30,893 research outputs found
M-Fivebrane from the Open Supermembrane
Covariant field equations of M-fivebrane in eleven dimensional curved
superspace are obtained from the requirement of kappa-symmetry of an open
supermembrane ending on a fivebrane. The worldvolume of the latter is a (6|16)
dimensional supermanifold embedded in the (11|32) dimensional target
superspace. The kappa-symmetry of the system imposes a constraint on this
embedding, and a constraint on a modified super 3-form field strength on the
fivebrane worldvolume. These constraints govern the dynamics of the
M-fivebrane.Comment: 11 pages, Latex, references and appendix adde
Loss of purity by wave packet scattering at low energies
We study the quantum entanglement produced by a head-on collision between two
gaussian wave packets in three-dimensional space. By deriving the two-particle
wave function modified by s-wave scattering amplitudes, we obtain an
approximate analytic expression of the purity of an individual particle. The
loss of purity provides an indicator of the degree of entanglement. In the case
the wave packets are narrow in momentum space, we show that the loss of purity
is solely controlled by the ratio of the scattering cross section to the
transverse area of the wave packets.Comment: 7 pages, 1 figur
Evidence for the Role of Instantons in Hadron Structure from Lattice QCD
Cooling is used as a filter on a set of gluon fields sampling the Wilson
action to selectively remove essentially all fluctuations of the gluon field
except for the instantons. The close agreement between quenched lattice QCD
results with cooled and uncooled configurations for vacuum correlation
functions of hadronic currents and for density-density correlation functions in
hadronic bound states provides strong evidence for the dominant role of
instantons in determining light hadron structure and quark propagation in the
QCD vacuum.Comment: 26 pages in REVTeX, plus 10 figures, uuencoded. Submitted to Physical
Review D. MIT-CTP-226
Temperature dependence of instantons in QCD
We investigate the temperature dependence of the instanton contents of gluon
fields, using unquenched lattice QCD and the cooling method. The instanton size
parameter deduced from the correlation function decreases from 0.44fm below the
phase-transition temperature (MeV) to 0.33fm at 1.3 .
The instanton charge distribution is Poissonian above , but it deviates
from the convoluted Poisson at low temperature. The topological susceptibility
decreases rapidly below , showing the apparent restoration of the
symmetry already at .Comment: 8 pages TEX, 3 Postscript figures available at
http://www.krl.caltech.edu/preprints/MAP.htm
Analysis of the effects of interpolation and enhancement of LANDSAT-1 Data on classification and area estimation accuracy
There are no author-identified significant results in this report
S-wave quantum entanglement in a harmonic trap
We analyze the quantum entanglement between two interacting atoms trapped in
a spherical harmonic potential. At ultra-cold temperature, ground state
entanglement is generated by the dominated s-wave interaction. Based on a
regularized pseudo-potential Hamiltonian, we examine the quantum entanglement
by performing the Schmidt decomposition of low-energy eigenfunctions. We
indicate how the atoms are paired and quantify the entanglement as a function
of a modified s-wave scattering length inside the trap.Comment: 10 pages, 5 figures, to be apear in PR
Finite element analysis of gradient coil deformation and vibration in NMR microscopy
Resolution degradation due to gradient coil deformation and vibration in NMR microscopy is investigated using finite element analysis. From the analysis, deformations due to the Lorentz force can be as large as 1-10 μm depending on the gradient strength and coil frame material. Thus, these deformations can be one of the major resolution limiting factors in NMR microscopy. Coil vibration, which depends on the input current waveform and resolution degradation due to time-variant deformation and time-invariant deformation are investigated by numerical simulations
Retarded Green's Functions In Perturbed Spacetimes For Cosmology and Gravitational Physics
Electromagnetic and gravitational radiation do not propagate solely on the
null cone in a generic curved spacetime. They develop "tails," traveling at all
speeds equal to and less than unity. If sizeable, this off-the-null-cone effect
could mean objects at cosmological distances, such as supernovae, appear dimmer
than they really are. Their light curves may be distorted relative to their
flat spacetime counterparts. These in turn could affect how we infer the
properties and evolution of the universe or the objects it contains. Within the
gravitational context, the tail effect induces a self-force that causes a
compact object orbiting a massive black hole to deviate from an otherwise
geodesic path. This needs to be taken into account when modeling the
gravitational waves expected from such sources. Motivated by these
considerations, we develop perturbation theory for solving the massless scalar,
photon and graviton retarded Green's functions in perturbed spacetimes,
assuming these Green's functions are known in the background spacetime. In
particular, we elaborate on the theory in perturbed Minkowski spacetime in
significant detail; and apply our techniques to compute the retarded Green's
functions in the weak field limit of the Kerr spacetime to first order in the
black hole's mass and angular momentum. Our methods build on and generalizes
work appearing in the literature on this topic to date, and lays the foundation
for a thorough, first principles based, investigation of how light propagates
over cosmological distances, within a spatially flat inhomogeneous
Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) universe. This perturbative
scheme applied to the graviton Green's function, when pushed to higher orders,
may provide approximate analytic (or semi-analytic) results for the self-force
problem in the weak field limits of the Schwarzschild and Kerr black hole
geometries.Comment: 23 pages, 5 figures. Significant updates in v2: Scalar, photon and
graviton Green's functions calculated explicitly in Kerr black hole spacetime
up to first order in mass and angular momentum (Sec. V); Visser's van Vleck
determinant result shown to be equivalent to ours in Sec. II. v3: JWKB
discussion moved to introduction; to be published in PR
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