共查询到20条相似文献,搜索用时 15 毫秒
1.
In this brief communication, we have studied the validity of the first law of thermodynamics for the universe bounded by event horizon with two examples. The key point is the appropriate choice of the temperature on the event horizon. Finally, we have concluded that universe bounded by the event horizon may be a Bekenstein system and Einstein?s equations and the first law of thermodynamics on the event horizons are equivalent. 相似文献
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We investigate the validity the generalized second law of thermodynamics in a general braneworld model with curvature correction terms on the brane and in the bulk, respectively. Employing the derived entropy expression associated with the apparent horizon, we examine the time evolution of the total entropy, including the derived entropy of the apparent horizon and the entropy of the matter fields inside the apparent horizon. We show that the generalized second law of thermodynamics is fulfilled on the 3-brane embedded in the 5D spacetime with curvature corrections. 相似文献
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Asit Banerjee Tanwi Bandyopadhyay Subenoy Chakraborty 《General Relativity and Gravitation》2008,40(8):1603-1607
A model of an emergent universe is obtained in brane world. Here the bulk energy is in the form of cosmological constant,
while the brane consists of a fluid satisfying an equation of state of the form , which is effectively a radiation equation of state at high energies. It is shown that with the positive bulk cosmological
constant, one of our models represents an emergent universe. 相似文献
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An apparent violation of the second law of thermodynamics occurs when an atom coupled to a zero-temperature bath, being necessarily in an excited state, is used to extract work from the bath. Here the fallacy is that it takes work to couple the atom to the bath and this work must exceed that obtained from the atom. For the example of an oscillator coupled to a bath described by the single relaxation time model, the mean oscillator energy and the minimum work required to couple the oscillator to the bath are both calculated explicitly and in closed form. It is shown that the minimum work always exceeds the mean oscillator energy, so there is no violation of the second law. 相似文献
6.
Christian?G.?B?hmer Francisco?S.?N.?Lobo 《The European Physical Journal C - Particles and Fields》2010,70(4):1111-1118
Recently, Hořava proposed a power counting renormalizable theory for (3+1)-dimensional quantum gravity, which reduces to Einstein
gravity with a non-vanishing cosmological constant in IR, but possesses improved UV behaviors. In this work, we analyze the
stability of the Einstein static universe by considering linear homogeneous perturbations in the context of an IR modification
of Hořava gravity, which implies a ‘soft’ breaking of the ‘detailed balance’ condition. The stability regions of the Einstein
static universe is parameterized by the linear equation of state parameter w=p/ρ and the parameters appearing in the Hořava theory, and it is shown that a large class of stable solutions exists in the respective
parameter space. 相似文献
7.
We consider spacetime with torsion in a Randall-Sundrum scenario where torsion, identified with the rank-2 Kalb-Ramond field, exists in the bulk together with gravity. While the interactions of both graviton and torsion in the bulk are controlled by the Planck mass, an additional exponential suppression comes for the torsion zero-mode on the visible brane. This may serve as a natural explanation of why the effect of torsion is so much weaker than that of curvature on the brane. The massive torsion modes, on the other hand, are correlated with the corresponding gravitonic modes and may be detectable in TeV-scale experiments. 相似文献
8.
We obtain cosmological solutions which admit emergent universe (EU) scenario in the framework of Einstein Gauss–Bonnet (GB)
gravity coupled with a dilaton field in 4-dimensions. The coupling parameter of the GB terms and the dilaton in the theory
are determined for obtaining an EU scenario. The corresponding dilaton potential which admits such scenario is determined.
It is found that the GB terms coupled with a dilaton field plays an important role in describing the dynamics of the evolution
of the early as well as the late universe. We note an interesting case where the GB term dominates initially in the asymptotic
past regime, subsequently it decreases and thereafter its contribution in determining the dynamics of the evolution dominates
once again. We note that the Einstein’s static universe solution permitted here is unstable which the asymptotic EU might
follow. We also compare our EU model with supernova data. 相似文献
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A theory for the voltage-current characteristic in high TC DC SQUIDs
(Superconducting Quantum Interference Devices), which accounts for a second
harmonic in the junction current-phase relation, is developed. It is shown
that the small inductance DC SQUIDs can be used for the investigation of the
second harmonic via its influence on the voltage-flux curve. If the second
harmonic is perceptible, then for large inductance DC SQUIDs the theory can
explain the substantial deviations of the experimental voltage modulation
from theoretical predictions and computer simulations based on conventional
sinusoidal current-phase relation. The detail comparison with the experiment
is performed. 相似文献
12.
