2,059 research outputs found
Reentrant phase transitions and van der Waals behaviour for hairy black holes
We study the extended phase space thermodynamics for hairy AdS black hole
solutions to Einstein-Maxwell- theory conformally coupled to a scalar
field in five dimensions. We find these solutions to exhibit van der Waals
behaviour in both the charged/uncharged cases, and reentrant phase transitions
in the charged case. This is the first example of reentrant phase transitions
in a five dimensional gravitational system which does not include higher
curvature corrections.Comment: 11 pages, 5 figures, REVTeX 4-
Hairy black holes in cubic quasi-topological gravity
We construct a class of five dimensional black hole solutions to cubic
quasi-topological gravity with conformal scalar hair and study their
thermodynamics. We find these black holes provide the second example of black
hole -lines: a line of second order (continuous) phase transitions,
akin to the fluid/superfluid transition of He. Examples of isolated
critical points are found for spherical black holes, marking the first in the
literature to date. We also find various novel and interesting phase
structures, including an isolated critical point occurring in conjunction with
a double reentrant phase transition. The AdS vacua of the theory are studied,
finding ghost-free configurations where the scalar field takes on a non-zero
constant value, in notable contrast to the five dimensional Lovelock case.Comment: 29 pages, 12 figure
Thermalon mediated phase transitions in Gauss-Bonnet gravity
Thermalons can mediate phase transitions between different vacua in higher
curvature gravity, potentially changing the asymptotic structure of the
spacetime. Treating the cosmological constant as a dynamical parameter, we
study these phase transitions in the context of extended thermodynamic phase
space. We find that in addition to the AdS to dS phase transitions previously
studied, thermal AdS space can undergo a phase transition to an asymptotically
flat black hole geometry. In the context of AdS to AdS transitions, we comment
on the similarities and differences between thermalon transitions and the
Hawking-Page transition.Comment: 20 pages, 11 figures; reference added, corrected to match published
versio
Thermodynamics of hairy black holes in Lovelock gravity
We perform a thorough study of the thermodynamic properties of a class of
Lovelock black holes with conformal scalar hair arising from coupling of a real
scalar field to the dimensionally extended Euler densities. We study the
linearized equations of motion of the theory and describe constraints under
which the theory is free from ghosts/tachyons. We then consider, within the
context of black hole chemistry, the thermodynamics of the hairy black holes in
the Gauss-Bonnet and cubic Lovelock theories. We clarify the connection between
isolated critical points and thermodynamic singularities, finding a one
parameter family of these critical points which occur for well-defined
thermodynamic parameters. We also report on a number of novel results,
including `virtual triple points' and the first example of a
`-line'---a line of second order phase transitions---in black hole
thermodynamics.Comment: 62 pages, 30 figures. Minor changes and typos corrected. Updated to
match published versio
P-V Criticality in Quasitopological Gravity
We investigate the thermodynamic behaviour of AdS quasitopological black hole
solutions in the context of extended thermodynamic phase space, in which the
cosmological constant induces a pressure with a conjugate volume. We find that
the third order exact quasitopological solution exhibits features consistent
with the third order Lovelock solutions for positive quasitopological coupling,
including multiple reentrant phase transitions and isolated critical points.
For negative coupling we find the first instances of both reentrant phase
transitions and thermodynamic singularities in five dimensions, along with
other modified thermodynamic behaviour compared to Einstein-AdS-Gauss Bonnet
gravity.Comment: 20 pages, 15 figures, REVTeX 4-1; updated to match published versio
The Effect of COBRA Training on First Responder Self-confidence to Work in a Toxic Chemical or Biological Agent Environment
First responders are our nation’s front line defense against intentional or accidental releases of toxic chemical or biological agents. Self-confidence which is a building block of self-efficacy is hypothesized to be malleable and increased through training. The purpose of this study was to determine the change if any, which first responders undergo during Chemical, Ordnance, Biological, and Radiological (COBRA) training, in their self-confidence to operate in a toxic chemical or biological agent environment. That is to determine if there is a correlation between increased self-confidence and COBRA training. The methodology of this study was based on quantitative methods of analysis and surveys to collect data from students attending COBRA training at the Center for Domestic Preparedness (CDP), Aniston, Alabama. Collaboration with the CDP ensured the data collected was captured from every student attending COBRA training, thus creating a survey environment wherein there was a 95% plus survey completion rate. The data was collected through a pre and post-training survey, which provided the before and after groups for the study. Descriptive statistics were used to analyze the delta between the groups, and the interrater agreement. Hypothesis testing was through paired sample t-testing, ANOVA, and regression analysis. Analysis of the data collected from students was conducted using SPSS statistical sampling software and a spreadsheet. Confidence was set at 95% with a t-score of 1.984 or greater, and a total case sample of 184 participants. Case sampling is based on standard probability sampling for the entire population of paid first responders in the United States
Quintessential Quartic Quasi-topological Quartet
We construct the quartic version of generalized quasi-topological gravity,
which was recently constructed to cubic order in arXiv: 1703.01631. This class
of theories includes Lovelock gravity and a known form of quartic
quasi-topological gravity as special cases and possess a number of remarkable
properties: (i) In vacuum, or in the presence of suitable matter, there is a
single independent field equation which is a total derivative. (ii) At the
linearized level, the equations of motion on a maximally symmetric background
are second order, coinciding with the linearized Einstein equations up to a
redefinition of Newton's constant. Therefore, these theories propagate only the
massless, transverse graviton on a maximally symmetric background. (iii) While
the Lovelock and quasi-topological terms are trivial in four dimensions, there
exist four new generalized quasi-topological terms (the quartet) that are
nontrivial, leading to interesting higher curvature theories in
dimensions that appear well suited for holographic study. We construct four
dimensional black hole solutions to the theory and study their properties. A
study of black brane solutions in arbitrary dimensions reveals that these
solutions are modified from the `universal' properties these solutions have.
This result may lead to interesting consequences for the dual CFTs.Comment: 46 pages, 1 figure. Discussion of black branes added to section
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