89 research outputs found
Infinitesimal Lyapunov functions for singular flows
We present an extension of the notion of infinitesimal Lyapunov function to
singular flows, and from this technique we deduce a characterization of
partial/sectional hyperbolic sets. In absence of singularities, we can also
characterize uniform hyperbolicity.
These conditions can be expressed using the space derivative DX of the vector
field X together with a field of infinitesimal Lyapunov functions only, and are
reduced to checking that a certain symmetric operator is positive definite at
the tangent space of every point of the trapping region.Comment: 37 pages, 1 figure; corrected the statement of Lemma 2.2 and item (2)
of Theorem 2.7; removed item (5) of Theorem 2.7 and its wrong proof since the
statement of this item was false; corrected items (1) and (2) of Theorem 2.23
and their proofs. Included Example 6 on smooth reduction of families of
quadratic forms. The published version in Math Z journal needs an errat
Observation of a J^PC = 1-+ exotic resonance in diffractive dissociation of 190 GeV/c pi- into pi- pi- pi+
The COMPASS experiment at the CERN SPS has studied the diffractive
dissociation of negative pions into the pi- pi- pi+ final state using a 190
GeV/c pion beam hitting a lead target. A partial wave analysis has been
performed on a sample of 420000 events taken at values of the squared
4-momentum transfer t' between 0.1 and 1 GeV^2/c^2. The well-known resonances
a1(1260), a2(1320), and pi2(1670) are clearly observed. In addition, the data
show a significant natural parity exchange production of a resonance with
spin-exotic quantum numbers J^PC = 1-+ at 1.66 GeV/c^2 decaying to rho pi. The
resonant nature of this wave is evident from the mass-dependent phase
differences to the J^PC = 2-+ and 1++ waves. From a mass-dependent fit a
resonance mass of 1660 +- 10+0-64 MeV/c^2 and a width of 269+-21+42-64 MeV/c^2
is deduced.Comment: 7 page, 3 figures; version 2 gives some more details, data unchanged;
version 3 updated authors, text shortened, data unchange
Super-W(infinity) Asymptotic Symmetry of Higher-Spin AdS(3) Supergravity
We consider (2+1)-dimensional (N, M)-extended higher-spin anti-de Sitter
supergravity and study its asymptotic symmetries. The theory is described by
the Chern-Simons action based on a real, infinite-dimensional higher-spin
superalgebra. We specify consistent boundary conditions on the higher-spin
super-gauge connection corresponding to asymptotically anti-de Sitter
spacetimes. We then determine the residual gauge transformations that preserve
these asymptotic conditions and compute their Poisson bracket algebra. We find
that the asymptotic symmetry is enhanced from the higher-spin superalgebra to
some (N,M)-extended super-W(infinity) nonlinear superalgebra. The latter has
the same classical central charge as pure Einstein gravity. Special attention
is paid to the (1,1)-case. Truncation to the bosonic sector yields the
previously found W(infinity) algebra, while truncation to the underlying
finite-dimensional superalgebra reproduces the N-extended superconformal
algebra (in its nonlinear version for N>2). We discuss string theory
realization of these higher-spin anti-de Sitter supergravity theories as well
as relations to previous treatments of super-W(infinity) in the literature.Comment: References added. (N>2)-Extended supersymmetric models argued to be
rigid with respect to lambda-deformation. Comments on G(3)-case adde
QCD and strongly coupled gauge theories : challenges and perspectives
We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.Peer reviewe
HSP70-binding protein HSPBP1 regulates chaperone expression at a posttranslational level and is essential for spermatogenesis
Molecular chaperones play key roles during growth, development, and stress survival. The ability to induce chaperone expression enables cells to cope with the accumulation of nonnative proteins under stress and complete developmental processes with an increased requirement for chaperone assistance. Here we generate and analyze transgenic mice that lack the cochaperone HSPBP1, a nucleotide-exchange factor of HSP70 proteins and inhibitor of chaperone-assisted protein degradation. Male HSPBP1(−/−) mice are sterile because of impaired meiosis and massive apoptosis of spermatocytes. HSPBP1 deficiency in testes strongly reduces the expression of the inducible, antiapoptotic HSP70 family members HSPA1L and HSPA2, the latter of which is essential for synaptonemal complex disassembly during meiosis. We demonstrate that HSPBP1 affects chaperone expression at a posttranslational level by inhibiting the ubiquitylation and proteasomal degradation of inducible HSP70 proteins. We further provide evidence that the cochaperone BAG2 contributes to HSP70 stabilization in tissues other than testes. Our findings reveal that chaperone expression is determined not only by regulated transcription, but also by controlled degradation, with degradation-inhibiting cochaperones exerting essential prosurvival functions
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