1,438 research outputs found
A study of neutron-deuteron scattering in configuration space
A new computational method for solving the configuration-space Faddeev
equations for the breakup scattering problem has been applied to nd scattering
both below and above the two-body threshold.Comment: 4 pages, 3 Postscript figures, uses espcrc1.sty Talk at the 18th
International IUPAP Conference on Few-Body Problems in Physics, Aug. 21-26,
2006, Santos, Brazi
Massive Supergravity and Deconstruction
We present a simple superfield Lagrangian for massive supergravity. It
comprises the minimal supergravity Lagrangian with interactions as well as mass
terms for the metric superfield and the chiral compensator. This is the natural
generalization of the Fierz-Pauli Lagrangian for massive gravity which
comprises mass terms for the metric and its trace. We show that the on-shell
bosonic and fermionic fields are degenerate and have the appropriate spins: 2,
3/2, 3/2 and 1. We then study this interacting Lagrangian using goldstone
superfields. We find that a chiral multiplet of goldstones gets a kinetic term
through mixing, just as the scalar goldstone does in the non-supersymmetric
case. This produces Planck scale (Mpl) interactions with matter and all the
discontinuities and unitarity bounds associated with massive gravity. In
particular, the scale of strong coupling is (Mpl m^4)^1/5, where m is the
multiplet's mass. Next, we consider applications of massive supergravity to
deconstruction. We estimate various quantum effects which generate non-local
operators in theory space. As an example, we show that the single massive
supergravity multiplet in a 2-site model can serve the function of an extra
dimension in anomaly mediation.Comment: 24 pages, 2 figures, some color. Typos fixed and refs added in v
Tverberg-type theorems for intersecting by rays
In this paper we consider some results on intersection between rays and a
given family of convex, compact sets. These results are similar to the center
point theorem, and Tverberg's theorem on partitions of a point set
Hidden breakpoints in genome alignments
During the course of evolution, an organism's genome can undergo changes that
affect the large-scale structure of the genome. These changes include gene
gain, loss, duplication, chromosome fusion, fission, and rearrangement. When
gene gain and loss occurs in addition to other types of rearrangement,
breakpoints of rearrangement can exist that are only detectable by comparison
of three or more genomes. An arbitrarily large number of these "hidden"
breakpoints can exist among genomes that exhibit no rearrangements in pairwise
comparisons.
We present an extension of the multichromosomal breakpoint median problem to
genomes that have undergone gene gain and loss. We then demonstrate that the
median distance among three genomes can be used to calculate a lower bound on
the number of hidden breakpoints present. We provide an implementation of this
calculation including the median distance, along with some practical
improvements on the time complexity of the underlying algorithm.
We apply our approach to measure the abundance of hidden breakpoints in
simulated data sets under a wide range of evolutionary scenarios. We
demonstrate that in simulations the hidden breakpoint counts depend strongly on
relative rates of inversion and gene gain/loss. Finally we apply current
multiple genome aligners to the simulated genomes, and show that all aligners
introduce a high degree of error in hidden breakpoint counts, and that this
error grows with evolutionary distance in the simulation. Our results suggest
that hidden breakpoint error may be pervasive in genome alignments.Comment: 13 pages, 4 figure
TIPS AND TRICKS FOR CHARACTERIZING SHAPE MEMORY ALLOY WIRE: PART 1âDIFFERENTIAL SCANNING CALORIMETRY AND BASIC PHENOMENA
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73961/1/j.1747-1567.2008.00410.x.pd
Quantization on a 2-dimensional phase space with a constant curvature tensor
Some properties of the star product of the Weyl type (i.e. associated with
the Weyl ordering) are proved. Fedosov construction of the *-product on a
2-dimensional phase spacewith a constant curvature tensor is presented.
Eigenvalue equations for momentum p and position q on a 2-dimensional phase
space with constant curvature tensors are solved.Comment: 33 pages, LaTeX, Annals of Physics (2003
Strong Coupling vs. 4-D Locality in Induced Gravity
We re-examine the problem of strong coupling in a regularized version of DGP
(or ``brane-induced'') gravity. We find that the regularization of ref.
hep-th/0304148 differs from DGP in that it does not exhibit strong coupling or
ghosts up to cubic order in the interactions. We suggest that the nonlocal
nature of the theory, when written in terms of the 4-D metric, is a plausible
reason for this phenomenon. Finally, we briefly discuss the possible behavior
of the model at higher-order in perturbation theory.Comment: 19 pages, accepted for publication in PR
Chiral symmetry breaking, color superconductivity and color neutral quark matter: a variational approach
We investigate the vacuum realignment for chiral symmetry breaking and color
superconductivity at finite density in Nambu-Jona-Lasinio model in a
variational method. The treatment allows us to investigate simultaneous
formation of condensates in quark antiquark as well as in diquark channels. The
methodology involves an explicit construction of a variational ground state and
minimisation of the thermodynamic potential. Color and electric charge
neutrality conditions are imposed through introduction of appropriate chemical
potentials. Color and flavor dependent condensate functions are determined
through minimisation of the thermodynamic potential. The equation of state is
calculated. Simultaneous existence of a mass gap and superconducting gap is
seen in a small window of quark chemical potential within the model when charge
neutrality conditions are not imposed. Enforcing color and electric charge
neutrality conditions gives rise to existence of gapless superconducting modes
depending upon the magnitude of the gap and the difference of the chemical
potentials of the condensing quarks.Comment: 13 pages, 6 figures,to appear in Phys. Rev.
Wave packet revivals and the energy eigenvalue spectrum of the quantum pendulum
The rigid pendulum, both as a classical and as a quantum problem, is an
interesting system as it has the exactly soluble harmonic oscillator and the
rigid rotor systems as limiting cases in the low- and high-energy limits
respectively. The energy variation of the classical periodicity () is
also dramatic, having the special limiting case of at the
'top' of the classical motion (i.e. the separatrix.) We study the
time-dependence of the quantum pendulum problem, focusing on the behavior of
both the (approximate) classical periodicity and especially the quantum revival
and superrevival times, as encoded in the energy eigenvalue spectrum of the
system. We provide approximate expressions for the energy eigenvalues in both
the small and large quantum number limits, up to 4th order in perturbation
theory, comparing these to existing handbook expansions for the characteristic
values of the related Mathieu equation, obtained by other methods. We then use
these approximations to probe the classical periodicity, as well as to extract
information on the quantum revival and superrevival times. We find that while
both the classical and quantum periodicities increase monotonically as one
approaches the 'top' in energy, from either above or below, the revival times
decrease from their low- and high-energy values until very near the separatrix
where they increase to a large, but finite value.Comment: 27 pages, 8 embedded .eps figures; to appear, Annals of Physic
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