Unruh Temperature Research Articles

Restoration of dynamically broken chiral and color symmetries for an accelerated observer

We study the behavior of quark and diquark condensates at finite Unruh temperature as seen by an accelerated observer. The gap equations for these condensates have been obtained with consideration of a finite chemical potential. Critical values of the acceleration for the restoration of chiral and color symmetries have been estimated.

Spontaneous excitation of an accelerated multilevel atom in dipole coupling to the derivative of a scalar field

We study the spontaneous excitation of an accelerated multilevel atom in dipole coupling to the derivative of a massless quantum scalar field and separately calculate the contributions of the vacuum fluctuation and radiation reaction to the rate of change of the mean atomic energy of the atom. It is found that, in contrast to the case where a monopole-like interaction between the atom and the field is assumed, there appear extra corrections proportional to the acceleration squared, in addition to corrections which can be viewed as a result of an ambient thermal bath at the Unruh temperature, as compared with the inertial case, and the acceleration induced correction terms show anisotropy with the contribution from longitudinal polarization being four times that from the transverse polarization for isotropically polarized accelerated atoms. Our results suggest that the effect of acceleration on the rate of change of the mean atomic energy is dependent not only on the quantum field to which the atom is coupled, but also on the type of the interaction even if the same scalar quantum field is considered.

Nonequilibrium Thermodynamics of Spacetime

It has previously been shown that the Einstein equation can be derived from the requirement that the Clausius relation dS=deltaQ/T hold for all local acceleration horizons through each spacetime point, where is one-quarter the horizon area change in Planck units and deltaQ and T are the energy flux across the horizon and the Unruh temperature seen by an accelerating observer just inside the horizon. Here we show that a curvature correction to the entropy that is polynomial in the Ricci scalar requires a nonequilibrium treatment. The corresponding field equation is derived from the entropy balance relation dS=deltaQ/T+diS, where diS is a bulk viscosity entropy production term that we determine by imposing energy-momentum conservation. Entropy production can also be included in pure Einstein theory by allowing for shear viscosity of the horizon.

Is there Unruh radiation?

We present an exact analysis of an oscillator (the detector) moving under a constant force with respect to zero-temperature vacuum and coupled to a one-dimensional scalar field. We show that this system does not radiate despite the fact that it thermalizes at the Unruh temperature. We remark upon a differing opinion expressed regarding a system coupled to the electromagnetic field.

Global embedding ofD-dimensional black holes with a cosmological constant in Minkowskian spacetimes: Matching between Hawking temperature and Unruh temperature

We study the matching between the Hawking temperature of a large class of static D-dimensional black holes and the Unruh temperature of the corresponding higher dimensional Rindler spacetime. In order to accomplish this task we find the global embedding of the D-dimensional black holes into a higher dimensional Minkowskian spacetime, called the global embedding Minkowskian spacetime procedure (GEMS procedure). These global embedding transformations are important on their own, since they provide a powerful tool that simplifies the study of black hole physics by working instead, but equivalently, in an accelerated Rindler frame in a flat background geometry. We discuss neutral and charged Tangherlini black holes with and without cosmological constant, and in the negative cosmological constant case, we consider the three allowed topologies for the horizons (spherical, cylindrical/toroidal and hyperbolic).

Stable quantum systems in anti–de Sitter space: Causality, independence, and spectral properties

If a state is passive for uniformly accelerated observers in n-dimensional (n⩾2) anti–de Sitter (Ads) space–time (i.e., cannot be used by them to operate a perpetuum mobile), they will (a) register a universal value of the Unruh temperature, (b) discover a PCT symmetry, and (c) find that observables in complementary wedge-shaped regions necessarily commute with each other in this state. The stability properties of such a passive state induce a “geodesic causal structure” on AdS and concommitant locality relations. It is shown that observables in these complementary wedge-shaped regions fulfill strong additional independence conditions. In two-dimensional AdS these even suffice to enable the derivation of a nontrivial, local, covariant net indexed by bounded space–time regions. All these results are model-independent and hold in any theory which is compatible with a weak notion of space–time localization. Examples are provided of models satisfying the hypotheses of these theorems.

Simplified derivation of the Hawking–Unruh temperature for an accelerated observer in vacuum

A detector undergoing uniform acceleration a in a vacuum field responds as though it were immersed in thermal radiation of temperature T=ℏa/2πkc. An intuitive derivation of this result is given for a scalar field in one spatial dimension. The approach is extended to the case where the field detected by the accelerated observer is a spin 1/2 Dirac field.

Entropy, holography, and the second law.

The geometric entropy in quantum field theory is not a Lorentz scalar and has no invariant meaning, while the black hole entropy is invariant. Renormalization of entropy and energy for reduced density matrices may lead to the negative free energy even if no boundary conditions are imposed. The presence of particles outside the horizon of a uniformly accelerated observer prevents the description in terms of a single Unruh temperature.

