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1.
G. Acquaviva R. Di Criscienzo M. Tolotti L. Vanzo S. Zerbini 《International Journal of Theoretical Physics》2012,51(5):1555-1571
In the present paper, Unruh–DeWitt detectors are used in order to investigate the issue of temperature associated with a spherically
symmetric dynamical space-times. Firstly, we review the semi-classical tunneling method, then we introduce the Unruh–DeWitt
detector approach. We show that for the generic static black hole case and the FRW de Sitter case, making use of peculiar
Kodama trajectories, semiclassical and quantum field theoretic techniques give the same standard and well known thermal interpretation,
with an associated temperature, corrected by appropriate Tolman factors. For a FRW space-time interpolating de Sitter space
with the Einstein–de Sitter universe (that is a more realistic situation in the frame of ΛCDM cosmologies), we show that the detector response splits into a de Sitter contribution plus a fluctuating term containing
no trace of Boltzmann-like factors, but rather describing the way thermal equilibrium is reached in the late time limit. As
a consequence, and unlike the case of black holes, the identification of the dynamical surface gravity of a cosmological trapping
horizon as an effective temperature parameter seems lost, at least for our co-moving simplified detectors. The possibility
remains that a detector performing a proper motion along a Kodama trajectory may register something more, in which case the
horizon surface gravity would be associated more likely to vacuum correlations than to particle creation. 相似文献
2.
Relativistic effects on the precision of quantum metrology for particle detectors, such as two-level atoms are studied. The quantum Fisher information is used to estimate the phase sensitivity of atoms in non-inertial motions or in gravitational fields. The Unruh–DeWitt model is applicable to the investigation of the dynamics of a uniformly accelerated atom weakly coupled to a massless scalar vacuum field. When a measuring device is in the same relativistic motion as the atom, the dynamical behavior of quantum Fisher information as a function of Rindler proper time is obtained. It is found out that monotonic decrease in phase sensitivity is characteristic of dynamics of relativistic quantum estimation. The origin of the decay of quantum Fisher information is the thermal bath that the accelerated detector finds itself in due to the Unruh effect. To improve relativistic quantum metrology, we reasonably take into account two reflecting plane boundaries perpendicular to each other. The presence of the reflecting boundary can shield the detector from the thermal bath in some sense. 相似文献
3.
Bryce DeWitt 《General Relativity and Gravitation》2009,41(2):413-419
Bryce DeWitt was one of the great pioneers of quantum gravity. This unpublished lecture gives his recent views on the topic,
which we believe will be of great interest not only to researchers involved in modern attempts to quantize Einstein’s theory,
but also to a much wider audience. It is the first installment of a book “The Pursuit of Quantum Gravity 1946–2004; Memoirs
of Bryce DeWitt” that Cecile DeWitt is preparing. We would like to thank her for the permission to publish this lecture separately
in General Relativity and Gravitation. Readers who have unpublished material such as letters from Bryce, and would be willing
to send copies to Cecile, are hereby invited to do so. She would be very grateful. G.F.R. Ellis, H. Nicolai (Editors-in-chief).
This article was found in Bryce’s files without references and without an indication of its purpose.
References and the name of a previously anonymous student have been supplied by Cecile DeWitt and Brandon DiNunno.
Bryce DeWitt (1923–2004).
An erratum to this article can be found at 相似文献
4.
We discuss the transient and steady state fluctuation relation for a mechanical system in contact with two deterministic thermostats
at different temperatures. The system is a modified Lorentz gas in which the fixed scatterers exchange energy with the gas
of particles, and the thermostats are modelled by two Nosé-Hoover thermostats applied at the boundaries of the system. The
transient fluctuation relation, which holds only for a precise choice of the initial ensemble, is verified at all times, as
expected. Times longer than the mesoscopic scale, needed for local equilibrium to be settled, are required if a different
initial ensemble is considered. This shows how the transient fluctuation relation asymptotically leads to the steady state
relation when, as explicitly checked in our systems, the condition found in (D.J. Searles, et al., J. Stat. Phys. 128:1337,
2007), for the validity of the steady state fluctuation relation, is verified. For the steady state fluctuations of the phase
space contraction rate Λ and of the dissipation function Ω, a similar relaxation regime at shorter averaging times is found.
The quantity Ω satisfies with good accuracy the fluctuation relation for times larger than the mesoscopic time scale; the
quantity Λ appears to begin a monotonic convergence after such times. This is consistent with the fact that Ω and Λ differ
by a total time derivative, and that the tails of the probability distribution function of Λ are Gaussian. 相似文献
5.
