Geometric phase under the Unruh effect with intermediate statistics

Utilizing the geometric phase (GP) acquired in a quantum evolution, we manifest the thermality and quantum nature of the Unruh effect of an accelerating detector. We consider an UDW detector coupling to a conformal field in Minkowski spacetime, whose response spectrum exhibits an intermediate statistics of (1+1) anyon field. We find that comparing to an inertial moving detector, the GP in accelerating frame is modified after the nonunitary evolution of the detector due to the Unruh effect. We show that such modification can distinguish the different thermalizing ways of the detector, which depends on the scaling dimension of the conformal primary field. Finally, we estimate the difference between the GP under the Unruh radiation and that in a thermal bath for a static observer, which reveals the quantum origin of the Unruh effect rather than a conventional thermal noise.     

Measurement-induced-nonlocality via the Unruh effect

Treated beyond the single-mode approximation, Measurement-Induced-Nonlocality (MIN) is investigated for both Dirac and Bosonic fields in non-inertial frames. Two distinct differences between the Dirac and Bosonic fields are: (i) the MIN for Dirac fields persists for any acceleration, while the quantity for Bosonic fields does decay to zero in the infinite acceleration limit; (ii) the dynamic behaviors of the MIN for Dirac fields is quite different from the Bosonic fields case. Besides, we also study the nonlocality for Dirac fields and find that the MIN is more general than the quantum nonlocality related to violation of Bell’s inequalities. Meanwhile some discussions of geometric discord are presented too.     

Does the Unruh effect exist?

It is shown that quantization on the Fulling modes presupposes that the field vanishes on the spatial boundaries of the Rindler manifold. For this reason, Rindler space is physically unrelated with Minkowski space and the state of a Rindler observer cannot be described by the equilibrium density matrix with the Fulling-Unruh temperature. Therefore it is pointless to talk about an Unruh effect. The question of the behavior of an accelerated detector in the physical formulation of the problem remains open. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 12, 861–866 (25 June 1997)     

Observable Dirac-type singularities in Berry's phase and the monopole

A three-dimensional generalization of the sign-change ( pi phase shift) rule for adiabatic cycles of spin-1/2 or two-state wave functions encircling a degeneracy in the parameter space of the Hamiltonian yields a Dirac-type singularity wherein any closed circuit of the adiabatic cycle in which the degeneracy is "looped" results in an observable +/-2pi phase shift. It is concluded that an interferometer loop similarly taken around a magnetic monopole of strength n/2 yields an observable +/-2npi phase shift, n being an integer.     

Nonlocality and entanglement via the Unruh effect

Modeling the qubit by a two-level semiclassical detector coupled to a massless scalar field, we investigate how the Unruh effect affects the nonlocality and entanglement of two-qubit and three-qubit states when one of the entangled qubits is accelerated. Two distinct differences with the results of free field model in non-inertial frames are (i) for the two-qubit state, the CHSH inequality cannot be violated for sufficiently large but finite acceleration, furthermore, the concurrence will experience “sudden death”; and (ii) for the three-qubit state, not only does the entanglement vanish in the infinite acceleration limit, but also the Svetlichny inequality cannot be violated in the case of large acceleration.     

Berry's phase,commutators, and the Dirac sea

We discuss the connection between the Berry phase and the Schwinger term in generators of symmetry groups, and stress the relative minus sign between the anomalous commutator of the currents and the anomalous commutator of the full group generators.     

On the physical meaning of the Unruh effect

Simple arguments are presented that detectors moving with constant acceleration (even acceleration for a finite time) should detect particles. The effect is seen to be universal. Moreover, detectors undergoing linear acceleration and uniform circular motion both detect particles for the same physical reason. It is shown that the Unruh effect for a circularly orbiting electron in a constant external magnetic field used as a Unruh-DeWitt detector physically coincides with the experimentally verified Sokolov-Ternov effect. The text was submitted by the authors in English.     

On the physical meaning of the Unruh effect

Simple arguments are presented that detectors moving with constant acceleration (even acceleration for a finite time) should detect particles. The effect is seen to be universal. Moreover, detectors undergoing linear acceleration and uniform circular motion both detect particles for the same physical reason. It is shown that the Unruh effect for a circularly orbiting electron in a constant external magnetic field used as a Unruh-DeWitt detector physically coincides with the experimentally verified Sokolov-Ternov effect.     

On the classical limit of Berry's phase integrable systems

Berry's Phase is given by integration of a characteristic two form. We consider integrable systems defined by Weyl quantized classical Hamiltonians. It is shown that the limit of /i times this tow form is the curvature of the classical connection whose holonomy is the Hannay angels. A result of this type was derived by Berry [B2].     

Damour-Ruffini and Unruh theories of the Hawking effect

Internal relations between the Damour-Ruffini approach and the Unruh approach to dealing with the Hawking effects are shown. The Unruh-type analytical wave functions can be obtained by means of the analytical continuation method suggested by Damour and Ruffini. In fact, Unruh-type analytical wave functions are complex conjugate functions of Damour-Ruffini type. Normalizing each of them, or making use of them to construct the Bogoliubov transformation, one can get the same Hawking thermal spectrum. The pure state wave function defined on the connected complexr space-time manifold is a mixture showing thermal properties in the realr space-time manifold, which is divided into two parts by the event horizon.     

Consistent Histories Approach to the Unruh Effect

Using the history projection operator (HPO) approach to consistent histories we rederive Unruh's result that an observer constantly accelerating through the Minkowski vacuum appears to be immersed in a thermal bath. We show that propositions about any symmetry of a system always form a consistent set and that the probabilities associated with such propositions are decided by their value in the initial state. We use this fact to postulate a condition on the decoherence functional in the HPO setup. Finally we show that the Unruh effect arises from the fact that the initial density matrix corresponding to the inertial vacuum can be written as a thermal density matrix in the Fock basis associated with the accelerating observer.