3,531 research outputs found
Comments on Critical Electric and Magnetic Fields from Holography
We discuss some aspects of critical electric and magnetic fields in a field
theory with holographic dual description. We extend the analysis of
arxiv:1109.2920, which finds a critical electric field at which the Schwinger
pair production barrier drops to zero, to the case of magnetic fields. We first
find that, unlike ordinary weakly coupled theories, the magnetic field is not
subject to any perturbative instability originating from the presence of a
tachyonic ground state in the W-boson spectrum. This follows from the large
value of the 't Hooft coupling \lambda, which prevents the Zeeman interaction
term to overcome the particle mass at high B. Consequently, we study the next
possible B-field instability, i.e. monopole pair production, which is the
S-dual version of the Schwinger effect. Also in this case a critical magnetic
field is expected when the tunneling barrier drops to zero. These
Schwinger-type criticalities are the holographic duals, in the bulk, to the
fields E or B reaching the tension of F1 or D1 strings respectively. We then
discuss how this effect is modified when electric and magnetic fields are
present simultaneously and dyonic states in the spectrum can be pair produced
by a generic E - B background. Finally, we analyze finite temperature effects
on Schwinger criticalities, i.e. in the AdS-Schwarzshild black hole background.Comment: 33 pages, 4 figures; v2: refs added; v3: typos corrected, to appear
on JHE
Frequency response of intracavity laser coupling modulation
A resonant energy coupling between the atomic system and the oscillating optical mode leads to severe output distortion in intracavity laser coupling modulation. This anomalous behavior, which places a lower limit on the modulation frequency, is investigated in a case of a CO2 laser and compared with theoretical predictions
Evidence of Non-Markovian Behavior in the Process of Bank Rating Migrations
This paper estimates transition matrices for the ratings on financial institutions, using an unusually informative data set. We show that the process of rating migration exhibits significant non-Markovian behavior, in the sense that the transition intensiFinancial institutions, macroeconomic variables, capitalization, supervision, transition intensities
The Coherence of Primordial Fluctuations Produced During Inflation
The behaviour of quantum metric perturbations produced during inflation is
considered at the stage after the second Hubble radius crossing. It is shown
that the classical correlation between amplitude and momentum of a perturbation
mode, previously shown to emerge in the course of an effective
quantum-to-classical transition, is maintained for a sufficiently long time,
and we present the explicit form in which it takes place using the Wigner
function. We further show with a simple diffraction experiment that quantum
interference, non-expressible in terms of a classical stochastic description of
the perturbations, is essentially suppressed. Rescattering of the perturbations
leads to a comparatively slow decay of this correlation and to a complete
stochastization of the system.Comment: LaTeX (7 pages
Decoherence in the cosmic background radiation
In this paper we analyze the possibility of detecting nontrivial quantum
phenomena in observations of the temperature anisotropy of the cosmic
background radiation (CBR), for example, if the Universe could be found in a
coherent superposition of two states corresponding to different CBR
temperatures. Such observations are sensitive to scalar primordial fluctuations
but insensitive to tensor fluctuations, which are therefore converted into an
environment for the former. Even for a free inflaton field minimally coupled to
gravity, scalar-tensor interactions induce enough decoherence among histories
of the scalar fluctuations as to render them classical under any realistic
probe of their amplitudes.Comment: 15 pages, accepted to be published in Classical and Quantum Gravit
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