Verlinde’s recent work, which showed that gravity may be explained as entropic force caused by the changes of information
associated with the positions of material bodies, is extended to study the Unruh–Verlinde temperature and energy of a static
spherically symmetric charged black hole. The results indicate that the Unruh–Verlinde temperature is equal to the Hawking
temperature at the outer and inner horizons. The energy is dependent on the radius of the screen, which is also a consequence
of the Gauss’ laws of gravity and electrostatics. 相似文献
6.
V. I. Ritus 《Journal of Experimental and Theoretical Physics》2006,102(4):582-602
The symmetry manifests itself in exact relations between the Bogoliubov coefficients for processes induced by an accelerated
point mirror in 1 + 1 dimensional space and the current (charge) densities for the processes caused by an accelerated point
charge in 3 + 1 dimensional space. The spectra of pairs of Bose (Fermi) massless quanta emitted by the mirror coincide with
the spectra of photons (scalar quanta) emitted by the electric (scalar) charge up to the factor e
2/ħc. The integral relation between the propagator of a pair of oppositely directed massless particles in 1 + 1 dimensional space
and the propagator of a single particle in 3 + 1 dimensional space leads to the equality of the vacuum-vacuum amplitudes for
the charge and the mirror if the mean number of created particles is small and the charge e = √ħc. Due to the symmetry, the mass shifts of electric and scalar charges (the sources of Bose fields with spin 1 and 0 in 3 +
1 dimensional space) for the trajectories with a subluminal relative velocity β12 of the ends and the maximum proper acceleration w
0 are expressed in terms of the heat capacity (or energy) spectral densities of Bose and Fermi gases of massless particles
with the temperature w
0/2π in 1 + 1 dimensional space. Thus, the acceleration excites 1-dimensional oscillation in the proper field of a charge,
and the energy of oscillation is partly deexcited in the form of real quanta and partly remains in the field. As a result,
the mass shift of an accelerated electric charge is nonzero and negative, while that of a scalar charge is zero. The symmetry
is extended to the mirror and charge interactions with the fields carrying spacelike momenta and defining the Bogoliubov coefficients
αB,F. The traces trαB,F, which describe the vector and scalar interactions of the accelerated mirror with a uniformly moving detector, were found
in analytic form for two mirror trajectories with subluminal velocities of the ends. The symmetry predicts one and the same
value e
0
= √ħc for the electric and scalar charges in 3 + 1 dimensional space. Arguments are adduced in favor of the conclusion that this
value and the corresponding value α0 = 1/4π of the fine structure constant are the bare, nonrenormalized values.
The text was submitted by the author in English. 相似文献
7.
Nima Khosravi Hamid Reza Sepangi Babak Vakili 《General Relativity and Gravitation》2010,42(5):1081-1102
We employ the familiar canonical quantization procedure in a given cosmological setting to argue that it is equivalent to
and results in the same physical picture if one considers the deformation of the phase-space instead. To show this we use
a probabilistic evolutionary process to make the solutions of these different approaches comparable. Specific model theories
are used to show that the independent solutions of the resulting Wheeler–DeWitt equation are equivalent to solutions of the
deformation method with different signs for the deformation parameter. We also argued that since the Wheeler–DeWitt equation
is a direct consequence of diffeomorphism invariance, this equivalence is only true provided that the deformation of phase-space
does not break such an invariance. 相似文献
8.
We study the response of a uniformly accelerated detector modeled by a two-level atom nonlinearly coupled to vacuum massless Rarita–Schwinger fields. We first generalize the formalism developed by Dalibard, Dupont-Roc, and Cohen-Tannoudji in the linear coupling case, and we then calculate the mean rate of change of the atomic energy of the accelerated atom. Our result shows that a uniformly accelerated atom in its ground state interacting with vacuum Rarita–Schwinger field fluctuations would spontaneously transition to an excited state and the unique feature in contrast to the case of the atom coupled to the scalar, electromagnetic and Dirac fields is the appearance of terms in the excitation rate which are proportional to the sixth and eighth powers of acceleration. 相似文献
9.
