2,671 research outputs found
Gravitational Interactions of integrable models
We couple non-linear -models to Liouville gravity, showing that
integrability properties of symmetric space models still hold for the matter
sector. Using similar arguments for the fermionic counterpart, namely
Gross--Neveu-type models, we verify that such conclusions must also hold for
them, as recently suggested.Comment: 8 pages, final version to appear in Physics Letters B Revised
version, with misprints corrected and some references adde
The Landau Pole at Finite Temperature
We study the Landau pole in the lambda phi^4 field theory at non-zero and
large temperatures. We show that the position of the thermal Landau pole
Lambda_L(T) is shifted to higher energies with respect to the zero temperature
Landau pole Lambda_L(0). We find for high temperatures T > Lambda_L(0),
Lambda_L(T) simeq pi^2 T / log (T / Lambda_L(0)). Therefore, the range of
applicability in energy of the lambda phi^4 field theory increases with the
temperature.Comment: LaTex, 6 pages, 2 .ps figures. Improved version. To appear in Phys.
Rev. D, Rapid Communication
Building up spacetime with quantum entanglement
In this essay, we argue that the emergence of classically connected
spacetimes is intimately related to the quantum entanglement of degrees of
freedom in a non-perturbative description of quantum gravity. Disentangling the
degrees of freedom associated with two regions of spacetime results in these
regions pulling apart and pinching off from each other in a way that can be
quantified by standard measures of entanglement.Comment: Gravity Research Foundation essay, 7 pages, LaTeX, 5 figure
New Record for the Coffee Berry Borer, Hypothenemus hampei, in Hawaii
The coffee berry borer, Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae) is endemic to Africa and is the most devastating pest of coffee worldwide. The female bores a hole in the coffee berry and deposits her eggs inside. Upon hatching, larvae feed on the seeds, thus reducing both quality and yields of the marketable product. The coffee berry borer was found in the district of Kona on the island of Hawaii in August 2010 and appears to be restricted to that area
Dynamical renormalization group approach to relaxation in quantum field theory
The real time evolution and relaxation of expectation values of quantum
fields and of quantum states are computed as initial value problems by
implementing the dynamical renormalization group (DRG).Linear response is
invoked to set up the renormalized initial value problem to study the dynamics
of the expectation value of quantum fields. The perturbative solution of the
equations of motion for the field expectation values of quantum fields as well
as the evolution of quantum states features secular terms, namely terms that
grow in time and invalidate the perturbative expansion for late times. The DRG
provides a consistent framework to resum these secular terms and yields a
uniform asymptotic expansion at long times. Several relevant cases are studied
in detail, including those of threshold infrared divergences which appear in
gauge theories at finite temperature and lead to anomalous relaxation. In these
cases the DRG is shown to provide a resummation akin to Bloch-Nordsieck but
directly in real time and that goes beyond the scope of Bloch-Nordsieck and
Dyson resummations. The nature of the resummation program is discussed in
several examples. The DRG provides a framework that is consistent, systematic
and easy to implement to study the non-equilibrium relaxational dynamics
directly in real time that does not rely on the concept of quasiparticle
widths.Comment: LaTex, 27 pages, 2 .ps figure
The Effect of Active Galactic Nuclei on the Mid-Infrared Aromatic Features
We present Spitzer measurements of the aromatic (also known as PAH) features
for 35 Seyfert galaxies from the revised Shapley-Ames sample and find that the
relative strengths of the features differ significantly from those observed in
star-forming galaxies. Specifically, the features at 6.2, 7.7, and 8.6 micron
are suppressed relative to the 11.3 micron feature in Seyferts. Furthermore, we
find an anti-correlation between the L(7.7 micron)/L(11.3 micron) ratio and the
strength of the rotational H2 (molecular hydrogen) emission, which traces
shocked gas. This suggests that shocks suppress the short-wavelength features
by modifying the structure of the aromatic molecules or destroying the smallest
grains. Most Seyfert nuclei fall on the relationship between aromatic emission
and [Ne II] emission for star-forming galaxies, indicating that aromatic-based
estimates of the star-formation rate in AGN host galaxies are generally
reasonable. For the outliers from this relationship, which have small L(7.7
micron)/L(11.3 micron) ratios and strong H2 emission, the 11.3 micron feature
still provides a valid measure of the star-formation rate.Comment: Accepted for publication in ApJ. 17 pages, 12 figure
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