion in its variation from low to high temperatures are discussed. The one-magnon peak acquires an asymmetric shape with increasing temperature. The two-magnon peak is dominated by the S=1 bound state which remains well defined up to temperatures of the order of J . The variation with temperature and wave vector of the integrated intensity for one-magnon and two-magnon scattering and of the central peak are discussed.
Energy and contact of the one-dimensional Fermi polaron at zero and finite temperature.
Doggen, E V H; Kinnunen, J J
2013-07-12
We use the T-matrix approach for studying highly polarized homogeneous Fermi gases in one dimension with repulsive or attractive contact interactions. Using this approach, we compute ground state energies and values for the contact parameter that show excellent agreement with exact and other numerical methods at zero temperature, even in the strongly interacting regime. Furthermore, we derive an exact expression for the value of the contact parameter in one dimension at zero temperature. The model is then extended and used for studying the temperature dependence of ground state energies and the contact parameter.
How to extract information from simulations of coarsening at finite temperature
Derrida, B.
1997-03-01
Certain properties of coarsening phenomena such as the fraction of space which remains always in the same phase are hard to measure in simulations, at nonzero temperature, because one needs to distinguish spin flips due to thermal fluctuations from those due to the motion of interfaces. By comparing the system where coarsening takes place with a fully ordered system submitted to the same thermal noise, one can measure in a simple way the fraction of space which remains in the same phase. Our numerical results indicate a power law decay (of the fraction of persistent spins) in the whole low temperature phase very similar to the zero temperature situation.
Large $N_{c}$, chiral approach to $M_{\\eta}'$ at finite temperature
Escribano, R; Tytgat, M H G
2000-01-01
We study the temperature dependence of the eta and eta' meson masses withinthe framework of U(3)_L x U(3)_R chiral perturbation theory, up tonext-to-leading order in a simultaneous expansion in momenta, quark masses andnumber of colours. We find that both masses decrease at low temperatures, butonly very slightly. We analyze higher order corrections and argue that largeN_c suggests a discontinuous drop of M_eta' at the critical temperature ofdeconfinement T_c, consistent with a first order transition to a phase withapproximate U(1)_A symmetry.
Leptonic Decay Constants of $D_{s}$ and $B_{s}$ Mesons at Finite Temperature
Veliev, Elsen Veli
2009-01-01
In the present work, $D_{s}$ and $B_{s}$ meson parameters are investigated in the framework of thermal QCD sum rules. The temperature dependence of the mass and the leptonic decay constants are investigated by using Borel transform sum rules and Hilbert moment sum rules. To increase sensitivity, the vacuum contributions are subtracted from thermal expressions and the temperature dependences of the leptonic decay constants and meson masses are studied.
Ge, Changfeng; Cheng, Yujie; Shen, Yan
2013-01-01
This study demonstrated an attempt to predict temperatures of a perishable product such as vaccine inside an insulated packaging container during transport through finite element analysis (FEA) modeling. In order to use the standard FEA software for simulation, an equivalent heat conduction coefficient is proposed and calculated to describe the heat transfer of the air trapped inside the insulated packaging container. The three-dimensional, insulated packaging container is regarded as a combination of six panels, and the heat flow at each side panel is a one-dimension diffusion process. The transit-thermal analysis was applied to simulate the heat transition process from ambient environment to inside the container. Field measurements were carried out to collect the temperature during transport, and the collected data were compared to the FEA simulation results. Insulated packaging containers are used to transport temperature-sensitive products such as vaccine and other pharmaceutical products. The container is usually made of an extruded polystyrene foam filled with gel packs. World Health Organization guidelines recommend that all vaccines except oral polio vaccine be distributed in an environment where the temperature ranges between +2 to +8 °C. The primary areas of concern in designing the packaging for vaccine are how much of the foam thickness and gel packs should be used in order to keep the temperature in a desired range, and how to prevent the vaccine from exposure to freezing temperatures. This study uses numerical simulation to predict temperature change within an insulated packaging container in vaccine cold chain. It is our hope that this simulation will provide the vaccine industries with an alternative engineering tool to validate vaccine packaging and project thermal equilibrium within the insulated packaging container.
Energy Technology Data Exchange (ETDEWEB)
Laurent, P; Vanderheyden, B; Vanderbemden, P [SUPRATECS and Department of Electrical Engineering and Computer Science B28, Sart-Tilman, B-4000 Liege (Belgium); Fagnard, J-F [SUPRATECS, Royal Military Academy of Belgium, Avenue de la Renaissance, B-1000 Brussels (Belgium); Babu, N Hari [Brunel Centre for Advanced Solidification Technology (BCAST), Brunel University, West London UB8 3PH (United Kingdom); Cardwell, D A, E-mail: Philippe.Vanderbemden@ulg.ac.b [Bulk Superconductivity Group, Engineering Department, University of Cambridge, Cambridge CB2 1PZ (United Kingdom)
2010-12-15
In this work we study, both experimentally and numerically, the self-heating of a bulk, large YBCO pellet of aspect ratio (thickness/diameter) {approx} 0.4 subjected to a large AC magnetic field. To ensure accurate temperature measurements, the sample was placed in an experimental vacuum chamber to achieve a small and reproducible heat transfer coefficient between the superconductor and the cryogenic fluid. The temperature was measured at several locations on the sample surface during the self-heating process. The experimentally determined temperature gradients are found to be very small in this arrangement (<0.2 K across the radius of the superconductor). The time-dependence of the average temperature T(t) is found to agree well with a theoretical prediction based on the one-dimensional (1D) Bean model, assuming a uniform temperature in the sample. A 2D magneto-thermal model was also used to determine the space and time-dependent temperature distribution T(r, z, t) during the application of the AC field. The losses in the bulk pellet were determined using an algorithm based on the numerical method of Brandt, which was combined with a heat diffusion algorithm implemented using a finite-difference method. The model is shown to be able to reproduce the main trends of the observed temperature evolution of the bulk sample during a self-heating process. Finally, the 2D model is used to study the effect of a non-uniform distribution of critical current density J{sub c}(r, z) on the losses within the bulk superconductor.
Ohno, H; Karsch, F; Mukherjee, S
2011-01-01
We report on the behavior of the eigenvalue distribution of the Dirac operator in (2+1)-flavor QCD at finite temperature, using the HISQ action. We calculate the eigenvalue density at several values of the temperature close to the pseudocritical temperature. For this study we use gauge field configurations generated on lattices of size $32^3 \\times 8$ with two light quark masses corresponding to pion masses of about 160 and 115 MeV. We find that the eigenvalue density below $T_c$ receives large contributions from near-zero modes which become smaller as the temperature increases or the light quark mass decreases. Moreover we find no clear evidence for a gap in the eigenvalue density up to 1.1$T_c$. We also analyze the eigenvalue density near $T_c$ where it appears to show a power-law behavior consistent with what is expected in the critical region near the second order chiral symmetry restoring phase transition in the massless limit.
Energy Technology Data Exchange (ETDEWEB)
Mohanty, Subhasish, E-mail: smohanty@anl.gov; Majumdar, Saurindranath
2015-10-15
Highlights: • High temperature gas cooled reactor. • Finite element based stress analysis. • H-451 graphite. • Irradiation creep model. • Graphite reflector stress analysis. - Abstract: Irradiation creep plays a major role in the structural integrity of the graphite components in high temperature gas cooled reactors. Finite element procedures combined with a suitable irradiation creep model can be used to simulate the time-integrated structural integrity of complex shapes, such as the reactor core graphite reflector and fuel bricks. In the present work a comparative study was undertaken to understand the effect of linear and nonlinear irradiation creep on results of finite element based stress analysis. Numerical results were generated through finite element simulations of a typical graphite reflector.
Directory of Open Access Journals (Sweden)
Schnorr Jörg
2005-04-01
Full Text Available Abstract Background Active Magnetic Resonance Imaging implants are constructed as resonators tuned to the Larmor frequency of a magnetic resonance system with a specific field strength. The resonating circuit may be embedded into or added to the normal metallic implant structure. The resonators build inductively coupled wireless transmit and receive coils and can amplify the signal, normally decreased by eddy currents, inside metallic structures without affecting the rest of the spin ensemble. During magnetic resonance imaging the resonators generate heat, which is additional to the usual one described by the specific absorption rate. This induces temperature increases of the tissue around the circuit paths and inside the lumen of an active implant and may negatively influence patient safety. Methods This investigation provides an overview of the supplementary power absorbed by active implants with a cylindrical geometry, corresponding to vessel implants such as stents, stent grafts or vena cava filters. The knowledge of the overall absorbed power is used in a finite volume analysis to estimate temperature maps around different implant structures inside homogeneous tissue under worst-case assumptions. The "worst-case scenario" assumes thermal heat conduction without blood perfusion inside the tissue around the implant and mostly without any cooling due to blood flow inside vessels. Results The additional power loss of a resonator is proportional to the volume and the quality factor, as well as the field strength of the MRI system and the specific absorption rate of the applied sequence. For properly working devices the finite volume analysis showed only tolerable heating during MRI investigations in most cases. Only resonators transforming a few hundred mW into heat may reach temperature increases over 5 K. This requires resonators with volumes of several ten cubic centimeters, short inductor circuit paths with only a few 10 cm and a quality
Spin-orbital order in the undoped manganite LaMnO3 at finite temperature
Snamina, Mateusz; Oleś, Andrzej M.
2016-12-01
We investigate the evolution of spin and orbital order in undoped LaMnO3 under increasing temperature with a model including both superexchange and Jahn-Teller interactions. We used several cluster mean field calculation schemes and find coexisting A -type antiferromagnetic and C -type alternating orbital order at low temperature. The value of the Jahn-Teller coupling between strongly correlated eg orbitals is estimated from the orbital transition temperature at TOO≃780 K. By a careful analysis of onsite and on-bond correlations, we demonstrate that spin-orbital entanglement is rather weak. We have verified that the magnetic transition temperature is influenced by entangled spin-orbital operators as well as by entangled orbital operators on the bonds, but the errors introduced by decoupling such operators partly compensate each other. Altogether, these results justify why the commonly used disentangled spin-orbital model is so successful in describing the magnetic properties and the temperature dependence of the optical spectral weights for LaMnO3.
