138 research outputs found
Towards a bulk description of higher spin SYK
We consider on the bulk side extensions of the Sachdev--Ye--Kitaev (SYK)
model to Yang--Mills and higher spins. To this end we study generalizations of
the Jackiw--Teitelboim (JT) model in the BF formulation. Our main goal is to
obtain generalizations of the Schwarzian action, which we achieve in two ways:
by considering the on-shell action supplemented by suitable boundary terms
compatible with all symmetries, and by applying the Lee--Wald--Zoupas formalism
to analyze the symplectic structure of dilaton gravity. We conclude with a
discussion of the entropy (including log-corrections from higher spins) and a
holographic dictionary for the generalized SYK/JT correspondence.Comment: 42 pages; v2: Typos correcte
Menagerie of AdS boundary conditions
We consider different sets of AdS boundary conditions for the
Jackiw-Teitelboim model in the linear dilaton sector where the dilaton is
allowed to fluctuate to leading order at the boundary of the Poincar\'e disk.
The most general set of boundary condtions is easily motivated in the gauge
theoretic formulation as a Poisson sigma model and has an
current algebra as asymptotic symmetries. Consistency of the variational
principle requires a novel boundary counterterm in the holographically
renormalized action, namely a kinetic term for the dilaton. The on-shell action
can be naturally reformulated as a Schwarzian boundary action. While there can
be at most three canonical boundary charges on an equal-time slice, we consider
all Fourier modes of these charges with respect to the Euclidean boundary time
and study their associated algebras. Besides the (centerless)
current algebra we find for stricter boundary conditions a
Virasoro algebra, a warped conformal algebra and a current
algebra. In each of these cases we get one half of a corresponding symmetry
algebra in three-dimensional Einstein gravity with negative cosmological
constant and analogous boundary conditions. However, on-shell some of these
algebras reduce to finite-dimensional ones, reminiscent of the on-shell
breaking of conformal invariance in SYK. We conclude with a discussion of
thermodynamical aspects, in particular the entropy and some Cardyology.Comment: 42 pp, 5 figs, v2: added ref
Cosmological Constant as Confining U(1) Charge in Two-Dimensional Dilaton Gravity
The cosmological constant is treated as a thermodynamical parameter in the framework of two-dimensional dilaton gravity. We find that the cosmological constant behaves as a U(1) charge with a confining potential, and that such potentials require a novel Born-Infeld boundary term in the action. The free energy and other thermodynamical quantities of interest are derived, from first principles, in a way that is essentially model independent. We discover that there is always a Schottky anomaly in the specific heat and explain its physical origin. Finally, we apply these results to specific examples, like anti-de Sitter–Schwarzschild–Tangherlini black holes, Bañados-Teitelboim-Zanelli black holes and the Jackiw-Teitelboim model
MEASURING & MONITORING Plant Populations
The root of the word monitoring means to warn, and an essential purpose of monitoring is to raise a warning flag that the current course of action is not working. Monitoring is a powerful tool for identifying problems in the early stages, before they become dramatically obvious or crises. If identified early, problems can be addressed while cost-effective solutions are still available. For example, an invasive species that threatens a rare plant population is much easier to control at the initial stages of invasion, compared to eradicating it once it is well established at a site. Monitoring is also critical for measuring management success. Good monitoring can demonstrate that the current management approach is working and provide evidence supporting the continuation of current management
Spatially resolved spectroscopy of the globular cluster RZ 2109 and the nature of its black hole
We present optical HST/STIS spectroscopy of RZ 2109, a globular cluster in
the elliptical galaxy NGC 4472. This globular cluster is notable for hosting an
ultraluminous X-ray source as well as associated strong and broad [OIII] 4959,
5007 emission. We show that the HST/STIS spectroscopy spatially resolves the
[OIII] emission in RZ 2109. While we are unable to make a precise determination
of the morphology of the emission line nebula, the best fitting models all
require that the [OIII] 5007 emission has a half light radius in the range 3-7
pc. The extended nature of the [OIII] 5007 emission is inconsistent with
published models that invoke an intermediate mass black hole origin. It is also
inconsistent with the ionization of ejecta from a nova in the cluster. The
spatial scale of the nebula could be produced via the photoionization of a
strong wind driven from a stellar mass black hole accreting at roughly its
Eddington rate.Comment: 7 pages, 4 figures - accepted for publication in Ap
Antibodies from a DNA peptide vaccination decrease the brain amyloid burden in a mouse model of Alzheimer's disease
The neuropathology of Alzheimer's disease (AD) is characterized by the accumulation of amyloid peptide Aβ in the brain derived from proteolytic cleavage of the amyloid precursor protein (APP). Vaccination of mice with plasmid DNA coding for the human Aβ42 peptide together with low doses of preaggregated peptide induced antibodies with detectable titers after only 2weeks. One serum was directed against the four aminoterminal amino acids DAEF and differs from previously described ones. Both immune sera and monoclonal antibodies solubilized preformed aggregates of Aβ42 in vitro and recognized amyloid plaques in brain sections of mice transgenic for human APP. Passive immunization of transgenic AD mice caused a significant and rapid reduction in brain amyloid plaques within 24h. The combined DNA peptide vaccine may prove useful for active immunization with few inoculations and low peptide dose which may prevent the recently described inflammatory reactions in patients. The monoclonal antibodies are applicable for passive immunization studies and may lead to a therapy of A
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