1,651 research outputs found
On First Order Formalism in String Theory
We consider the first order formalism in string theory, providing a new
off-shell description of the nontrivial backgrounds around an "infinite
metric". The OPE of the vertex operators, corresponding to the background
fields in some "twistor representation", and conditions of conformal invariance
results in the quadratic equation for the background fields, which appears to
be equivalent to the Einstein equations with a Kalb-Ramond B-field and a
dilaton. Using a new representation for the Einstein equations with B-field and
dilaton we find a new class of solutions including the plane waves for metric
(graviton) and the B-field. We discuss the properties of these background
equations and main features of the BRST operator in this approach.Comment: LaTeX2e, 18 pages, Phys. Lett. B, in press, corrected typo
-opers, the -Langlands correspondence, and quantum/classical duality
A special case of the geometric Langlands correspondence is given by the
relationship between solutions of the Bethe ansatz equations for the Gaudin
model and opers - connections on the projective line with extra structure. In
this paper, we describe a deformation of this correspondence for . We
introduce a difference equation version of opers called -opers and prove a
-Langlands correspondence between nondegenerate solutions of the Bethe
ansatz equations for the XXZ model and nondegenerate twisted -opers with
regular singularities on the projective line. We show that the
quantum/classical duality between the XXZ spin chain and the trigonometric
Ruijsenaars-Schneider model may be viewed as a special case of the
-Langlands correspondence. We also describe an application of -opers to
the equivariant quantum -theory of the cotangent bundles to partial flag
varieties.Comment: v3: 32 pages, 2 figures; minor revisions, to appear in Commun. Math.
Phy
Medication Use in Pregnant Women with Chronic Medical Conditions
Dr. Deborah Zeitlin addresses medication options for pregnant women with chronic conditions such as: hypertension, asthma, diabetes, and depression. Risks of medication use to the fetus are addressed
Do Antibiotics Improve Outcomes for Patients Hospitalized with COPD Exacerbations?
EVIDENCE-BASED ANSWER
YES. Antibiotic use reduced mortality and treatment failure in patients hospitalized with acute exacerbations of chronic obstructive pulmonary disease (COPD) (strength of recommendation [SOR]: A, systematic reviews of randomized controlled trials [RCTs]).
Giving antibiotics early to hospitalized patients decreased the need for later ventilation and readmission within 30 days for exacerbation of COPD (SOR: B, a retrospective cohort study)
Opers on the projective line, Wronskian relations, and the Bethe Ansatz
It is well-known that the spectra of the Gaudin model may be described in
terms of solutions of the Bethe Ansatz equations. A conceptual explanation for
the appearance of the Bethe Ansatz equations is provided by appropriate
-opers: -connections on the projective line with extra structure. In
fact, solutions of the Bethe Ansatz equations are parameterized by an enhanced
version of opers called Miura opers; here, the opers appearing have only
regular singularities. Feigin, Frenkel, Rybnikov, and Toledano Laredo have
introduced an inhomogeneous version of the Gaudin model; this model
incorporates an additional twist factor, which is an element of the Lie algebra
of . They exhibited the Bethe Ansatz equations for this model and gave a
geometric interpretation of the spectra in terms of opers with an irregular
singularity. In this paper, we consider a new approach to the study of the
spectra of the inhomogeneous Gaudin model in terms of a further enhancement of
opers called twisted Miura-Pl\"ucker opers and a certain system of nonlinear
differential equations called the -system. We show that there is a close
relationship between solutions of the inhomogeneous Bethe Ansatz equations and
polynomial solutions of the -system and use this fact to construct a
bijection between the set of solutions of the inhomogeneous Bethe Ansatz
equations and the set of nondegenerate twisted Miura-Pl\"ucker opers. We
further prove that as long as certain combinatorial conditions are satisfied,
nondegenerate twisted Miura-Pl\"ucker opers are in fact Miura opers.Comment: 38 pages, revised versio
SFT-inspired Algebraic Structures in Gauge Theories
We consider gauge theories in a String Field Theory-inspired formalism. The
constructed algebraic operations lead in particular to homotopy algebras of the
related BV theories. We discuss invariant description of the gauge fixing
procedure and special algebraic features of gauge theories coupled to matter
fields.Comment: LaTeX2e, 26 pages; minor revisions after referee's remarks, typos
corrected, title changed, references added, J. Mathematical Physics, in pres
A Series of N-terminal Epitope Tagged Hdh Knock-In Alleles Expressing Normal and Mutant Huntingtin: Their Application to Understanding the Effect of Increasing the Length of Normal Huntingtin’s Polyglutamine Stretch on CAG140 Mouse Model Pathogenesis
Background: Huntington’s disease (HD) is an autosomal dominant neurodegenerative disease that is caused by the expansion of a polyglutamine (polyQ) stretch within Huntingtin (htt), the protein product of the HD gene. Although studies in vitro have suggested that the mutant htt can act in a potentially dominant negative fashion by sequestering wild-type htt into insoluble protein aggregates, the role of the length of the normal htt polyQ stretch, and the adjacent proline-rich region (PRR) in modulating HD mouse model pathogenesis is currently unknown. Results: We describe the generation and characterization of a series of knock-in HD mouse models that express versions of the mouse HD gene (Hdh) encoding N-terminal hemaglutinin (HA) or 3xFlag epitope tagged full-length htt with different polyQ lengths (HA7Q-, 3xFlag7Q-, 3xFlag20Q-, and 3xFlag140Q-htt) and substitution of the adjacent mouse PRR with the human PRR (3xFlag20Q- and 3xFlag140Q-htt). Using co-immunoprecipitation and immunohistochemistry analyses, we detect no significant interaction between soluble full-length normal 7Q- htt and mutant (140Q) htt, but we do observe N-terminal fragments of epitope-tagged normal htt in mutant htt aggregates. When the sequences encoding normal mouse htt’s polyQ stretch and PRR are replaced with non-pathogenic human sequence in mice also expressing 140Q-htt, aggregation foci within the striatum, and the mean size of htt inclusions are increased, along with an increase in striatal lipofuscin and gliosis. Conclusion: In mice, soluble full-length normal and mutant htt are predominantly monomeric. In heterozygous knock-in HD mouse models, substituting the normal mouse polyQ and PRR with normal human sequence can exacerbate some neuropathological phenotypes
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