Finite Element Analysis of RF Coupler in Normal-Low Temperature
Energy Technology Data Exchange (ETDEWEB)
Kim, Hansol; Lee, Hak Yong; Park, Chan; Lee, Jaeyeol; Lim, Dong Yeal; Yoo, Jeonghoon [Yonsei University, Seoul (Korea, Republic of); Hyun, Myung Wook [Institute of Basic Science, Daejeon (Korea, Republic of)
2014-10-15
A heavy ion accelerator is a device that accelerates heavy ions in the radio frequency (RF) range. The electric field that flows into the RF cavity continuously accelerates heavy ions in accordance with the phase of the input electromagnetic wave. For the purpose, it is necessary to design a coupler shape that can stably transfer the RF wave into the cavity. The RF coupler in a heavy ion accelerator has a large temperature difference between the input port and output port, which radiates the RF waves. It is necessary to consider the heat deflection on the RF coupler that occurs as a result of the rapid temperature gradient from an ultra-low temperature about 0 K to a room temperature about 300 K. The purpose of this study was to improve the system performance through an analysis of the intensity of the output electric field and temperature distribution considering various shapes of the RF coupler, along with an analysis of the durability considering the heat deflection and heat loss.
Finite-temperature modification of heavy particle decay and dark matter annihilation
Beneke, Martin; Hryczuk, Andrzej
2016-01-01
We apply the operator product expansion (OPE) technique to the decay and annihilation of heavy particles in a thermal medium with temperature below the heavy particle mass, m_chi. This allows us to explain two interesting observations made before: a) that the leading thermal correction to the decay width of a charged particle is the same multiplicative factor of the zero-temperature width for a two-body decay and muon decay, and b) that the leading thermal correction to fermionic dark matter annihilation arises only at order T^4/m_chi^4. The OPE further considerably simplifies the computation and factorizes it into model-independent matrix elements in the thermal background, and short-distance coefficients to be computed in zero-temperature field theory.
Phase diagram for charged scalars in a magnetic field at finite temperature
Ayala, Alejandro; Lopez, Jesus; Mizher, Ana Julia; Rojas, Juan Cristobal; Villavicencio, Cristian
2013-01-01
We investigate the nature of the phase transition for charged scalars in the presence of a magnetic background for a theory with spontaneous symmetry breaking. We perform a careful treatment of the negative mass squared as a function of the order parameter and present a suitable method to obtain magnetic and thermal corrections up to ring order for the high temperature limit and the case where the magnetic field strength is larger than the absolute value of the square of the mass parameter. We show that for a given value of the self-coupling, the phase transition is first order for a small magnetic field strength and becomes second order as this last grows. We also show that the critical temperature in the presence of the magnetic field is always below the critical temperature for the case where the field is absent.
Fixed-scale approach to finite-temperature lattice QCD with shifted boundaries
Umeda, Takashi
2014-01-01
We study the thermodynamics of the SU(3) gauge theory using the fixed-scale approach with shifted boundary conditions. The fixed-scale approach can reduce the numerical cost of the zero-temperature part in the equation of state calculations, while the number of possible temperatures is limited by the integer $N_t$, which represents the temporal lattice extent. The shifted boundary conditions can overcome such a limitation while retaining the advantages of the fixed-scale approach. Therefore, our approach enables the investigation of not only the equation of state in detail, but also the calculation of the critical temperature with increased precision even with the fixed-scale approach. We also confirm numerically that the boundary conditions suppress the lattice artifact of the equation of state, which has been confirmed in the non-interacting limit.
Screening of heavy quarks and hadrons at finite temperature and density
Energy Technology Data Exchange (ETDEWEB)
Doering, M.
2006-09-22
Heavy quarks and hadrons placed in a strongly interacting thermal and baryon chemical quantum field are screened by the medium. I calculate the free energies of heavy quarks and anti-quarks and hadron correlation functions on a 16{sup 3} x 4 lattice in 2-flavour QCD with a bare quark mass of m/T=0.4. The dependence on the interparticle distance determines the screening masses as a function of temperature and density. The Taylor expansion method is used for the baryon chemical potential. The heavy quark screening masses turn out to be in good agreement with perturbation theory for temperatures T>2T{sub c}. The hadron screening masses are consistent with the free quark propagation in the large temperature regime. (orig.)
Finite-temperature phase transition of $N_{f}=3$ QCD with exact center symmetry
Misumi, Tatsuhiro; Itou, Etsuko
2015-01-01
For the $Z_{3}$-symmetric lattice QCD-like theory ($Z_3$-QCD), in which $SU(3)$ gauge theory is coupled with three fundamental Wilson quarks with flavor-dependent twisted boundary conditions, we calculate the expectation values of Polyakov loop and chiral condensate as functions of temperature on $16^3 \\times4$ and $20^3 \\times 4$ lattices with $m_{PS}/m_{V}=0.70$ fixed. We find the first-order phase transition with respect to the $Z_{3}$ center symmetry, where the Polyakov loop exhibits a hysteresis depending on the initial condition of thermalization process. We also show that the crossover behavior of chiral condensate around the critical temperature of the center transition and the manifestation of flavor symmetry breaking in the high-temperature phase.
Vibrational frequency of a strong-coupling polaron in a quantum rod at finite temperatures
Institute of Scientific and Technical Information of China (English)
Ding Zhao-Hua; Xiao Jing-Lin
2011-01-01
The Hamiltonian of a quantum rod with a boundary is presented after a coordinate transformation that changes the original ellipsoidal boundary into a spherical one. We then study the effect of temperature on the vibrational frequency and the ground state binding energy of the strong-coupling polaron in the rod. The two quantities are expressed as functions of the aspect ratio of the ellipsoid,the transverse and the longitudinal effective confinement lengths,the temperature and the electron-phonon coupling strength by linear combination operator and unitary transformation methods. It is found that the vibrational frequency and the ground state binding energy will increase rapidly with decreasing transverse and longitudinal effective confinement lengths. They are increasing functions of the electronphonon coupling strength but become decreasing ones of the temperature and the aspect ratio.
Finite temperature collective modes in a two phase coexistence region of asymmetric nuclear matter
Aguirre, R M
2010-01-01
The relation between collective modes and the phase transition in low density nuclear matter is examined. The dispersion relations for collective modes in a linear approach are evaluated within a Landau-Fermi liquid scheme by assuming coexisting phases in thermodynamical equilibrium. Temperature and isospin composition are taken as relevant parameters. The in-medium nuclear interaction is taken from a recently proposed density functional model. We found significative modifications in the energy spectrum, within certain range of temperatures and isospin asymmetry, due to the separation of matter into independent phases. We conclude that detailed calculations should not neglect this effect.
Finite-Temperature Collective Dynamics of a Fermi Gas in the BEC-BCS Crossover
Wright, M. J.; Riedl, S.; Altmeyer, A.; Kohstall, C.; Guajardo, E. R. Sánchez; Denschlag, J. Hecker; Grimm, R.
2007-10-01
We report on experimental studies on the collective behavior of a strongly interacting Fermi gas with tunable interactions and variable temperature. A scissors mode excitation in an elliptical trap is used to characterize the dynamics of the quantum gas in terms of hydrodynamic or near-collisionless behavior. We obtain a crossover phase diagram for collisional properties, showing a large region where a nonsuperfluid strongly interacting gas shows hydrodynamic behavior. In a narrow interaction regime on the BCS side of the crossover, we find a novel temperature-dependent damping peak, suggesting a relation to the superfluid phase transition.
Finite temperature spectral function of the $\\sigma$ meson from large N expansion
Patkós, András; Szépfalusy, P; Szep, Zs.
2003-01-01
The spectral function of the scalar-isoscalar channel of the O(N) symmetric linear $\\sigma$ model is studied in the broken symmetry phase. The investigation is based on the leading order evaluation of the self-energy in the limit of large number of Goldstone bosons. We describe its temperature dependent variation in the whole low temperature phase. This variation closely reflects the trajectory of the scalar-isoscalar quasiparticle pole. In the model with no explicit chiral symmetry breaking we have studied near the critical point also the corresponding dynamical exponent.
Franco-Pérez, Marco; Ayers, Paul W; Gázquez, José L; Vela, Alberto
2015-12-28
We explore the local and nonlocal response functions of the grand canonical potential density functional at nonzero temperature. In analogy to the zero-temperature treatment, local (e.g., the average electron density and the local softness) and nonlocal (e.g., the softness kernel) intrinsic response functions are defined as partial derivatives of the grand canonical potential with respect to its thermodynamic variables (i.e., the chemical potential of the electron reservoir and the external potential generated by the atomic nuclei). To define the local and nonlocal response functions of the electron density (e.g., the Fukui function, the linear density response function, and the dual descriptor), we differentiate with respect to the average electron number and the external potential. The well-known mathematical relationships between the intrinsic response functions and the electron-density responses are generalized to nonzero temperature, and we prove that in the zero-temperature limit, our results recover well-known identities from the density functional theory of chemical reactivity. Specific working equations and numerical results are provided for the 3-state ensemble model.
Energy Technology Data Exchange (ETDEWEB)
Franco-Pérez, Marco, E-mail: francopj@mcmaster.ca, E-mail: ayers@mcmaster.ca, E-mail: jlgm@xanum.uam.mx, E-mail: avela@cinvestav.mx [Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, México, D.F. 09340 (Mexico); Ayers, Paul W., E-mail: francopj@mcmaster.ca, E-mail: ayers@mcmaster.ca, E-mail: jlgm@xanum.uam.mx, E-mail: avela@cinvestav.mx [Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Gázquez, José L., E-mail: francopj@mcmaster.ca, E-mail: ayers@mcmaster.ca, E-mail: jlgm@xanum.uam.mx, E-mail: avela@cinvestav.mx [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, México, D.F. 09340 (Mexico); Vela, Alberto, E-mail: francopj@mcmaster.ca, E-mail: ayers@mcmaster.ca, E-mail: jlgm@xanum.uam.mx, E-mail: avela@cinvestav.mx [Departamento de Química, Centro de Investigación y de Estudios Avanzados (Cinvestav), Av. Instituto Politécnico Nacional 2508, México, D.F. 07360 (Mexico)
2015-12-28
We explore the local and nonlocal response functions of the grand canonical potential density functional at nonzero temperature. In analogy to the zero-temperature treatment, local (e.g., the average electron density and the local softness) and nonlocal (e.g., the softness kernel) intrinsic response functions are defined as partial derivatives of the grand canonical potential with respect to its thermodynamic variables (i.e., the chemical potential of the electron reservoir and the external potential generated by the atomic nuclei). To define the local and nonlocal response functions of the electron density (e.g., the Fukui function, the linear density response function, and the dual descriptor), we differentiate with respect to the average electron number and the external potential. The well-known mathematical relationships between the intrinsic response functions and the electron-density responses are generalized to nonzero temperature, and we prove that in the zero-temperature limit, our results recover well-known identities from the density functional theory of chemical reactivity. Specific working equations and numerical results are provided for the 3-state ensemble model.
