621 research outputs found
Mathematical Modeling of Boson-Fermion Stars in the Generalized Scalar-Tensor Theories of Gravity
A model of static boson-fermion star with spherical symmetry based on the
scalar-tensor theory of gravity with massive dilaton field is investigated
numerically.
Since the radius of star is \textit{a priori} an unknown quantity, the
corresponding boundary value problem (BVP) is treated as a nonlinear spectral
problem with a free internal boundary. The Continuous Analogue of Newton Method
(CANM) for solving this problem is applied.
Information about basic geometric functions and the functions describing the
matter fields, which build the star is obtained. In a physical point of view
the main result is that the structure and properties of the star in presence of
massive dilaton field depend essentially both of its fermionic and bosonic
components.Comment: 16 pages, amstex, 5 figures, changed conten
The geometrical form for the string space-time action
In the present article, we derive the space-time action of the bosonic string
in terms of geometrical quantities. First, we study the space-time geometry
felt by probe bosonic string moving in antisymmetric and dilaton background
fields. We show that the presence of the antisymmetric field leads to the
space-time torsion, and the presence of the dilaton field leads to the
space-time nonmetricity. Using these results we obtain the integration measure
for space-time with stringy nonmetricity, requiring its preservation under
parallel transport. We derive the Lagrangian depending on stringy curvature,
torsion and nonmetricity.Comment: 13 page
SRAO CO Observation of 11 Supernova Remnants in l = 70 to 190 deg
We present the results of 12CO J = 1-0 line observations of eleven Galactic
supernova remnants (SNRs) obtained using the Seoul Radio Astronomy Observatory
(SRAO) 6-m radio telescope. The observation was made as a part of the SRAO CO
survey of SNRs between l = 70 and 190 deg, which is intended to identify SNRs
interacting with molecular clouds. The mapping areas for the individual SNRs
are determined to cover their full extent in the radio continuum. We used
halfbeam grid spacing (60") for 9 SNRs and full-beam grid spacing (120") for
the rest. We detected CO emission towards most of the remnants. In six SNRs,
molecular clouds showed a good spatial relation with their radio morphology,
although no direct evidence for the interaction was detected. Two SNRs are
particularly interesting: G85.4+0.7, where there is a filamentary molecular
cloud along the radio shell, and 3C434.1, where a large molecular cloud appears
to block the western half of the remnant. We briefly summarize the results
obtained for individual SNRs.Comment: Accepted for publication in Astrophysics & Space Science. 12 pages,
12 figures, and 3 table
Subsurface Supergranular Vertical Flows as Measured Using Large Distance Separations in Time-Distance Helioseismology
As large--distance rays (say, 10\,-\,) approach the solar surface
approximately vertically, travel times measured from surface pairs for these
large separations are mostly sensitive to vertical flows, at least for shallow
flows within a few Mm of the solar surface. All previous analyses of
supergranulation have used smaller separations and have been hampered by the
difficulty of separating the horizontal and vertical flow components. We find
that the large separation travel times associated with supergranulation cannot
be studied using the standard phase-speed filters of time-distance
helioseismology. These filters, whose use is based upon a refractive model of
the perturbations, reduce the resultant travel time signal by at least an order
of magnitude at some distances. More effective filters are derived. Modeling
suggests that the center--annulus travel time difference
in the separation range \,-\, is insensitive to the
horizontally diverging flow from the centers of the supergranules and should
lead to a constant signal from the vertical flow. Our measurement of this
quantity, 5.1 \pm 0.1\secs, is constant over the distance range. This
magnitude of signal cannot be caused by the level of upflow at cell centers
seen at the photosphere of 10\ms extended in depth. It requires the vertical
flow to increase with depth. A simple Gaussian model of the increase with depth
implies a peak upward flow of 240\ms at a depth of 2.3\Mm and a peak
horizontal flow of 700\ms at a depth of 1.6\Mm.Comment: Solar Physics; 15 pages, 6 figure
Moduli Spaces for Principal Bundles in Arbitrary Characteristic
In this article, we solve the problem of constructing moduli spaces of
semistable principal bundles (and singular versions of them) over smooth
projective varieties over algebraically closed ground fields of positive
characteristic.Comment: V4: Final version, to appear in Advances in Mathematics, 69p
Stability of the Minimal Heterotic Standard Model Bundle
The observable sector of the "minimal heterotic standard model" has precisely
the matter spectrum of the MSSM: three families of quarks and leptons, each
with a right-handed neutrino, and one Higgs-Higgs conjugate pair. In this
paper, it is explicitly proven that the SU(4) holomorphic vector bundle leading
to the MSSM spectrum in the observable sector is slope-stable.Comment: LaTeX, 19 page
Moduli Dependent mu-Terms in a Heterotic Standard Model
In this paper, we present a formalism for computing the non-vanishing Higgs
mu-terms in a heterotic standard model. This is accomplished by calculating the
cubic product of the cohomology groups associated with the vector bundle moduli
(phi), Higgs (H) and Higgs conjugate (Hbar) superfields. This leads to terms
proportional to phi H Hbar in the low energy superpotential which, for non-zero
moduli expectation values, generate moduli dependent mu-terms of the form
H Hbar. It is found that these interactions are subject to two very restrictive
selection rules, each arising from a Leray spectral sequence, which greatly
reduce the number of moduli that can couple to Higgs-Higgs conjugate fields. We
apply our formalism to a specific heterotic standard model vacuum. The
non-vanishing cubic interactions phi H Hbar are explicitly computed in this
context and shown to contain only four of the nineteen vector bundle moduli.Comment: 23 pages, LaTe
Yukawa Couplings in Heterotic Standard Models
In this paper, we present a formalism for computing the Yukawa couplings in
heterotic standard models. This is accomplished by calculating the relevant
triple products of cohomology groups, leading to terms proportional to Q*H*u,
Q*Hbar*d, L*H*nu and L*Hbar*e in the low energy superpotential. These
interactions are subject to two very restrictive selection rules arising from
the geometry of the Calabi-Yau manifold. We apply our formalism to the
"minimal" heterotic standard model whose observable sector matter spectrum is
exactly that of the MSSM. The non-vanishing Yukawa interactions are explicitly
computed in this context. These interactions exhibit a texture rendering one
out of the three quark/lepton families naturally light.Comment: 21 pages, LaTe
Heterotic Compactification, An Algorithmic Approach
We approach string phenomenology from the perspective of computational
algebraic geometry, by providing new and efficient techniques for proving
stability and calculating particle spectra in heterotic compactifications. This
is done in the context of complete intersection Calabi-Yau manifolds in a
single projective space where we classify positive monad bundles. Using a
combination of analytic methods and computer algebra we prove stability for all
such bundles and compute the complete particle spectrum, including gauge
singlets. In particular, we find that the number of anti-generations vanishes
for all our bundles and that the spectrum is manifestly moduli-dependent.Comment: 36 pages, Late
The Relativistic Electrodynamics Least Action Principles Revisited: New Charged Point Particle and Hadronic String Models Analysis
The classical relativistic least action principle is revisited from the
vacuum field theory approach. New physically motivated versions of relativistic
Lorentz type forces are derived, a new relativistic hadronic string model is
proposed and analyzed in detail.Comment: n/
- …