155 research outputs found
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
Chemical Abundances of Seven Irregular and Three Tidal Dwarf Galaxies in the M81 Group
We have derived nebular abundances for 10 dwarf galaxies belonging to the M81
Group, including several galaxies which do not have abundances previously
reported in the literature. For each galaxy, multiple H \ii regions were
observed with GMOS-N at the Gemini Observatory in order to determine abundances
of several elements (oxygen, nitrogen, sulfur, neon, and argon). For seven
galaxies, at least one H \ii region had a detection of the temperature
sensitive [OIII] 4363 line, allowing a "direct" determination of the
oxygen abundance. No abundance gradients were detected in the targeted galaxies
and the observed oxygen abundances are typically in agreement with the well
known metallicity-luminosity relation. However, three candidate "tidal dwarf"
galaxies lie well off this relation, UGC 5336, Garland, and KDG 61. The nature
of these systems suggests that UGC 5336 and Garland are indeed recently formed
systems, whereas KDG 61 is most likely a dwarf spheroidal galaxy which lies
along the same line of sight as the M81 tidal debris field. We propose that
these H \ii regions formed from previously enriched gas which was stripped from
nearby massive galaxies (e.g., NGC 3077 and M81) during a recent tidal
interaction.Comment: 37 pages, 10 figures, accepted for publication in ApJ. Slit positions
in Table 2 have been update
Behavioral economic methods to inform infectious disease response: Prevention, testing, and vaccination in the COVID-19 pandemic
The role of human behavior to thwart transmission of infectious diseases like COVID-19 is evident. Psychological and behavioral science are key areas to understand decision-making processes underlying engagement in preventive health behaviors. Here we adapt well validated methods from behavioral economic discounting and demand frameworks to evaluate variables (e.g., delay, cost, probability) known to impact health behavior engagement. We examine the contribution of these mechanisms within a broader response class of behaviors reflecting adherence to public health recommendations made during the COVID-19 pandemic. Four crowdsourced samples (total N = 1,366) completed individual experiments probing a response class including social (physical) distancing, facemask wearing, COVID-19 testing, and COVID-19 vaccination. We also measure the extent to which choice architecture manipulations (e.g., framing, opt-in/opt-out) may promote (or discourage) behavior engagement. We find that people are more likely to socially distance when specified activities are framed as high risk, that facemask use during social interaction decreases systematically with greater social relationship, that describing delay until testing (rather than delay until results) increases testing likelihood, and that framing vaccine safety in a positive valence improves vaccine acceptance. These findings collectively emphasize the flexibility of methods from diverse areas of behavioral science for informing public health crisis management
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