Vortex line in a neutral finite-temperature superfluid Fermi gas
DEFF Research Database (Denmark)
Nygaard, Nicolai; Bruun, G. M.; Schneider, B. I.;
2004-01-01
The structure of an isolated vortex in a dilute two-component neutral superfluid Fermi gas is studied within the context of self-consistent Bogoliubov-de Gennes theory. Various thermodynamic properties are calculated, and the shift in the critical temperature due to the presence of the vortex...
Casimir Effect at Finite Temperature in the Presence of Compactified Universal Extra Dimensions
Institute of Scientific and Technical Information of China (English)
CHENG Hong-Bo
2005-01-01
@@ We analyse the Casimir effect for parallel plates atfinite temperature in the presence of compactified universal extra dimensions and analytically show the thermal corrections to the effect in detail. The Casimir effect for different sizes of universal extra dimensions is investigated to test the five-dimensional Kaluza-Klein theory.
Postmortem time estimation using body temperature and a finite-element computer model
Hartog, E.A. den; Lotens, W.A.
2004-01-01
In the Netherlands most murder victims are found 2-24 h after the crime. During this period, body temperature decrease is the most reliable method to estimate the postmortem time (PMT). Recently, two murder cases were analysed in which currently available methods did not provide a su.ciently reliabl
Finite-temperature Casimir effect in piston geometry and its classical limit
Energy Technology Data Exchange (ETDEWEB)
Lim, S.C. [Multimedia University, Faculty of Engineering, Cyberjaya, Selangor Darul Ehsan (Malaysia); Teo, L.P. [Multimedia University, Faculty of Information Technology, Cyberjaya, Selangor Darul Ehsan (Malaysia)
2009-03-15
We consider the Casimir force acting on a d-dimensional rectangular piston due to a massless scalar field with periodic, Dirichlet and Neumann boundary conditions and an electromagnetic field with perfect electric-conductor and perfect magnetic-conductor boundary conditions. The Casimir energy in a rectangular cavity is derived using the cut-off method. It is shown that the divergent part of the Casimir energy does not contribute to the Casimir force acting on the piston, thus renders an unambiguously defined Casimir force acting on the piston. At any temperature, it is found that the Casimir force acting on the piston increases from -{infinity} to 0 when the separation a between the piston and the opposite wall increases from 0 to {infinity}. This implies that the Casimir force is always an attractive force pulling the piston towards the closer wall, and the magnitude of the force gets larger as the separation a gets smaller. Explicit exact expressions for the Casimir force for small and large plate separations and for low and high temperatures are computed. The limits of the Casimir force acting on the piston when some pairs of transversal plates are large are also derived. An interesting result regarding the influence of temperature is that in contrast to the conventional result that the leading term of the Casimir force acting on a wall of a rectangular cavity at high temperature is the Stefan-Boltzmann (or black-body radiation) term which is of order T {sup d+1}, it is found that the contributions of this term from the two regions separating the piston cancel with each other in the case of piston. The high-temperature leading-order term of the Casimir force acting on the piston is of order T, which shows that the Casimir force has a nontrivial classical {Dirac_h}{yields}0 limit. Explicit formulas for the classical limit are computed. (orig.)
Inglis, Stephen; Melko, Roger G
2013-01-01
We implement a Wang-Landau sampling technique in quantum Monte Carlo (QMC) simulations for the purpose of calculating the Rényi entanglement entropies and associated mutual information. The algorithm converges an estimate for an analog to the density of states for stochastic series expansion QMC, allowing a direct calculation of Rényi entropies without explicit thermodynamic integration. We benchmark results for the mutual information on two-dimensional (2D) isotropic and anisotropic Heisenberg models, a 2D transverse field Ising model, and a three-dimensional Heisenberg model, confirming a critical scaling of the mutual information in cases with a finite-temperature transition. We discuss the benefits and limitations of broad sampling techniques compared to standard importance sampling methods.
Loze, M K; Wright, C D
1998-10-01
The temperature distributions produced within semi-infinite and finite-thickness media heated by a moving laser beam with a Gaussian power-density profile are examined by use of a time-domain method. Convective losses, described by Newton's law of cooling, from the medium surfaces are included. Various medium absorption models are considered. The solutions are given as single integrals with respect to time of simple functions. The resulting expressions have been used to examine the role of surface losses in information storage and medical applications. The role of convective losses in optical recording systems is found to be insignificant. However, for medical applications, combined convective and evaporative surface losses represent an important surface-heat-loss mechanism.
Zhao, Xing-Dong; Zhao, Xu; Jing, Hui; Zhou, Lu; Zhang, Weiping
2013-05-01
We propose to realize controllable squeezing states of ferromagnetic magnons with a spinor Bose-Einstein condensate confined in an optical lattice. We use an external laser field to induce optical dipole-dipole interaction, which leads to magnon excitations of the system. By focusing on the role of the long-range magnetic and the optical dipole-dipole interactions, we show that the existence and properties of the produced squeezed magnons can be well controlled by tuning the transverse trapping widths of the condensates. We also show that the magnon excitations in this system have a close analogy with the dynamical Casimir effect at finite temperature predicted by Plunien [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.84.1882 84, 1882 (2000)] and Jing [Phys. Lett. APYLAAG0375-960110.1016/S0375-9601(00)00165-1 268, 174 (2000)].
Kuramashi, Yoshinobu; Nakamura, Yoshifumi; Takeda, Shinji; Ukawa, Akira
2016-12-01
We investigate the critical endline of the finite temperature phase transition of QCD around the SU(3)-flavor symmetric point at zero chemical potential. We employ the renormalization-group improved Iwasaki gauge action and nonperturbatively O (a )-improved Wilson-clover fermion action. The critical endline is determined by using the intersection point of kurtosis, employing the multiparameter, multiensemble reweighting method to calculate observables off the SU(3)-symmetric point, at the temporal size NT=6 and lattice spacing as low as a ≈0.19 fm . We confirm that the slope of the critical endline takes the value of -2 , and find that the second derivative is positive, at the SU(3)-flavor symmetric point on the Columbia plot parametrized with the strange quark mass ms and degenerated up-down quark mass ml.
Dynamical properties of the sine-Gordon quantum spin magnet Cu-PM at zero and finite temperature
Tiegel, Alexander C.; Honecker, Andreas; Pruschke, Thomas; Ponomaryov, Alexey; Zvyagin, Sergei A.; Feyerherm, Ralf; Manmana, Salvatore R.
2016-03-01
The material copper pyrimidine dinitrate (Cu-PM) is a quasi-one-dimensional spin system described by the spin-1/2 X X Z Heisenberg antiferromagnet with Dzyaloshinskii-Moriya interactions. Based on numerical results obtained by the density-matrix renormalization group, exact diagonalization, and accompanying electron spin resonance (ESR) experiments we revisit the spin dynamics of this compound in an applied magnetic field. Our calculations for momentum and frequency-resolved dynamical quantities give direct access to the intensity of the elementary excitations at both zero and finite temperature. This allows us to study the system beyond the low-energy description by the quantum sine-Gordon model. We find a deviation from the Lorentz invariant dispersion for the single-soliton resonance. Furthermore, our calculations only confirm the presence of the strongest boundary bound state previously derived from a boundary sine-Gordon field theory, while composite boundary-bulk excitations have too low intensities to be observable. Upon increasing the temperature, we find a temperature-induced crossover of the soliton and the emergence of new features, such as interbreather transitions. The latter observation is confirmed by our ESR experiments on Cu-PM over a wide range of the applied field.
Jain, Rahul; Pal, Surjya Kanta; Singh, Shiv Brat
2017-02-01
Friction Stir Welding (FSW) is a solid state joining process and is handy for welding aluminum alloys. Finite Element Method (FEM) is an important tool to predict state variables of the process but numerical simulation of FSW is highly complex due to non-linear contact interactions between tool and work piece and interdependency of displacement and temperature. In the present work, a three dimensional coupled thermo-mechanical method based on Lagrangian implicit method is proposed to study the thermal history, strain distribution and thermo-mechanical process in butt welding of Aluminum alloy 2024 using DEFORM-3D software. Workpiece is defined as rigid-visco plastic material and sticking condition between tool and work piece is defined. Adaptive re-meshing is used to tackle high mesh distortion. Effect of tool rotational and welding speed on plastic strain is studied and insight is given on asymmetric nature of FSW process. Temperature distribution on the workpiece and tool is predicted and maximum temperature is found in workpiece top surface.
Jain, Rahul; Pal, Surjya Kanta; Singh, Shiv Brat
2016-06-01
Friction Stir Welding (FSW) is a solid state joining process and is handy for welding aluminum alloys. Finite Element Method (FEM) is an important tool to predict state variables of the process but numerical simulation of FSW is highly complex due to non-linear contact interactions between tool and work piece and interdependency of displacement and temperature. In the present work, a three dimensional coupled thermo-mechanical method based on Lagrangian implicit method is proposed to study the thermal history, strain distribution and thermo-mechanical process in butt welding of Aluminum alloy 2024 using DEFORM-3D software. Workpiece is defined as rigid-visco plastic material and sticking condition between tool and work piece is defined. Adaptive re-meshing is used to tackle high mesh distortion. Effect of tool rotational and welding speed on plastic strain is studied and insight is given on asymmetric nature of FSW process. Temperature distribution on the workpiece and tool is predicted and maximum temperature is found in workpiece top surface.
Sabaeian, Mohammad; Shahzadeh, Mohammadreza
2015-02-01
The authors report the simulation of temperature distribution and thermally induced stresses of human tooth under CO2 pulsed laser beam. A detailed tooth structure comprising enamel, dentin, and pulp with realistic shapes and thicknesses were considered, and a numerical method of finite element was adopted to solve time-dependent bio-heat and stress equations. The realistic boundary conditions of constant temperature for those parts embedded in the gingiva and heat flux condition for those parts out of the gingiva were applied. The results which were achieved as a function of energy density (J/cm(2)) showed when laser beam is irradiated downward (from the top of the tooth), the temperature and thermal stresses decrease quickly as a function of depth that is a result of strong absorption of CO2 beams by enamel. This effect is so influential that one can use CO2 beams to remove micrometer layers while underlying tissues, especially the pulp, are safe from thermal effects.
