194 research outputs found
Original use of MUSE's laser tomography adaptive optics to directly image young accreting exoplanets
Stars and planetary system
Notes on D-branes in 2D Type 0 String Theory
In this paper we construct complete macroscopic operators in two dimensional
type 0 string theory. They represent D-branes localized in the time direction.
We give another equivalent description of them as deformed Fermi surfaces. We
also discuss a continuous array of such D-branes and show that it can be
described by a matrix model with a deformed potential. For appropriate values
of parameters, we find that it has an additional new sector hidden inside its
strongly coupled region.Comment: harvmac, 18 pages, 2 figures, references adde
Flux Backgrounds in 2D String Theory
We study RR flux backgrounds in two dimensional type 0 string theories. In
particular, we study the relation between the 0A matrix model and the extremal
black hole in two dimensions. Using T-duality we find a dual flux background in
type 0B theory and propose its matrix model description. When the Fermi level
is set to zero this system remains weakly coupled and exhibits a larger
symmetry related to the structure of flux vacua. Finally, we construct a two
dimensional type IIB background as an orbifold of the 0B background.Comment: Harvmac, 40 pages, 6 figs, minor changes, references adde
On The Problem of Particle Production in c=1 Matrix Model
We reconsider and analyze in detail the problem of particle production in the
time dependent background of matrix model where the Fermi sea drains away
at late time. In addition to the moving mirror method, which has already been
discussed in hep-th/0403169 and hep-th/0403275, we describe yet another method
of computing the Bogolubov coefficients which gives the same result. We
emphasize that these Bogolubov coefficients are approximately correct for small
value of the deformation parameter.
We also study the time evolution of the collective field theory stress-tensor
with a special point-splitting regularization. Our computations go beyond the
approximation of the previous treatments and are valid at large coordinate
distances from the boundary at a finite time and up-to a finite coordinate
distance from the boundary at late time. In this region of validity our
regularization produces a certain singular term that is precisely canceled by
the collective field theory counter term in the present background. The energy
and momentum densities fall off exponentially at large distance from the
boundary to the values corresponding to the static background. This clearly
shows that the radiated energy reaches the asymptotic region signaling the
space-time decay.Comment: 37 pages, 5 figures. Section 6 is modified to clarify main
accomplishments of the paper including a discussion comparing stress-tensor
analysis with those preexisted in literature. Other modifications include
minor changes in the text and addition of one reference. Version accepted for
publication in JHE
Holographic Correlators in a Flow to a Fixed Point
Using holographic renormalization, we study correlation functions throughout
a renormalization group flow between two-dimensional superconformal field
theories. The ultraviolet theory is an N=(4,4) CFT which can be thought of as a
symmetric product of U(2) super WZW models. It is perturbed by a relevant
operator which preserves one-quarter supersymmetry and drives the theory to an
infrared fixed point. We compute correlators of the stress-energy tensor and of
the relevant operators dual to supergravity scalars. Using the former, we put
together Zamolodchikov's C function, and contrast it with proposals for a
holographic C function. In passing, we address and resolve two puzzles also
found in the case of five-dimensional bulk supergravity.Comment: LaTeX2e, 48 pages, 4 figure
Minimal Superstrings and Loop Gas Models
We reformulate the matrix models of minimal superstrings as loop gas models
on random surfaces. In the continuum limit, this leads to the identification of
minimal superstrings with certain bosonic string theories, to all orders in the
genus expansion. RR vertex operators arise as operators in a Z_2 twisted sector
of the matter CFT. We show how the loop gas model implements the sum over spin
structures expected from the continuum RNS formulation. Open string boundary
conditions are also more transparent in this language.Comment: 36 pages, 3 figure
Likelihood Functions for Supersymmetric Observables in Frequentist Analyses of the CMSSM and NUHM1
On the basis of frequentist analyses of experimental constraints from
electroweak precision data, g-2, B physics and cosmological data, we
investigate the parameters of the constrained MSSM (CMSSM) with universal soft
supersymmetry-breaking mass parameters, and a model with common non-universal
Higgs masses (NUHM1). We present chi^2 likelihood functions for the masses of
supersymmetric particles and Higgs bosons, as well as b to s gamma, b to mu mu
and the spin-independent dark matter scattering cross section. In the CMSSM we
find preferences for sparticle masses that are relatively light. In the NUHM1
the best-fit values for many sparticle masses are even slightly smaller, but
with greater uncertainties. The likelihood functions for most sparticle masses
are cut off sharply at small masses, in particular by the LEP Higgs mass
constraint. Both in the CMSSM and the NUHM1, the coannihilation region is
favoured over the focus-point region at about the 3-sigma level, largely but
not exclusively because of g-2. Many sparticle masses are highly correlated in
both the CMSSM and NUHM1, and most of the regions preferred at the 95% C.L. are
accessible to early LHC running. Some slepton and chargino/neutralino masses
should be in reach at the ILC. The masses of the heavier Higgs bosons should be
accessible at the LHC and the ILC in portions of the preferred regions in the
(M_A, tan beta) plane. In the CMSSM, the likelihood function for b to mu mu is
peaked close to the Standard Model value, but much larger values are possible
in the NUHM1. We find that values of the DM cross section > 10^{-10} pb are
preferred in both the CMSSM and the NUHM1. We study the effects of dropping the
g-2, b to s gamma, relic density and M_h constraints.Comment: 34 pages, 24 figure
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
Measurement of isolated photon production in pp and PbPb collisions at sqrt(sNN) = 2.76 TeV
Isolated photon production is measured in proton-proton and lead-lead
collisions at nucleon-nucleon centre-of-mass energies of 2.76 TeV in the
pseudorapidity range |eta|<1.44 and transverse energies ET between 20 and 80
GeV with the CMS detector at the LHC. The measured ET spectra are found to be
in good agreement with next-to-leading-order perturbative QCD predictions. The
ratio of PbPb to pp isolated photon ET-differential yields, scaled by the
number of incoherent nucleon-nucleon collisions, is consistent with unity for
all PbPb reaction centralities.Comment: Submitted to Physics Letters
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