14,193 research outputs found
Towards general super Casimir equations for SCFTs
Applying the Casimir operator to four-point functions in CFTs allows us to
find the conformal blocks for any external operators. In this work, we initiate
the program to find the superconformal blocks, using the super Casimir
operator, for SCFTs. We begin by finding the most general
four-point function with zero -charge, including all the possible
nilpotent structures allowed by the superconformal algebra. We then study
particular cases where some of the operators satisfy shortening conditions.
Finally, we obtain the super Casimir equations for four point-functions which
contain a chiral and an anti-chiral field. We solve the super Casimir equations
by writing the superconformal blocks as a sum of several conformal blocks.Comment: Added a missing term in eqs. (3.31) and (3.39). Section 4.3
corrected. Abstract fixe
Noncommutative Koszul Algebras from Combinatorial Topology
Associated to any uniform finite layered graph Gamma there is a
noncommutative graded quadratic algebra A(Gamma) given by a construction due to
Gelfand, Retakh, Serconek and Wilson. It is natural to ask when these algebras
are Koszul. Unfortunately, a mistake in the literature states that all such
algebras are Koszul. That is not the case and the theorem was recently
retracted. We analyze the Koszul property of these algebras for two large
classes of graphs associated to finite regular CW complexes, X. Our methods are
primarily topological. We solve the Koszul problem by introducing new
cohomology groups H_X(n,k), generalizing the usual cohomology groups H^n(X).
Along with several other results, our methods give a new and primarily
topological proof of a result of Serconek and Wilson and of Piontkovski.Comment: 22 pages, 1 figur
Interior of Distorted Black Holes
We study the interior of distorted static axisymmetric black holes. We obtain
a general interior solution and study its asymptotics both near the horizon and
singularity. As a special example, we apply the obtained results to the case of
the so-called `caged' black holes.Comment: 12 pages, 16 figure
The irradiated ISM of ULIRGs
The nuclei of ULIRGs harbor massive young stars, an accreting central black
hole, or both. Results are presented for molecular gas that is exposed to
X-rays (1-100 keV, XDRs) and far-ultraviolet radiation (6-13.6 eV, PDRs).
Attention is paid to species like HCO+, HCN, HNC, OH, H2O and CO. Line ratios
of HCN/HCO+ and HNC/HCN discriminate between PDRs and XDRs. Very high J (>10)
CO lines, observable with HIFI/Herschel, discriminate very well between XDRs
and PDRs. In XDRs, it is easy to produce large abundances of warm (T>100 K) H2O
and OH. In PDRs, only OH is produced similarly well.Comment: 5 pages, 6 figures, to appear in: IAU Symposium 242 Astrophysical
Masers and their Environment
The Drosophila DIAP1 protein is required to prevent accumulation of a continuously generated, processed form of the apical caspase DRONC
Although loss of the inhibitor of apoptosis (LAP) protein DIAP1 has been shown to result in caspase activation and spontaneous cell death in Drosophila cells and embryos, the point at which DIAP1 normally functions to inhibit caspase activation is unknown. Depletion of the DIAP1 protein in Drosophila S2 cells or the Sf-IAP protein in Spodoptera frugiperda Sf21 cells by RNA interference (RNAi) or cycloheximide treatment resulted in rapid and widespread caspase-dependent apoptosis. Co-silencing of dronc or dark largely suppressed this apoptosis, indicating that DIAP1 is normally required to inhibit an activity dependent on these proteins. Silencing of dronc also inhibited DRICE processing following stimulation of apoptosis, demonstrating that DRONC functions as an apical caspase in S2 cells. Silencing of diap1 or treatment with UV light induced DRONC processing, which occurred in two steps. The first step appeared to occur continuously even in the absence of an apoptotic signal and to be dependent on DARK because full-length DRONC accumulated when dark was silenced in non-apoptotic cells. In addition, treatment with the proteasome inhibitor MG132 resulted in accumulation of this initially processed form of DRONC, but not full-length DRONC, in non-apoptotic cells. The second step in DRONC processing was observed only in apoptotic cells. These results indicate that the initial step in DRONC processing occurs continuously via a DARK-dependent mechanism in Drosophila cells and that DIAP1 is required to prevent excess accumulation of this first form of processed DRONC, presumably through its ability to act as a ubiquitin-protein ligase
Comments on geometric and universal open string tachyons near fivebranes
In a recent paper (hep-th/0703157), Sen studied unstable D-branes in
NS5-branes backgrounds and argued that in the strong curvature regime the
universal open string tachyon (on D-branes of the wrong dimensionality) and the
geometric tachyon (on D-branes that are BPS in flat space but not in this
background) may become equivalent. We study in this note an example of a
non-BPS suspended D-brane vs. a BPS D-brane at equal distance between two
fivebranes. We use boundary worldsheet CFT methods to show that these two
unstable branes are identical.Comment: 8 pages, 1 figure; ver. 2 to appear in JHEP: one comment, refs and
appendices adde
On Scaling Solutions with a Dissipative Fluid
We study the asymptotic behaviour of scaling solutions with a dissipative
fluid and we show that, contrary to recent claims, the existence of stable
accelerating attractor solution which solves the `energy' coincidence problem
depends crucially on the chosen equations of state for the thermodynamical
variables. We discuss two types of equations of state, one which contradicts
this claim, and one which supports it.Comment: 8 pages and 5 figures; to appear in Class. Quantum Gra
Generalised Bose-Einstein phase transition in large- component spin glasses
It is proposed to understand finite dimensional spin glasses using a
expansion, where is the number of spin components. It is shown that this
approach predicts a replica symmetric state in finite dimensions. The point
about which the expansion is made, the infinite- limit, has been studied in
the mean-field limit in detail and has a very unusual phase transition, rather
similar to a Bose-Einstein phase transition but with macroscopically
occupied low-lying states.Comment: 4 pages (plus a few lines), 3 figures. v2: minor error corrected. v3:
numerics supplemented by analytical arguments, references added, figure of
density of states adde
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