Thaunay, Florian; Dognon, Jean-Pierre; Ohanessian, Gilles; Clavaguéra, Carine
2015-10-21
The calculation of infrared spectra by molecular dynamics simulations based on the AMOEBA polarizable force field has recently been demonstrated [Semrouni et al., J. Chem. Theory Comput., 2014, 10, 3190]. While this approach allows access to temperature and anharmonicity effects, band assignment requires additional tools, which we describe in this paper. The Driven Molecular Dynamics approach, originally developed by Bowman, Kaledin et al. [Bowman et al. J. Chem. Phys., 2003, 119, 646, Kaledin et al. J. Chem. Phys., 2004, 121, 5646] has been adapted and associated with AMOEBA. Its advantages and limitations are described. The IR spectrum of the Ac-Phe-Ala-NH2 model peptide is analyzed in detail. In addition to differentiation of conformations by reproducing frequency shifts due to non-covalent interactions, DMD allows visualizing the temperature-dependent vibrational modes.
Spin-polarized versus chiral condensate in quark matter at finite temperature and density
DEFF Research Database (Denmark)
Matsuoka, Hiroaki; Tsue, Yasuhiko; da Providencia, Joao
2016-01-01
It is shown that the spin-polarized condensate appears in quark matter at high baryon density and low temperature due to the tensor-type four-point interaction in the Nambu-Jona-Lasiniotype model as a low-energy effective theory of quantum chromodynamics. It is indicated within this low-energy ef......It is shown that the spin-polarized condensate appears in quark matter at high baryon density and low temperature due to the tensor-type four-point interaction in the Nambu-Jona-Lasiniotype model as a low-energy effective theory of quantum chromodynamics. It is indicated within this low......-energy effective model that the chiral symmetry is broken again by the spin-polarized condensate on increasing the quark number density, while chiral symmetry restoration occurs, in which the chiral condensate disappears at a certain density....
Magnetic catalysis (and inverse catalysis) at finite temperature in two-color lattice QCD
Ilgenfritz, E -M; Petersson, B; Schreiber, A
2013-01-01
Two-color lattice QCD with N_f=4 staggered fermion degrees of freedom (no rooting trick is applied) with equal electric charge q is studied in a homogeneous magnetic background field B and at non-zero temperature T. In order to circumvent renormalization as a function of the bare coupling we apply a fixed-scale approach. We study the influence of the magnetic field on the critical temperature. At rather small pseudo-scalar meson mass (m_pi \\approx 175 MeV \\approx T_c(B=0)) we confirm magnetic catalysis for sufficiently strong magnetic field strength, while at T=195 MeV and weak magnetic field (qB {\\lesssim} 0.8 GeV^2) we find a rise of the Polyakov loop with qB and thus, indications for an inverse magnetic catalysis.
Calvo, F.; Parneix, P.; Van-Oanh, N.-T.
2010-03-01
The vibrational spectra of the naphthalene, pyrene, and coronene molecules have been computed in the 0-3500 cm-1 infrared range using classical and quantum molecular dynamics simulations based on a dedicated tight-binding potential energy surface. The ring-polymer molecular dynamics (RPMD) and partially adiabatic centroid molecular dynamics (CMD) methods have been employed to account for quantum nuclear effects. The contributions of quantum delocalization to the line shift and broadening are significant in the entire spectral range and of comparable magnitude as pure thermal effects. While the two methods generally produce similar results, the CMD method may converge slower at low temperature with increasing Trotter discretization number. However, and contrary to the CMD method, the RPMD approach suffers from serious resonance problems at high frequencies and low temperatures.
Meson screening masses at finite temperature with Highly Improved Staggered Quarks
Maezawa, Y; Karsch, F; Petreczky, P; Mukherjee, S
2013-01-01
We report on the first study of the screening properties of the mesonic excitations with strange ($s$) and charm ($c$) quarks, specifically the ground states of the pseudo-scalar and vector meson excitations for the $\\bar{s}s$, $\\bar{s}c$ and $\\bar{c}c$ flavor combinations, using the Highly Improved Staggered Quark action with dynamical physical strange quark and nearly-physical up and down quarks. By comparing with their respective vacuum meson masses and by investigating the influence of the changing temporal boundary conditions of the valence quarks we study the thermal modifications of these mesonic excitations. While the $\\bar{s}s$ states show significant modifications even below the chiral crossover temperature $T_c$, the modifications of the open-charm and charmonium like states become visible only for temperatures $T\\gtrsim T_c$ and $T\\gtrsim1.2T_c$, respectively.
Color Screening and Quark-Quark Interactions in Finite Temperature QCD
Döring, M; Kaczmarek, O; Karsch, F
2007-01-01
We analyze the screening of static diquark sources in 2-flavor QCD and compare results with the screening of static quark-antiquark pairs. We show that a two quark system in a fixed color representations is screened at short distances like a single quark source in the same color representation whereas at large distances the two quarks are screened independently. At high temperatures we observe that the relative strength of the interaction in diquark and quark-antiquark systems, respectively, obeys Casimir scaling. We use this result to examine the possible existence of heavy quark-quark bound states in the high temperature phase of QCD. We find support for the existence of $bb$ states up to about $2T_c$ while $cc$ states are unlikely to be formed above $T_c$.
Measurement of isospin mixing at a finite temperature in 80Zr via giant dipole resonance decay
Corsi, A.; Wieland, O.; Barlini, S.; Bracco, A.; Camera, F.; Kravchuk, V. L.; Baiocco, G.; Bardelli, L.; Benzoni, G.; Bini, M.; Blasi, N.; Brambilla, S.; Bruno, M.; Casini, G.; Ciemala, M.; Cinausero, M.; Crespi, F. C. L.; D'Agostino, M.; Degerlier, M.; Giaz, A.; Gramegna, F.; Kmiecik, M.; Leoni, S.; Maj, A.; Marchi, T.; Mazurek, K.; Meczynski, W.; Million, B.; Montanari, D.; Morelli, L.; Myalski, S.; Nannini, A.; Nicolini, R.; Pasquali, G.; Poggi, G.; Vandone, V.; Vannini, G.
2011-10-01
Isospin mixing in the hot compound nucleus 80Zr was studied by measuring and comparing the γ-ray emission from the fusion reactions 40Ca+40Ca at Ebeam=200 MeV and 37Cl+44Ca at Ebeam=153 MeV. The γ yield associated with the giant dipole resonance is found to be different in the two reactions because, in self-conjugate nuclei, the E1 selection rules forbid the decay between states with isospin I=0. The degree of mixing is deduced from statistical-model analysis of the γ-ray spectrum emitted by the compound nucleus 80Zr with the standard parameters deduced from the γ decay of the nucleus 81Rb. The results are used to deduce the zero-temperature value, which is then compared with the latest predictions. The Coulomb spreading width is found to be independent of temperature.
CP asymmetry in heavy Majorana neutrino decays at finite temperature: the nearly degenerate case
Biondini, Simone; Escobedo, Miguel Angel; Vairo, Antonio
2015-01-01
In a model where Majorana neutrinos heavier than the electroweak scale couple to Standard Model Higgs bosons and leptons, we compute systematically thermal corrections to the direct and indirect CP asymmetries in the Majorana neutrino decays. These are key ingredients entering the equations that describe the thermodynamic evolution of the induced lepton-number asymmetry eventually leading to the baryon asymmetry in the universe. We compute the thermal corrections in an effective field theory framework that assumes the temperature smaller than the masses of the Majorana neutrinos and larger than the electroweak scale, and we provide the leading corrections in an expansion of the temperature over the mass. In this work, we consider the case of two Majorana neutrinos with nearly degenerate masses.
Klyushina, E. S.; Tiegel, A. C.; Fauseweh, B.; Islam, A. T. M. N.; Park, J. T.; Klemke, B.; Honecker, A.; Uhrig, G. S.; Manmana, S. R.; Lake, B.
2016-06-01
Unlike most quantum systems which rapidly become incoherent as temperature is raised, strong correlations persist at elevated temperatures in S =1/2 dimer magnets, as revealed by the unusual asymmetric line shape of their excitations at finite temperatures. Here, we quantitatively explore and parametrize the strongly correlated magnetic excitations at finite temperatures using high-resolution inelastic neutron scattering of the model compound BaCu2V2O8 which we show to be an alternating antiferromagnetic-ferromagnetic spin -1/2 chain. Comparison to state of the art computational techniques shows excellent agreement over a wide temperature range. Our findings hence demonstrate the possibility to quantitatively predict coherent behavior at elevated temperatures in quantum magnets.
Masuda, Hiroshi; Okubo, Tsuyoshi; Kawamura, Hikaru
2012-08-03
Motivated by the recent experiment on kagome-lattice antiferromagnets, we study the zero-field ordering behavior of the antiferromagnetic classical Heisenberg model on a uniaxially distorted kagome lattice by Monte Carlo simulations. A first-order transition, which has no counterpart in the corresponding undistorted model, takes place at a very low temperature. The origin of the transition is ascribed to a cooperative proliferation of topological excitations inherent to the model.
Disentanglement of Two Qubits Coupled to an XY Spin Chain at Finite Temperature
Institute of Scientific and Technical Information of China (English)
NIE Jing; WANG Lin-Cheng; YI Xue-Xi
2009-01-01
The disentanglement evolution of bipartite spin-1/2 system coupled to a common surrounding XY chain in transverse fields at nonzero temperature is studied in this letter. The dynamical process of the entanglement is numerically and anaiytically investigated. We find that thermal effects can enhance disentanglement if the entangled initial state of the central spins does not in the decoherenee free space. The critical phenomenon of quantum phase transitions reflected in the disentanglement can be washed out by the thermal effect eventually.
Gluon and ghost propagator studies in lattice QCD at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Aouane, Rafik
2013-04-29
Gluon and ghost propagators in quantum chromodynamics (QCD) computed in the infrared momentum region play an important role to understand quark and gluon confinement. They are the subject of intensive research thanks to non-perturbative methods based on Dyson-Schwinger (DS) and functional renormalization group (FRG) equations. Moreover, their temperature behavior might also help to explore the chiral and deconfinement phase transition or crossover within QCD at non-zero temperature. Our prime tool is the lattice discretized QCD (LQCD) providing a unique ab-initio non-perturbative approach to deal with the computation of various observables of the hadronic world. We investigate the temperature dependence of Landau gauge gluon and ghost propagators in pure gluodynamics and in full QCD. Regarding the gluon propagator, we compute its longitudinal D{sub L} as well its transversal D{sub T} components. The aim is to provide a data set in terms of fitting formulae which can be used as input for DS (or FRG) equations. We deal with full (N{sub f}=2) LQCD with the twisted mass fermion discretization. We employ gauge field configurations provided by the tmfT collaboration for temperatures in the crossover region and for three fixed pion mass values in the range [300,500] MeV. Finally, within SU(3) pure gauge theory (at T=0) we compute the Landau gauge gluon propagator according to different gauge fixing criteria. Our goal is to understand the influence of gauge copies with minimal (non-trivial) eigenvalues of the Faddeev-Popov operator.
