388 research outputs found
Holographic Gravitational Anomalies
In the AdS/CFT correspondence one encounters theories that are not invariant
under diffeomorphisms. In the boundary theory this is a gravitational anomaly,
and can arise in 4k+2 dimensions. In the bulk, there can be gravitational
Chern-Simons terms which vary by a total derivative. We work out the
holographic stress tensor for such theories, and demonstrate agreement between
the bulk and boundary. Anomalies lead to novel effects, such as a nonzero
angular momentum for global AdS(3). In string theory such Chern-Simons terms
are known with exact coefficients. The resulting anomalies, combined with
symmetries, imply corrections to the Bekenstein-Hawking entropy of black holes
that agree exactly with the microscopic counting.Comment: 25 page
Stochastic Quantization of the Chern-Simons Theory
We discuss Stochastic Quantization of =3 dimensional non-Abelian
Chern-Simons theory. We demonstrate that the introduction of an appropriate
regulator in the Langevin equation yields a well-defined equilibrium limit,
thus leading to the correct propagator. We also analyze the connection between
=3 Chern-Simons and =4 Topological Yang-Mills theories showing the
equivalence between the corresponding regularized partition functions. We study
the construction of topological invariants and the introduction of a
non-trivial kernel as an alternative regularization.Comment: 30 page
Causality and Cosmic Inflation
In the context of inflationary models with a pre-inflationary stage, in which
the Einstein equations are obeyed, the weak energy condition is satisfied, and
spacetime topology is trivial, we argue that homogeneity on super-Hubble scales
must be assumed as an initial condition. Models in which inflation arises from
field dynamics in a Friedman-Robertson-Walker background fall into this class
but models in which inflation originates at the Planck epoch, {\it eg.} chaotic
inflation, may evade this conclusion. Our arguments rest on causality and
general relativistic constraints on the structure of spacetime. We discuss
modifications to existing scenarios that may avoid the need for initial
large-scale homogeneity.Comment: 4 pages, 3 figures, RevTeX, expanded and sharpened discussion of
result, figures improved, references adde
The alpha-prime stretched horizon in the Heterotic string
The linear alpha-prime corrections and the field redefinition ambiguities are
studied for half-BPS singular backgrounds representing a wrapped fundamental
string. It is showed that there exist schemes in which the inclusion of all the
linear alpha-prime corrections converts these singular solutions to black holes
with a regular horizon for which the modified Hawking-Bekenstein entropy is in
agreement with the statistical entropy.Comment: 22 pages JHEP; new discussions and more details added to section
Vacuum Bubbles Nucleation and Dark Matter Production through Gauge Symmetry Rearrangement
Modern particle physics and cosmology support the idea that a background of
invisible material pervades the whole universe, and identify in the cosmic
vacuum the ultimate source of matter-energy, both seen and unseen. Within the
framework of the theory of fundamental relativistic membranes, we suggest a
self-consistent, vacuum energy-driven mechanism for dark matter creation
through gauge symmetry rearrangement.Comment: 22pages, RevTeX, no figures; accepted for publication in Phys.Rev.
Organizational Adaptation to Changing Environments
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66531/2/10.1177_000276428502800507.pd
Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at TeV
The elliptic, , triangular, , and quadrangular, , azimuthal
anisotropic flow coefficients are measured for unidentified charged particles,
pions and (anti-)protons in Pb-Pb collisions at TeV
with the ALICE detector at the Large Hadron Collider. Results obtained with the
event plane and four-particle cumulant methods are reported for the
pseudo-rapidity range at different collision centralities and as a
function of transverse momentum, , out to GeV/.
The observed non-zero elliptic and triangular flow depends only weakly on
transverse momentum for GeV/. The small dependence
of the difference between elliptic flow results obtained from the event plane
and four-particle cumulant methods suggests a common origin of flow
fluctuations up to GeV/. The magnitude of the (anti-)proton
elliptic and triangular flow is larger than that of pions out to at least
GeV/ indicating that the particle type dependence persists out
to high .Comment: 16 pages, 5 captioned figures, authors from page 11, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/186
Centrality dependence of charged particle production at large transverse momentum in Pb-Pb collisions at TeV
The inclusive transverse momentum () distributions of primary
charged particles are measured in the pseudo-rapidity range as a
function of event centrality in Pb-Pb collisions at
TeV with ALICE at the LHC. The data are presented in the range
GeV/ for nine centrality intervals from 70-80% to 0-5%.
The Pb-Pb spectra are presented in terms of the nuclear modification factor
using a pp reference spectrum measured at the same collision
energy. We observe that the suppression of high- particles strongly
depends on event centrality. In central collisions (0-5%) the yield is most
suppressed with at -7 GeV/. Above
GeV/, there is a significant rise in the nuclear modification
factor, which reaches for GeV/. In
peripheral collisions (70-80%), the suppression is weaker with almost independently of . The measured nuclear
modification factors are compared to other measurements and model calculations.Comment: 17 pages, 4 captioned figures, 2 tables, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/284
Measurement of charm production at central rapidity in proton-proton collisions at TeV
The -differential production cross sections of the prompt (B
feed-down subtracted) charmed mesons D, D, and D in the rapidity
range , and for transverse momentum GeV/, were
measured in proton-proton collisions at TeV with the ALICE
detector at the Large Hadron Collider. The analysis exploited the hadronic
decays DK, DK, DD, and their charge conjugates, and was performed on a
nb event sample collected in 2011 with a
minimum-bias trigger. The total charm production cross section at TeV and at 7 TeV was evaluated by extrapolating to the full phase space
the -differential production cross sections at TeV
and our previous measurements at TeV. The results were compared
to existing measurements and to perturbative-QCD calculations. The fraction of
cdbar D mesons produced in a vector state was also determined.Comment: 20 pages, 5 captioned figures, 4 tables, authors from page 15,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/307
Particle-yield modification in jet-like azimuthal di-hadron correlations in Pb-Pb collisions at = 2.76 TeV
The yield of charged particles associated with high- trigger
particles ( GeV/) is measured with the ALICE detector in
Pb-Pb collisions at = 2.76 TeV relative to proton-proton
collisions at the same energy. The conditional per-trigger yields are extracted
from the narrow jet-like correlation peaks in azimuthal di-hadron correlations.
In the 5% most central collisions, we observe that the yield of associated
charged particles with transverse momenta GeV/ on the
away-side drops to about 60% of that observed in pp collisions, while on the
near-side a moderate enhancement of 20-30% is found.Comment: 15 pages, 2 captioned figures, 1 table, authors from page 10,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/350
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