2,551 research outputs found
Investigations on transparent liquid-miscibility gap systems
Sedimentation and phase separation is a well known occurrence in monotectic or miscibility gap alloys. Previous investigations indicate that it may be possible to prepare such alloys in a low-gravity space environment but recent experiments indicate that there may be nongravity dependent phase separation processes which can hinder the formation of such alloys. Such phase separation processes are studied using transparent liquid systems and holography. By reconstructing holograms into a commercial-particle-analysis system, real time computer analysis can be performed on emulsions with diameters in the range of 5 micrometers or greater. Thus dynamic effects associated with particle migration and coalescence can be studied. Characterization studies on two selected immiscible systems including an accurate determination of phase diagrams, surface and interfacial tension measurements, surface excess and wetting behavior near critical solution temperatures completed
Transmission Phase of an Isolated Coulomb-Blockade Resonance
In two recent papers, O. Entin-Wohlman et al. studied the question: ``Which
physical information is carried by the transmission phase through a quantum
dot?'' In the present paper, this question is answered for an islolated
Coulomb-blockade resonance and within a theoretical model which is more closely
patterned after the geometry of the actual experiment by Schuster et al. than
is the model of O. Entin-Wohlman et al. We conclude that whenever the number of
leads coupled to the Aharanov-Bohm interferometer is larger than two, and the
total number of channels is sufficiently large, the transmission phase does
reflect the Breit-Wigner behavior of the resonance phase shift.Comment: 6 pages and one figur
Preventing transition to turbulence: a viscosity stratification does not always help
In channel flows a step on the route to turbulence is the formation of
streaks, often due to algebraic growth of disturbances. While a variation of
viscosity in the gradient direction often plays a large role in
laminar-turbulent transition in shear flows, we show that it has, surprisingly,
little effect on the algebraic growth. Non-uniform viscosity therefore may not
always work as a flow-control strategy for maintaining the flow as laminar.Comment: 9 pages, 8 figure
Stoner gap in the superconducting ferromagnet UGe2
We report the temperature () dependence of ferromagnetic Bragg peak
intensities and dc magnetization of the superconducting ferromagnet UGe2 under
pressure (). We have found that the low- behavior of the uniform
magnetization can be explained by a conventional Stoner model. A functional
analysis of the data produces the following results: The ferromagnetic state
below a critical pressure can be understood as the perfectly polarized state,
in which heavy quasiparticles occupy only majority spin bands. A Stoner gap
decreases monotonically with increasing pressure and increases
linearly with magnetic field. We show that the present analysis based on the
Stoner model is justified by a consistency check, i.e., comparison of density
of states at the Fermi energy deduced from the analysis with observed
electronic specific heat coeffieients. We also argue the influence of the
ferromagnetism on the superconductivity.Comment: 5 pages, 4 figures. to be published in Phys. Rev.
Entanglement Entropy and Wilson Loop in St\"{u}ckelberg Holographic Insulator/Superconductor Model
We study the behaviors of entanglement entropy and vacuum expectation value
of Wilson loop in the St\"{u}ckelberg holographic insulator/superconductor
model. This model has rich phase structures depending on model parameters. Both
the entanglement entropy for a strip geometry and the heavy quark potential
from the Wilson loop show that there exists a "confinement/deconfinement" phase
transition. In addition, we find that the non-monotonic behavior of the
entanglement entropy with respect to chemical potential is universal in this
model. The pseudo potential from the spatial Wilson loop also has a similar
non-monotonic behavior. It turns out that the entanglement entropy and Wilson
loop are good probes to study the properties of the holographic superconductor
phase transition.Comment: 23 pages,12 figures. v2: typos corrected, accepted in JHE
The cosmological light-cone effect on the power spectrum of galaxies and quasars in wide-field redshift surveys
We examine observational consequences of the cosmological light-cone effect
on the power spectrum of the distribution of galaxies and quasars from upcoming
redshift surveys. First we derive an expression for the power spectrum of
cosmological objects in real space on a light cone, , which is exact in linear theory of density perturbations. Next we
incorporate corrections for the nonlinear density evolution and redshift-space
distortion in the formula in a phenomenological manner which is consistent with
recent numerical simulations. On the basis of this formula, we predict the
power spectrum of galaxies and quasars on the light cone for future redshift
surveys taking account of the selection function properly. We demonstrate that
this formula provides a reliable and useful method to compute the power
spectrum on the light cone given an evolution model of bias.Comment: 18 pages, 3 figures, to be published in the Astrophysical Journa
Entanglement entropy in lattice gauge theories
We report on the recent progress in theoretical and numerical studies of
entanglement entropy in lattice gauge theories. It is shown that the concept of
quantum entanglement between gauge fields in two complementary regions of space
can only be introduced if the Hilbert space of physical states is extended in a
certain way. In the extended Hilbert space, the entanglement entropy can be
partially interpreted as the classical Shannon entropy of the flux of the gauge
fields through the boundary between the two regions. Such an extension leads to
a reduction procedure which can be easily implemented in lattice simulations by
constructing lattices with special topology. This enables us to measure the
entanglement entropy in lattice Monte-Carlo simulations. On the simplest
example of Z2 lattice gauge theory in (2 + 1) dimensions we demonstrate the
relation between entanglement entropy and the classical entropy of the field
flux. For SU(2) lattice gauge theory in four dimensions, we find a signature of
non-analytic dependence of the entanglement entropy on the size of the region.
We also comment on the holographic interpretation of the entanglement entropy.Comment: Talk presented at the Confinement8 conference (Mainz, Germany,
September 1 - 6, 2008) and at the conference "Liouville Field Theory and
Statistical Models", dedicated to Alexey Zamolodchikov memory (Moscow,
Russia, June 21 - 24, 2008
Zero Order Estimates for Analytic Functions
The primary goal of this paper is to provide a general multiplicity estimate.
Our main theorem allows to reduce a proof of multiplicity lemma to the study of
ideals stable under some appropriate transformation of a polynomial ring. In
particular, this result leads to a new link between the theory of polarized
algebraic dynamical systems and transcendental number theory. On the other
hand, it allows to establish an improvement of Nesterenko's conditional result
on solutions of systems of differential equations. We also deduce, under some
condition on stable varieties, the optimal multiplicity estimate in the case of
generalized Mahler's functional equations, previously studied by Mahler,
Nishioka, Topfer and others. Further, analyzing stable ideals we prove the
unconditional optimal result in the case of linear functional systems of
generalized Mahler's type. The latter result generalizes a famous theorem of
Nishioka (1986) previously conjectured by Mahler (1969), and simultaneously it
gives a counterpart in the case of functional systems for an important
unconditional result of Nesterenko (1977) concerning linear differential
systems. In summary, we provide a new universal tool for transcendental number
theory, applicable with fields of any characteristic. It opens the way to new
results on algebraic independence, as shown in Zorin (2010).Comment: 42 page
Periodic-Orbit Bifurcations and Superdeformed Shell Structure
We have derived a semiclassical trace formula for the level density of the
three-dimensional spheroidal cavity. To overcome the divergences occurring at
bifurcations and in the spherical limit, the trace integrals over the
action-angle variables were performed using an improved stationary phase
method. The resulting semiclassical level density oscillations and
shell-correction energies are in good agreement with quantum-mechanical
results. We find that the bifurcations of some dominant short periodic orbits
lead to an enhancement of the shell structure for "superdeformed" shapes
related to those known from atomic nuclei.Comment: 4 pages including 3 figure
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