Real-time quantum field theory at finite temperature in an inhomogeneous media
Bibilashvili, T M
1995-01-01
The method of the real time perturbative calculations of nonequilibrium averages is generalised to the case of varying chemical potential. Calculations are performed in the frame of Zubarev's nonequilibrium density matrix approach. In this approach perturbations of temperature and other thermodynamical parameters are taken into account explicitly including nonlinear terms. It differs from the Schwinger-Keldysh approach through the choice of more general initial conditions for the density matrix.
Quantum-annealing correction at finite temperature: Ferromagnetic p -spin models
Matsuura, Shunji; Nishimori, Hidetoshi; Vinci, Walter; Albash, Tameem; Lidar, Daniel A.
2017-02-01
The performance of open-system quantum annealing is adversely affected by thermal excitations out of the ground state. While the presence of energy gaps between the ground and excited states suppresses such excitations, error correction techniques are required to ensure full scalability of quantum annealing. Quantum annealing correction (QAC) is a method that aims to improve the performance of quantum annealers when control over only the problem (final) Hamiltonian is possible, along with decoding. Building on our earlier work [S. Matsuura et al., Phys. Rev. Lett. 116, 220501 (2016), 10.1103/PhysRevLett.116.220501], we study QAC using analytical tools of statistical physics by considering the effects of temperature and a transverse field on the penalty qubits in the ferromagnetic p -body infinite-range transverse-field Ising model. We analyze the effect of QAC on second (p =2 ) and first (p ≥3 ) order phase transitions, and construct the phase diagram as a function of temperature and penalty strength. Our analysis reveals that for sufficiently low temperatures and in the absence of a transverse field on the penalty qubit, QAC breaks up a single, large free-energy barrier into multiple smaller ones. We find theoretical evidence for an optimal penalty strength in the case of a transverse field on the penalty qubit, a feature observed in QAC experiments. Our results provide further compelling evidence that QAC provides an advantage over unencoded quantum annealing.
The bottomonium spectrum at finite temperature from $N_f=2+1$ lattice QCD
Aarts, Gert; Harris, Tim; Kim, Seyong; Lombardo, Maria Paola; Ryan, Sinéad M; Skullerud, Jon-Ivar
2014-01-01
We present results on the bottomonium spectrum at temperatures above and below the deconfinement crossover temperature, $T_c$, from dynamical lattice QCD simulations. The heavy quark is treated with a non-relativistic effective field theory on the lattice and serves as a probe of the hot medium. Ensembles with a finer spatial lattice spacing and a greater range of temperatures below $T_c$ than those previously employed by this collaboration are used. In addition, there are $N_f=2+1$ flavours of Wilson clover quark in the sea with $M_\\pi\\approx400$ MeV and we perform a more careful tuning of the bottom quark mass in this work. We calculate the spectral functions of S and P wave bottomonium states using the maximum entropy method and confirm earlier findings on the survival of the ground state S wave states up to at least $2T_c$ and the immediate dissociation of the P wave states above $T_c$.
Añaños, G N J
2000-01-01
We discuss three-dimensional $ \\lambda\\phi^4+\\eta\\phi^6 $ theory in the context of the 1/N expansion at finite temperature. We use the method of the composite operator (CJT) for summing a large sets of Feynman graphs. We analyse the behavior of the thermal square mass and the thermal coupling constant in the low and high temperature limit. The existent of the tricritical point at some temperature is found using this non-pertubative method.
Pair Fluctuations in Ultra-small Fermi Systems within Self-Consistent RPA at Finite Temperature
Storozhenko, A; Dukelsky, J; Röpke, G; Vdovin, A I
2003-01-01
A self-consistent version of the Thermal Random Phase Approximation (TSCRPA) is developed within the Matsubara Green's Function (GF) formalism. The TSCRPA is applied to the many level pairing model. The normal phase of the system is considered. The TSCRPA results are compared with the exact ones calculated for the Grand Canonical Ensemble. Advantages of the TSCRPA over the Thermal Mean Field Approximation (TMFA) and the standard Thermal Random Phase Approximation (TRPA) are demonstrated. Results for correlation functions, excitation energies, single particle level densities, etc., as a function of temperature are presented.
Emmons, Samuel; Acharya, Bijaya; Platter, Lucas
2017-01-01
For an ultracold heteronuclear mixture with a large positive interspecies scattering length and negligible intraspecies scattering length, we determine the three-body recombination rate as a function of collision energy using universal functions of a single scaling variable. We use the zero-range approximation and the Skorniakov -Ter-Martirosian equation to calculate these scaling functions for a range of collision energies. Further, we explore the effects that a nonzero temperature has on three-body recombination, as well as the effects of the formation of deep dimers, for experimentally relevant heteronuclear gases such as the 6Li-133Cs mixture. NSF Grant Nos. PHY-1516077 and PHY-1555030.
Symmetry breaking patterns of the 3-3-1 model at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Borges, J.S. [Universidade do Estado do Rio de Janeiro, Departamento de Fisica de Altas Energias, Rio de Janeiro, RJ (Brazil); Ramos, Rudnei O. [Universidade do Estado do Rio de Janeiro, Departamento de Fisica Teorica, Rio de Janeiro, RJ (Brazil)
2016-06-15
We consider the minimal version of an extension of the standard electroweak model based on the SU(3){sub c} x SU(3){sub L} x U(1){sub X} gauge symmetry (the 3-3-1 model). We analyze the most general potential constructed from three scalars in the triplet representation of SU(3){sub L}, whose neutral components develop nonzero vacuum expectation values, giving mass for all the model's massive particles. For different choices of parameters, we obtain the particle spectrum for the two symmetry breaking scales: one where the SU(3){sub L} x U(1){sub X} group is broken down to SU(2){sub L} x U(1){sub Y} and a lower scale similar to the standard model one. Within the considerations used, we show that the model encodes two first-order phase transitions, respecting the pattern of symmetry restoration. The last transition, corresponding to the standard electroweak one, is found to be very weak first-order, most likely turning second-order or a crossover in practice. However, the first transition in this model can be strongly first-order, which might happen at a temperature not too high above the second one. We determine the respective critical temperatures for symmetry restoration for the model. (orig.)
Calculation of spin and orbital magnetizations in Fe slab systems at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Garibay-Alonso, R [Facultad de Ciencias FIsico Matematicas, Universidad Autonoma de Coahuila, Conjunto Universitario Camporredondo, Edificio ' D' , 25000 Saltillo (Mexico); Reyes-Reyes, M [Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis PotosI, Alvaro Obregon 64, San Luis PotosI (Mexico); Urrutia-Banuelos, EfraIn [Departamento de Investigacion en Fisica, Universidad de Sonora, Apartado Postal 5-088, Hermosillo, Sonora 83190 (Mexico); Lopez-Sandoval, R [Instituto Potosino de Investigacion CientIfica y Tecnologica, Camino a la presa San Jose 2055, CP 78216, San Luis PotosI (Mexico)
2010-02-10
The temperature dependence of spin and orbital local magnetizations is theoretically determined for the non-bulk atomic region of (001) and (110) Fe slab systems. A d band Hamiltonian, including spin-orbit coupling terms, was used to model the slabs, which were emulated by using Fe films of sufficient thickness to reach a bulk behavior at their most inner atomic layers. The temperature effects were considered within the static approximation and a simple mean field theory was used to integrate the local magnetic moment and charge thermal fluctuations. The results reflect a clear interplay between electronic itinerancy and the local atomic environment and they can be physically interpreted from the local small charge transfers occurring in the superficial region of the slabs. For recovering the experimental behavior on the results for the (001) slab system, the geometrical relaxations at its non-bulk atomic layers and a d band filling variation are required. A study on the magnetic anisotropy aspects in the superficial region of the slabs is additionally performed by analyzing the results for the orbital local magnetization calculated along two different magnetization directions in both slab systems.
混凝土温度场差分法求解精度研究%Solution precision of concrete temperature fields with finite difference method
Institute of Scientific and Technical Information of China (English)
张宇鑫; 黄达海; 刘海成
2008-01-01
With the finite difference method to calculate the temperature distribution in mass concrete structures, the solution precision will increase with a smaller step size, at the cost of computational time. In view of the basic characteristics of the finite difference method, a simple yet powerful improvement is introduced. By multiplying the adiabatic temperature function with a correction factor, the precision of the solution can be assured without an increase in the computation time. In addition, the correction rules for three types of commonly used concrete hydration formulas are investigated.
Directory of Open Access Journals (Sweden)
Grönemeyer Dietrich HW
2006-05-01
investigations. The finite volume analysis calculates the time developing temperature maps for the model of a broken linear metallic wire embedded in tissue. Half of the total hot spot power loss is assumed to diffuse into both wire parts at the location of a defect. The energy is distributed from there by heat conduction. Additionally the effect of blood perfusion and blood flow is respected in some simulations because the simultaneous appearance of all worst case conditions, especially the absence of blood perfusion and blood flow near the hot spot, is very unlikely for vessel implants. Results The analytical solution as worst case scenario as well as the finite volume analysis for near worst case situations show not negligible volumes with critical temperature increases for part of the modeled hot spot situations. MR investigations with a high rf-pulse density lasting below a minute can establish volumes of several cubic millimeters with temperature increases high enough to start cell destruction. Longer exposure times can involve volumes larger than 100 mm3. Even temperature increases in the range of thermal ablation are reached for substantial volumes. MR sequence exposure time and hot spot power loss are the primary factors influencing the volume with critical temperature increases. Wire radius, wire material as well as the physiological parameters blood perfusion and blood flow inside larger vessels reduce the volume with critical temperature increases, but do not exclude a volume with critical tissue heating for resonators with a large product of resonator volume and quality factor. Conclusion The worst case scenario assumes thermal equilibrium for a hot spot embedded in homogeneous tissue without any cooling due to blood perfusion or flow. The finite volume analysis can calculate the results for near and not close to worst case conditions. For both cases a substantial volume can reach a critical temperature increase in a short time. The analytical solution, as absolute
CP asymmetry in heavy Majorana neutrino decays at finite temperature: the hierarchical case
Biondini, Simone; Vairo, Antonio
2016-01-01
We consider the simplest realization of leptogenesis with one heavy Majorana neutrino species much lighter than the other ones. In this scenario, when the temperature of the early universe is smaller than the lightest Majorana neutrino mass, we compute at first order in the Standard Model couplings and, for each coupling, at leading order in the termperature the CP asymmetry in the decays of the lightest neutrino into leptons and anti-leptons. We perform the calculation using a hierarchy of two effective field theories organized as expansions in the inverse of the heavy-neutrino masses. In the ultimate effective field theory, leading thermal corrections proportional to the Higgs self coupling and the gauge couplings are encoded in one single operator of dimension five, whereas corrections proportional to the top Yukawa coupling are encoded in four operators of dimension seven, which we compute.