José Edgar Madriz Aguilar Carlos Romero Adriano Barros 《General Relativity and Gravitation》2008,40(1):117-130
We investigate, in the context of five-dimensional (5D) Brans–Dicke theory of gravity, the idea that macroscopic matter configurations
can be generated from pure vacuum in five dimensions, an approach first proposed by Wesson and collaborators in the framework
of 5D general relativity. We show that the 5D Brans–Dicke vacuum equations when reduced to four dimensions (4D) lead to a
modified version of Brans–Dicke theory in 4D. As an application of the formalism, we obtain two 5D extensions of 4D O’Hanlon
and Tupper vacuum solution and show that they lead two different cosmological scenarios in 4D. 相似文献
10.
P. Pedram M. Mirzaei S. Jalalzadeh S. S. Gousheh 《General Relativity and Gravitation》2008,40(8):1663-1681
We present perfect fluid Friedmann–Robertson–Walker quantum cosmological models in the presence of negative cosmological constant.
In this work the Schutz’s variational formalism is applied for radiation, dust, cosmic string, and domain wall dominated Universes
with positive, negative, and zero constant spatial curvature. In this approach the notion of time can be recovered. These
give rise to Wheeler–DeWitt equations for the scale factor. We find their eigenvalues and eigenfunctions by using Spectral
Method. After that, we use the eigenfunctions in order to construct wave packets for each case and evaluate the time-dependent
expectation value of the scale factors, which are found to oscillate between finite maximum and minimum values. Since the
expectation values of the scale factors never tends to the singular point, we have an initial indication that these models
may not have singularities at the quantum level. 相似文献
11.
R. Aldrovandi R. R. Cuzinatto L. G. Medeiros 《The European Physical Journal C - Particles and Fields》2008,58(3):483-497
Equations of state for the early universe including realistic interactions between constituents are formulated. Under certain
hypotheses, these equations are able to generate an inflationary regime prior to the period of the nucleosynthesis. The resulting
accelerated expansion is intense enough to solve the flatness and horizon problems. In the cases of a curvature parameter
κ equal to 0 or +1, the model is able to avoid the initial singularity and offers a natural explanation for why the universe
is in expansion. All the results are valid only for a matter–antimatter symmetric universe. 相似文献
12.
A. G. Pakhomov 《Russian Physics Journal》2007,50(9):885-890
A condition for accelerated expansion of the Universe is derived from multidimensional formulas of gravitation, which is a
generalization of the general theory of relativity for n dimensions. The model of a one-component ideal isotropic substance
with a power-law diagonal metric is used as initial one. Restrictions on the state equations of our 3D space and accompanying
additional dimensions are obtained.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 36–40, September, 2007. 相似文献
13.
V.A. Khoze M.I. Konchatnij N.P. Merenkov G. Pancheri L. Trentadue O.N. Shekhovzova 《The European Physical Journal C - Particles and Fields》2001,18(3):481-490
The hadronic invariant mass distribution for the process of electron–positron annihilation into a pair of charged pions accompanied by a photon radiated from the initial state has been studied for the region of DANE energies. The Born cross–section and the electromagnetic radiative corrections to it are calculated for realistic conditions of the KLOE detector. The dependence on the physical parameters which define the event selection is obtained. 相似文献
14.
S. De Nicola R. Fedele D. Jovanovic B. Malomed M. A. Man'ko V. I. Man'ko P. K. Shukla 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(1):113-119
We present one-dimensional (1D) stability analysis of a recently
proposed method to filter and control localized states of the
Bose–Einstein condensate (BEC), based on novel trapping
techniques that allow one to conceive methods to select a
particular BEC shape by controlling and manipulating the external
potential well in the three-dimensional (3D)
Gross–Pitaevskii equation (GPE). Within the framework of this
method, under suitable conditions, the GPE can be exactly
decomposed into a pair of coupled equations: a transverse
two-dimensional (2D) linear Schr?dinger equation and a
one-dimensional (1D) longitudinal nonlinear Schr?dinger
equation (NLSE) with, in a general case, a time-dependent
nonlinear coupling coefficient. We review the general idea how
to filter and control localized solutions of the GPE. Then,
the 1D longitudinal NLSE is numerically solved
with suitable non-ideal controlling potentials that differ from
the ideal one so as to introduce relatively small errors
in the designed spatial profile. It is shown that a BEC with an
asymmetric initial position in the confining potential exhibits
breather-like oscillations in the longitudinal direction but,
nevertheless, the BEC state remains confined within the potential
well for a long time. In particular, while the condensate remains
essentially stable, preserving its longitudinal soliton-like
shape, only a small part is lost into “radiation”. 相似文献
15.
16.
