16,130 research outputs found
String amplitudes in the Hpp-wave limit of AdS3xS3
We compute string amplitudes on pp-waves supported by NS-NS 3-form fluxes and
arising in the Penrose limit of AdS3xS3xM. We clarify the role of the
non-chiral accidental SU(2) symmetry of the background. We comment on the
extension of our results to the superstring and propose a holographic formula
in the BMN limit of the AdS3/CFT2 correspondence valid for any correlator.Comment: Latex,no figures, 47 p
Precision Spectroscopy and Higher Spin symmetry in the ABJM model
We revisit Kaluza-Klein compactification of 11-d supergravity on S^7/Z_k
using group theory techniques that may find application in other flux vacua
with internal coset spaces. Among the SO(2) neutral states, we identify
marginal deformations and fields that couple to the recently discussed
world-sheet instanton of Type IIA on CP^3. We also discuss charged states, dual
to monopole operators, and the Z_k projection of the Osp(4|8) singleton and its
tensor products. In particular, we show that the doubleton spectrum may account
for N=6 higher spin symmetry enhancement in the limit of vanishing 't Hooft
coupling in the boundary Chern-Simons theory.Comment: 44 page
Generalized definition of time delay in scattering theory
We advocate for the systematic use of a symmetrized definition of time delay
in scattering theory. In two-body scattering processes, we show that the
symmetrized time delay exists for arbitrary dilated spatial regions symmetric
with respect to the origin. It is equal to the usual time delay plus a new
contribution, which vanishes in the case of spherical spatial regions. We also
prove that the symmetrized time delay is invariant under an appropriate mapping
of time reversal. These results are also discussed in the context of classical
scattering theory.Comment: 18 page
Correlation functions in a cascading N=1 gauge theory from supergravity
We study fluctuations around the warped conifold supergravity solution of
Klebanov and Tseytlin [hep-th/0002159], known to be dual to a cascading N=1
gauge theory. Although this supergravity background is not asymptotically AdS,
corresponding to a non-conformal field theory, it is possible to apply the
usual methods of AdS/CFT duality to extract the high energy behavior of field
theory correlators by solving linearized equations of motion for fluctuations
around the background. We consider the Goldstone vector dual to the anomalous
R-symmetry current and compute its mass, which exactly matches the general
prediction of [hep-th/0009156]. We find the high energy 2-point functions for
the R-current and two other vectors. As expected, the R-current 2-point
function has a longitudinal part because R-symmetry is broken. We also
calculate the high energy 2-point function of the energy-momentum tensor from
fluctuations of modes in the graviton sector. This 2-point function has a trace
part corresponding to broken conformal symmetry.Comment: JHEP, 29 page
Evolution of the disc atmosphere in the X-ray binary MXB 1659-298, during its 2015-2017 outburst
We report on the evolution of the X-ray emission of the accreting neutron
star (NS) low mass X-ray binary (LMXB), MXB 1659-298, during its most recent
outburst in 2015-2017. We detected 60 absorption lines during the soft state
(of which 21 at more than 3 ), that disappeared in the hard state
(e.g., the Fe xxv and Fe xxvi lines). The absorbing plasma is at rest, likely
part of the accretion disc atmosphere. The bulk of the absorption features can
be reproduced by a high column density () of highly
ionised () plasma. Its disappearance during the
hard state is likely the consequence of a thermal photo-ionisation instability.
MXB 1659-298's continuum emission can be described by the sum of an absorbed
disk black body and its Comptonised emission, plus a black body component. The
observed spectral evolution with state is in line with that typically observed
in atoll and stellar mass black hole LMXB. The presence of a relativistic Fe
K disk-line is required during the soft state. We also tentatively
detect the Fe xxii doublet, whose ratio suggests an electron density of the
absorber of , hence, the absorber is likely located at
from the illuminating source, well inside the Compton and
outer disc radii. MXB 1659-298 is the third well monitored atoll LMXB
showcasing intense Fe xxv and Fe xxvi absorption during the soft state that
disappears during the hard state.Comment: MNRAS in pres
Glueball Scattering Amplitudes from Holography
Using techniques developed in a previous paper three-point functions in field
theories described by holographic renormalization group flows are computed. We
consider a system of one active scalar and one inert scalar coupled to gravity.
For the GPPZ flow, their dual operators create states that are interpreted as
glueballs of the N=1 SYM theory, which lies at the infrared end of the
renormalization group flow. The scattering amplitudes for three-glueball
processes are calculated providing precise predictions for glueball decays in
N=1 SYM theory. Numerical results for low-lying glueballs are included.Comment: 34 pages v2: comments on local terms and references added, v3:
version published in JHE
Boundary multi-trace deformations and OPEs in AdS/CFT correspondence
We argue that multi-trace deformations of the boundary CFT in AdS/CFT
correspondence can arise through the OPE of single-trace operators. We work out
the example of a scalar field in AdS_5 with cubic self interaction. By an
appropriate reparametrization of the boundary data we are able to deform the
boundary CFT by a marginal operator that couples to the conformal anomaly. Our
method can be used in the analysis of multi-trace deformations in N=4 SYM where
the OPEs of various single-trace operators are known.Comment: 18 pages, v2 refinements and acknowledgements adde
Tpz1TPP1 SUMOylation reveals evolutionary conservation of SUMO-dependent Stn1 telomere association
Elongation of the telomeric overhang by telomerase is counteracted by synthesis of the complementary strand by the CST complex, CTC1(Cdc13)/Stn1/Ten1. Interaction of budding yeast Stn1 with overhang-binding Cdc13 is increased by Cdc13
SUMOylation. Human and fission yeast CST instead interact with overhang-binding TPP1/POT1. We show that the fission yeast TPP1 ortholog, Tpz1, is SUMOylated. Tpz1 SUMOylation restricts telomere elongation and promotes Stn1/Ten1 telomere association,and a SUMO-Tpz1 fusion protein has increased affinity for Stn1. Our data suggest that SUMO inhibits telomerase through stimulation of Stn1/Ten1 action by Tpz1, highlighting the evolutionary conservation of the regulation of CST function by SUMOylation
On the dynamics of demersal fish assemblages off Namibia in the 1990s
Demersal fish surveys carried out off Namibia from 1990 to 2000 were used to study the dynamics of demersal fish assemblages on the shelf and upper slope. The study was performed on each major assemblage, i.e. over the shelf (100–300 m deep) and the slope (300–600 m). Changes in size spectrum, diversity, species composition and trends in abundance of the dominating species were analysed. The most evident changes were those related to overall abundance and diversity of the slope assemblage.Keywords: community dynamics, diversity, Namibia, size spectrum, species compositionAfrican Journal of Marine Science 2001, 23: 419–42
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