6,217 research outputs found
The bosonic string and superstring models in 26+2 and 10+2 dimensional space--time, and the generalized Chern-Simons action
We have covariantized the Lagrangians of the U(1)_V * U(1)_A models, which
have U(1)_V * U(1)_A gauge symmetry in two dimensions, and studied their
symmetric structures. The special property of the U(1)_V * U(1)_A models is the
fact that all these models have an extra time coordinate in the target
space-time. The U(1)_V * U(1)_A models coupled to two-dimensional gravity are
string models in 26+2 dimensional target space-time for bosonic string and in
10+2 dimensional target space-time for superstring. Both string models have two
time coordinates. In order to construct the covariant Lagrangians of the U(1)_V
* U(1)_A models the generalized Chern-Simons term plays an important role. The
supersymmetric generalized Chern-Simons action is also proposed. The
Green-Schwarz type of U(1)_V * U(1)_A superstring model has another fermionic
local symmetry as well as \kappa-symmetry. The supersymmetry of target
space-time is different from the standard one.Comment: 27 pages, no figure
A Nonliearly Dispersive Fifth Order Integrable Equation and its Hierarchy
In this paper, we study the properties of a nonlinearly dispersive integrable
system of fifth order and its associated hierarchy. We describe a Lax
representation for such a system which leads to two infinite series of
conserved charges and two hierarchies of equations that share the same
conserved charges. We construct two compatible Hamiltonian structures as well
as their Casimir functionals. One of the structures has a single Casimir
functional while the other has two. This allows us to extend the flows into
negative order and clarifies the meaning of two different hierarchies of
positive flows. We study the behavior of these systems under a hodograph
transformation and show that they are related to the Kaup-Kupershmidt and the
Sawada-Kotera equations under appropriate Miura transformations. We also
discuss briefly some properties associated with the generalization of second,
third and fourth order Lax operators.Comment: 11 pages, LaTex, version to be published in Journal of Nonlinear
Mathematical Physics, has expanded discussio
Structural Characterization of Amorfrutins Bound to the Peroxisome Proliferator-Activated Receptor gamma
Amorfrutins are a family of natural products with high affinity to the peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear receptor regulating lipid and glucose metabolism. The PPARgamma agonist rosiglitazone increases insulin sensitivity and is effective against type II diabetes but has severe adverse effects including weight gain. Amorfrutins improve insulin sensitivity and dyslipidemia but do not enhance undesired fat storage. They bear potential as therapeutics or prophylactic dietary supplements. We identified amorfrutin B as a novel partial agonist of PPARgamma with a considerably higher affinity than that of previously reported amorfrutins, similar to that of rosiglitazone. Crystal structures reveal the geranyl side chain of amorfrutin B as the cause of its particularly high affinity. Typical for partial agonists, amorfrutins 1, 2, and B bind helix H3 and the beta-sheet of PPARgamma but not helix H12
Mott Transition vs Multicritical Phenomenon of Superconductivity and Antiferromagnetism -- Application to -(BEDT-TTF)X --
Interplay between the Mott transition and the multicritical phenomenon of
d-wave superconductivity (SC) and antiferromagnetism (AF) is studied
theoretically. We describe the Mott transition, which is analogous to a
liquid-gas phase transition, in terms of an Ising-type order parameter .
We reveal possible mean-field phase diagrams produced by this interplay.
Renormalization group analysis up to one-loop order gives flows of coupling
constants, which in most cases lead to fluctuation-induced first-order phase
transitions even when the SO(5) symmetry exists betwen the SC and AF. Behaviors
of various physical quantities around the Mott critical point are predicted.
Experiments in -(BEDT-TTF)X are discussed from this viewpoint.Comment: 4 pages, 9 figures, to appear in J. Phys. Soc. Jp
Twisted Superspace for N=D=2 Super BF and Yang-Mills with Dirac-K\"ahler Fermion Mechanism
We propose a twisted D=N=2 superspace formalism. The relation between the
twisted super charges including the BRST charge, vector and pseudo scalar super
charges and the N=2 spinor super charges is established. We claim that this
relation is essentially related with the Dirac-K\"ahler fermion mechanism. We
show that a fermionic bilinear form of twisted N=2 chiral and anti-chiral
superfields is equivalent to the quantized version of BF theory with the Landau
type gauge fixing while a bosonic bilinear form leads to the N=2 Wess-Zumino
action. We then construct a Yang-Mills action described by the twisted N=2
chiral and vector superfields, and show that the action is equivalent to the
twisted version of the D=N=2 super Yang-Mills action, previously obtained from
the quantized generalized topological Yang-Mills action with instanton gauge
fixing.Comment: 36 page
Transport criticality of the first-order Mott transition in a quasi-two-dimensional organic conductor, -(BEDT-TTF)Cu[N(CN)]Cl
An organic Mott insulator, -(BEDT-TTF)Cu[N(CN)]Cl, was
investigated by resistance measurements under continuously controllable He gas
pressure. The first-order Mott transition was demonstrated by observation of
clear jump in the resistance variation against pressure. Its critical endpoint
at 38 K is featured by vanishing of the resistive jump and critical divergence
in pressure derivative of resistance, , which are consistent with the prediction of the dynamical mean field
theory and have phenomenological correspondence with the liquid-gas transition.
