8,944 research outputs found
Schroedinger functional formalism with domain-wall fermion
Finite volume renormalization scheme is one of the most fascinating scheme
for non-perturbative renormalization on lattice.
By using the step scaling function one can follow running of renormalized
quantities with reasonable cost.
It has been established the Schroedinger functional is very convenient to
define a field theory in a finite volume for the renormalization scheme.
The Schroedinger functional, which is characterized by a
Dirichlet boundary condition in temporal direction, is well defined and works
well for the Yang-Mills theory and QCD with the Wilson fermion.
However one easily runs into difficulties if one sets the same sort of the
Dirichlet boundary condition for the overlap Dirac operator or the domain-wall
fermion.
In this paper we propose an orbifolding projection procedure to impose the
Schroedinger functional Dirichlet boundary condition on the domain-wall
fermion.Comment: 32 page
Downsizing of Star-Forming Galaxies by Gravitational Processes
There is observed a trend that a lower mass galaxy forms stars at a later
epoch. This downsizing of star-forming galaxies has been attributed to
hydrodynamical or radiative feedback processes that regulate star formation.
However, here we explain the downsizing by gravitational processes alone, in
the bottom-up scenario where galaxies evolve from subgalactic-scale objects.
Within a region of the initial density field that is to evolve into a lower
mass galaxy, subgalactic-scale fluctuation is of a smaller amplitude. The
formation of subgalactic-scale objects, i.e., gravitational collapse of the
subgalactic-scale fluctuation, and the subsequent onset of star formation
accordingly occur at a later epoch for a lower mass galaxy. As a function of
galaxy mass, we calculate the peak epoch of formation of subgalactic-scale
objects. The peak epoch is consistent with the peak epoch of star formation
derived from observations. [abridged]Comment: 4 pages, to appear in Astronomy and Astrophysics (Research Note
Inversion doublets of reflection-asymmetric clustering in 28Si and their isoscalar monopole and dipole transitions
[Background] Various cluster states of astrophysical interest are expected to
exist in the excited states of . However, they have not been
identified firmly, because of the experimental and theoretical difficulties.
[Purpose] To establish the Mg+, O+C and
Ne+2 cluster bands, we theoretically search for the
negative-parity cluster bands that are paired with the positive-parity bands to
constitute the inversion doublets. We also offer the isoscalar monopole and
dipole transitions as a promising probe for the clustering. We numerically show
that these transition strengths from the ground state to the cluster states are
very enhanced. [Method] The antisymmetrized molecular dynamics with Gogny D1S
effective interaction is employed to calculate the excited states of . The isoscalar monopole and dipole transition strengths are directly
evaluated from wave functions of the ground and excited states. [Results]
Negative-parity bands having Mg+ and O+C cluster
configurations are obtained in addition to the newly calculated
Ne+2 cluster bands. All of them are paired with the
corresponding positive-parity bands to constitute the inversion doublets with
various cluster configurations. The calculation show that the band-head of the
Mg+ and Ne+2 cluster bands are strongly excited
by the isoscalar monopole and dipole transitions. [Conclusions] The present
calculation suggests the existence of the inversion doublets with the
Mg+, O+C and Ne+2
configurations.Because of the enhanced transition strengths, we offer the
isoscalar monopole and dipole transitions as good probe for the
Mg+ and Ne+2 cluster bands.Comment: 28 pages, 8 figure
Orbital Decay and Tidal Disruption of a Star Cluster: Analytical Calculation
The orbital decay and tidal disruption of a star cluster in a galaxy is
studied in an analytical manner. Owing to dynamical friction, the star cluster
spirals in toward the center of the galaxy. Simultaneously, the galactic tidal
field strips stars from the outskirts of the star cluster. Under an assumption
that the star cluster undergoes a self-similar evolution, we obtain the
condition and timescale for the star cluster to reach the galaxy center before
its disruption. The result is used to discuss the fate of so-called
intermediate-mass black holes with >10^3 M(sun) found recently in young star
clusters of starburst galaxies and also the mass function of globular clusters
in galaxies.Comment: 12 pages, 1 PS file for 2 figures, to appear in The Astrophysical
Journa
A Geometrical Relationship between Broad-Line Clouds and an Accretion Disk around Active Galactic Nuclei
Recent hard X-ray spectroscopy of active galactic nuclei has strongly
suggested that double-peaked, very broad Fe K emission arises from an accretion
disk around the central engine. Model fitting of the observed Fe K emission
line profile makes it possible to estimate a probable inclination angle of the
accretion disk. In order to study the geometrical relationship between the
accretion disk and broad emission-line regions (BLRs), we investigate the
correlation between the inclination angle of the accretion disk and the
velocity width of BLRs for 18 type-1 Seyfert galaxies. We found that there may
be a negative correlation between them, i.e., Seyfert nuclei with a more
face-on accretion disk tend to have larger BLR velocity widths, suggesting that
the BLRs are not coplanar with respect to the accretion disk. The most probable
interpretation may be that the BLRs arise from outer parts ({\it r} 0.01
pc) of a warped accretion disk illuminated by the central engine.Comment: 11 pages, 3 figures; accepted for Publications of the Astronomical
Society of Japa
Dynamical Gauge Boson and Strong-Weak Reciprocity
It is proposed that asymptotically nonfree gauge theories are consistently
interpreted as theories of composite gauge bosons. It is argued that when
hidden local symmetry is introduced, masslessness and coupling universality of
dynamically generated gauge boson are ensured. To illustrate these ideas we
take a four dimensional Grassmannian sigma model as an example and show that
the model should be regarded as a cut-off theory and there is a critical
coupling at which the hidden local symmetry is restored. Propagator and vertex
functions of the gauge field are calculated explicitly and existence of the
massless pole is shown. The beta function determined from the factor of
the dynamically generated gauge boson coincides with that of an asymptotic
nonfree elementary gauge theory. Using these theoretical machinery we construct
a model in which asymptotic free and nonfree gauge bosons coexist and their
running couplings are related by the reciprocally proportional relation.Comment: 19 pages, latex, 6 eps figures, a numbers of corrections are made in
the tex
The Volume Fraction of Ionized Intergalactic Gas at Redshift z=6.5
The observed number density of Lyman-alpha sources implies a minimum volume
of the inter-galactic medium that must be ionized, in order to allow the
Lyman-alpha photons to escape attenuation. We estimate this volume by assigning
to each Lyman-alpha emitter the minimum Stromgren sphere that would allow half
its Lyman-alpha photons to escape. This implies a lower limit to ionized gas
volume fraction of 20-50% at redshift z=6.5. This is a lower limit in two ways:
First, we conservatively assume that the Lyman-alpha sources seen (at a
relatively bright flux limit) are the only ones present; and second, we assume
the smallest Stromgren sphere volume that will allow the photons to escape.
This limit is completely independent of what ionizing photon sources produced
the bubbles. Deeper Lyman-alpha surveys are possible with present technology,
and can strengthen these limits by detecting a higher density of Lyman-alpha
galaxies.Comment: Submitted to ApJ Letter
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