193 research outputs found
Minkowski superspaces and superstrings as almost real-complex supermanifolds
In 1996/7, J. Bernstein observed that smooth or analytic supermanifolds that
mathematicians study are real or (almost) complex ones, while Minkowski
superspaces are completely different objects. They are what we call almost
real-complex supermanifolds, i.e., real supermanifolds with a non-integrable
distribution, the collection of subspaces of the tangent space, and in every
subspace a complex structure is given.
An almost complex structure on a real supermanifold can be given by an even
or odd operator; it is complex (without "always") if the suitable superization
of the Nijenhuis tensor vanishes. On almost real-complex supermanifolds, we
define the circumcised analog of the Nijenhuis tensor. We compute it for the
Minkowski superspaces and superstrings. The space of values of the circumcised
Nijenhuis tensor splits into (indecomposable, generally) components whose
irreducible constituents are similar to those of Riemann or Penrose tensors.
The Nijenhuis tensor vanishes identically only on superstrings of
superdimension 1|1 and, besides, the superstring is endowed with a contact
structure. We also prove that all real forms of complex Grassmann algebras are
isomorphic although singled out by manifestly different anti-involutions.Comment: Exposition of the same results as in v.1 is more lucid. Reference to
related recent work by Witten is adde
Topology Change in Canonical Quantum Cosmology
We develop the canonical quantization of a midisuperspace model which
contains, as a subspace, a minisuperspace constituted of a
Friedman-Lema\^{\i}tre-Robertson-Walker Universe filled with homogeneous scalar
and dust fields, where the sign of the intrinsic curvature of the spacelike
hypersurfaces of homogeneity is not specified, allowing the study of topology
change in these hypersurfaces. We solve the Wheeler-DeWitt equation of the
midisuperspace model restricted to this minisuperspace subspace in the
semi-classical approximation. Adopting the conditional probability
interpretation, we find that some of the solutions present change of topology
of the homogeneous hypersurfaces. However, this result depends crucially on the
interpretation we adopt: using the usual probabilistic interpretation, we find
selection rules which forbid some of these topology changes.Comment: 23 pages, LaTex file. We added in the conclusion some comments about
path integral formalism and corrected litle misprinting
Notes on Stein-Sahi representations and some problems of non harmonic analysis
We discuss one natural class of kernels on pseudo-Riemannian symmetric
spaces.Comment: 40p
Immunological Mechanisms Mediating Hantavirus Persistence in Rodent Reservoirs
Hantaviruses, similar to several emerging zoonotic viruses, persistently infect their natural reservoir hosts, without causing overt signs of disease. Spillover to incidental human hosts results in morbidity and mortality mediated by excessive proinflammatory and cellular immune responses. The mechanisms mediating the persistence of hantaviruses and the absence of clinical symptoms in rodent reservoirs are only starting to be uncovered. Recent studies indicate that during hantavirus infection, proinflammatory and antiviral responses are reduced and regulatory responses are elevated at sites of increased virus replication in rodents. The recent discovery of structural and non-structural proteins that suppress type I interferon responses in humans suggests that immune responses in rodent hosts could be mediated directly by the virus. Alternatively, several host factors, including sex steroids, glucocorticoids, and genetic factors, are reported to alter host susceptibility and may contribute to persistence of hantaviruses in rodents. Humans and reservoir hosts differ in infection outcomes and in immune responses to hantavirus infection; thus, understanding the mechanisms mediating viral persistence and the absence of disease in rodents may provide insight into the prevention and treatment of disease in humans. Consideration of the coevolutionary mechanisms mediating hantaviral persistence and rodent host survival is providing insight into the mechanisms by which zoonotic viruses have remained in the environment for millions of years and continue to be transmitted to humans
Estimation of the effective growth rate of a plate of bainitic ferrite in dynamic theory
Specific features of cast high-entropy AlCrFeCoNiCu alloys produced by ultrarapid quenching from the melt
Some problems of recrystallization of austenite during high-temperature thermomechanical treatment of chromium steels
Strain-hardening of martensite as a means of strengthening thermomechanically treated 55KhFA steel
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