409 research outputs found
A risk evaluation of traces of packaging materials in former food products intended as feed materials
The Photon Dispersion as an Indicator for New Physics ?
We first comment on the search for a deviation from the linear photon
dispersion relation, in particular based on cosmic photons from Gamma Ray
Bursts. Then we consider the non-commutative space as a theoretical concept
that could lead to such a deviation, which would be a manifestation of Lorentz
Invariance Violation. In particular we review a numerical study of pure U(1)
gauge theory in a 4d non-commutative space. Starting from a finite lattice, we
explore the phase diagram and the extrapolation to the continuum and infinite
volume. These simultaneous limits - taken at fixed non-commutativity - lead to
a phase of broken Poincare symmetry, where the photon appears to be IR stable,
despite a negative IR divergence to one loop.Comment: 8 pages, 4 figures, talk presented at the VI International Workshop
on the Dark Side of the Universe, Leon (Mexico), June 1-6, 2010. References
adde
Oncogenic GNAQ mutations are not correlated with disease-free survival in uveal melanoma
BackgroundRecently, oncogenic G protein alpha subunit q (GNAQ) mutations have been described in about 50% of uveal melanomas and in the blue nevi of the skin.MethodsGNAQ exon 5 was amplified from 75 ciliary body and choroidal melanoma DNAs and sequenced directly. GNAQ mutation status was correlated with disease-free survival (DFS), as well as other clinical and histopathological factors, and with chromosomal variations detected by FISH and CGH.ResultsOf the 75 tumour DNA samples analysed, 40 (53.3%) harboured oncogenic mutations in GNAQ codon 209. Univariate and multivariate analysis showed that GNAQ mutation status was not significantly correlated with DFS.ConclusionThe GNAQ mutation status is not suitable to predict DFS. However, the high frequency of GNAQ mutations may render it a promising target for therapeutic intervention
Emergent Gravity, Matrix Models and UV/IR Mixing
We verify explicitly that UV/IR mixing for noncommutative gauge theory can be
understood in terms of an induced gravity action, as predicted by the
identification [1] of gravity within matrix models of NC gauge theory. More
precisely, we obtain the Einstein-Hilbert action by integrating out a scalar
field in the adjoint. It arises from the well-known UV/IR mixing of NC gauge
theory, which is carefully re-analyzed and interpreted in terms of gravity. The
matrix model therefore contains gravity as an IR effect, due to UV/IR mixing.Comment: 33 pages, 3 figures. V2: references adde
Nonuniform symmetry breaking in noncommutative theory
The spontaneous symmetry breaking in noncommutative theory
has been analyzed by using the formalism of the effective action for composite
operators in the Hartree-Fock approximation. It turns out that there is no
phase transition to a constant vacuum expectation of the field and the broken
phase corresponds to a nonuniform background. By considering the generated mass gap depends on the angles among
the momenta and and the noncommutativity parameter
. The order of the transition is not easily determinable in our
approximation.Comment: 18 pages, 4 figures, added reference
On the structure of k-Lie algebras
We show that the structure constants of -Lie algebras, , with a
positive definite metric are the sum of the volume forms of orthogonal
-planes. This generalizes the result for in arXiv:0804.2662 and
arXiv:0804.3078, and confirms a conjecture in math/0211170.Comment: 4 pages, minor changes and a reference adde
Superconformal M2-branes and generalized Jordan triple systems
Three-dimensional conformal theories with six supersymmetries and SU(4)
R-symmetry describing stacks of M2-branes are here proposed to be related to
generalized Jordan triple systems. Writing the four-index structure constants
in an appropriate form, the Chern-Simons part of the action immediately
suggests a connection to such triple systems. In contrast to the previously
considered three-algebras, the additional structure of a generalized Jordan
triple system is associated to a graded Lie algebra, which corresponds to an
extension of the gauge group. In this note we show that the whole theory with
six manifest supersymmetries can be naturally expressed in terms of such a
graded Lie algebra. Also the BLG theory with eight supersymmetries is included
as a special case.Comment: 15 pages, v2 and v3: minor corrections and clarifications, references
added, v2: section 4 extended, v3: published versio
On The Interaction Of D0-Brane Bound States And RR Photons
We consider the problem of the interaction between D0-brane bound state and
1-form RR photons by the world-line theory. Based on the fact that in the
world-line theory the RR gauge fields depend on the matrix coordinates of
D0-branes, the gauge fields also appear as matrices in the formulation. At the
classical level, we derive the Lorentz-like equations of motion for D0-branes,
and it is observed that the center-of-mass is colourless with respect to the
SU(N) sector of the background. Using the path integral method, the
perturbation theory for the interaction between the bound state and the RR
background is developed. We discuss what kind of field theory may be
corresponded to the amplitudes which are calculated by the perturbation
expansion in world-line theory. Qualitative considerations show that the
possibility of existence of a map between the world-line theory and the
non-Abelian gauge theory is very considerable.Comment: LaTeX, 28 pages, 4 eps figures. v2 and v3: eqs. (3.18) and (B.2) are
corrected, very small change
Branes from a non-Abelian (2,0) tensor multiplet with 3-algebra
In this paper, we study the equations of motion for non-Abelian N=(2,0)
tensor multiplets in six dimensions, which were recently proposed by Lambert
and Papageorgakis. Some equations are regarded as constraint equations. We
employ a loop extension of the Lorentzian three-algebra (3-algebra) and examine
the equations of motion around various solutions of the constraint equations.
The resultant equations take forms that allow Lagrangian descriptions. We find
various (5+d)-dimensional Lagrangians and investigate the relation between them
from the viewpoint of M-theory duality.Comment: 44+1 pages, reference added, typos corrected, and several discussions
added; v3, reference added, many typos corrected, the language improved; v4,
some typos and references corrected, final version to appear in J. Phys.
Classical Solutions of the TEK Model and Noncommutative Instantons in Two Dimensions
The twisted Eguchi-Kawai (TEK) model provides a non-perturbative definition
of noncommutative Yang-Mills theory: the continuum limit is approached at large
by performing suitable double scaling limits, in which non-planar
contributions are no longer suppressed. We consider here the two-dimensional
case, trying to recover within this framework the exact results recently
obtained by means of Morita equivalence. We present a rather explicit
construction of classical gauge theories on noncommutative toroidal lattice for
general topological charges. After discussing the limiting procedures to
recover the theory on the noncommutative torus and on the noncommutative plane,
we focus our attention on the classical solutions of the related TEK models. We
solve the equations of motion and we find the configurations having finite
action in the relevant double scaling limits. They can be explicitly described
in terms of twist-eaters and they exactly correspond to the instanton solutions
that are seen to dominate the partition function on the noncommutative torus.
Fluxons on the noncommutative plane are recovered as well. We also discuss how
the highly non-trivial structure of the exact partition function can emerge
from a direct matrix model computation. The quantum consistency of the TEK
formulation is eventually checked by computing Wilson loops in a particular
limit.Comment: 41 pages, JHEP3. Minor corrections, references adde
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