181 research outputs found
Molien Function for Duality
The Molien function counts the number of independent group invariants of a
representation. For chiral superfields, it is invariant under duality by
construction. We illustrate how it calculates the spectrum of supersymmetric
gauge theories.Comment: 6 pages, clarifications to sections 3,4 and a reference added, thanks
to O. Aharony, C. Cummins and A. Schwimme
Quantum Determinism for Free Vector Bosons in 3 Dimensions
We apply 't Hooft's deterministic quantum mechanics approach to free vector
bosons in three dimensions and check Lorentz invariance. This approach does not
work for the conformal group, for free bosons in two dimensions. This presents
a technical difficulty for constructing a ``deterministic string theory''.Comment: 8 pages, no figure
Evidence for Winding States in Noncommutative Quantum Field Theory
We study noncommutative field theories at finite temperature to learn more
about the degrees of freedom in the non-planar sector of these systems. We find
evidence for winding states. At temperatures for which the thermal wavelength
is smaller than the noncommutativity scale, there is a drastic reduction of the
degrees of freedom in the non-planar sector. In this regime, the non-planar
sector has thermodynamics resembling that of a 1+1 dimensional field theory.Comment: 15 pages, 3 figures. Typos corrected and minor clarifications adde
A Comment on Zero-brane Quantum Mechanics
We consider low energy, non-relativistic scattering of two Dirichlet
zero-branes as an exercise in quantum mechanics. For weak string coupling and
sufficiently small velocity, the dynamics is governed by an effective U(2)
gauge theory in 0+1 dimensions. At low energies, D-brane scattering can
reliably probe distances much shorter than the string scale. The only length
scale in the quantum mechanics problem is the eleven dimensional Planck length.
This provides evidence for the role of scales shorter than the string length in
the weakly coupled dynamics of type IIA strings.Comment: 9 pages, harvmac, improved treatment of 2+1 proble
Myeloid-Specific Rictor Deletion Induces M1 Macrophage Polarization and Potentiates In Vivo Pro-Inflammatory Response to Lipopolysaccharide
The phosphoinositide-3-kinase (PI3K)/protein kinase B (Akt) axis plays a central role in attenuating inflammation upon macrophage stimulation with toll-like receptor (TLR) ligands. The mechanistic target of rapamycin complex 2 (mTORC2) relays signal from PI3K to Akt but its role in modulating inflammation in vivo has never been investigated. To evaluate the role of mTORC2 in the regulation of inflammation in vivo, we have generated a mouse model lacking Rictor, an essential mTORC2 component, in myeloid cells. Primary macrophages isolated from myeloid-specific Rictor null mice exhibited an exaggerated response to TLRs ligands, and expressed high levels of M1 genes and lower levels of M2 markers. To determine whether the loss of Rictor similarly affected inflammation in vivo, mice were either fed a high fat diet, a situation promoting chronic but low-grade inflammation, or were injected with lipopolysaccharide (LPS), which mimics an acute, severe septic inflammatory condition. Although high fat feeding contributed to promote obesity, inflammation, macrophage infiltration in adipose tissue and systemic insulin resistance, we did not observe a significant impact of Rictor loss on these parameters. However, mice lacking Rictor exhibited a higher sensitivity to sceptic shock when injected with LPS. Altogether, these results indicate that mTORC2 is a key negative regulator of macrophages TLR signalling and that its role in modulating inflammation is particularly important in the context of severe inflammatory challenges. These observations suggest that approaches aimed at modulating mTORC2 activity may represent a possible therapeutic approach for diseases linked to excessive inflammation.Howard Hughes Medical Institute (Investigator)National Institutes of Health (U.S.) (NIH grant CA103866)National Institutes of Health (U.S.) (NIH grant CA129105)National Institutes of Health (U.S.) (NIH grant AI47389)Canadian Institutes of Health ResearchNatural Sciences and Engineering Research Council of CanadaFonds de la recherche en santeÌ du QueÌbe
(S)quark Masses and Non-Abelian Horizontal Symmetries
We present a model of quark and squark masses which is based on a non-Abelian
horizontal symmetry. It leads to order of magnitude relations between quark
mass ratios and mixing angles and to the successful exact relation to better than accuracy. The non-Abelian
symmetry also ensures the necessary squark degeneracy to suppress FCNC mediated
by loops with squarks and gluinos, in the neutral meson systems.Comment: 9 pages, RU-93-3
Measurement of Local Partial Pressure of Oxygen in the Brain Tissue under Normoxia and Epilepsy with Phosphorescence Lifetime Microscopy
In this work a method for measuring brain oxygen partial pressure with confocal phosphorescence lifetime microscopy system is reported. When used in conjunction with a dendritic phosphorescent probe, Oxyphor G4, this system enabled minimally invasive measurements of oxygen partial pressure (pO2) in cerebral tissue with high spatial and temporal resolution during 4-AP induced epileptic seizures. Investigating epileptic events, we characterized the spatio-temporal distribution of the "initial dip" in pO2 near the probe injection site and along nearby arterioles. Our results reveal a correlation between the percent change in the pO2 signal during the "initial dip" and the duration of seizure-like activity, which can help localize the epileptic focus and predict the length of seizure
- âŠ