628 research outputs found
Two-loop commuting charges and the string/gauge duality
We briefly review the status quo of the application of integrable systems
techniques to the AdS/CFT correspondence in the large charge approximation, a
rapidly evolving topic. Intricate string and gauge computations of,
respectively, energies and scaling dimensions agree at the one and two-loop
level, but disagree starting from three loops. To add to this pattern, we
present further computations which demonstrate that for folded and circular
spinning strings the full tower of infinitely many hidden commuting charges,
responsible for the integrability, also agrees up to two, but not three, loops.Comment: 12 pages, Latex, contribution to 5th International Workshop on Lie
Theory and Its Applications in Physics, Varna, Bulgaria, 16-22 Jun 2003; v2:
references adde
Redirection of the immune response to Staphylococcus aureus biofilm infection
Staphylococcus aureus (S. aureus) is a leading cause of community- and healthcare-associated infections and has a propensity to form biofilms. Biofilm infections are recalcitrant to host immune-mediated clearance as well as antibiotics, making them exceptionally difficult to eradicate. The biofilm environment has been shown to skew the host immune response towards an anti-inflammatory phenotype, characterized by alternatively activated macrophages, recruitment of myeloid-derived suppressor cells (MDSCs), and minimal neutrophil and T cell infiltrates. Our laboratory has attempted to redirect the host immune response towards one that would favor bacterial clearance by employing strategies to augment pro-inflammatory mechanisms. One such approach was to utilize lipopolysaccharide (LPS), which was expected to promote pro-inflammatory activation of peripheral immune cells infiltrating the biofilm and subsequent clearance of infection. This theory was partially correct, as pro-inflammatory cytokines in the serum were significantly increased, and peripheral immune cells in the blood were more effective at killing S. aureus ex vivo following LPS treatment; however biofilm infection was exacerbated. Specifically, bacterial titers increased nearly 2-log with administration of LPS, and although infiltration of Ly6G+Ly6C+ MDSCs was decreased, a new population of Ly6GintLy6C+ cells appeared. Additionally, both Ly6G+Ly6C+ and Ly6GintLy6C+ populations were more suppressive with LPS treatment, partially explaining the expansion of S. aureus biofilm burdens. This study highlights the resilient nature of S. aureus biofilm infections to influence the immune response, particularly through MDSCs, even in the face of a strong pro-inflammatory stimulus. Gaining a better understanding of the mechanisms that cause this ineffective host immune response to staphylococcal biofilms is a necessary step towards eradicating these debilitating infections
Strong coupling from the Hubbard model
It was recently observed that the one dimensional half-filled Hubbard model
reproduces the known part of the perturbative spectrum of planar N=4 super
Yang-Mills in the SU(2) sector. Assuming that this identification is valid
beyond perturbation theory, we investigate the behavior of this spectrum as the
't Hooft parameter \lambda becomes large. We show that the full dimension
\Delta of the Konishi superpartner is the solution of a sixth order polynomial
while \Delta for a bare dimension 5 operator is the solution of a cubic. In
both cases the equations can be solved easily as a series expansion for both
small and large \lambda and the equations can be inverted to express \lambda as
an explicit function of \Delta. We then consider more general operators and
show how \Delta depends on \lambda in the strong coupling limit. We are also
able to distinguish those states in the Hubbard model which correspond to the
gauge invariant operators for all values of \lambda. Finally, we compare our
results with known results for strings on AdS_5\times S^5, where we find
agreement for a range of R-charges.Comment: 14 pages; v2: 17 pages, 2 figures, appendix and references added;
typos fixed, minor changes; v3 fixed figures; v4 more references added, minor
correctio
Magic identities for conformal four-point integrals
We propose an iterative procedure for constructing classes of off-shell
four-point conformal integrals which are identical. The proof of the identity
is based on the conformal properties of a subintegral common for the whole
class. The simplest example are the so-called `triple scalar box' and `tennis
court' integrals. In this case we also give an independent proof using the
method of Mellin--Barnes representation which can be applied in a similar way
for general off-shell Feynman integrals.Comment: 13 pages, 12 figures. New proof included with neater discussion of
contact terms. Typo correcte
On the Scattering Phase for AdS_5 x S^5 Strings
We propose a phase factor of the worldsheet S-matrix for strings on AdS_5 x
S^5 apparently solving Janik's crossing relation.Comment: 9 pages, v2: revised conclusions about agreement with perturbative
string theory; minor changes, v3: resolution to above problems indicated, to
appear in Mod. Phys. Lett.