Finite-Temperature Fidelity-Metric Approach to the Lipkin-Meshkov-Glick Model
Scherer, D D; Kästner, M
2009-01-01
The fidelity metric has recently been proposed as a useful and elegant approach to identify and characterize both quantum and classical phase transitions. We study this metric on the manifold of thermal states for the Lipkin-Meshkov-Glick (LMG) model. For the isotropic LMG model, we find that the metric reduces to a Fisher-Rao metric, reflecting an underlying classical probability distribution. Furthermore, this metric can be expressed in terms of derivatives of the free energy, indicating a relation to Ruppeiner geometry. This allows us to obtain exact expressions for the (suitably rescaled) metric in the thermodynamic limit. The phase transition of the isotropic LMG model is signalled by a degeneracy of this (improper) metric in the paramagnetic phase. Due to the integrability of the isotropic LMG model, ground state level crossings occur, leading to an ill-defined fidelity metric at zero temperature.
D* and B* mesons in strange hadronic medium at finite temperature
Directory of Open Access Journals (Sweden)
Chhabra Rahul
2016-01-01
Full Text Available We calculate the effect of density and temperature of isospin symmetric strange medium on the shift in masses and decay constants of vector D and B mesons using chiral SU(3 model and QCD sum rule approach. In the present investigation the values of quark and gluon condensates are calculated from the chiral SU(3 model and these condensatesare further used as input in the QCD Sum rule framework to calculate the in-medium masses and decay constants of vector D and B mesons. These in medium properties of vector D and B mesons may be helpful to understand the experimental observables of the experiments like CBM and PANDA under FAIR project at GSI, Germany. The results which are observed in present work are also compared with the previous predictions.
The Two-Loop Finite-Temperature Effective Potential of the MSSM and Baryogenesis
Losada, M
1999-01-01
We construct an effective three dimensional theory for the MSSM at high temperatures in the limit of large-$m_{A}$. We analyse the two-loop effective potential of the 3D theory for the case of a light right handed stop to determine the precise region in the $m_{h}$-$m_{\\tilde{t}_{R}}$ plane for which the sphaleron constraint for preservation of the baryon asymmetry is satisfied. We also compare with results previously obtained usind 3D and 4D calculations of the effective potential. A two-stage phase transition still persists for a small range of values of $m_{\\tilde{t}_{R}}$. The allowed region requires a value of $m_{\\tilde{t}_{R}} \\lsi m_{t}$ and $m_{h} \\lsi 100$ (110) GeV for $m_{Q} = 300$ GeV (1 TeV).
Multispinon continua at zero and finite temperature in a near-ideal Heisenberg chain.
Lake, B; Tennant, D A; Caux, J-S; Barthel, T; Schollwöck, U; Nagler, S E; Frost, C D
2013-09-27
The space-and time-dependent response of many-body quantum systems is the most informative aspect of their emergent behavior. The dynamical structure factor, experimentally measurable using neutron scattering, can map this response in wave vector and energy with great detail, allowing theories to be quantitatively tested to high accuracy. Here, we present a comparison between neutron scattering measurements on the one-dimensional spin-1/2 Heisenberg antiferromagnet KCuF3, and recent state-of-the-art theoretical methods based on integrability and density matrix renormalization group simulations. The unprecedented quantitative agreement shows that precise descriptions of strongly correlated states at all distance, time, and temperature scales are now possible, and highlights the need to apply these novel techniques to other problems in low-dimensional magnetism.
Time-Dependent Hartree-Fock Approach to Nuclear Pasta at Finite Temperature
Schuetrumpf, Bastian; Iida, Kei; Maruhn, Joachim; Mecke, Klaus; Reinhard, Paul-Gerhard
2013-01-01
We present simulations of neutron-rich matter at subnuclear densities, like supernova matter, with the time-dependent Hartree-Fock approximation at temperatures of several MeV. The initial state consists of $\\alpha$ particles randomly distributed in space that have a Maxwell-Boltzmann distribution in momentum space. Adding a neutron background initialized with Fermi distributed plane waves the calculations reflect a reasonable approximation of astrophysical matter. This matter evolves into spherical, rod-like, and slab-like shapes and mixtures thereof. The simulations employ a full Skyrme interaction in a periodic three-dimensional grid. By an improved morphological analysis based on Minkowski functionals, all eight pasta shapes can be uniquely identified by the sign of only two valuations, namely the Euler characteristic and the integral mean curvature.
Multiply quantized vortices and finite temperature effects in the BEC/BCS crossover regime
Energy Technology Data Exchange (ETDEWEB)
Tempere, Jacques [TFVS, Universiteit Antwerpen (UIA), Universiteitsplein 1, B2610 Antwerpen (Belgium); Lyman Laboratory of Physics, Harvard University, Cambridge, MA 02138 (United States); Devreese, Jozef T. [TFVS, Universiteit Antwerpen (UIA), Universiteitsplein 1, B2610 Antwerpen (Belgium)]. E-mail: jozef.devreese@ua.ac.be
2006-05-15
The interatomic interaction strength in ultracold fermionic gases can be manipulated using Feshbach resonances, allowing to probe both the regime where atoms form molecules that Bose condense (BEC) and the Bardeen-Cooper-Schrieffer (BCS) regime. We use a path-integral formalism to investigate the properties of multiply quantized vortices in these systems. Although the vortex core region expands when more quanta of circulation are present, the qualitative result is the same: in the BEC regime, the atoms do not penetrate into the vortex core, whereas in the BCS regime they do. The system undergoes a smooth crossover between the two regimes. When the temperature is increased, the penetration of atoms into the vortex core becomes more pronounced.
Spin glass in a field: a new zero-temperature fixed point in finite dimensions.
Angelini, Maria Chiara; Biroli, Giulio
2015-03-06
By using real-space renormalization group (RG) methods, we show that spin glasses in a field display a new kind of transition in high dimensions. The corresponding critical properties and the spin-glass phase are governed by two nonperturbative zero-temperature fixed points of the RG flow. We compute the critical exponents and discuss the RG flow and its relevance for three-dimensional systems. The new spin-glass phase we discovered has unusual properties, which are intermediate between the ones conjectured by droplet and full replica symmetry-breaking theories. These results provide a new perspective on the long-standing debate about the behavior of spin glasses in a field.
Zanchini, E.; Jahanbin, A.
2016-09-01
In the evaluation of Thermal Response Tests (TRTs) and in the design of Borehole Heat Exchanger (BHE) fields, the mean temperature of the fluid Tm is usually approximated by the arithmetic mean Tave of inlet and outlet temperatures. This approximation can yield errors in the estimation of the thermal conductivity of the ground, of the BHE thermal resistance, and of the heat pump performance. An expression for the evaluation of Tm has been proposed by Marcotte and Pasquier (Marcotte D, Pasquier P 2008, Renewable Energy, 33 2407) for single U-tube BHEs. In this paper, the difference between Tm and Tave is determined by 3D finite- element simulations for a typical double U-tube BHE in 6 unsteady working conditions. The results are validated qualitatively through an approximate analytical method, and show that the expression proposed by Marcotte and Pasquier underestimates the difference between Tm and Tave when applied to a typical double U-tube BHE. Therefore, new relations to evaluate this difference for double U-tube BHEs would be useful.
Equation of state of a quark-Polyakov loop-meson mixture in the PNJL model at finite temperature
Torres-Rincon, Juan M
2016-01-01
Recent consensus on the $N_f=2+1$ equation of state at vanishing chemical potential from different lattice-QCD groups has spoiled the previous agreement with the outcome from the mean-field Polyakov-Nambu-Jona-Lasinio model. In this letter we review the thermodynamics of the PNJL model introducing two important aspects needed to describe the pressure computed in the lattice QCD. First, we consider the thermodynamics of the model beyond the mean-field approach to include pseudoscalar and scalar mesonic-like fluctuations into the grand-canonical potential. This accounts for the hadronic pressure of the system below the critical temperature. On the other hand we also implement the back reaction of quarks into the Polyakov-loop effective potential bringing a reduction of the pressure above $T_c$ from the Stefan-Boltzmann limit. We get a good agreement with lattice-QCD data at low and moderate temperatures, opening the door to a straightforward extension to finite chemical potential.
The rate dependent response of a bistable chain at finite temperature
Benichou, Itamar; Zhang, Yaojun; Dudko, Olga K.; Givli, Sefi
2016-10-01
We study the rate dependent response of a bistable chain subjected to thermal fluctuations. The study is motivated by the fact that the behavior of this model system is prototypical to a wide range of nonlinear processes in materials physics, biology and chemistry. To account for the stochastic nature of the system response, we formulate a set of governing equations for the evolution of the probability density of meta-stable configurations. Based on this approach, we calculate the behavior for a wide range of parametric values, such as rate, temperature, overall stiffness, and number of elements in the chain. Our results suggest that fundamental characteristics of the response, such as average transition stress and hysteresis, can be captured by a simple law which folds the influence of all these factors into a single non-dimensional quantity. We also show that the applicability of analytical results previously obtained for single-well systems can be extended to systems having multiple wells by proper definition of rate and of the transition stress.
Nuclear Pasta at Finite Temperature with the Time-Dependent Hartree-Fock Approach
Schuetrumpf, B.; Klatt, M. A.; Iida, K.; Maruhn, J. A.; Mecke, K.; Reinhard, P.-G.
