5,434 research outputs found
Population bound effects on bosonic correlations in non-inertial frames
We analyse the effect of bounding the occupation number of bosonic field
modes on the correlations among all the different spatial-temporal regions in a
setting in which we have a space-time with a horizon along with an inertial
observer. We show that the entanglement between A (inertial observer) and R
(uniformly accelerated observer) depends on the bound N, contrary to the
fermionic case. Whether or not decoherence increases with N depends on the
value of the acceleration a. Concerning the bipartition A-antiR (Alice with an
observer in Rindler's region IV), we show that no entanglement is created
whatever the value of N and a. Furthermore, AR entanglement is very quickly
lost for finite N and for infinite N. We will study in detail the mutual
information conservation law found for bosons and fermions. By means of the
boundary effects associated to N finiteness, we will show that for bosons this
law stems from classical correlations while for fermions it has a quantum
origin. Finally, we will present the strong N dependence of the entanglement in
R-antiR bipartition and compare the fermionic cases with their finite N bosonic
analogs. We will also show the anti-intuitive dependence of this entanglement
on statistics since more entanglement is created for bosons than for their
fermion counterparts.Comment: revtex 4, 12 pages, 10 figures. Added Journal ref
Nonholonomic constraints in -symplectic Classical Field Theories
A -symplectic framework for classical field theories subject to
nonholonomic constraints is presented. If the constrained problem is regular
one can construct a projection operator such that the solutions of the
constrained problem are obtained by projecting the solutions of the free
problem. Symmetries for the nonholonomic system are introduced and we show that
for every such symmetry, there exist a nonholonomic momentum equation. The
proposed formalism permits to introduce in a simple way many tools of
nonholonomic mechanics to nonholonomic field theories.Comment: 27 page
Unveiling quantum entanglement degradation near a Schwarzschild black hole
We analyze the entanglement degradation provoked by the Hawking effect in a
bipartite system Alice-Rob when Rob is in the proximities of a Schwarzschild
black hole while Alice is free falling into it. We will obtain the limit in
which the tools imported from the Unruh entanglement degradation phenomenon can
be used properly, keeping control on the approximation. As a result, we will be
able to determine the degree of entanglement as a function of the distance of
Rob to the event horizon, the mass of the black hole, and the frequency of
Rob's entangled modes. By means of this analysis we will show that all the
interesting phenomena occur in the vicinity of the event horizon and that the
presence of event horizons do not effectively degrade the entanglement when Rob
is far off the black hole. The universality of the phenomenon is presented:
There are not fundamental differences for different masses when working in the
natural unit system adapted to each black hole. We also discuss some aspects of
the localization of Alice and Rob states. All this study is done without using
the single mode approximation.Comment: 16 pages, 10 figures, revtex4. Added Journal referenc
Hamiltonian Dynamics of Linearly Polarized Gowdy Models Coupled to Massless Scalar Fields
The purpose of this paper is to analyze in detail the Hamiltonian formulation
for the compact Gowdy models coupled to massless scalar fields as a necessary
first step towards their quantization. We will pay special attention to the
coupling of matter and those features that arise for the three-handle and
three-sphere topologies that are not present in the well studied three torus
case -in particular the polar constraints that come from the regularity
conditions on the metric. As a byproduct of our analysis we will get an
alternative understanding, within the Hamiltonian framework, of the appearance
of initial and final singularities for these models.Comment: Final version to appear in Classical and Quantum Gravit
On the Hamilton-Jacobi Theory for Singular Lagrangian Systems
We develop a Hamilton-Jacobi theory for singular lagrangian systems using the
Gotay-Nester-Hinds constraint algorithm. The procedure works even if the system
has secondary constraints.Comment: 36 page
Addressed qubit manipulation in radio-frequency dressed lattices
Precise control over qubits encoded as internal states of ultracold atoms in arrays of potential wells is a key element for atomtronics applications in quantum information, quantum simulation and atomic microscopy. Here we theoretically study atoms trapped in an array of radio-frequency dressed potential wells and propose a scheme for engineering fast and high-fidelity single-qubit gates with low error due to cross-talk. In this proposal, atom trapping and qubit manipulation relies exclusively on long-wave radiation making it suitable for atom-chip technology. We demonstrate that selective qubit addressing with resonant microwaves can be programmed by controlling static and radio-frequency currents in microfabricated conductors. These results should enable studies of neutral-atom quantum computing architectures, powered by low-frequency electromagnetic fields with the benefit of simple schemes for controlling individual qubits in large ensembles
A Generalization of Chetaev's Principle for a Class of Higher Order Non-holonomic Constraints
The constraint distribution in non-holonomic mechanics has a double role. On
one hand, it is a kinematic constraint, that is, it is a restriction on the
motion itself. On the other hand, it is also a restriction on the allowed
variations when using D'Alembert's Principle to derive the equations of motion.
We will show that many systems of physical interest where D'Alembert's
Principle does not apply can be conveniently modeled within the general idea of
the Principle of Virtual Work by the introduction of both kinematic constraints
and variational constraints as being independent entities. This includes, for
example, elastic rolling bodies and pneumatic tires. Also, D'Alembert's
Principle and Chetaev's Principle fall into this scheme. We emphasize the
geometric point of view, avoiding the use of local coordinates, which is the
appropriate setting for dealing with questions of global nature, like
reduction.Comment: 27 pages. Journal of Mathematical Physics (to zappear
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