217 research outputs found
Phase Transitions for Flat adS Black Holes
We reexamine the thermodynamics of adS black holes with Ricci flat horizons
using the adS soliton as the thermal background. We find that there is a phase
transition which is dependent not only on the temperature, but also on the
black hole area, which is an independent parameter. As in the spherical adS
black hole, this phase transition is related via the adS/CFT correspondence to
a confinement-deconfinement transition in the large N gauge theory on the
conformal boundary at infinity.Comment: 5 pages, Revtex, no figures. Minor changes, typos corrected, some
references adde
Topological Censorship
All three-manifolds are known to occur as Cauchy surfaces of asymptotically
flat vacuum spacetimes and of spacetimes with positive-energy sources. We prove
here the conjecture that general relativity does not allow an observer to probe
the topology of spacetime: any topological structure collapses too quickly to
allow light to traverse it. More precisely, in a globally hyperbolic,
asymptotically flat spacetime satisfying the null energy condition, every
causal curve from \scri^- to {\scri}^+ is homotopic to a topologically
trivial curve from \scri^- to {\scri}^+. (If the Poincar\'e conjecture is
false, the theorem does not prevent one from probing fake 3-spheres).Comment: 12 pages, REVTEX; 1 postscript figure in a separate uuencoded file.
Our earlier version (PRL 71, 1486 (1993)) contained a secondary result,
mistakenly attributed to Schoen and Yau, regarding ``passive topological
censorship'' of a certain class of topologies. As Gregory Burnett has pointed
out (gr-qc/9504012), this secondary result is false. The main topological
censorship theorem is unaffected by the erro
Action-Specific Effects Underwater
Action-specific effects on perception are apparent in terrestrial environments. For example, targets that require more effort to walk, jump, or throw to look farther away than when the targets require less effort. Here, we examined whether action-specific effects would generalize to an underwater environment. Instead, perception might be geometrically precise, rather than action-specific, in an environment that is novel from an evolutionary perspective. We manipulated ease to swim by giving participants swimming flippers or taking them away. Those who estimated distance while wearing the flippers judged underwater targets to be closer than did participants who had taken them off. In addition, participants with better swimming ability judged the targets to be closer than did those with worse swimming ability. These results suggest perceived distance underwater is a function of the perceiver’s ability to swim to the targets
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