2016-01-01
We present simulations of neutron-rich matter at sub-nuclear densities, like supernova matter. With the time-dependent Hartree-Fock approximation we can study the evolution of the system at temperatures of several MeV employing a full Skyrme interaction in a periodic three-dimensional grid [1]. The initial state consists of α particles randomly distributed in space that have a Maxwell-Boltzmann distribution in momentum space. Adding a neutron background initialized with Fermi distributed plane waves the calculations reflect a reasonable approximation of astrophysical matter. The matter evolves into spherical, rod-like, connected rod-like and slab-like shapes. Further we observe gyroid-like structures, discussed e.g. in [2], which are formed spontaneously choosing a certain value of the simulation box length. The ρ-T-map of pasta shapes is basically consistent with the phase diagrams obtained from QMD calculations [3]. By an improved topological analysis based on Minkowski functionals [4], all observed pasta shapes can be uniquely identified by only two valuations, namely the Euler characteristic and the integral mean curvature. In addition we propose the variance in the cell-density distribution as a measure to distinguish pasta matter from uniform matter.
Finite-Temperature Non-equilibrium Quasicontinuum Method based on Langevin Dynamics
Energy Technology Data Exchange (ETDEWEB)
Marian, J; Venturini, G; Hansen, B; Knap, J; Ortiz, M; Campbell, G
2009-05-08
The concurrent bridging of molecular dynamics and continuum thermodynamics presents a number of challenges, mostly associated with energy transmission and changes in the constitutive description of a material across domain boundaries. In this paper, we propose a framework for simulating coarse dynamic systems in the canonical ensemble using the Quasicontinuum method (QC). The equations of motion are expressed in reduced QC coordinates and are strictly derived from dissipative Lagrangian mechanics. The derivation naturally leads to a classical Langevin implementation where the timescale is governed by vibrations emanating from the finest length scale occurring in the computational cell. The equations of motion are integrated explicitly via Newmark's ({beta} = 0; {gamma} = 1/2) method, leading to a robust numerical behavior and energy conservation. In its current form, the method only allows for wave propagations supported by the less compliant of the two meshes across a heterogeneous boundary, which requires the use of overdamped dynamics to avoid spurious heating due to reflected vibrations. We have applied the method to two independent crystallographic systems characterized by different interatomic potentials (Al and Ta) and have measured thermal expansion in order to quantify the vibrational entropy loss due to homogenization. We rationalize the results in terms of system size, mesh coarseness, and nodal cluster diameter within the framework of the quasiharmonic approximation. For Al, we find that the entropy loss introduced by mesh coarsening varies linearly with the element size, and that volumetric effects are not critical in driving the anharmonic behavior of the simulated systems. In Ta, the anomalies of the interatomic potential employed result in negative and zero thermal expansion at low and high temperatures, respectively.
Energy Technology Data Exchange (ETDEWEB)
Wang, Zhiyuan [School of Physics and State Key Laboratory of Nuclear Physics and Technology, Beijing (China); Ma, Bo-Qiang [School of Physics and State Key Laboratory of Nuclear Physics and Technology, Beijing (China); Collaborative Innovation Center of Quantum Matter, Beijing (China); Peking University, Center for High Energy Physics, Beijing (China)
2016-05-15
We propose a unified approach to study meson, nucleon and Δ-baryon properties at zero and finite temperatures in the context of hard-wall AdS/QCD model. We first combine some previous works dealing with mesons and baryons separately, and introduce a new parameter ξ so that the model could give a universal description of spectrum and couplings of both sectors in a self-consistent way. All observables calculated numerically show reasonable agreement with experimental data. We then study these observables at nonzero temperature by modifying the AdS space-time into AdS-Schwarzschild space-time. Numerically solving the model, we find an interesting temperature dependence of the spectrum and the couplings. We also make a prediction on the finite-temperature decay width of some nucleon and Δ excited states. (orig.)
Coluzzi, Barbara; Yeramian, Edouard
2016-04-01
We perform an extensive numerical study of the disordered Poland-Scheraga (PS) model for DNA denaturation in which self-avoidance is completely taken into account. To complement to our previous work, we focus here on the finite size scaling in terms of pseudo-critical temperatures. Notably, we find that the mean value and the fluctuations of the pseudo-T c scale with the same exponent, the correlation length exponent {ν\\text{r}} (for which we provide the refined evaluation {ν\\text{r}}=2.9+/- 0.4 ). This result (coherent with the typical picture that describes random ferromagnets when disorder is relevant) is at variance with the numerical results reported in the literature for the PS model with self-avoidance, leading to an alternative scenario with a pseudo-first-order transition. We moreover introduce a crossover chain length N *, which we evaluate, appropriate for characterizing the approach to the asymptotic regime in this model. Essentially, below N *, the behaviour of the model in our study could also agree with such an alternative scenario. Based on an approximate prediction of the dependence of N * on the parameters of the model, we show that following the choice of such parameters it would not be possible to reach the asymptotic regime in practice. In such a context it becomes then possible to reconcile the apparently contradictory numerical studies.
Casana, Rodolfo; Ferreira, Manoel M., Jr.; Rodrigues, Josberg S.; Silva, Madson R. O.
2009-10-01
In this work, we examine the finite temperature properties of the CPT-even and Lorentz-invariance-violating (LIV) electrodynamics of the standard model extension, represented by the term WανρφFανFρφ. We begin analyzing the Hamiltonian structure following the Dirac’s procedure for constrained systems and construct a well-defined and gauge invariant partition function in the functional integral formalism. Next, we specialize for the nonbirefringent coefficients of the tensor Wανρφ. In the sequel, the partition function is explicitly carried out for the parity-even sector of the tensor Wανρφ. The modified partition function is a power of the Maxwell’s partition function. It is observed that the LIV coefficients induce an anisotropy in the black body angular energy density distribution. The Planck’s radiation law, however, retains its frequency dependence and the Stefan-Boltzmann law keeps the usual form, except for a change in the Stefan-Boltzmann constant by a factor containing the LIV contributions.
Watari, Minoru
2009-06-01
Two problems exist in the current studies on the application of the lattice Boltzmann method (LBM) to rarefied gas dynamics. First, most studies so far are applications of two-dimensional models. The numbers of velocity particles are small. Consequently, the boundary-condition methods of these studies are not directly applicable to a multispeed finite-difference lattice Boltzmann method (FDLBM) that has many velocity particles. Second, the LBM and FDLBM share their origins with the Boltzmann equation. Therefore, the results of LBM and FDLBM studies should be verified by the results of the continuous Boltzmann equation. In my review to date on the LBM studies, it appears that such verifications were seldom done. In this study, velocity slip and temperature jump simulations in the slip-flow regime were conducted using a three-dimensional FDLBM model. The results were compared with preceding theoretical studies based on the continuous Boltzmann equation. The results agreed with the theory with errors of a few percent. To further improve the accuracy of the FDLBM, it seems necessary to increase the number of velocity particles.
Energy Technology Data Exchange (ETDEWEB)
Yazici, E.; Sundu, H.; Veliev, E.V. [Kocaeli University, Department of Physics, Izmit (Turkey)
2016-02-15
The strong form factor of the B{sub c}B{sub c}J/ψ vertex is calculated in the framework of the QCD sum rules method at finite temperature. Taking into account additional operators appearing at finite temperature, a thermal Wilson expansion is obtained and QCD sum rules are derived. While increasing the temperature, the strong form factor remains unchanged up to T ≅ 100 MeV but slightly increases after this point. After T ≅ 160 MeV, the form factor suddenly decreases up to T ≅ 170 MeV. The obtained result of the coupling constant by fitting the form factor at Q{sub 2} = -m{sup 2}{sub offshell} at T = 0 is in a very good agreement with the QCD sum rules calculations in the case of vacuum. Our prediction can be checked in future experiments. (orig.)
Acevedo, Pedro; Vázquez, Mónica; Durán, Joel; Petrearce, Rodolfo
A simulation case is presented using the Finite Element Method (FEM) to simulate the performance of PVDF arrays to measure temperature gradients through the determination of phase shifts, i.e. time shifts of the waveform of the echo due to a change in the speed of propagation of ultrasound as a result of a change in temperature, they can be interpreted as phase shifts in the frequency domain. Making it possible to determine the change in temperature from the phase shifts; in a medium of propagation previously characterized.
Energy Technology Data Exchange (ETDEWEB)
Ovchinnikov, Victor, E-mail: ovchinnv@georgetown.edu [Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138 (United States); Karplus, Martin, E-mail: marci@tammy.harvard.edu [Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138 (United States); Laboratoire de Chimie Biophysique, ISIS, Université de Strasbourg, 67000 Strasbourg (France)
2014-05-07
A parallel implementation of the finite-temperature string method is described, which takes into account the invariance of coordinates with respect to rigid-body motions. The method is applied to the complex α-helix↔β-sheet transition in a β-hairpin miniprotein in implicit solvent, which exhibits much of the complexity of conformational changes in proteins. Two transition paths are considered, one derived from a linear interpolant between the endpoint structures and the other derived from a targeted dynamics simulation. Two methods for computing the conformational free energy (FE) along the string are compared, a restrained method, and a tessellation method introduced by E. Vanden-Eijnden and M. Venturoli [J. Chem. Phys. 130, 194103 (2009)]. It is found that obtaining meaningful free energy profiles using the present atom-based coordinates requires restricting sampling to a vicinity of the converged path, where the hyperplanar approximation to the isocommittor surface is sufficiently accurate. This sampling restriction can be easily achieved using restraints or constraints. The endpoint FE differences computed from the FE profiles are validated by comparison with previous calculations using a path-independent confinement method. The FE profiles are decomposed into the enthalpic and entropic contributions, and it is shown that the entropy difference contribution can be as large as 10 kcal/mol for intermediate regions along the path, compared to 15–20 kcal/mol for the enthalpy contribution. This result demonstrates that enthalpic barriers for transitions are offset by entropic contributions arising from the existence of different paths across a barrier. The possibility of using systematically coarse-grained representations of amino acids, in the spirit of multiple interaction site residue models, is proposed as a means to avoid ad hoc sampling restrictions to narrow transition tubes.
