3,353 research outputs found
Supersymmetry algebras in arbitrary signature and their R-symmetry groups
String theory, specifically type-II superstring theory, can be formulated in
any ten-dimensional signature. To facilitate the study of supergravity and
superstring theories in this setting, we present a uniform construction of
supersymmetry algebras in arbitrary dimension and signature, which generalizes
the ideas underlying symplectic Majorana spinors. In our formalism R-symmetry
acts on an auxiliary multiplicity space which makes its action manifest. This
allows us to provide extensive tables which list the R-symmetry groups of
extended supersymmetry algebras for all signatures together with other useful
information. Twisted (`type-*') supersymmetry algebras in Lorentz signature
with non-compact R-symmetry groups are shown to be part of a general pattern
resulting from the interplay between complex superbrackets and reality
conditions. As an application we show how the relations between type-II string
theories in ten and nine dimensions can be extracted from their supersymmetry
algebras. We also use our results to determine the special geometry of vector
and hypermultiplet scalar manifolds of four-dimensional and
three-dimensional supergravity theories for all signatures.Comment: 14 Tables, 76 pages plus 32 pages of appendice
Information Loss in Coarse Graining of Polymer Configurations via Contact Matrices
Contact matrices provide a coarse grained description of the configuration
omega of a linear chain (polymer or random walk) on Z^n: C_{ij}(omega)=1 when
the distance between the position of the i-th and j-th step are less than or
equal to some distance "a" and C_{ij}(omega)=0 otherwise. We consider models in
which polymers of length N have weights corresponding to simple and
self-avoiding random walks, SRW and SAW, with "a" the minimal permissible
distance. We prove that to leading order in N, the number of matrices equals
the number of walks for SRW, but not for SAW. The coarse grained Shannon
entropies for SRW agree with the fine grained ones for n <= 2, but differs for
n >= 3.Comment: 18 pages, 2 figures, latex2e Main change: the introduction is
rewritten in a less formal way with the main results explained in simple
term
Canonical-basis solution of the Hartree-Fock-Bogoliubov equation on three-dimensional Cartesian mesh
A method is presented to obtain the canonical-form solutions of the HFB
equation for atomic nuclei with zero-range interactions like the Skyrme force.
It is appropriate to describe pairing correlations in the continuum in
coordinate-space representations. An improved gradient method is used for
faster convergences under constraint of orthogonality between orbitals. To
prevent high-lying orbitals to shrink into a spatial point, a repulsive
momentum dependent force is introduced, which turns out to unveil the nature of
high-lying canonical-basis orbitals. The asymptotic properties at large radius
and the relation with quasiparticle states are discussed for the obtained
canonical basis.Comment: 23 pages including 17 figures, REVTeX4, revised version, scheduled to
appear in Phys. Rev. C, Vol.69, No.
A simple proof of Duquesne's theorem on contour processes of conditioned Galton-Watson trees
We give a simple new proof of a theorem of Duquesne, stating that the
properly rescaled contour function of a critical aperiodic Galton-Watson tree,
whose offspring distribution is in the domain of attraction of a stable law of
index , conditioned on having total progeny , converges in
the functional sense to the normalized excursion of the continuous-time height
function of a strictly stable spectrally positive L\'evy process of index
. To this end, we generalize an idea of Le Gall which consists in using
an absolute continuity relation between the conditional probability of having
total progeny exactly and the conditional probability of having total
progeny at least . This new method is robust and can be adapted to establish
invariance theorems for Galton-Watson trees having vertices whose degrees
are prescribed to belong to a fixed subset of the positive integers.Comment: 16 pages, 2 figures. Published versio
Analysis of repeated high-intensity running performance in professional soccer
The aims of this study conducted in a professional soccer team were two-fold: to characterise repeated high-intensity movement activity profiles in official match-play; b) to inform and verify the construct validity of tests commonly used to determine repeated-sprint ability in soccer by investigating the relationship between the results from a test of repeated-sprint ability and repeated high-intensity performance in competition. High-intensity running performance (movement at velocities >19.8 km/h for a minimum of 1-s duration) in 20 players was measured using computerised time motion analysis. Performance in 80 French League 1 matches was analysed. In addition, 12 out of the 20 players performed a repeated-sprint test on a non-motorized treadmill consisting of 6 consecutive 6s sprints separated by 20s passive recovery intervals. In all players, the majority of consecutive high-intensity actions in competition were performed after recovery durations ≥61s, recovery activity separating these efforts was generally active in nature with the major part of this spent walking, and players performed 1.1±1.1 repeated high-intensity bouts (a minimum of 3 consecutive high-intensity with a mean recovery time ≤20s separating efforts) per game. Players reporting lowest performance decrements in the repeated-sprint ability test performed more high-intensity actions interspersed by short recovery times (≤20s, p<0.01 and ≤30s, p<0.05) compared to those with higher decrements. Across positional roles, central-midfielders performed a greater number of high-intensity actions separated by short recovery times (≤20s) and spent a larger proportion of time running at higher intensities during recovery periods while fullbacks performed the most repeated high-intensity bouts (statistical differences across positional roles from p<0.05 to p<0.001). These findings have implications for repeated high-intensity testing and physical conditioning regimens
Influence of ion implantation on the magnetic and transport properties of manganite films
We have used oxygen ions irradiation to generate controlled structural
disorder in thin manganite films. Conductive atomic force microscopy CAFM),
transport and magnetic measurements were performed to analyze the influence of
the implantation process in the physical properties of the films. CAFM images
show regions with different conductivity values, probably due to the random
distribution of point defect or inhomogeneous changes of the local Mn3+/4+
ratio to reduce lattice strains of the irradiated areas. The transport and
magnetic properties of these systems are interpreted in this context.
