2,001,971 research outputs found
A Curie-Weiss model with dissipation
We consider stochastic dynamics for a spin system with mean field
interaction, in which the interaction potential is subject to noisy and
dissipative stochastic evolution. We show that, in the thermodynamic limit and
at sufficiently low temperature, the magnetization of the system has a time
periodic behavior, despite of the fact that no periodic force is applied
Time-evolution and dynamical phase transitions at a critical time in a system of one dimensional bosons after a quantum quench
A renormalization group approach is used to show that a one dimensional
system of bosons subject to a lattice quench exhibits a finite-time dynamical
phase transition where an order parameter within a light-cone increases as a
non-analytic function of time after a critical time. Such a transition is also
found for a simultaneous lattice and interaction quench where the effective
scaling dimension of the lattice becomes time-dependent, crucially affecting
the time-evolution of the system. Explicit results are presented for the
time-evolution of the boson interaction parameter and the order parameter for
the dynamical transition as well as for more general quenches.Comment: final published versio
The coming community: The singular time of the subject
We observe that the ideas of community and time in Agamben are strongly linked. At the moment of thinking the community we consider inevitable its interaction with the idea of time, in fact we see that such a correspondence is implicit in the thought of community. Nevertheless it is necessary to demonstrate the nucleus of this correlation, given that it is not possible to talk about the community without referring to the time of the subject. The subject is who does experiment the time and who is able to perceive the own time and to assume it, and for whom to self recognize into the time is possible at well as to experiment (it), to occupy (it) and to live (it) in common is. In the present analysis we will see that the time, as a place for the experience, is itself in the community. In fact, it becomes evident that the community is continuously disclosing1 within the time in which it is. Moreover, the community produces an idea of time that neither is related to a destiny nor is linked with an eventual delimitated future. In this context the time is not only a subjective condition of the subject but it deals with a practice both subjective and intersubjective. Because, at the moment of the time experience, simultaneously occurs that the subject appropriates and communicates it. By this way the community be-comes in the experience of the subject and belongs to the now time of the occurring, where the singular be being and the common future are conjugated.Fil: Campero, MarĂa BelĂ©n. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentina. Universidad Nacional de Rosario; Argentin
Entanglement and Quantum Noise Due to a Thermal Bosonic Field
We analyze the indirect exchange interaction between two two-state systems,
e.g., spins 1/2, subject to a common finite-temperature environment modeled by
bosonic modes. The environmental modes, e.g., phonons or cavity photons, are
also a source of quantum noise. We analyze the coherent vs noise-induced
features of the two-spin dynamics and predict that for low enough temperatures
the induced interaction is coherent over time scales sufficient to create
entanglement. A nonperturbative approach is utilized to obtain an exact
solution for the onset of the induced interaction, whereas for large times, a
Markovian scheme is used. We identify the time scales for which the spins
develop entanglement for various spatial separations. For large enough times,
the initially created entanglement is erased by quantum noise. Estimates for
the interaction and the level of quantum noise for localized impurity electron
spins in Si-Ge type semiconductors are given.Comment: 12 pages, 9 figures; typos correcte
The DKP oscillator with a linear interaction in the cosmic string space-time
We study the relativistic quantum dynamics of a DKP oscillator field subject
to a linear interaction in cosmic string space-time in order to better
understand the effects of gravitational fields produced by topological defects
on the scalar field. We obtain the solution of DKP oscillator in the cosmic
string background. Also, we solve it with an ansatz in presence of linear
interaction. We obtain the eigenfunctions and the energy levels of the
relativistic field in that background.Comment: 14 pages, no figure, comments are welcom
Photon-Phonon-assisted tunneling through a single-molecular quantum dot
Based on exactly mapping of a many-body electron-phonon interaction problem
onto a one-body problem, we apply the well-established nonequilibrium Green
function technique to solve the time-dependent phonon-assisted tunneling at low
temperature through a single-molecular quantum dot connected to two leads,
which is subject to a microwave irradiation field. It is found that in the
presence of the electron-phonon interaction and the microwave irradiation
field, the time-average transmission and the nonlinear differential conductance
display additional peaks due to pure photon absorption or emission processes
and photon-absorption-assisted phonon emission processes. The variation of the
time-average current with frequency of the microwave irradiation field is also
studied.Comment: 9 pages, 6 figures, submitted to Phys. Rev. B. accepted by Phys. Rev.
The Quantum Speed Limit of Optimal Controlled Phasegates for Trapped Neutral Atoms
We study controlled phasegates for ultracold atoms in an optical potential. A
shaped laser pulse drives transitions between the ground and electronically
excited states where the atoms are subject to a long-range 1/R^3 interaction.
We fully account for this interaction and use optimal control theory to
calculate the pulse shapes. This allows us to determine the minimum pulse
duration, respectively, gate time T that is required to obtain high fidelity.
We accurately analyze the speed limiting factors, and we find the gate time to
be limited either by the interaction strength in the excited state or by the
ground state vibrational motion in the trap. The latter needs to be resolved by
the pulses in order to fully restore the motional state of the atoms at the end
of the gate.Comment: 11 pages, 10 figures, 1 tabl
The low energy effective Lagrangian for photon interactions in any dimension
The subject of low energy photon-photon scattering is considered in arbitrary
dimensional space-time and the interaction is widened to include scattering
events involving an arbitrary number of photons. The effective interaction
Lagrangian for these processes in QED has been determined in a manifestly
invariant form. This generalisation resolves the structure of the weak-field
Euler-Heisenberg Lagrangian and indicates that the component invariant
functions have coefficients related, not only to the space-time dimension, but
also to the coefficients of the Bernoulli polynomial.Comment: In the revised version, the results have been expressed in terms of
Bernoulli polynomials instead of generalized zeta functions; they agree for
spinor QED with those of Schubert and Schmidt (obtained differently by path
integral methods)
A low temperature analysis of the boundary driven Kawasaki Process
Low temperature analysis of nonequilibrium systems requires finding the
states with the longest lifetime and that are most accessible from other
states. We determine these dominant states for a one-dimensional diffusive
lattice gas subject to exclusion and with nearest neighbor interaction. They do
not correspond to lowest energy configurations even though the particle current
tends to zero as the temperature reaches zero. That is because the dynamical
activity that sets the effective time scale, also goes to zero with
temperature. The result is a non-trivial asymptotic phase diagram, which
crucially depends on the interaction coupling and the relative chemical
potentials of the reservoirs.Comment: 14 pages, 1 figur
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