In this paper we discuss the integrability of the generalized Lane–Emden equations of the first and second kinds. We carry
out their Noether symmetry classification. Various cases for the arbitrary functions in the equations are obtained for which
the equations have Noether point symmetries. First integrals of such cases are obtained and also reduction to quadrature of
the corresponding Lane–Emden equations are presented. New cases are found. 相似文献
13.
F. Yang Z. Wang Y. Zhou F. Li J. Xu Y. Xu X. Cheng Y. Lu Y. Bo Q. Peng D. Cui X. Zhang X. Wang Y. Zhu Z. Xu 《Applied physics. B, Lasers and optics》2009,96(2-3):415-422
We have presented theoretical and experimental investigations of nanosecond (ns) deep-ultraviolet (DUV) 177.3 nm radiation by means of second harmonic generation (SHG) from a frequency-tripled Nd:YAG laser (355 nm, 49 ns and 10 kHz) in KBe2BO3F2 (KBBF) nonlinear crystal for the first time. A DUV KBBF-SHG numerical model, accounting for linear absorption, pump depletion, beam spatial birefringent walk-off and diffraction, is performed in the Gaussian approximation of spatial and temporal profiles. In the experiment, a maximum average output power of 14.1 mW at 177.3 nm was obtained. The dependence of 177.3 nm output power on the 355 nm pump power was simulated. The calculated results are in good agreement with the measured data. We used the model further to investigate the optical conversion efficiency, pulse width, beam spatial intensity profile and beam quality factor of the generated 177.3 nm light, in particular the effect of beam birefringent walk-off. 相似文献
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D. Dudal S. P. Sorella N. Vandersickel 《The European Physical Journal C - Particles and Fields》2010,68(1-2):283-298
In this paper we provide strong evidence that there is no ambiguity in the choice of the horizon function underlying the Gribov–Zwanziger action. We show that there is only one correct possibility which is determined by the requirement of multiplicative renormalizability. As a consequence, this means that relations derived from other horizon functions cannot be given a consistent interpretation in terms of a local and renormalizable quantum field theory. In addition, we also discuss that the Kugo–Ojima functions u(p 2) and w(p 2) can only be defined after renormalization of the underlying Green function(s). 相似文献
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Based on general expressions for quantum contributions to the free energy of a statistical system, an approach is developed making it possible to carry out a complete theoretical analysis of the equilibrium thermodynamic characteristics of argon-type crystals as a function of the isotopic mass. The theory is based on independently calculated (in fact, without fitting parameters) one-particle and two-particle distribution functions of the classical crystal and permits one to quantitatively describe the data on the lattice parameters of isotope crystals obtained from numerical experiments. It is pointed out that real experiments are needed to study the isotope effect in crystals of noble gases, especially in view of the fact that, according to the literature data, xenon undergoes an fcc-hcp phase transition under increased pressure. 相似文献
19.
C. Volk J. Schubert K. Weis S. Estévez?Hernández M. Akabori K. Sladek H. Hardtdegen T. Sch?pers 《Applied Physics A: Materials Science & Processing》2010,100(1):305-308
We investigated the properties of gadolinium scandate (GdScO3) as a gate dielectric for top-gate electrodes on undoped InAs nanowires. It is demonstrated that due to the high dielectric
constant of GdScO3 (k=22), a better control of the conductance of the nanowire is achieved compared to a reference SiO2-isolated back-gate electrode. We analyzed the output and transfer characteristics of top-gate-controlled InAs wires at room
temperature and at temperatures down to 4 K. Owing to the good coverage of the InAs nanowire by the 50-nm-thick GdScO3 layer, which was deposited by pulsed-laser deposition, the gate leakage current is sufficiently suppressed. 相似文献
20.
We present analytically the exact solution of the radial Schrödinger equation with the pseudoharmonic oscillator potential in constant positive curvature representation. Exact bound state eigenfunctions and eigenvalues obtained using factorization method. Finally, energy eigenvalues obtained here compared with the results of the theoretical methods in the limit of flat space. 相似文献