31,961 research outputs found
Aging dynamics of ferromagnetic and reentrant spin glass phases in stage-2 CuCCl graphite intercalation compound
Aging dynamics of a reentrant ferromagnet stage-2
CuCoCl graphite intercalation compound has been studied
using DC magnetic susceptibility. This compound undergoes successive
transitions at the transition temperatures ( K) and
( K). The relaxation rate exhibits a
characteristic peak at below . The peak time as a
function of temperature shows a local maximum around 5.5 K, reflecting a
frustrated nature of the ferromagnetic phase. It drastically increases with
decreasing temperature below . The spin configuration imprinted at the
stop and wait process at a stop temperature () during the
field-cooled aging protocol, becomes frozen on further cooling. On reheating,
the memory of the aging at is retrieved as an anomaly of the
thermoremnant magnetization at . These results indicate the occurrence
of the aging phenomena in the ferromagnetic phase () as well
as in the reentrant spin glass phase ().Comment: 9 pages, 9 figures; submitted to Physical Review
Modified Reconstruction of Standard Model in Non-Commutative Differential Geometry
Sogami recently proposed the new idea to express Higgs particle as a kind of
gauge particle by prescribing the generalized covariant derivative with gauge
and Higgs fields operating on quark and lepton fields. The field strengths for
both the gauge and Higgs fields are defined by the commutators of the covariant
derivative by which he could obtain the Yang-Mills Higgs Lagrangian in the
standard model. Inspired by Sogami's work, we present a modification of our
previous scheme to formulate the spontaneously broken gauge theory in
non-commutative geometry on the discrete space; Minkowski space multiplied by
two points space by introducing the generation mixing matrix in operation of
the generalized derivative on the more fundamental fields a_i(x,y) which
compose the gauge and Higgs fields. The standard model is reconstructed
according to the modified scheme, which does not yields not only any special
relations between the particle masses but also the special restriction on the
Higgs potential.Comment: 21 page
Suppression of compressible edge channels and spatial spin polarization in the integer quantum Hall regime
We perform systematic numerical studies of the structure of spin-resolved
compressible strips in split-gate quantum wires taking into account the
exchange and correlation interactions within the density functional theory in
the local spin-density approximation. We find that for realistic parameters of
the wire the exchange interaction can completely suppress the formation of the
compressible strips. As the depletion length or magnetic field are increased,
the compressible strips starts to form first for the spin-down and then for
spin-up edge channels. We demonstrate that the widths of these strips plus the
spatial separation between them caused by the exchange interaction are equal to
the width of the compressible strip calculated in the Hartree approximation for
spinless electrons. We also discuss the effect of electron density on the
suppression of the compressible strips in quantum wires.Comment: 5 pages, 4 figures, submitted to Phys. Rev.
Vacuum type of SU(2) gluodynamics in maximally Abelian and Landau gauges
The vacuum type of SU(2) gluodynamics is studied using Monte-Carlo
simulations in maximally Abelian (MA) gauge and in Landau (LA) gauge, where the
dual Meissner effect is observed to work. The dual Meissner effect is
characterized by the coherence and the penetration lengths. Correlations
between Wilson loops and electric fields are evaluated in order to measure the
penetration length in both gauges. The coherence length is shown to be fixed in
the MA gauge from measurements of the monopole density around the static
quark-antiquark pair. It is also shown numerically that a dimension 2 gluon
operator A^+A^-(s) and the monopole density has a strong correlation as
suggested theoretically. Such a correlation is observed also between the
monopole density and A^2(s)= A^+A^-(s) + A^3A^3(s) condensate if the remaining
U(1) gauge degree of freedom is fixed to U(1) Landau gauge (U1LA). The
coherence length is determined numerically also from correlations between
Wilson loops and A^+A^-(s) and A^2(s) in MA + U1LA gauge. Assuming that the
same physics works in the LA gauge, we determine the coherence length from
correlations between Wilson loops and A^2(s). Penetration lengths and coherence
lengths in the two gauges are almost the same. The vacuum type of the
confinement phase in both gauges is near to the border between the type 1 and
the type 2 dual superconductors.Comment: 13 pages, 22 figures, RevTeX 4 styl
One-loop N-point equivalence among negative-dimensional, Mellin-Barnes and Feynman parametrization approaches to Feynman integrals
We show that at one-loop order, negative-dimensional, Mellin-Barnes' (MB) and
Feynman parametrization (FP) approaches to Feynman loop integrals calculations
are equivalent. Starting with a generating functional, for two and then for
-point scalar integrals we show how to reobtain MB results, using
negative-dimensional and FP techniques. The point result is valid for
different masses, arbitrary exponents of propagators and dimension.Comment: 11 pages, LaTeX. To be published in J.Phys.
An Almost Perfect Quantum Lattice Action for Low-energy SU(2) Gluodynamics
We study various representations of infrared effective theory of SU(2)
Gluodynamics as a (quantum) perfect lattice action. In particular we derive a
monopole action and a string model of hadrons from SU(2) Gluodynamics. These
are lattice actions which give almost cut-off independent physical quantities
even on coarse lattices. The monopole action is determined by numerical
simulations in the infrared region of SU(2) Gluodynamics. The string model of
hadrons is derived from the monopole action by using BKT transformation. We
illustrate the method and evaluate physical quantities such as the string
tension and the mass of the lowest state of the glueball analytically using the
string model of hadrons. It turns out that the classical results in the string
model is near to the one in quantum SU(2) Gluodynamics.Comment: 39 pages, 10 figure
Compact lattice formulation of Cho-Faddeev-Niemi decomposition: gluon mass generation and infrared Abelian dominance
This paper complements a new lattice formulation of SU(2) Yang-Mills theory
written in terms of new variables in a compact form proposed in the previous
paper. The new variables used in the formulation were once called the
Cho--Faddeev--Niemi or Cho--Faddeev--Niemi--Shabanov decomposition. Our
formulation enables us to explain the infrared ``Abelian'' dominance, in
addition to magnetic monopole dominance shown in the previous paper, in the
gauge invariant way without relying on the specific gauge fixing called the
maximal Abelian gauge used in the conventional investigations. In this paper,
especially, we demonstrate by numerical simulations that gluon degrees of
freedom other than the ``Abelian'' part acquire the mass to be decoupled in the
low-energy region leading to the infrared Abelian dominance.Comment: 14 pages 5 figures,[v2]explanations added and improved, a reference
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Ultraviolet Behavior of the Gluon Propagator in the Maximal Abelian Gauge
The ultraviolet asymptotic behavior of the gluon propagator is evaluated in
the maximal Abelian gauge in the SU(2) gauge theory on the basis of the
renormalization-group improved perturbation theory at the one-loop level.
Square-root singularities obtained in the Euclidean domain are attributed to
artifacts of the one-loop approximation in the maximal Abelian gauge and the
standard normalization condition for the propagator used in our study. It is
argued that this gauge is essentially nonperturbative.Comment: 15 pages, 2 figure
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