Hugo A. Morales-Técotl Omar Pedraza Luis O. Pimentel 《General Relativity and Gravitation》2007,39(8):1185-1202
Testing extra dimensions at low-energies may lead to interesting effects. In this work a test point charge is taken to move
uniformly in the 3D subspace of a (3 + n)-brane embedded in a (3 + n + 1)-space with n compact and one warped infinite spatial extra dimensions. We found that the electromagnetic potentials of the point charge
match standard Liennard–Wiechert’s at large distances but differ from them close to it. These are finite at the position of
the charge and produce finite self-energies. We also studied a localized Hydrogen atom and take the deviation from the standard
Coulomb potential as a perturbation. This produces a Lamb shift that is compared with known experimental data to set bounds
for the parameter of the model. This work provides details and extends results reported in a previous Letter.
We are pleased to dedicate this work to Professor Octavio Obregón on occasion of his 60th birthday. H. A. Morales-Técotl is
an associate member of the Abdus Salam ICTP, Trieste Italy. 相似文献
17.
Time Differential gamma–gamma Perturbed Angular Correlation spectroscopy has traditionally been done using scintillation detectors
along with constant–fraction discriminators, spectroscopy amplifiers, single channel analyzers, and time to amplitude detectors.
We describe a new generation spectrometer where these electronics are replaced by high speed digital transient recorders that
record the output from each scintillation detector. The energy and time-of-arrival of gamma rays in any detector can be determined
accurately. Many experimental difficulties related to electronics are eliminated; the number of detectors can be increased
with no increase in complexity of the apparatus; coincidences among any two detectors are measurable; and coincidences separated
by as little as a ns are detectable in principle within one detector. All energies are collected, and energy windows are imposed
by software filtering, permitting both high energy resolution and high data-gathering power. 相似文献
18.
The structure, thermal expansion coefficients, electrical and electrochemical properties of Ce1−xMxO2−δ (M=Bi, La, Pr, Eu, Tb; x=0–0.30) solid solutions, prepared hydrothermally for the first time, are surveyed. For all cation
substitution a solubility limit depending on the cation size was found.
The uniformly small particle size (10–50 nm) of the hydrothermally prepared materials allows sintering of the samples into
highly dense ceramic pellets at 1300–1400 °C, a significantly lower temperature, compared to that at 1600–1650 °C required
for samples prepared by solid state techniques. X-ray absorption near edge spectroscopy (XANES) was used for the identification
of Tb3+/Tb4+ or Pr3+/Pr4+ ions. The maximum of total conductivity in all solid solutions was found for x ∼ 0.15–0.25 with electronic contribution to
the total conductivity ∼ 50 % for Tb/Pr substitution and close to zero in all other cases. The conductivity becomes more ionic
with decreasing Tb/Pr substitution. The thermal expansion coefficients, determined from high-temperature X-ray diffraction
data, are 11.7×10−6 K−1 for CeO2 and slowly decrease for Tb and increase for all other cases with increasing substitution.
Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000. 相似文献
19.
The quantization of a homogeneous isotropic Friedmann model of the universe that is occupied by a quantized scalar field is considered in the superspace approach of Wheeler and DeWitt. Steady-state perturbation theory is used to show that in the region N 1, 10–23, N=1, 2,..., where it is applicable, the steady-state solutions of the DeWitt equation have a discrete spectrum corresponding to discrete energy levels of the steady state of the cosmological model M= (2N + 1)Mo, Mo = 10–5 g.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 113–117, July, 1977.In conclusion the authors thank Sen. Sci. Colleague D. V. Galtsov and Sen. Sci. Colleague V. R. Khalilov, and also the members of the seminar conducted by Profs. V. P. Shelest and K. P. Stanyukovich. 相似文献
20.
Various aspects of the C-metric representing two rotating charged black holes accelerated in opposite directions are summarized
and its limits are considered. A particular attention is paid to the special-relativistic limit in which the electromagnetic
field becomes the “magic field” of two oppositely accelerated rotating charged relativistic discs. When the acceleration vanishes
the usual electromagnetic magic field of the Kerr–Newman black hole with gravitational constant set to zero arises. Properties
of the accelerated discs and the fields produced are studied and illustrated graphically. The charges at the rim of the accelerated
discs move along spiral trajectories with the speed of light. If the magic field has some deeper connection with the field
of the Dirac electron, as is sometimes conjectured because of the same gyromagnetic ratio, the “accelerating magic field”
represents the electromagnetic field of a uniformly accelerated spinning electron. It generalizes the classical Born’s solution
for two uniformly accelerated monopole charges. 相似文献