41,861 research outputs found
Locating the critical end point using the linear sigma model coupled to quarks
We use the linear sigma model coupled to quarks to compute the effective
potential beyond the mean field approximation, including the contribution of
the ring diagrams at finite temperature and baryon density. We determine the
model couplings and use them to study the phase diagram in the baryon chemical
potential-temperature plane and to locate the Critical End Point.Comment: 8 pages, 2 figures, conference paper from ISMD 201
Diffuse interstellar bands in fullerene planetary nebulae: the fullerenes - diffuse interstellar bands connection
We present high-resolution (R~15000) VLT/UVES optical spectra of two
planetary nebulae (PNe; Tc 1 and M 1-20) where C60 (and C70) fullerenes have
already been found. These spectra are of high-quality (S/N > 300) for PN Tc 1,
which permits us to search for the expected electronic transitions of neutral
C60 and diffuse interstellar bands (DIBs). Surprisingly, we report the
non-detection of the most intense optical bands of C60 in Tc 1, although this
could be explained by the low C60 column density estimated from the C60
infrared bands if the C60 emission peaks far away from the central star. The
strongest and most common DIBs in both fullerene PNe are normal for their
reddening. Interestingly, the very broad 4428 A DIB and the weaker 6309 A DIB
are found to be unusually intense in Tc 1. We also report the detection of a
new broad (FWHM~5 A) unidentified band at ~6525 A. We propose that the 4428 A
DIB (probably also the 6309 A DIB and the new 6525 A band) may be related to
the presence of larger fullerenes (e.g., C80, C240, C320, and C540) and
buckyonions (multishell fullerenes such as C60@C240 and C60@C240@C540) in the
circumstellar envelope of Tc 1.Comment: Accepted for publication in Astronomy & Astrophysics Letters (6
pages, 4 figures, and 1 Table
The seesaw portal in testable models of neutrino masses
A Standard Model extension with two Majorana neutrinos can explain the
measured neutrino masses and mixings, and also account for the
matter-antimatter asymmetry in a region of parameter space that could be
testable in future experiments. The testability of the model relies to some
extent on its minimality. In this paper we address the possibility that the
model might be extended by extra generic new physics which we parametrize in
terms of a low-energy effective theory. We consider the effects of the
operators of the lowest dimensionality, , and evaluate the upper bounds on
the coefficients so that the predictions of the minimal model are robust. One
of the operators gives a new production mechanism for the heavy neutrinos at
LHC via higgs decays. The higgs can decay to a pair of such neutrinos that,
being long-lived, leave a powerful signal of two displaced vertices. We
estimate the LHC reach to this process.Comment: 19 pages, 11 figure
On the Jacobi-Metric Stability Criterion
We investigate the exact relation existing between the stability equation for
the solutions of a mechanical system and the geodesic deviation equation of the
associated geodesic problem in the Jacobi metric constructed via the
Maupertuis-Jacobi Principle. We conclude that the dynamical and geometrical
approaches to the stability/instability problem are not equivalent.Comment: 14 pages, no figure
Symmetric and Asymmetric Coalescence of Drops on a Substrate
The coalescence of viscous drops on a substrate is studied experimentally and
theoretically. We consider cases where the drops can have different contact
angles, leading to a very asymmetric coalescence process. Side view experiments
reveal that the "bridge" connecting the drops evolves with self-similar
dynamics, providing a new perspective on the coalescence of sessile drops. We
show that the universal shape of the bridge is accurately described by
similarity solutions of the one-dimensional lubrication equation. Our theory
predicts a bridge that grows linearly in time and stresses the strong
dependence on the contact angles. Without any adjustable parameters, we find
quantitative agreement with all experimental observations.Comment: 5 pages, 4 figure
On the Presence of Thermal SZ Induced Signal in the First Year WMAP Temperature Maps
Using available optical and X-ray catalogues of clusters and superclusters of
galaxies, we build templates of tSZ emission as they should be detected by the
WMAP experiment. We compute the cross-correlation of our templates with WMAP
temperature maps, and interpret our results separately for clusters and for
superclusters of galaxies. For clusters of galaxies, we claim 2-5
detections in our templates built from BCS Ebeling et al. (1998), NORAS
(Boehringer et al. 2000) and de Grandi et al. (1999) catalogues. In these
templates, the typical cluster temperature decrements in WMAP maps are around
15-35 K in the RJ range (no beam deconvolution applied). Several tests
probing the possible influence of foregrounds in our analyses demonstrate that
our results are robust against galactic contamination. On supercluster scales,
we detect a diffuse component in the V & W WMAP bands which cannot be generated
by superclusters in our catalogues (Einasto et al. 1994, 1997), and which is
not present in the clean map of Tegmark, de Oliveira-Costa & Hamilton (2003).
Using this clean map, our analyses yield, for Einasto's supercluster
catalogues, the following upper limit for the comptonization parameter
associated to supercluster scales: y_{SC} < 2.18 \time s 10^{-8} at the 95%
confidence limit.Comment: MNRAS accepted. New section and minor changes include
- …