4,515 research outputs found
Investigation of the soret effect in aqueous and non-aqueous mixtures by the thermal lens technique
In the present work we investigate the thermal diffusion behavior of three different binary mixtures with a thermal lens (TL) setup. In the setup used in this study we avoid the addition of a dye for systems, such as aqueous mixtures, with a weak absorption band at a wavelength of 980 nm. In some aqueous systems with a complex phase behavior the addition of dye significantly affects the apparent measured thermal diffusion properties. The studied systems are dimethylsulfoxide (DMSO) in water, the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate (EMIES) in butanol and a non-ionic surfactant hexaethylene glycol monododecyl ether (C(12)E(6)) in water. The Soret coefficients of the selected systems cover a range of two orders of magnitude. For DMSO in water with a very low Soret coefficient of the order of S(T) approximately 10(-3) K(-1) we find for a low DMSO content (c = 0.33) a reasonable agreement with previous measurements, while the weak thermal lens signal for the DMSO-rich mixture (c = 0.87) leads to 20% too large Soret coefficients with an uncertainty of more than 30%. Secondly we studied a liquid salt 1-ethyl-3-methylimidazolium ethylsulfate (EMIES) in butanol with a roughly ten times higher Soret coefficient of S(T) approximately 10(-2) K(-1). For this system we performed additional measurements with another experimental technique, the classical thermal diffusion forced Rayleigh scattering (TDFRS), which requires the addition of a small amount of dye to increase the absorption. In the entire investigated concentration range the results obtained with the TL and classical TDFRS technique agree within the error bars. As a third system we studied a non-ionic surfactant hexaethylene glycol monododecyl ether (C(12)E(6)) in water with a Soret coefficient of the order of S(T) approximately 10(-1) K(-1). For this system we find good agreement with previous measurements. We conclude that the TL technique is a reliable method for systems with a strong optical contrast and fairly large Soret coefficient of the order of S(T) approximately 10(-2) K(-1)
The Hopf Skyrmion in QCD with Adjoint Quarks
We consider a modification of QCD in which conventional fundamental quarks
are replaced by Weyl fermions in the adjoint representation of the color SU(N).
In the case of two flavors the low-energy chiral Lagrangian is that of the
Skyrme-Faddeev model. The latter supports topologically stable solitons with
mass scaling as N^2. Topological stability is due to the existence of a
nontrivial Hopf invariant in the Skyrme-Faddeev model. Our task is to identify,
at the level of the fundamental theory, adjoint QCD, an underlying reason
responsible for the stability of the corresponding hadrons. We argue that all
"normal" mesons and baryons, with mass O(N^0), are characterized by (-1)^Q
(-1)^F =1, where Q is a conserved charge corresponding to the unbroken U(1)
surviving in the process of the chiral symmetry breaking (SU(2) \to U(1) for
two adjoint flavors). Moreover, F is the fermion number (defined mod 2 in the
case at hand). We argue that there exist exotic hadrons with mass O(N^2) and
(-1)^Q (-1)^F = -1. They are in one-to-one correspondence with the Hopf
Skyrmions. The transition from nonexotic to exotic hadrons is due to a shift in
F, namely F \to F - {\cal H} where {\cal H} is the Hopf invariant. To detect
this phenomenon we have to extend the Skyrme-Faddeev model by introducing
fermions.Comment: 18 pages, 3 figures; v.2: a reference and a comment added; v.3: two
comments added, figures improve
Non-Abelian statistics versus the Witten anomaly
This paper is motivated by prospects for non-Abelian statistics of deconfined
particle-like objects in 3+1 dimensions, realized as solitons with localized
Majorana zeromodes. To this end, we study the fermionic collective coordinates
of magnetic monopoles in 3+1 dimensional spontaneously-broken SU(2) gauge
theories with various spectra of fermions. We argue that a single Majorana
zeromode of the monopole is not compatible with cancellation of the Witten
SU(2) anomaly. We also compare this approach with other attempts to realize
deconfined non-Abelian objects in 3+1 dimensions.Comment: 11 pages, 3 figures; v2: added refs, minor corrections, published
versio
