8,268 research outputs found
Superpartner Solutions of a BPS Monopole in Noncommutative Space
We construct U(2) BPS monopole superpartner solutions in N=2 non-commutative
super Yang-Mills theory. Calculation to the second order in the noncommutative
parameter shows that there is no electric quadrupole moment that is
expected from the magnetic dipole structure of noncommtative U(2) monopole.
This might give an example of the nature of how supersymmetry works not
changing between the commutative and noncommutative theories.Comment: 8 page
Radial Correlations between two quarks
In nuclear many-body problems the short-range correlation between two
nucleons is well described by the corresponding correlation in the {two}-body
problem. Therefore, as a first step in any attempt at an analogous description
of many-quark systems, it is necessary to know the two-quark correlation. With
this in mind, we study the light quark distribution in a heavy-light meson with
a static heavy quark. The charge and matter radial distributions of these
heavy-light mesons are measured on a lattice with a light quark mass about that
of the strange quark. Both distributions can be well fitted upto r approx 0.7
fm with the exponential form w_i^2(r), where w_i(r)=A exp(-r/r_i). For the
charge(c) and matter(m) distributions r_c approx 0.32(2) fm and r_m \approx
0.24(2) fm. We also discuss the normalisation of the total charge (defined to
be unity in the continuum limit) and matter integrated over all space, finding
1.30(5) and 0.4(1) respectively for a lattice spacing approx 0.17 fm.Comment: 8 pages, 3 ps figure
Stringy Derivation of Nahm Construction of Monopoles
We derive the Nahm construction of monopoles from exact tachyon condensation
on unstable D-branes. The Dirac operator used in the Nahm construction is
identified with the tachyon profile in our D-brane approach, and we provide
physical interpretation of the procedures Nahm gave. Crucial is the
introduction of infinite number of brane-antibranes from which arbitrary
D-brane can be constrcuted, exhibitting a unified view of various D-branes. We
explicitly show the equivalence of the D3-brane boundary state with the
monopole profile and the D1-brane boundary state with the Nahm data as
transverse scalars.Comment: 18 pages, 4 eps figures, JHEP style, comments about low energy limits
added, references adde
Inhomogeneity driven by Higgs instability in gapless superconductor
The fluctuations of the Higgs and pseudo Nambu-Goldstone fields in the 2SC
phase with mismatched pairing are described in the nonlinear realization
framework of the gauged Nambu--Jona-Lasinio model. In the gapless 2SC phase,
not only Nambu-Goldstone currents can be spontaneously generated, but the Higgs
field also exhibits instablity. The Nambu-Goldstone currents generation
indicates the formation of the single plane wave LOFF state and breaks rotation
symmetry, while the Higgs instability favors spatial inhomogeneity and breaks
translation invariance. In this paper, we focus on the Higgs instability which
has not drawn much attention yet. The Higgs instability cannot be removed
without a long range force, thus it persists in the gapless superfluidity and
induces phase separation. In the case of g2SC state, the Higgs instability can
only be partially removed by the electric Coulomb energy. However, it is not
excluded that the Higgs instability might be completely removed in the charge
neutral gCFL phase by the color Coulomb energy.Comment: 21 pages, 5 figure
ARPES studies of cuprate Fermiology: superconductivity, pseudogap, and quasiparticle dynamics
We present angle-resolved photoemission spectroscopy (ARPES) studies of the
cuprate high-temperature superconductors which elucidate the relation between
superconductivity and the pseudogap and highlight low-energy quasiparticle
dynamics in the superconducting state. Our experiments suggest that the
pseudogap and superconducting gap represent distinct states, which coexist
below T. Studies on Bi-2212 demonstrate that the near-nodal and
near-antinodal regions behave differently as a function of temperature and
doping, implying that different orders dominate in different momentum-space
regions. However, the ubiquity of sharp quasiparticles all around the Fermi
surface in Bi-2212 indicates that superconductivity extends into the
momentum-space region dominated by the pseudogap, revealing subtlety in this
dichotomy. In Bi-2201, the temperature dependence of antinodal spectra reveals
particle-hole asymmetry and anomalous spectral broadening, which may constrain
the explanation for the pseudogap. Recognizing that electron-boson coupling is
an important aspect of cuprate physics, we close with a discussion of the
multiple 'kinks' in the nodal dispersion. Understanding these may be important
to establishing which excitations are important to superconductivity.Comment: To appear in a focus issue on 'Fermiology of Cuprates' in New Journal
of Physic
First study of semileptonic decay form factors using NRQCD
We present a quenched calculation of the form factors of the semileptonic
weak decay with NRQCD heavy quark and Wilson
light quark on a lattice at . The form factors are
evaluated at six heavy quark masses, in the range of GeV.
