10,703 research outputs found
Eleven-dimensional massless superparticles and matrix theory spin-orbit couplings revisited
The classical probe dynamics of the eleven-dimensional massless
superparticles in the background geometry produced by N source M-momenta is
investigated in the framework of N-sector DLCQ supergravity. We expand the
probe action up to the two fermion terms and find that the fermionic
contributions are the spin-orbit couplings, which precisely agree with the
matrix theory calculations. We comment on the lack of non-perturbative
corrections in the one-loop matrix quantum mechanics effective action and its
compatibility with the supergravity analysis.Comment: 11 pages, Latex, no figure
Effective field theory of the deuteron with dibaryon field
Pionless effective field theory with dibaryon fields is reexamined for
observables involving the deuteron. The electromagnetic form factors of the
deuteron and the total cross sections of radiative neutron capture on the
proton, , are calculated. The low energy constants of
vector(photon)-dibaryon-dibaryon vertices in the effective lagrangian are fixed
primarily by the one-body vector(photon)-nucleon-nucleon interactions. This
scheme for fixing the values of the low energy constants satisfactorily
reproduces the results of the effective range theory. We also show that, by
including higher order corrections, one can obtain results that are close to
those of Argonne v18 potential model.Comment: 25 pages and 11 figures; 16 references added, Figure 6 and 7
replotted, text revised a lot. To be published in Phys. Rev.
Geodesic Motions in 2+1 Dimensional Charged Black Holes
We study the geodesic motions of a test particle around 2+1 dimensional
charged black holes. We obtain a class of exact geodesic motions for the
massless test particle when the ratio of its energy and angular momentum is
given by square root of cosmological constant. The other geodesic motions for
both massless and massive test particles are analyzed by use of numerical
method.Comment: 13page
Structure in Supersymmetric Yang-Mills Theory
We show that requiring sixteen supersymmetries in quantum mechanical gauge
theory implies the existence of a web of constrained interactions. Contrary to
conventional wisdom, these constraints extend to arbitrary orders in the
momentum expansion.Comment: 22 pages, LaTe
Euler number of Instanton Moduli space and Seiberg-Witten invariants
We show that a partition function of topological twisted N=4 Yang-Mills
theory is given by Seiberg-Witten invariants on a Riemannian four manifolds
under the condition that the sum of Euler number and signature of the four
manifolds vanish. The partition function is the sum of Euler number of
instanton moduli space when it is possible to apply the vanishing theorem. And
we get a relation of Euler number labeled by the instanton number with
Seiberg-Witten invariants, too. All calculation in this paper is done without
assuming duality.Comment: LaTeX, 34 page
Conformal anomaly and the vector coupling in dense matter
We construct an effective chiral Lagrangian for hadrons implemented by the
conformal invariance and discuss the properties of nuclear matter at high
density. The model is formulated based on two alternative assignment, "naive"
and mirror, of chirality to the nucleons. It is shown that taking the dilaton
limit, in which the mended symmetry of Weinberg is manifest, the vector-meson
Yukawa coupling becomes suppressed and the symmetry energy becomes softer as
one approaches the chiral phase transition. This leads to softer equations of
state (EoS) and could accommodate the EoS without any exotica consistent with
the recent measurement of a neutron star.Comment: v2:10 pages, 2 figures, typos corrected, a rough estimate of m0 adde
Limits on the evolution of galaxies from the statistics of gravitational lenses
We use gravitational lenses from the Cosmic Lens All-Sky Survey (CLASS) to
constrain the evolution of galaxies since redshift in the current
\LCDM cosmology. This constraint is unique as it is based on a mass-selected
lens sample of galaxies. Our method of statistical analysis is the same as in
Chae (2003). We parametrise the early-type number density evolution in the form
of and the velocity dispersion as . We find that
() if we assume , implying
that the number density of early-type galaxies is within 50% to 164% of the
present-day value at redshift . Allowing the velocity dispersion to
evolve, we find that (), indicating that
the velocity dispersion must be within 57% and 107% of the present-day value at
. These results are consistent with the early formation and passive
evolution of early-type galaxies. More stringent limits from lensing can be
obtained from future large lens surveys and by using very high-redshift quasars
(z \ga 5) such as those found from the Sloan Digital Sky Survey.Comment: 10 pages (preprint format), 2 figures, ApJL in press (December 20th
issue
Radiative neutron capture on a proton at BBN energies
The total cross section for radiative neutron capture on a proton, , is evaluated at big bang nucleosynthesis (BBN) energies. The
electromagnetic transition amplitudes are calculated up to next-to leading
order within the framework of pionless effective field theory with dibaryon
fields. We also calculate the cross section and the photon
analyzing power for the process from the amplitudes. The
values of low energy constants that appear in the amplitudes are estimated by a
Markov Chain Monte Carlo analysis using the relevant low energy experimental
data. Our result agrees well with those of other theoretical calculations
except for the cross section at some energies estimated by an
R-matrix analysis. We also study the uncertainties in our estimation of the
cross section at relevant BBN energies and find that the
estimated cross section is reliable to within 1% error.Comment: 21 pages and 12 eps figures; 6 eps figures and 2 references added,
and accepted for publication in Phys. Rev.
New Modeling of the Lensing Galaxy and Cluster of Q0957+561: Implications for the Global Value of the Hubble Constant
The gravitational lens 0957+561 is modeled utilizing recent observations of
the galaxy and the cluster as well as previous VLBI radio data which have been
re-analyzed recently. The galaxy is modeled by a power-law elliptical mass
density with a small core while the cluster is modeled by a non-singular
power-law sphere as indicated by recent observations. Using all of the current
available data, the best-fit model has a reduced chi-squared of approximately 6
where the chi-squared value is dominated by a small portion of the
observational constraints used; this value of the reduced chi-squared is
similar to that of the recent FGSE best-fit model by Barkana et al. However,
the derived value of the Hubble constant is significantly different from the
value derived from the FGSE model. We find that the value of the Hubble
constant is given by H_0 = 69 +18/-12 (1-K) and 74 +18/-17 (1-K) km/s/Mpc with
and without a constraint on the cluster's mass, respectively, where K is the
convergence of the cluster at the position of the galaxy and the range for each
value is defined by Delta chi-squared = reduced chi-squared. Presently, the
best achievable fit for this system is not as good as for PG 1115+080, which
also has recently been used to constrain the Hubble constant, and the
degeneracy is large. Possibilities for improving the fit and reducing the
degeneracy are discussed.Comment: 22 pages in aaspp style including 6 tables and 5 figures, ApJ in
press (Nov. 1st issue
Giant Gravitons in type IIA PP-wave Background
We examine giant gravitons with a worldvolume magnetic flux in type IIA
pp-wave background and find that they can move away from the origin along
direction in target space satisfying . This nontrivial relation can be
regarded as a complementary relation of the giant graviton on IIA pp-wave and
is shown to be connected to the spacetime uncertainty principle. The giant
graviton is also investigated in a system of N D0-branes as a fuzzy sphere
solution. It is observed that enters into the fuzzy algebra as a
deformation parameter. Such a background dependent Myers effect guarantees that
we again get the crucial relation of our giant graviton. In the paper, we also
find a BIon configuration on the giant graviton in this background.Comment: 10 pages, no figure, content added, typo corrected, reference adde
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