Quantum gravity, Clifford algebras, fuzzy set theory and the fundamental constants of nature

In a recent paper entitled “Quantum gravity from descriptive set theory”, published in Chaos, Solitons & Fractals, we considered following the P-adic quantum theory, the possibility of abandoning the Archimedean axiom and introducing a fundamental physical limitation on the smallest length in quantum spacetime. Proceeding that way we arrived at the conclusion that maximising the Hawking–Bekenstein informational content of spacetime makes the existence of a transfinite geometry for physical “spacetime” plausible or even inevitable. Subsequently we introduced a mathematical description of a transfinite, non-Archimedean geometry using descriptive set theory where a similar conclusion regarding the transfiniteness of quantum spacetime may be drawn from the existence of the Unruh temperature. In particular we introduced a straight forward logarithmic gauge transformation linking, as far as we are aware for the first time, classical gravity with the electroweak via a version of informational entropy. That way we found using ε (∞) and complexity theory that α ̄ G =(2) α ̄ ew −1 =1.7×10 38 where α ̄ G is the dimensionless Newton gravity constant and α ̄ ew =128 is the fine structure constant at the electroweak unification scale. The present work is concerned with more or less the same category of fundamental questions pertinent to quantum gravity. However we switch our mathematical apparatus to a combination of Clifford algebras and set theory. In doing that, the central and vital role of the work of D. Finkelstein becomes much more tangible and clearer than in most of our previous works.

Diamond's temperature: Unruh effect for bounded trajectories and thermal time hypothesis

We study the Unruh effect for an observer with a finite lifetime, using the thermal time hypothesis. The thermal time hypothesis maintains that: (i) time is the physical quantity determined by the flow defined by a state over an observable algebra and (ii) when this flow is proportional to a geometric flow in spacetime, the temperature is the ratio between flow parameter and proper time. An eternal accelerated Unruh observer has access to the local algebra associated with a Rindler wedge. The flow defined by the Minkowski vacuum of a field theory over this algebra is proportional to a flow in spacetime and the associated temperature is the Unruh temperature. An observer with a finite lifetime has access to the local observable algebra associated with a finite spacetime region called a ‘diamond’. The flow defined by the Minkowski vacuum of a (four-dimensional, conformally invariant) quantum field theory over this algebra is also proportional to a flow in spacetime. The associated temperature generalizes the Unruh temperature to finite lifetime observers. Furthermore, this temperature does not vanish even in the limit in which the acceleration is zero. The temperature associated with an inertial observer with lifetime , which we denote as ‘diamond's temperature’, is . This temperature is related to the fact that a finite lifetime observer does not have access to all the degrees of freedom of the quantum field theory. However, we do not attempt to provide any physical interpretation of our proposed assignment of a temperature.

On the Gravitational Energy of the Hawking Wormhole

The surface energy for a conformally flat space–time which represents the Hawking wormhole in spherical (static) Rindler coordinates is computed using the Hawking–Hunter formalism for nonasymptotically flat space–times. The physical gravitational Hamiltonian is proportional to the Rindler acceleration g of the hyperbolic observer and is finite on the event horizon ξ=b (b — the Planck length, ξ — the Minkowski interval). The corresponding temperature of the system of particles associated to the massless scalar field Ψ=1-b2/ξ2, coupled conformally to Einstein's equations, is given by the Davies–Unruh temperature up to a constant factor of order unity.

Uniformly accelerated black holes

The static and stationary C-metric are revisited in a generic framework and their interpretations studied in some detail. Specially those with two event horizons, one for the black hole and another for the acceleration. We found that: i) The spacetime of an accelerated static black hole is plagued by either conical singularities or lack of smoothness and compactness of the black hole horizon; ii) By using standard black hole thermodynamics we show that accelerated black holes have higher Hawking temperature than Unruh temperature of the accelerated frame; iii) The usual upper bound on the product of the mass and acceleration parameters <1/sqrt(27) is just a coordinate artifact. The main results are extended to accelerated rotating black holes with no significant changes.

Replica-deformation of the SU(2)-invariant Thirring model via solutions of the qKZ equation

The response of an integrable QFT under variation of the Unruh temperature has recently been shown to be computable from an S-matrix preserving (“replica”) deformation of the form factor approach. We show that replica-deformed form factors of the SU(2)-invariant Thirring model can be found among the solutions of the rational sl 2 -type quantum Knizhnik–Zamolodchikov equation at generic level. We show that modulo conserved charge solutions the deformed form factors are in one-to-one correspondence to the ones at level zero and use this to conjecture the deformed form factors of the Noether current in our model.