The present results provide the experimental basis for physics of the Mott
transition criticality.Comment: 4 pages, 5 figure
Distributed Graph Clustering using Modularity and Map Equation
We study large-scale, distributed graph clustering. Given an undirected
graph, our objective is to partition the nodes into disjoint sets called
clusters. A cluster should contain many internal edges while being sparsely
connected to other clusters. In the context of a social network, a cluster
could be a group of friends. Modularity and map equation are established
formalizations of this internally-dense-externally-sparse principle. We present
two versions of a simple distributed algorithm to optimize both measures. They
are based on Thrill, a distributed big data processing framework that
implements an extended MapReduce model. The algorithms for the two measures,
DSLM-Mod and DSLM-Map, differ only slightly. Adapting them for similar quality
measures is straight-forward. We conduct an extensive experimental study on
real-world graphs and on synthetic benchmark graphs with up to 68 billion
edges. Our algorithms are fast while detecting clusterings similar to those
detected by other sequential, parallel and distributed clustering algorithms.
Compared to the distributed GossipMap algorithm, DSLM-Map needs less memory, is
up to an order of magnitude faster and achieves better quality.Comment: 14 pages, 3 figures; v3: Camera ready for Euro-Par 2018, more
details, more results; v2: extended experiments to include comparison with
competing algorithms, shortened for submission to Euro-Par 201
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Internal charge behaviour of nanocomposites
The incorporation of 23 nm titanium dioxide nanoparticles into an epoxy matrix to form a nanocomposite structure is described. It is shown that the use of nanometric particles results in a substantial change in the behaviour of the composite, which can be traced to the mitigation of internal charge when a comparison is made with conventional TiO2 fillers. A variety of diagnostic techniques (including dielectric spectroscopy, electroluminescence, thermally stimulated current, photoluminescence) have been used to augment pulsed electro-acoustic space charge measurement to provide a basis for understanding the underlying physics of the phenomenon. It would appear that, when the size of the inclusions becomes small enough, they act co-operatively with the host structure and cease to exhibit interfacial properties leading to Maxwell-Wagner polarization. It is postulated that the particles are surrounded by high charge concentrations in the Gouy-Chapman-Stern layer. Since nanoparticles have very high specific areas, these regions allow limited charge percolation through nano-filled dielectrics. The practical consequences of this have also been explored in terms of the electric strength exhibited. It would appear that there was a window in which real advantages accrue from the nano-formulated material. An optimum loading of about 10% (by weight) is indicated
Hyperelliptic Solutions of KdV and KP equations: Reevaluation of Baker's Study on Hyperelliptic Sigma Functions
Explicit function forms of hyperelliptic solutions of Korteweg-de Vries (KdV)
and \break Kadomtsev-Petviashvili (KP) equations were constructed for a given
curve whose genus is three. This study was based upon the fact
that about one hundred years ago (Acta Math. (1903) {\bf{27}}, 135-156), H. F.
Baker essentially derived KdV hierarchy and KP equation by using bilinear
differential operator , identities of Pfaffians, symmetric
functions, hyperelliptic -function and -functions; . The connection between his theory and the modern
soliton theory was also discussed.Comment: AMS-Tex, 12 page
Dynamical Wilson fermions and the problem of the chiral limit in compact lattice QED
We compare the approach to the chiral transition line ~\kappa_c(\bt)~ in
quenched and full compact lattice QED with Wilson fermions within the
confinement phase, especially in the pseudoscalar sector of the theory. We show
that in the strong coupling limit () the quenched theory is a good
approximation to the full one, in contrast to the case of . At the
larger -value the transition in the full theory is inconsistent with the
zero--mass limit of the pseudoscalar particle, thus prohibiting the definition
of a chiral limit.Comment: 13 pages LaTeX (epsf), all figures include
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