5,562 research outputs found
Supersymmetric SO(10) Grand Unification at the LHC and Beyond
We study models of supersymmetric grand unification based on the SO(10) gauge
group. We investigate scenarios of non-universal gaugino masses including
models containing a mixture of two representations of hidden sector chiral
superfields. We analyse the effect of excluding mu from the fine-tuning
measure, and confront the results with low energy constraints, including the
Higgs boson mass, dark matter relic density and supersymmetry bounds. We also
determine high scale Yukawa coupling ratios and confront the results with
theoretical predictions. Finally, we present two additional benchmarks that
should be explored at the LHC and future colliders.Comment: Published versio
Creep of current-driven domain-wall lines: intrinsic versus extrinsic pinning
We present a model for current-driven motion of a magnetic domain-wall line,
in which the dynamics of the domain wall is equivalent to that of an overdamped
vortex line in an anisotropic pinning potential. This potential has both
extrinsic contributions due to, e.g., sample inhomogeneities, and an intrinsic
contribution due to magnetic anisotropy. We obtain results for the domain-wall
velocity as a function of current for various regimes of pinning. In
particular, we find that the exponent characterizing the creep regime depends
strongly on the presence of a dissipative spin transfer torque. We discuss our
results in the light of recent experiments on current-driven domain-wall creep
in ferromagnetic semiconductors, and suggest further experiments to corroborate
our model.Comment: For figure in GIF format, see
http://www.phys.uu.nl/~duine/mapping.gif v2: (hopefully) visible EPS figure
added. v2: expanded new versio
Staircase to Higher-Order Topological Phase Transitions
We find a series of topological phase transitions of increasing order, beyond
the more standard second-order phase transition in a one-dimensional
topological superconductor. The jumps in the order of the transitions depend on
the range of the pairing interaction, which is parametrized by an algebraic
decay with exponent . Remarkably, in the limit the order
of the topological transition becomes infinite. We compute the critical
exponents for the series of higher-order transitions in exact form and find
that they fulfill the hyperscaling relation. We also study the critical
behaviour at the boundary of the system and discuss potential experimental
platforms of magnetic atoms in superconductors.Comment: 5+5pages, 7 figures. Accepted as a Rapid Communicatio
Vortex-lattice pinning in two-component Bose-Einstein condensates
We investigate the vortex-lattice structure for single- and two-component
Bose-Einstein condensates in the presence of an optical lattice, which acts as
a pinning potential for the vortices. The problem is considered in the
mean-field quantum-Hall regime, which is reached when the rotation frequency
of the condensate in a radially symmetric trap approaches the (radial)
trapping frequency and the interactions between the atoms are weak. We
determine the vortex-lattice phase diagram as a function of optical-lattice
strength and geometry. In the limit of strong pinning the vortices are always
pinned at the maxima of the optical-lattice potential, similar to the
slow-rotation case. At intermediate pinning strength, however, due to the
competition between interactions and pinning energy, a structure arises for the
two-component case where the vortices are pinned on lines of minimal potential
Finite-momentum condensate of magnetic excitons in a bilayer quantum Hall system
We study the bilayer quantum Hall system at total filling factor \nu_T = 1
within a bosonization formalism which allows us to approximately treat the
magnetic exciton as a boson. We show that in the region where the distance
between the two layers is comparable to the magnetic length, the ground state
of the system can be seen as a finite-momentum condensate of magnetic excitons
provided that the excitation spectrum is gapped. We analyze the stability of
such a phase within the Bogoliubov approximation firstly assuming that only one
momentum Q0 is macroscopically occupied and later we consider the same
situation for two modes \pm Q0. We find strong evidences that a first-order
quantum phase transition at small interlayer separation takes place from a
zero-momentum condensate phase, which corresponds to Halperin 111 state, to a
finite-momentum condensate of magnetic excitons.Comment: 18 pages, 11 figures, final versio
The Weibull-Geometric distribution
In this paper we introduce, for the first time, the Weibull-Geometric
distribution which generalizes the exponential-geometric distribution proposed
by Adamidis and Loukas (1998). The hazard function of the last distribution is
monotone decreasing but the hazard function of the new distribution can take
more general forms. Unlike the Weibull distribution, the proposed distribution
is useful for modeling unimodal failure rates. We derive the cumulative
distribution and hazard functions, the density of the order statistics and
calculate expressions for its moments and for the moments of the order
statistics. We give expressions for the R\'enyi and Shannon entropies. The
maximum likelihood estimation procedure is discussed and an algorithm EM
(Dempster et al., 1977; McLachlan and Krishnan, 1997) is provided for
estimating the parameters. We obtain the information matrix and discuss
inference. Applications to real data sets are given to show the flexibility and
potentiality of the proposed distribution
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