Exact two-particle matrix elements in S-matrix preserving deformation of integrable QFTs

In a recent paper it was shown that the response of an integrable QFT under variation of the Unruh temperature can be computed from a S-matrix preserving deformation of the form factor approach. We give explicit expressions for the deformed two-particle form factors for various integrable models: The Sine-Gordon and SU(2) Thirring model, several perturbed minimal CFTs and the real coupling affine Toda series. A uniform pattern is found to emerge when both the S-matrix and the deformed form factors are expressed in terms Barnes' multi-periodic functions.

Varying the Unruh temperature in integrable quantum field theories

A computational scheme is developed to determine the response of a quantum field theory (QFT) with a factorized scattering operator under a variation of the Unruh temperature. To this end a new family of integrable systems is introduced, obtained by deforming such QFTs in a way that preserves the bootstrap S-matrix. The deformation parameter β plays the role of an inverse temperature for the thermal equilibrium states associated with the Rindler wedge, β = 2 π being the QFT value. The form factor approach provides an explicit computational scheme for the β ≠ 2 π systems, enforcing in particular a modification of the underlying kinematical arena. As examples deformed counterparts of the Ising model and the sinh-Gordon model are considered.

Unruh effect with back reaction—A first-quantized treatment

First order corrections to the Unruh effect are calculated from a model of an accelerated particle detector of finite mass. We show that quantum smearing of the trajectory and large recoil essentially do not modify the Unruh effect. Nevertheless, we find corrections to the thermal distribution and to the Unruh temperature. In a certain limit, when the distribution at equilibrium remains exactly thermal, the corrected temperature is found to be $T = T_U( 1 - T_U/M)$, where $T_U$ is the Unruh temperature. We estimate the consequent corrections to the Hawking temperature and the black hole entropy, and comment on the relationship to the problem of trans-planckian frequencies.

Schwinger mechanism, Unruh effect, and production of accelerated black holes

We compute the corrections to the transition amplitudes of an accelerated Unruh ``box'' that arise when the accelerated box is replaced by a ``two level ion'' immersed in a constant electric field and treated in second quantization. There are two kinds of corrections, those due to recoil effects induced by the momentum transfers and those due to pair creation. Taken together, these corrections show that there is a direct relationship between pair creation amplitudes described by the Heisenberg-Euler-Schwinger mechanism and the Unruh effect, i.e. the thermalisation of accelerated systems at temperature $a/ 2 \pi$ where $a$ is the acceleration. In particular, there is a thermodynamical consistency between both effects whose origin is that the euclidean action governing pair creation rates acts as an entropy in delivering the Unruh temperature. Upon considering pair creation of charged black holes in an electric field, these relationships explain why black holes are created from vacuum in thermal equilibrium, i.e. with their Hawking temperature equal to their Unruh temperature.

Thermodynamics of spacetime: The Einstein equation of state.

The Einstein equation is derived from the proportionality of entropy and horizon area together with the fundamental relation $\delta Q=TdS$ connecting heat, entropy, and temperature. The key idea is to demand that this relation hold for all the local Rindler causal horizons through each spacetime point, with $\delta Q$ and $T$ interpreted as the energy flux and Unruh temperature seen by an accelerated observer just inside the horizon. This requires that gravitational lensing by matter energy distorts the causal structure of spacetime in just such a way that the Einstein equation holds. Viewed in this way, the Einstein equation is an equation of state. This perspective suggests that it may be no more appropriate to canonically quantize the Einstein equation than it would be to quantize the wave equation for sound in air.

Von Neumann algebra automorphisms and time-thermodynamics relation in generally covariant quantum theories

We consider the cluster of problems raised by the relation between the notion of time, gravitational theory, quantum theory and thermodynamics; in particular, we address the problem of relating the `timelessness' of the hypothetical, fundamental generally covariant quantum field theory with the `evidence' of the flow of time. By using the algebraic formulation of quantum theory, we propose a unifying perspective on these problems, based on the hypothesis that in a generally covariant quantum theory the physical time flow is not a universal property of the mechanical theory, but rather it is determined by the thermodynamical state of the system (`thermal time hypothesis'). We implement this hypothesis by using a key structural property of von Neumann algebras: the Tomita--Takesaki theorem, which allows us to derive a time flow, namely a one-parameter group of automorphisms of the observable algebra, from a generic thermal physical state. We study this time flow, its classical limit, and we relate it to various characteristic theoretical facts, such as the Unruh temperature and the Hawking radiation. We point out the existence of a state-independent notion of `time', given by the canonical one-parameter subgroup of outer automorphisms provided by the co-cycle Radon--Nikodym theorem.

Evidence for Unruh's effect in hardon physics

In order that confinement should survive, light quarks inside hadrons have a very high acceleration and will feel a thermal bath with an Unruh temperature near 137 MeV. We show that this temperature is consistent with the experimentally observed departure from the Gottfried sum rule for the difference of the proton and neutron structure functions in deep inelastic electron scattering.