6,227 research outputs found
Combinatorial realizations of crystals via torus actions on quiver varieties
Consider Kashiwara's crystal associated to a highest weight representation of
a symmetric Kac-Moody algebra. There is a geometric realization of this object
using Nakajima's quiver varieties, but in many particular cases it can also be
realized by elementary combinatorial methods. Here we propose a framework for
extracting combinatorial realizations from the geometric picture: We construct
certain torus actions on the quiver varieties and use Morse theory to index the
irreducible components by connected components of the subvariety of torus fixed
points. We then discuss the case of affine sl(n). There the fixed point
components are just points, and are naturally indexed by multi-partitions.
There is some choice in our construction, leading to a family of combinatorial
models for each highest weight crystal. Applying this construction to the
crystal of the fundamental representation recovers a family of combinatorial
realizations recently constructed by Fayers. This gives a more conceptual proof
of Fayers' result as well as a generalization to higher level. We also discuss
a relationship with Nakajima's monomial crystal.Comment: 23 pages, v2: added Section 8 on monomial crystals and some
references; v3: many small correction
Weight Vectors of the Basic A_1^(1)-Module and the Littlewood-Richardson Rule
The basic representation of \A is studied. The weight vectors are
represented in terms of Schur functions. A suitable base of any weight space is
given. Littlewood-Richardson rule appears in the linear relations among weight
vectors.Comment: February 1995, 7pages, Using AMS-Te
Non-universal Efimov Atom-Dimer Resonances in a Three-Component Mixture of 6Li
We observed an enhanced atom-dimer relaxation due to the existence of Efimov
states in a three-component mixture of 6Li atoms. We measured the
magnetic-field dependence of the atom-dimer loss coefficient in the mixture of
atoms in state |1> and dimers formed in states |2> and |3>, and found two peaks
corresponding to the degeneracy points of the |23> dimer energy level and
energy levels of Efimov trimers. We found that the locations of these peaks
disagree with universal theory predictions, in a way that cannot be explained
by non-universal two-body properties. We constructed theoretical models that
characterize the non-universal three-body physics of three-component 6Li atoms
in the low energy domain.Comment: 5 pages, 3 figure
Cloud absorption properties as derived from airborne measurements of scattered radiation within clouds
Researchers briefly review the diffusion domain method for deriving the cloud similarity parameter and present preliminary analyses of the results thus far obtained. The presentation concentrates on the following points: (1) intercomparison of calibrated reflected intensities between the cloud absorption radiometer and the U.K. multispectral cloud radiometer; (2) quality control tests required to select those portions of an aircraft flight for which measurements are obtained within the diffusion domain; (3) case studies of the spectral similarity parameter of marine stratocumulus clouds; and comparisons of the experimentally-derived similarity parameter spectrum with that expected theoretically from the cloud droplet size distribution obtained from in situ observations
A-site Randomness Effect on Structural and Physical Properties of Ba-based Perovskite Manganites
The discovery of novel structural and physical properties in the -site
ordered manganite BaMnO ( = Y and rare earth elements) has
demanded new comprehension about perovskite manganese oxides. In the present
study, the -site disordered form, BaMnO, has been
investigated and compared with both BaMnO and
MnO (: Sr, Ca) in the structures and electromagnetic
properties. BaMnO has a primitive cubic perovskite cell
in the structure and magnetic glassy states are dominant as its ground state,
in contrast to the ordinary disordered MnO (: Sr, Ca).
In Pr-compounds with various degrees of Pr/Ba randomness at the -sites, the
-site disorder gradually suppresses both ferromagnetic and A-type
antiferromagnetic transitions and finally leads to a magnetic glassy state in
PrBaMnO. A peculiar behavior, multi-step magnetization
and resistivity change, has been observed in PrBaMnO.
These properties could be closely related to any spatial heterogeneity caused
by the random distribution of Ba and with much different
ionic radius.Comment: 9 pages, to be published in J. Phys. Soc. Jpn. 73 Aug. (2004
On minimal affinizations of representations of quantum groups
In this paper we study minimal affinizations of representations of quantum
groups (generalizations of Kirillov-Reshetikhin modules of quantum affine
algebras introduced by Chari). We prove that all minimal affinizations in types
A, B, G are special in the sense of monomials. Although this property is not
satisfied in general, we also prove an analog property for a large class of
minimal affinization in types C, D, F. As an application, the Frenkel-Mukhin
algorithm works for these modules. For minimal affinizations of type A, B we
prove the thin property (the l-weight spaces are of dimension 1) and a
conjecture of Nakai-Nakanishi (already known for type A). The proof of the
special property is extended uniformly for more general quantum affinizations
of quantum Kac-Moody algebras.Comment: 38 pages; references and additional results added. Accepted for
publication in Communications in Mathematical Physic
Langlands duality for finite-dimensional representations of quantum affine algebras
We describe a correspondence (or duality) between the q-characters of
finite-dimensional representations of a quantum affine algebra and its
Langlands dual in the spirit of q-alg/9708006 and 0809.4453. We prove this
duality for the Kirillov-Reshetikhin modules and their irreducible tensor
products. In the course of the proof we introduce and construct "interpolating
(q,t)-characters" depending on two parameters which interpolate between the
q-characters of a quantum affine algebra and its Langlands dual.Comment: 40 pages; several results and comments added. Accepted for
publication in Letters in Mathematical Physic
Instantons on ALE spaces and Super Liouville Conformal Field Theories
We provide evidence that the conformal blocks of N=1 super Liouville
conformal field theory are described in terms of the SU(2) Nekrasov partition
function on the ALE space O_{P^1}(-2).Comment: 10 page
Footprints in the wind of Vela X-1 traced with MAXI
The stellar wind around the compact object in luminous wind-accreting high
mass X-ray binaries is expected to be strongly ionized with the X-rays coming
from the compact object. The stellar wind of hot stars is mostly driven by
light absorption in lines of heavier elements, and X-ray photo-ionization
significantly reduces the radiative force within the so-called Stroemgren
region leading to wind stagnation around the compact object. In close binaries
like Vela X-1 this effect might alter the wind structure throughout the system.
Using the spectral data from Monitor of All-sky X-ray Image (MAXI), we study
the observed dependence of the photoelectric absorption as function of orbital
phase in Vela X-1, and find that it is inconsistent with expectations for a
spherically-symmetric smooth wind. Taking into account previous investigations
we develop a simple model for wind structure with a stream-like photoionization
wake region of slower and denser wind trailing the neutron star responsible for
the observed absorption curve.Comment: 5 pages, 3 figures, accepted in A&
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