2,635 research outputs found
Quantum Interference to Measure Spacetime Curvature: A Proposed Experiment at the Intersection of Quantum Mechanics and General Relativity
An experiment in Low Earth Orbit (LEO) is proposed to measure components of
the Riemann curvature tensor using atom interferometry. We show that the
difference in the quantum phase of an atom that can travel along
two intersecting geodesics is given by times the spacetime
volume contained within the geodesics. Our expression for also
holds for gravitational waves in the long wavelength limit.Comment: 7 pages LaTeXed with RevTeX 4.0, 2 figures. Submitted to the 2003
Gravity Research Foundation Essay Contes
Thermal-Fluid Flow Transport Phenomenon over Slot-Perforated Flat Plates Placed in Narrow Channel
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76151/1/AIAA-25872-119.pd
Modelling multi-scale cell-tissue interaction of tissue-engineered muscle constructs
Expectation on engineered tissue substitute continues to grow and for an effective development of
a functional tissue and to control its quality, cellular mehcanoresponse plays a key role. Although the
mechanoresponse – in terms of cell-tissue interaction across scales – has been understood better in
recent years, there are still technical limitations to quantitatively monitor the processes involved in
the development of both native and engineered tissues. Computational (in silico) studies have been
utilised to complement the experimental limitations and successfully applied to prediction of tissue
growth. We here review recent activities in the area of combined experimental and computational
analyses of tissue growth, especially in tissue-engineering context, and highlight the advantages of
such an approach for the future of the tissue engineering, using our own case study of predicting
musculoskeletal tissue-engineering construct development
Spacetime structure of static solutions in Gauss-Bonnet gravity: neutral case
We study the spacetime structures of the static solutions in the
-dimensional Einstein-Gauss-Bonnet- system systematically. We
assume the Gauss-Bonnet coefficient is non-negative. The solutions
have the -dimensional Euclidean sub-manifold, which is the Einstein
manifold with the curvature and -1. We also assume , where is the curvature radius, in order for the
sourceless solution (M=0) to be defined. The general solutions are classified
into plus and minus branches. The structures of the center, horizons, infinity
and the singular point depend on the parameters , , ,
and branches complicatedly so that a variety of global structures for the
solutions are found. In the plus branch, all the solutions have the same
asymptotic structure at infinity as that in general relativity with a negative
cosmological constant. For the negative mass parameter, a new type of
singularity called the branch singularity appears at non-zero finite radius
. The divergent behavior around the singularity in Gauss-Bonnet
gravity is milder than that around the central singularity in general
relativity. In the cases the plus-branch solutions do not have any
horizon. In the case, the radius of the horizon is restricted as
) in the plus (minus)
branch. There is also the extreme black hole solution with positive mass in
spite of the lack of electromagnetic charge. We briefly discuss the effect of
the Gauss-Bonnet corrections on black hole formation in a collider and the
possibility of the violation of third law of the black hole thermodynamics.Comment: 19 pages, 11 figure
Perturbations of global monopoles as a black hole's hair
We study the stability of a spherically symmetric black hole with a global
monopole hair. Asymptotically the spacetime is flat but has a deficit solid
angle which depends on the vacuum expectation value of the scalar field. When
the vacuum expectation value is larger than a certain critical value, this
spacetime has a cosmological event horizon. We investigate the stability of
these solutions against the spherical and polar perturbations and confirm that
the global monopole hair is stable in both cases. Although we consider some
particular modes in the polar case, our analysis suggests the conservation of
the "topological charge" in the presence of the event horizons and violation of
black hole no-hair conjecture in asymptotically non-flat spacetime.Comment: 11 pages, 2 figures, some descriptions were improve
Dangerous implications of a minimum length in quantum gravity
The existence of a minimum length and a generalization of the Heisenberg
uncertainty principle seem to be two fundamental ingredients required in any
consistent theory of quantum gravity. In this letter we show that they would
predict dangerous processes which are phenomenologically unacceptable. For
example, long--lived virtual super--Planck mass black holes may lead to rapid
proton decay. Possible solutions of this puzzle are briefly discussed.Comment: 5 pages, no figure. v3: refereed versio
Meanfield treatment of Bragg scattering from a Bose-Einstein condensate
A unified semiclassical treatment of Bragg scattering from Bose-Einstein
condensates is presented. The formalism is based on the Gross-Pitaevskii
equation driven by classical light fields far detuned from atomic resonance. An
approximate analytic solution is obtained and provides quantitative
understanding of the atomic momentum state oscillations, as well as a simple
expression for the momentum linewidth of the scattering process. The validity
regime of the analytic solution is derived, and tested by three dimensional
cylindrically symmetric numerical simulations.Comment: 21 pages, 10 figures. Minor changes made to documen
Do stringy corrections stabilize coloured black holes?
We consider hairy black hole solutions of Einstein-Yang-Mills-Dilaton theory,
coupled to a Gauss-Bonnet curvature term, and we study their stability under
small, spacetime-dependent perturbations. We demonstrate that the stringy
corrections do not remove the sphaleronic instabilities of the coloured black
holes with the number of unstable modes being equal to the number of nodes of
the background gauge function. In the gravitational sector, and in the limit of
an infinitely large horizon, the coloured black holes are also found to be
unstable. Similar behaviour is exhibited by the magnetically charged black
holes while the bulk of the neutral black holes are proven to be stable under
small, gauge-dependent perturbations. Finally, the electrically charged black
holes are found to be characterized only by the existence of a gravitational
sector of perturbations. As in the case of neutral black holes, we demonstrate
that for the bulk of electrically charged black holes no unstable modes arise
in this sector.Comment: 17 pages, Revtex, comments and a reference added, version to appear
in Physical Review
Spatial interference of coherent atomic waves by manipulation of the internal quantum state
A trapped 87Rb Bose-Einstein condensate is initially put into a superposition
of two internal states. Under the effect of gravity and by means of a second
transition, we prepare two vertically displaced condensates in the same
internal state. These constitute two coherent sources of matter waves with
adjustable spatial separation. Fringe patterns, observed after free expansion,
are associated with the interplay between internal and external degrees of
freedom and substantially agree with those for a double slit experiment
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