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Is there emitted radiation in Unruh effect?  [PDF]
B. L. Hu,Alpan Raval
Physics , 2000,
Abstract: The thermal radiance felt by a uniformly accelerated detector/oscillator/atom--the Unruh effect-- is often mistaken to be some emitted radiation detectable by an observer/probe/sensor. Here we show by an explicit calculation of the energy momentum tensor of a quantum scalar field that, at least in 1+1 dimension, while a polarization cloud is found to exist around the particle trajectory, there is no emitted radiation from a uniformly accelerated oscillator in equilibrium conditions. Under nonequilibrium conditions which can prevail for non-uniformly accelerated trajectories or before the atom or oscillator reaches equilibrium, there is conceivably radiation emitted, but that is not what Unruh effect entails.
Unruh gamma radiation at RHIC?  [PDF]
T. S. Biro,M. Gyulassy,Z. Schram
Physics , 2011, DOI: 10.1016/j.physletb.2011.12.062
Abstract: Varying the proposition that acceleration itself would simulate a thermal environment, we investigate the semiclassical photon radiation as a possible telemetric thermometer of accelerated charges. Based on the classical Jackson formula we obtain the equivalent photon intensity spectrum stemming from a constantly accelerated charge and demonstrate its resemblances to a thermal distribution for high transverse momenta. The inverse transverse slope differs from the famous Unruh temperature: it is larger by a factor of pi. We compare the resulting direct photon spectrum with experimental data for AuAu collisions at RHIC and speculate about further, analytically solvable acceleration histories.
On the Cancellation Mechanism of Radiation from the Unruh detector  [PDF]
S. Iso,K. Yamamoto,S. Zhang
Physics , 2013,
Abstract: A uniformly accelerated detector (Unruh detector) in the Minkowski vacuum is excited as if it is exposed to the thermal bath with temperature proportional to its acceleration. In the inertial frame, since both of an excitation and a deexcitation of the detector are accompanied by emission of radiation into the Minkowski vacuum, one may suspect that the Unruh detector emits radiation like the Larmor radiation from an accelerated charged particle. However, it is known that the radiation is miraculously cancelled by a quantum interference effect. In this paper, we investigate under what condition the radiation cancels out. We first show that the cancellation occurs if the Green function satisfies a relation similar to the Kubo-Martin-Schwinger (KMS) condition. We then study two examples, Unruh detectors in the 3+1 dimensional Minkowski spacetime and in the de Sitter spacetime. In both cases, the relation holds only in a restricted region of the spacetime, but the radiation is cancelled in the whole spacetime. Hence the KMS-like relation is necessary but not sufficient for the cancellation to occur.
Unruh effect as particular Frenet-Serret vacuum radiation and detection proposals  [PDF]
H. C. Rosu
Physics , 2003,
Abstract: The paradigmatic Unruh radiation is an ideal and simple case of stationary scalar vacuum radiation patterns related to worldlines defined as Frenet-Serret curves. We briefly review the corresponding body of theoretical literature as well as the proposals that have been suggested to detect these types of quantum field radiation patterns
On Hawking/Unruh Process: Where does the Radiation Come from?  [PDF]
Tadas K. Nakamura
Physics , 2008,
Abstract: The energy source of the radiation in Unruh/Hawking process is investigated with emphasis on the particle number definition based on conservation laws. It has been shown that the particle radiation is not the result of pair creation by the gravitational force, but the result of difference in the conservation laws to define the particle number. The origin of the radiated energy in the distant future corresponds to the zero point oscillations with infinitely large wave numbers. This result implies the need of reconsideration on the scenario of black hole evaporation.
Hawking radiation via Anomaly and Tunneling method from Unruh's and Canonical acoustic black hole  [PDF]
Ramon Becar,Pablo Gonzalez,Gustavo Pulgar,Joel Saavedra
Physics , 2008,
Abstract: Hawking radiation from Unruh's and Canonical acoustic black hole is considered from viewpoint of anomaly cancellation method developed by Robinson and Wilczek. Thus, the physics near the horizon can be described using an infinite collection of massless two-dimensional scalar fields in the background of a dilaton and the gravitational anomaly is canceled by the flux of a 1 + 1 dimensional blackbody at the Hawking temperature of the space-time. Consequently, by this method, we can get the Hawking's temperature for Canonical and Unruh's acoustic black hole.
Why does the Unruh effect rely on Lorentz invariance, while Hawking radiation does not ?  [PDF]
David Campo,Nathaniel Obadia
Physics , 2010,
Abstract: We show that without Lorentz invariance, the Unruh effect does not exist. We use modified dispersion relations and describe in turn: the non-thermal nature of the vacuum (defined in the preferred frame) restricted to the Rindler wedge, the loss of the KMS property of the Wigthman function, the transition amplitudes and transition rates of a uniformaly accelerated detector. This situation seems to contrast with the Hawking radiation of acoustic black holes, which under certain assumptions has been shown to be robust to a breaking of Lorentz symmetry. We explain this discrepancy.
Uniformly Accelerated Charge in a Quantum Field: From Radiation Reaction to Unruh Effect  [PDF]
Philip R. Johnson,B. L. Hu
Physics , 2005, DOI: 10.1007/s10701-005-6404-1
Abstract: We present a stochastic theory for the nonequilibrium dynamics of charges moving in a quantum scalar field based on the worldline influence functional and the close-time-path (CTP or in-in) coarse-grained effective action method. We summarize (1) the steps leading to a derivation of a modified Abraham-Lorentz-Dirac equation whose solutions describe a causal semiclassical theory free of runaway solutions and without pre-acceleration patholigies, and (2) the transformation to a stochastic effective action which generates Abraham-Lorentz-Dirac-Langevin equations depicting the fluctuations of a particle's worldline around its semiclassical trajectory. We point out the misconceptions in trying to directly relate radiation reaction to vacuum fluctuations, and discuss how, in the framework that we have developed, an array of phenomena, from classical radiation and radiation reaction to the Unruh effect, are interrelated to each other as manifestations at the classical, stochastic and quantum levels. Using this method we give a derivation of the Unruh effect for the spacetime worldline coordinates of an accelerating charge. Our stochastic particle-field model, which was inspired by earlier work in cosmological backreaction, can be used as an analog to the black hole backreaction problem describing the stochastic dynamics of a black hole event horizon.
Refractive index perturbations -- Unruh effect, Hawking radiation or dynamical Casimir effect?  [PDF]
Ralf Schützhold
Physics , 2011,
Abstract: Motivated by recent experimental progress to manipulate the refractive index of dielectric materials by strong laser beams, we study some aspects of the quantum radiation created by such refractive index perturbations.
Accelerated Electrons and the Unruh Effect  [PDF]
Jon Magne Leinaas
Physics , 1998,
Abstract: Quantum effects for electrons in a storage ring are studied in a co-moving, accelerated frame. The polarization effect due to spin flip synchrotron radiation is examined by treating the electron as a simple quantum mechanical two-level system coupled to the orbital motion and to the radiation field. The excitations of the spin system are related to the Unruh effect, i.e. the effect that an accelerated radiation detector is thermally excited by vacuum fluctuations. The importance of orbital fluctuations is pointed out and the vertical fluctuations are examined.
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