1,662 research outputs found
The Structure of F-Quasigroups
We solve a problem of Belousov which has been open since 1967: to
characterize the loop isotopes of F-quasigroups. We show that every
F-quasigroup has a Moufang loop isotope which is a central product of its
nucleus and Moufang center. We then use the loop to reveal the structure of the
associated F-quasigroup.Comment: 24 pages. v.2 incorporates minor changes suggested by the referee. To
appear in the Journal of Algebr
Spontaneous symmetry breaking in the linear sigma model at finite chemical potential: One-loop corrections
We investigate spontaneous symmetry breaking within the linear sigma model
with the SU(2)xU(1) internal symmetry at finite chemical potential, which was
suggested as a model for kaon condensation in the CFL phase of dense quark
matter. One-loop corrections to the scalar field effective potential as well as
its propagator are calculated. Particular attention is paid to the type-II
Goldstone boson that appears in the Bose--Einstein condensed phase.
Furthermore, we show that the type-I Goldstone boson -- the superfluid phonon
-- is allowed to decay due to the nonlinearity of its dispersion relation at
high momentum, and determine its decay width.Comment: 13 pages, REVTeX4, 37 eps figures; v2: substantial error in Sec. IV
corrected, references added, other minor corrections; version to appear in
Phys. Rev.
Goldstone boson counting in linear sigma models with chemical potential
We analyze the effects of finite chemical potential on spontaneous breaking
of internal symmetries within the class of relativistic field theories
described by the linear sigma model. Special attention is paid to the emergence
of ``abnormal'' Goldstone bosons with quadratic dispersion relation. We show
that their presence is tightly connected to nonzero density of the Noether
charges, and formulate a general counting rule. The general results are
demonstrated on an SU(3)xU(1) invariant model with an SU(3)-sextet scalar
field, which describes one of the color-superconducting phases of QCD.Comment: 10 pages, REVTeX4, 4 eps figures, v2: general discussion in Sec. IV
expanded and improved, references added, other minor corrections throughout
the tex
Understanding the Josephson current through a Kondo-correlated quantum dot
We study the Josephson current 0- transition of a quantum dot tuned to
the Kondo regime. The physics can be quantitatively captured by the numerically
exact continuous time quantum Monte Carlo method applied to the single-impurity
Anderson model with BCS superconducting leads. For a comparison to an
experiment the tunnel couplings are determined by fitting the normal-state
linear conductance. Excellent agreement for the dependence of the critical
Josephson current on the level energy is achieved. For increased tunnel
couplings the Kondo scale becomes comparable to the superconducting gap and the
regime of the strongest competition between superconductivity and Kondo
correlations is reached; we predict the gate voltage dependence of the critical
current in this regime.Comment: 5 pages, 3 figure
An exact solution of the five-dimensional Einstein equations with four-dimensional de Sitter-like expansion
We present an exact solution to the Einstein field equations which is Ricci
and Riemann flat in five dimensions, but in four dimensions is a good model for
the early vacuum-dominated universe.Comment: 6 pages; to appear in Journal of Mathematical Physics; v2: reference
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TEMPERATURE-DEPENDENCE OF DOMAIN-WALL COERCIVE FIELD IN MAGNETIC GARNET-FILMS
The coercive properties of magnetically uniaxial liquid-phase epitaxy garnet films were investigated between 10 K and the Neel temperature (T(N) less-than-or-equal-to 500 K). Two independent methods, the results of which are nearly identical (magnetical response of oscillating domain walls and the method of coercive loops measured in a vibrating sample magnetometer), were used. Besides the usual domain-wall coercive field, H(dw), the critical coercive pressure, p(dw), was also introduced as it describes in a direct way the interactions of the domain walls with the wall-pinning traps. Both H(dw) and p(dw) were found to increase exponentially with decreasing temperature. Three different types of wall-pinning traps were identified in the sample and their strength, their rate of change with temperature, and their temperature range of activity were determined
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