Cerezo, Javier; Zúñiga, José; Requena, Alberto; Ávila Ferrer, Francisco J; Santoro, Fabrizio
2013-11-12
When large structural displacements take place between the ground state (GS) and excited state (ES) minima of polyatomic molecules, the choice of a proper set of coordinates can be crucial for a reliable simulation of the vibrationally resolved absorption spectrum. In this work, we study two carotenoids that undergo structural displacements from GS to ES minima of different magnitude, from small displacements for violaxanthin to rather large ones for β-carotene isomers. Their finite-temperature (77 and 300 K) spectra are simulated at the harmonic level, including Duschinsky effect, by time-dependent (TD) and time-independent (TI) approaches, using (TD)DFT computed potential energy surfaces (PES). We adopted two approaches to construct the harmonic PES, the Adiabatic (AH) and Vertical Hessian (VH) models and, for AH, two reference coordinate frames: Cartesian and valence internal coordinates. Our results show that when large displacements take place, Cartesian coordinates dramatically fail to describe curvilinear displacements and to account for the Duschinsky matrix, preventing a realistic simulation of the spectra within the AH model, where the GS and ES PESs are quadratically expanded around their own equilibrium geometry. In contrast, internal coordinates largely amend such deficiencies and deliver reasonable spectral widths. As expected, both coordinate frames give similar results when small displacements occur. The good agreement between VH and experimental line shapes indicates that VH model, in which GS and ES normal modes are both evaluated at the GS equilibrium geometry, is a good alternative to deal with systems exhibiting large displacements. The use of this model can be, however, problematic when imaginary frequencies arise. The extent of the nonorthogonality of the Dushinsky matrix in internal coordinates and its correlation with the magnitude of the displacement of the GS and ES geometries is analyzed in detail.
Reddy, G. J.; Raju, R. S.; Rao, J. A.; Gorla, R. S. R.
2017-02-01
An unsteady magnetohydromagnetic natural convection on the Couette flow of electrically conducting water at 4°C (Pr = 11.40) in a rotating system has been considered. A Finite Element Method (FEM) was employed to find the numerical solutions of the dimensionless governing coupled boundary layer partial differential equations. The primary velocity, secondary velocity and temperature of water at 4°C as well as shear stresses and rate of heat transfer have been obtained for both ramped temperature and isothermal plates. The results are independent of the mesh (grid) size and the present numerical solutions through the Finite Element Method (FEM) are in good agreement with the existing analytical solutions by the Laplace Transform Technique (LTT). These are shown in tabular and graphical forms.
Directory of Open Access Journals (Sweden)
Reddy G.J.
2017-02-01
Full Text Available An unsteady magnetohydromagnetic natural convection on the Couette flow of electrically conducting water at 4°C (Pr = 11.40 in a rotating system has been considered. A Finite Element Method (FEM was employed to find the numerical solutions of the dimensionless governing coupled boundary layer partial differential equations. The primary velocity, secondary velocity and temperature of water at 4°C as well as shear stresses and rate of heat transfer have been obtained for both ramped temperature and isothermal plates. The results are independent of the mesh (grid size and the present numerical solutions through the Finite Element Method (FEM are in good agreement with the existing analytical solutions by the Laplace Transform Technique (LTT. These are shown in tabular and graphical forms.
Held, M.; Wiesenberger, M.; Madsen, J.; Kendl, A.
2016-12-01
Thermal effects on the perpendicular convection of seeded pressure blobs in the scrape-off layer of magnetised fusion plasmas are investigated. Our numerical study is based on a four field full-F gyrofluid model, which entails the consistent description of high fluctuation amplitudes and dynamic finite Larmor radius effects. We find that the maximal radial blob velocity increases with the square root of the initial pressure perturbation and that a finite Larmor radius contributes to highly compact blob structures that propagate in the poloidal direction. An extensive parameter study reveals that a smooth transition to this compact blob regime occurs when the finite Larmor radius effect strength, defined by the ratio of the magnetic field aligned component of the ion diamagnetic to the \\boldsymbol{E}× \\boldsymbol{B} vorticity, exceeds unity. The maximal radial blob velocities agree excellently with the inertial velocity scaling law over more than an order of magnitude. We show that the finite Larmor radius effect strength affects the poloidal and total particle transport and present an empirical scaling law for the poloidal and total blob velocities. Distinctions to the blob behaviour in the isothermal limit with constant finite Larmor radius effects are highlighted.
Institute of Scientific and Technical Information of China (English)
殷雯; 张国锋; 杜建红; 梁九卿
2003-01-01
The Monte Carlo simulation and the finite element methods have been used to calculate the heat deposition and temperature distribution in tungsten plate target when the target is bombarded by high-energy protons from the accelerator with nuclear power of 100 kW. The results show that the heat deposition in the target, reflector and shield will be 48 kW, 15 kW and 11 kW, respectively, and the highest temperature in the target plates will be lower than 100 ℃when the surfaces of plates are cooled by water.
Yoshitake, Junki; Nasu, Joji; Kato, Yasuyuki; Motome, Yukitoshi
2017-07-01
A prominent feature of quantum spin liquids is fractionalization of the spin degree of freedom. Fractionalized excitations have their own dynamics in different energy scales, and hence, affect finite-temperature (T ) properties in a peculiar manner even in the paramagnetic state harboring the quantum spin liquid state. We here present a comprehensive theoretical study of the spin dynamics in a wide T range for the Kitaev model on a honeycomb lattice, whose ground state is a quantum spin liquid. In this model, the fractionalization occurs to break up quantum spins into itinerant matter fermions and localized Z2 fluxes, which results in two crossovers at very different T scales. Extending the previous study for the isotropic coupling case [J. Yoshitake, J. Nasu, and Y. Motome, Phys. Rev. Lett. 117, 157203 (2016), 10.1103/PhysRevLett.117.157203], we calculate the dynamical spin structure factor S (q ,ω ) , the NMR relaxation rate 1 /T1 , and the magnetic susceptibility χ while changing the anisotropy in the exchange coupling constants, by using the dynamical mean-field theory based on a Majorana fermion representation. We describe the details of the methodology including the continuous-time quantum Monte Carlo method for computing dynamical spin correlations and the maximum entropy method for analytic continuation. We confirm that the combined method provides accurate results in a wide T range including the region where the spins are fractionalized. We find that also in the anisotropic cases the system exhibits peculiar behaviors below the high-T crossover whose temperature is comparable to the average of the exchange constants: S (q ,ω ) shows an inelastic response at the energy scale of the averaged exchange constant, 1 /T1 continues to grow even though the equal-time spin correlations are saturated and almost T independent, and χ deviates from the Curie-Weiss behavior. In particular, when the exchange interaction in one direction is stronger than the other two
Palma, G.; Niedermayer, F.; Rácz, Z.; Riveros, A.; Zambrano, D.
2016-08-01
The zero-temperature, classical X Y model on an L ×L square lattice is studied by exploring the distribution ΦL(y ) of its centered and normalized magnetization y in the large-L limit. An integral representation of the cumulant generating function, known from earlier works, is used for the numerical evaluation of ΦL(y ) , and the limit distribution ΦL →∞(y ) =Φ0(y ) is obtained with high precision. The two leading finite-size corrections ΦL(y ) -Φ0(y ) ≈a1(L ) Φ1(y ) +a2(L ) Φ2(y ) are also extracted both from numerics and from analytic calculations. We find that the amplitude a1(L ) scales as ln(L /L0) /L2 and the shape correction function Φ1(y ) can be expressed through the low-order derivatives of the limit distribution, Φ1(y ) =[yΦ0(y ) +Φ0'(y ) ] ' . Thus, Φ1(y ) carries the same universal features as the limit distribution and can be used for consistency checks of universality claims based on finite-size systems. The second finite-size correction has an amplitude a2(L ) ∝1 /L2 and one finds that a2Φ2(y ) ≪a1Φ1(y ) already for small system size (L >10 ). We illustrate the feasibility of observing the calculated finite-size corrections by performing simulations of the X Y model at low temperatures, including T =0 .
2011-01-01
Finite element method analysis of main lines of hydraulic central loading system installation expansion loops mounted on product and chemical tankers has been presented in the paper. The axial forces problem in installations mounted along the ship's open decks executed from hull deformations on waves and thermal stresses is given. Use of "U" type expansion loops is described. Results of forces in anchor points and stresses of Mises due to expansion loop deformations are shown. Calculations we...
Directory of Open Access Journals (Sweden)
Cuihua Wang
2014-09-01
Full Text Available An incompressible fully developed laminar flow in a helical rectangular duct having finite pitch and curvature with temperature-dependent viscosity under heating condition is studied in this work. Both the cases of one wall heated and four walls heated are studied. The cross-sectional dimensions of the rectangular duct are 2a and 2b. The aspect ratio n=2b/2a is 0.5. Water is used as the fluid and Reynolds number (Re is varied in the range of 100 to 400. The secondary flow with temperature-dependent viscosity is enhanced markedly as compared to constant viscosity. An additional pair of vortices is obtained near the center of the outer wall at Re=400 for the model of four walls heated with temperature-dependent viscosity, y, while for constant viscosity, the appearance of two additional vortices near the outer wall cannot be found. Besides, the axial velocity decreases and the temperature increases at the central region of the rectangular duct when the temperature-dependent viscosity is considered. Due to the decrease of the viscosity near the walls, the friction factor obtained with temperature-dependent viscosity is lower than that of constant viscosity, while the convective heat transfer for temperature-dependent viscosity is significantly enhanced owing to the strengthened secondary flow. Especially for four heated walls, the effects of viscosity variation on the flow resistance and heat transfer are more significant.
Energy Technology Data Exchange (ETDEWEB)
Shimizu, Takeshi [Toshiba Corp., Kawasaki, Kanagawa (Japan). Nuclear Engineering Lab.
1996-05-01
A two-dimensional steady-state distributed parameter code SPOTBOW has been developed for predicting the fine structure of cladding temperature in an liquid metal fast breeder reactor (LMFBR) fuel assembly where the deformation of fuel pins is induced by irradiation swelling, creep and thermal distortion under high burn-up operating condition. When the deformed fuel pin approaches adjacent pins and wrapper tube and comes in contact with those, the peak temperature, known as the hot spot temperature, can appear somewhere on the outer surface of the cladding. The temperature rise across the film is an important consideration in the cladding temperature analysis. Fully developed turbulent momentum and heat transfer equations based on the empirical turbulent model are solved by using the Galerkin finite element method which is suitable for the problem of the complicated boundary shape, such as the wire-wrapped fuel pin bundle. A new iteration procedure has been developed for solving the above equations by using the rise in coolant temperature, which is obtained with subchannel analysis codes, as a boundary condition. Calculated results are presented for local temperature distribution in normal and bowing pin bundle geometry, as compared with experiments. (author).
Bhardwaj, Rajneesh; Longtin, Jon P.; Attinger, Daniel
2010-01-01
The objective of this work is to investigate the coupling of fluid dynamics, heat transfer and mass transfer during the impact and evaporation of droplets on a heated solid substrate. A laser-based thermoreflectance method is used to measure the temperature at the solid-liquid interface, with a time and space resolution of 100 {\\mu}s and 20 {\\mu}m, respectively. Isopropanol droplets with micro- and nanoliter volumes are considered. A finite-element model is used to simulate the transient flui...