4,222,609 research outputs found
Willamette Valley Epilogue
Rusty Gaffney gives a brief overview of the culture of the wine industry in Oregon, focusing on the wineries of the Willamette Valley, in this article from his Prince of Pinot blog, volume 9, issue 42. Gaffney highlights information on the area, a travel guide with advice, and places not to miss
On the volume inside old black holes
Black holes that have nearly evaporated are often thought of as small
objects, due to their tiny exterior area. However, the horizon bounds large
spacelike hypersurfaces. A compelling geometric perspective on the evolution of
the interior geometry was recently shown to be provided by a generally
covariant definition of the volume inside a black hole using maximal surfaces.
In this article, we expand on previous results and show that finding the
maximal surfaces in an arbitrary spherically symmetric spacetime is equivalent
to a 1+1 geodesic problem. We then study the effect of Hawking radiation on the
volume by computing the volume of maximal surfaces inside the apparent horizon
of an evaporating black hole as a function of time at infinity: while the area
is shrinking, the volume of these surfaces grows monotonically with advanced
time, up to when the horizon has reached Planckian dimensions. The physical
relevance of these results for the information paradox and the remnant
scenarios are discussed.Comment: 9 pages, 5 figure
Why multi-tracer surveys beat cosmic variance
Galaxy surveys that map multiple species of tracers of large-scale structure
can improve the constraints on some cosmological parameters far beyond the
limits imposed by a simplistic interpretation of cosmic variance. This
enhancement derives from comparing the relative clustering between different
tracers of large-scale structure. We present a simple but fully generic
expression for the Fisher information matrix of surveys with any (discrete)
number of tracers, and show that the enhancement of the constraints on
bias-sensitive parameters are a straightforward consequence of this
multi-tracer Fisher matrix. In fact, the relative clustering amplitudes between
tracers are eigenvectors of this multi-tracer Fisher matrix. The diagonalized
multi-tracer Fisher matrix clearly shows that while the effective volume is
bounded by the physical volume of the survey, the relational information
between species is unbounded. As an application, we study the expected
enhancements in the constraints of realistic surveys that aim at mapping
several different types of tracers of large-scale structure. The gain obtained
by combining multiple tracers is highest at low redshifts, and in one
particular scenario we analyzed, the enhancement can be as large as a factor of
~3 for the accuracy in the determination of the redshift distortion parameter,
and a factor ~5 for the local non-Gaussianity parameter. Radial and angular
distance determinations from the baryonic features in the power spectrum may
also benefit from the multi-tracer approach.Comment: New references included; 9 pages, 9 figure
Information processing with Page-Wootters states
In order to perceive that a physical system evolves in time, two requirements
must be met: (a) it must be possible to define a "clock" and (b) it must be
possible to make a copy of the state of the system, that can be reliably
retrieved to make a comparison. We investigate what constraints quantum
mechanics poses on these issues, in light of recent experiments with entangled
photons.Comment: 9 pages LaTeX2e, 1 eps figure. Contribution to the special volume
"Chaos, Information Processing and Paradoxical Games", World Scientific
(2014
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