2,268 research outputs found
Strongly Coupled Semi-Direct Mediation of Supersymmetry Breaking
Strongly coupled semi-direct gauge mediation models of supersymmetry breaking
through massive mediators with standard model charges are investigated by means
of composite degrees of freedom. Sizable mediation is realized to generate the
standard model gaugino masses for a small mediator mass without breaking the
standard model symmetries.Comment: 7 pages; v2: the model generalized, gaugino mass corrected; v3:
explanations expanded, references adde
Dynamical Supersymmetry Breaking without Messenger Gauge Interactions
We investigate low-energy models of supersymmetry (SUSY) breaking by means of
vector-like gauge theories for dynamical SUSY breaking. It is not necessary to
introduce messenger gauge interactions utilized so far to mediate the SUSY
breaking to the standard-model sector, which reduces complication in the model
building. We also consider various other ways of SUSY-breaking transmission.Comment: 10 pages, LaTeX, 1 Postscript figur
Anisotropy of in-plane magnetization due to nodal gap structure in the vortex state
We examine the interplay between anisotropy of the in-plane magnetization and
the nodal gap structure on the basis of the approximate analytic solution in
the quasiclassical formalism. We show that a four-fold oscillation appears in
the magnetization, and its amplitude changes sign at an intermediate field. The
high-field oscillation originates from the anisotropy of the upper critical
field, while the low-field behavior can be understood by the thermally
activated quasiparticles near nodes depending on the applied field angles. The
temperature dependence of the magnetization also shows a similar sign change.
The anisotropy of the magnetization offers a possible measurement to identify
the gap structure directly for a wide class of type II superconductors.Comment: 4 pages, 4 figure
Unconventional superconductors under rotating magnetic field II: thermal transport
We present a microscopic approach to the calculations of thermal conductivity
in unconventional superconductors for a wide range of temperatures and magnetic
fields. Our work employs the non-equilibrium Keldysh formulation of the
quasiclassical theory. We solve the transport equations using a variation of
the Brandt-Pesch-Tewordt (BPT) method, that accounts for the quasiparticle
scattering on vortices. We focus on the dependence of the thermal conductivity
on the direction of the field with the respect to the nodes of the order
parameter, and discuss it in the context of experiments aiming to determine the
shape of the gap from such anisotropy measurements. We consider quasi-two
dimensional Fermi surfaces with vertical line nodes and use our analysis to
establish the location of gap nodes in heavy fermion CeCoIn and organic
superconductor -(BEDT-TTF)Cu(NCS).Comment: 17 pages, 13 figure
Interplane and intraplane heat transport in quasi two-dimensional nodal superconductors
We analyze the behavior of the thermal conductivity in quasi-two dimensional
superconductors with line nodes. Motivated by measurements of the anisotropy
between the interplane and intraplane thermal transport in CeIrIn_5 we show
that a simple model of the open Fermi surface with vertical line nodes is
insufficient to describe the data. We propose two possible extensions of the
model taking into account a) additional modulation of the gap along the axial
direction of the open Fermi surface; and b) dependence of the interplane
tunneling on the direction of the in-plane momentum. We discuss the temperature
dependence of the thermal conductivity anisotropy and its low T limit in these
two models and compare the results with a model with a horizontal line of nodes
(``hybrid gap''). We discuss possible relevance of each model for the symmetry
of the order parameter in CeIrIn_5, and suggest further experiments aimed at
clarifying the shape of the superconducting gap.Comment: 14pages, 12 figure
Field-angle resolved specific heat and thermal conductivity in the vortex phase of UPd_2Al_3
The field-angle dependent specific heat and thermal conductivity in the
vortex phase of UPd_2Al_3 is studied using the Doppler shift approximation for
the low energy quasiparticle excitations. We first give a concise presentation
of the calculation procedure of magnetothermal properties with vortex and FS
averages performed numerically. The comparison of calculated field-angle
oscillations and the experimental results obtained previously leads to a strong
reduction of the possible SC candidate states in UPd_2Al_3. The possible SC gap
functions have node lines in hexagonal symmetry planes containing either the
zone center or the AF zone boundary along c. Node lines in non-symmetry planes
can be excluded. We also calculate the field and temperature dependence of
field-angular oscillation amplitudes. We show that the observed nonmonotonic
field dependence and sign reversal of the oscillation amplitude is due to small
deviations from unitary scattering.Comment: 16 pages, 8 figure
Spectral properties and geology of bright and dark material on dwarf planet Ceres
Variations and spatial distributions of bright and dark material on dwarf
planet Ceres play a key role in understanding the processes that have led to
its present surface composition. We define limits for bright and dark material
in order to distinguish them consistently, based on the reflectance of the
average surface using Dawn Framing Camera data. A systematic classification of
four types of bright material is presented based on their spectral properties,
composition, spatial distribution, and association with specific
geomorphological features. We found obvious correlations of reflectance with
spectral shape (slopes) and age; however, this is not unique throughout the
bright spots. Although impact features show generally more extreme reflectance
variations, several areas can only be understood in terms of inhomogeneous
distribution of composition as inferred from Dawn Visible and Infrared
Spectrometer data. Additional material with anomalous composition and spectral
properties are rare. The identification of the composition and origin of the
dark, particularly the darkest material, remains to be explored. The spectral
properties and the morphology of the dark sites suggest an endogenic origin,
but it is not clear whether they are more or less primitive surficial exposures
or excavated subsurface but localized material. The reflectance, spectral
properties, inferred composition, and geologic context collectively suggest
that the bright and dark material tends to gradually change toward the average
surface over time. This could be because of multiple processes, i.e., impact
gardening/space weathering, and lateral mixing, including thermal and aqueous
alteration, accompanied by changes in composition and physical properties such
as grain size, surface temperature, and porosity (compaction).Comment: Meteoritics and Planetary Science; Dawn at Ceres special issu
Algebroid Yang-Mills Theories
A framework for constructing new kinds of gauge theories is suggested.
Essentially it consists in replacing Lie algebras by Lie or Courant algebroids.
Besides presenting novel topological theories defined in arbitrary spacetime
dimensions, we show that equipping Lie algebroids E with a fiber metric having
sufficiently many E-Killing vectors leads to an astonishingly mild deformation
of ordinary Yang-Mills theories: Additional fields turn out to carry no
propagating modes. Instead they serve as moduli parameters gluing together in
part different Yang-Mills theories. This leads to a symmetry enhancement at
critical points of these fields, as is also typical for String effective field
theories.Comment: 4 pages; v3: Minor rewording of v1, version to appear in Phys. Rev.
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