Metal-insulator transition can be described in the frame of a percolative
model. Disorder increases the distance between conducting regions, lowering the
observed TMI. Point defect disorder increases localization of the carriers due
to increased disorder and locally enhanced strain field. Remarkably, even with
the inhomogeneous nature of the samples, no sign of low field magnetoresistance
was found. Point defect disorder decreases the system magnetization but doesn t
seem to change the magnetic transition temperature. As a consequence, an
important decoupling between the magnetic and the metal-insulator transition is
found for ion irradiated films as opposed to the classical double exchange
model scenario.Comment: 27 pages, 11 Figure
Random Planar Lattices and Integrated SuperBrownian Excursion
In this paper, a surprising connection is described between a specific brand
of random lattices, namely planar quadrangulations, and Aldous' Integrated
SuperBrownian Excursion (ISE). As a consequence, the radius r_n of a random
quadrangulation with n faces is shown to converge, up to scaling, to the width
r=R-L of the support of the one-dimensional ISE. More generally the
distribution of distances to a random vertex in a random quadrangulation is
described in its scaled limit by the random measure ISE shifted to set the
minimum of its support in zero.
The first combinatorial ingredient is an encoding of quadrangulations by
trees embedded in the positive half-line, reminiscent of Cori and Vauquelin's
well labelled trees. The second step relates these trees to embedded (discrete)
trees in the sense of Aldous, via the conjugation of tree principle, an
analogue for trees of Vervaat's construction of the Brownian excursion from the
bridge.
From probability theory, we need a new result of independent interest: the
weak convergence of the encoding of a random embedded plane tree by two contour
walks to the Brownian snake description of ISE.
Our results suggest the existence of a Continuum Random Map describing in
term of ISE the scaled limit of the dynamical triangulations considered in
two-dimensional pure quantum gravity.Comment: 44 pages, 22 figures. Slides and extended abstract version are
available at http://www.loria.fr/~schaeffe/Pub/Diameter/ and
http://www.iecn.u-nancy.fr/~chassain
RIPK3-mediated cell death is involved in DUX4-mediated toxicity in facioscapulohumeral dystrophy
BACKGROUND: Facioscapulohumeral dystrophy (FSHD) is caused by mutations leading to the aberrant expression of the DUX4 transcription factor in muscles. DUX4 was proposed to induce cell death, but the involvement of different death pathways is still discussed. A possible pro-apoptotic role of DUX4 was proposed, but as FSHD muscles are characterized by necrosis and inflammatory infiltrates, non-apoptotic pathways may be also involved. METHODS: We explored DUX4-mediated cell death by focusing on the role of one regulated necrosis pathway called necroptosis, which is regulated by RIPK3. We investigated the effect of necroptosis on cell death in vitro and in vivo experiments using RIPK3 inhibitors and a RIPK3-deficient transgenic mouse model. RESULTS: We showed in vitro that DUX4 expression causes a caspase-independent and RIPK3-mediated cell death in both myoblasts and myotubes. In vivo, RIPK3-deficient animals present improved body and muscle weights, a reduction of the aberrant activation of the DUX4 network genes, and an improvement of muscle histology. CONCLUSIONS: These results provide evidence for a role of RIPK3 in DUX4-mediated cell death and open new avenues of research
Bare vs effective pairing forces. A microscopic finite-range interaction for HFB calculations in coordinate space
We propose a microscopic effective interaction to treat pairing correlations
in the channel. It is introduced by recasting the gap equation
written in terms of the bare force into a fully equivalent pairing problem.
Within this approach, the proposed interaction reproduces the pairing
properties provided by the realistic force very accurately. Written in
the canonical basis of the actual Bogolyubov transformation, the force takes
the form of an off-shell in-medium two-body matrix in the superfluid phase
multiplied by a BCS occupation number . This interaction is finite
ranged, non local, total-momentum dependent and density dependent. The factor
emerging from the recast of the gap equation provides a natural
cut-off and makes zero-range approximations of the effective vertex meaningful.
Performing such an approximation, the roles of the range and of the density
dependence of the interaction can be disentangled. The isoscalar and isovector
density-dependences derived ab-initio provide the pairing force with a strong
predictive power when extrapolated toward the drip-lines. Although finite
ranged and non local, the proposed interaction makes HFB calculations of finite
nuclei in coordinate space tractable. Through the two-basis method, its
computational cost is of the same order as for a zero-range force.Comment: 43 pages, 13 figures. Published versio
- …