dependence of matrix elements are investigated and compared with HQET
predictions. We observe clear signal for the form factors near ,
even at the -quark mass range. is compared with
based on the soft pion theorem and significant difference is
observed.Comment: 3 pages, 5 ps figures, uses espcrc2.sty and epsf.sty, Talk presented
at Lattice'9
Magnetohydrodynamic Simulations of A Rotating Massive Star Collapsing to A Black Hole
We perform two-dimensional, axisymmetric, magnetohydrodynamic simulations of
the collapse of a rotating star of 40 Msun and in the light of the collapsar
model of gamma-ray burst. Considering two distributions of angular momentum, up
to \sim 10^{17} cm^2/s, and the uniform vertical magnetic field, we investigate
the formation of an accretion disk around a black hole and the jet production
near the hole. After material reaches to the black hole with the high angular
momentum, the disk is formed inside a surface of weak shock. The disk becomes
in a quasi-steady state for stars whose magnetic field is less than 10^{10} G
before the collapse. We find that the jet can be driven by the magnetic fields
even if the central core does not rotate as rapidly as previously assumed and
outer layers of the star has sufficiently high angular momentum. The magnetic
fields are chiefly amplified inside the disk due to the compression and the
wrapping of the field. The fields inside the disk propagate to the polar region
along the inner boundary near the black hole through the Alfv{\'e}n wave, and
eventually drive the jet. The quasi-steady disk is not an advection-dominated
disk but a neutrino cooling-dominated one. Mass accretion rates in the disks
are greater than 0.01 Msun/sec with large fluctuations. The disk is transparent
for neutrinos. The dense part of the disk, which locates near the hole, emits
neutrino efficiently at a constant rate of < 8 \times 10^{51} erg/s. The
neutrino luminosity is much smaller than those from supernovae after the
neutrino burst.Comment: 42 pages, accepted for publication in the Astrophysical Journal. A
paper with higher-resolution figures available at
http://www.ec.knct.ac.jp/~fujimoto/collapsar/mhd-color.pd
The Environment of ``E+A'' Galaxies
The violent star formation history of ``E+A'' galaxies and their detection
almost exclusively in distant clusters is frequently used to link them to the
``Butcher-Oemler effect'' and to argue that cluster environment influences
galaxy evolution. From 11113 spectra in the Las Campanas Redshift Survey, we
have obtained a unique sample of 21 nearby ``E+A" galaxies. Surprisingly, a
large fraction (about 75%) of these ``E+A''s lie in the field. Therefore,
interactions with the cluster environment, in the form of the ICM or cluster
potential, are not essential for ``E+A'' formation. If one mechanism is
responsible for ``E+A''s, their existence in the field and the tidal features
in at least 5 of the 21 argue that galaxy-galaxy interactions and mergers are
that mechanism. The most likely environments for such interactions are poor
groups, which have lower velocity dispersions than clusters and higher galaxy
densities than the field. In hierarchical models, groups fall into clusters in
greater numbers at intermediate redshifts than they do today. Thus, the
Butcher-Oemler effect may reflect the typical evolution of galaxies in groups
and in the field rather than the influence of clusters on star formation in
galaxies. This abstract is abridged.Comment: 39 uuencoded, compressed pages (except Fig 1), complete preprint at
ftp://ociw.edu/pub/aiz/eplusa.ps, ApJ, submitte
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