Numerical Investigation of Monopole Chains
We present numerical results for chains of SU(2) BPS monopoles constructed
from Nahm data. The long chain limit reveals an asymmetric behavior transverse
to the periodic direction, with the asymmetry becoming more pronounced at
shorter separations. This analysis is motivated by a search for semiclassical
finite temperature instantons in the 3D SU(2) Georgi-Glashow model, but it
appears that in the periodic limit the instanton chains either have
logarithmically divergent action or wash themselves out.Comment: 14 pages, 6 figures; v2 minor changes, published versio
Large-scale Ferrofluid Simulations on Graphics Processing Units
We present an approach to molecular-dynamics simulations of ferrofluids on
graphics processing units (GPUs). Our numerical scheme is based on a
GPU-oriented modification of the Barnes-Hut (BH) algorithm designed to increase
the parallelism of computations. For an ensemble consisting of one million of
ferromagnetic particles, the performance of the proposed algorithm on a Tesla
M2050 GPU demonstrated a computational-time speed-up of four order of magnitude
compared to the performance of the sequential All-Pairs (AP) algorithm on a
single-core CPU, and two order of magnitude compared to the performance of the
optimized AP algorithm on the GPU. The accuracy of the scheme is corroborated
by comparing the results of numerical simulations with theoretical predictions
BRST invariance and de Rham-type cohomology of 't Hooft-Polyakov monopole
We exploit the 't Hooft-Polyakov monopole to define closed algebra of the
quantum field operators and the BRST charge . In the first-class
configuration of the Dirac quantization, by including the -exact
gauge fixing term and the Faddeev-Popov ghost term, we find the BRST invariant
Hamiltonian to investigate the de Rham-type cohomology group structure for the
monopole system. The Bogomol'nyi bound is also discussed in terms of the
first-class topological charge defined on the extended internal 2-sphere.Comment: 8 page
Gravitating magnetic monopole in Vaidya geometry
A magnetic-monopole solution of a non-Abelian gauge theory as proposed by 't
Hooft and Polyakov is studied in the Vaidya spacetime. We find that the
solutions of Einstein equations generates a geometry of the Bonnor-Vaidya
corresponding to magnetically charged null fluid with Higgs field contributing
a cosmological term. In the absence of the scalar fields the corresponding
Wu-Yang solution of the gauge theory still generates the Bonnor-Vaidya
geometry, but with no cosmological term.Comment: 5 RevTeX pages, no figures, minor changes, to appear in Physical
Review
Positive Operator-Valued Measure reconstruction of a beam-splitter tree based photon-number-resolving detector
Here we present a reconstruction of the Positive Operator-Value Measurement
of a photon-number-resolving detector comprised of three 50:50 beamsplitters in
a tree configuration, terminated with four single-photon avalanche detectors.
The four detectors' outputs are processed by an electronic board that
discriminates detected photon number states from 0 to 4 and implements a "smart
counting" routine to compensate for dead time issues at high count rates
Holographic models and the QCD trace anomaly
Five dimensional dilaton models are considered as possible holographic duals
of the pure gauge QCD vacuum. In the framework of these models, the QCD trace
anomaly equation is considered. Each quantity appearing in that equation is
computed by holographic means. Two exact solutions for different dilaton
potentials corresponding to perturbative and non-perturbative beta-functions
are studied. It is shown that in the perturbative case, where the beta-function
is the QCD one at leading order, the resulting space is not asymptotically AdS.
In the non-perturbative case, the model considered presents confinement of
static quarks and leads to a non-vanishing gluon condensate, although it does
not correspond to an asymptotically free theory. In both cases analyses based
on the trace anomaly and on Wilson loops are carried out.Comment: 18 pages 1 figure In this revised version, the section on the
analysis of the Wilson loop was improved, and a section was added on the
matching of the calculations of the gluon condensate via the d+1 dim action
and the Wilson loo
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