Decoupling limits of N=4 super Yang-Mills on R x S^3
We find new decoupling limits of N=4 super Yang-Mills (SYM) on R x S^3 with
gauge group SU(N). These decoupling limits lead to decoupled theories that are
much simpler than the full N=4 SYM but still contain many of its interesting
features. The decoupling limits correspond to being in a near-critical region,
near a point with zero temperature and critical chemical potentials. The new
decoupling limits are found by generalizing the limits of hep-th/0605234 to
include not only the chemical potentials for the SU(4) R-symmetry of N=4 SYM
but also the chemical potentials corresponding to the SO(4) symmetry. In the
decoupled theories it is possible to take a strong coupling limit in a
controllable manner since the full effective Hamiltonian is known. For planar
N=4 SYM on R x S^3 all the decoupled theories correspond to fully integrable
spin chains. We study the thermodynamics of the decoupled theories and find the
Hagedorn temperature for small and large values of the effective coupling. We
find an alternative formulation of the decoupling limits in the microcanonical
ensemble. This leads to a characterization of certain regimes of weakly coupled
N=4 SYM in which there are string-like states. Finally, we find a similar
decoupling limit for pure Yang-Mills theory, which for the planar limit leads
to a fully integrable decoupled theory.Comment: 48 pages, 1 figure; added references, published versio
On highest-energy state in the su(1|1) sector of N=4 super Yang-Mills theory
We consider the highest-energy state in the su(1|1) sector of N=4 super
Yang-Mills theory containing operators of the form tr(Z^{L-M} \psi^M) where Z
is a complex scalar and \psi is a component of gaugino. We show that this state
corresponds to the operator tr(\psi^L) and can be viewed as an analogue of the
antiferromagnetic state in the su(2) sector. We find perturbative expansions of
the energy of this state in both weak and strong 't Hooft coupling regimes
using asymptotic gauge theory Bethe ansatz equations. We also discuss a
possible analog of this state in the conjectured string Bethe ansatz equations.Comment: 23 pages, Late
Yangian Symmetry at Two Loops for the su(2|1) Sector of N=4 SYM
We present the perturbative Yangian symmetry at next-to-leading order in the
su(2|1) sector of planar N=4 SYM. Just like the ordinary symmetry generators,
the bi-local Yangian charges receive corrections acting on several neighboring
sites. We confirm that the bi-local Yangian charges satisfy the necessary
conditions: they transform in the adjoint of su(2|1), they commute with the
dilatation generator, and they satisfy the Serre relations. This proves that
the sector is integrable at two loops.Comment: 13 pages, v2: minor correction
Character Expansion Methods for Matrix Models of Dually Weighted Graphs
We consider generalized one-matrix models in which external fields allow
control over the coordination numbers on both the original and dual lattices.
We rederive in a simple fashion a character expansion formula for these models
originally due to Itzykson and Di Francesco, and then demonstrate how to take
the large N limit of this expansion. The relationship to the usual matrix model
resolvent is elucidated. Our methods give as a by-product an extremely simple
derivation of the Migdal integral equation describing the large limit of
the Itzykson-Zuber formula. We illustrate and check our methods by analyzing a
number of models solvable by traditional means. We then proceed to solve a new
model: a sum over planar graphs possessing even coordination numbers on both
the original and the dual lattice. We conclude by formulating equations for the
case of arbitrary sets of even, self-dual coupling constants. This opens the
way for studying the deep problem of phase transitions from random to flat
lattices.Comment: 22 pages, harvmac.tex, pictex.tex. All diagrams written directly into
the text in Pictex commands. (Two minor math typos corrected.
Acknowledgements added.
Planar N=4 Gauge Theory and the Hubbard Model
Recently it was established that a certain integrable long-range spin chain
describes the dilatation operator of N=4 gauge theory in the su(2) sector to at
least three-loop order, while exhibiting BMN scaling to all orders in
perturbation theory. Here we identify this spin chain as an approximation to an
integrable short-ranged model of strongly correlated electrons: The Hubbard
model.Comment: 35 pages, 2 figures; v2: typos and references fixed, published
versio
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