8,185 research outputs found
Electronic Phase Separation Transition as the Origin of the Superconductivity and the Pseudogap Phase of Cuprates
We propose a new phase of matter, an electronic phase separation transition
that starts near the upper pseudogap and segregates the holes into high and low
density domains. The Cahn-Hilliard approach is used to follow quantitatively
this second order transition. The resulting grain boundary potential confines
the charge in domains and favors the development of intragrain superconducting
amplitudes. The zero resistivity transition arises only when the intergrain
Josephson coupling is of the order of the thermal energy and phase
locking among the superconducting grains takes place. We show that this
approach explains the pseudogap and superconducting phases in a natural way and
reproduces some recent scanning tunneling microscopy dataComment: 4 pages and 5 eps fig
Statistical fluctuations of the parametric derivative of the transmission and reflection coefficients in absorbing chaotic cavities
Motivated by recent theoretical and experimental works, we study the
statistical fluctuations of the parametric derivative of the transmission T and
reflection R coefficients in ballistic chaotic cavities in the presence of
absorption. Analytical results for the variance of the parametric derivative of
T and R, with and without time-reversal symmetry, are obtained for both
asymmetric and left-right symmetric cavities. These results are valid for
arbitrary number of channels, in completely agreement with the one channel case
in the absence of absorption studied in the literature.Comment: Modified version as accepted in PR
global monopole revisited
In this paper the global monopole is reexamined. We provide an exact
solution for the modified field equations in the presence of a global monopole
for regions outside its core, generalizing previous results. Additionally, we
discuss some particular cases obtained from this solution. We consider a setup
consisting of a possible Schwarzschild black hole that absorbs the topological
defect, giving rise to a static black hole endowed with a monopole's charge.
Besides, we demonstrate how the asymptotic behavior of the Higgs field far from
the monopole's core is shaped by a class of spacetime metrics which includes
those ones analyzed here. In order to assess the gravitational properties of
this system, we analyse the geodesic motion of both massive and massless test
particles moving in the vicinity of such configuration. For the material
particles we set the requirements they have to obey in order to experience
stable orbits. On the other hand, for the photons we investigate how their
trajectories are affected by the gravitational field of this black hole.Comment: 16 pages, 1 figure and 1 table. Minor changes to match published
version in EPJ
Statistical wave scattering through classically chaotic cavities in the presence of surface absorption
We propose a model to describe the statistical properties of wave scattering
through a classically chaotic cavity in the presence of surface absorption.
Experimentally, surface absorption could be realized by attaching an "absorbing
patch" to the inner wall of the cavity. In our model, the cavity is connected
to the outside by a waveguide with N open modes (or channels), while an
experimental patch is simulated by an "absorbing mirror" attached to the inside
wall of the cavity; the mirror, consisting of a waveguide that supports Na
channels, with absorption inside and a perfectly reflecting wall at its end, is
described by a subunitary scattering matrix Sa. The number of channels Na, as a
measure of the geometric cross section of the mirror, and the lack of unitarity
of Sa as a measure of absorption, are under our control: these parameters have
an important physical significance for real experiments. The absorption
strength in the cavity is quantified by the trace of the lack of unitarity. The
statistical distribution of the resulting S matrix for N=1 open channel and
only one absorbing channel, Na =1, is solved analytically for the orthogonal
and unitary universality classes, and the results are compared with those
arising from numerical simulations. The relation with other models existing in
the literature, in some of which absorption has a volumetric character, is also
studied.Comment: 6 pages, 3 figures, submitted to Phys. Rev.
Mesoscopic Transport Through Ballistic Cavities: A Random S-Matrix Theory Approach
We deduce the effects of quantum interference on the conductance of chaotic
cavities by using a statistical ansatz for the S matrix. Assuming that the
circular ensembles describe the S matrix of a chaotic cavity, we find that the
conductance fluctuation and weak-localization magnitudes are universal: they
are independent of the size and shape of the cavity if the number of incoming
modes, N, is large. The limit of small N is more relevant experimentally; here
we calculate the full distribution of the conductance and find striking
differences as N changes or a magnetic field is applied.Comment: 4 pages revtex 3.0 (2-column) plus 2 postscript figures (appended),
hub.pam.94.
Nonplanar integrability at two loops
In this article we compute the action of the two loop dilatation operator on
restricted Schur polynomials that belong to the su(2) sector, in the displaced
corners approximation. In this non-planar large N limit, operators that
diagonalize the one loop dilatation operator are not corrected at two loops.
The resulting spectrum of anomalous dimensions is related to a set of decoupled
harmonic oscillators, indicating integrability in this sector of the theory at
two loops. The anomalous dimensions are a non-trivial function of the 't Hooft
coupling, with a spectrum that is continuous and starting at zero at large N,
but discrete at finite N.Comment: version to appear in JHE
Vacuum Polarization for a Massless Spin-1/2 Field in the Global Monopole Spacetime at Nonzero Temperature
In this paper we present the effects produced by the temperature in the
renormalized vacuum expectation value of the zero-zero component of the
energy-momentum tensor associated with massless left-handed spinor field in the
pointlike global monopole spacetime. In order to develop this calculation we
had to obtain the Euclidean thermal Green function in this background. Because
the expression obtained for the thermal energy density cannot be expressed in a
closed form, its explicit dependence on the temperature is not completely
evident. So, in order to obtain concrete information about its thermal
behavior, we develop a numerical analysis of our result in the high-temperature
limit for specific values of the parameter which codify the presence
of the monopole.Comment: 22 pages, LaTex format, 5 figure
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