9,098 research outputs found
Non-Abelian Proca model based on the improved BFT formalism
We present the newly improved Batalin-Fradkin-Tyutin (BFT) Hamiltonian
formalism and the generalization to the Lagrangian formulation, which provide
the much more simple and transparent insight to the usual BFT method, with
application to the non-Abelian Proca model which has been an difficult problem
in the usual BFT method. The infinite terms of the effectively first class
constraints can be made to be the regular power series forms by ingenious
choice of and -matrices. In this new
method, the first class Hamiltonian, which also needs infinite correction terms
is obtained simply by replacing the original variables in the original
Hamiltonian with the BFT physical variables. Remarkably all the infinite
correction terms can be expressed in the compact exponential form. We also show
that in our model the Poisson brackets of the BFT physical variables in the
extended phase space are the same structure as the Dirac brackets of the
original phase space variables. With the help of both our newly developed
Lagrangian formulation and Hamilton's equations of motion, we obtain the
desired classical Lagrangian corresponding to the first class Hamiltonian which
can be reduced to the generalized St\"uckelberg Lagrangian which is non-trivial
conjecture in our infinitely many terms involved in Hamiltonian and Lagrangian.Comment: Notable improvements in Sec. I
BRST Quantization of the Proca Model based on the BFT and the BFV Formalism
The BRST quantization of the Abelian Proca model is performed using the
Batalin-Fradkin-Tyutin and the Batalin-Fradkin-Vilkovisky formalism. First, the
BFT Hamiltonian method is applied in order to systematically convert a second
class constraint system of the model into an effectively first class one by
introducing new fields. In finding the involutive Hamiltonian we adopt a new
approach which is more simpler than the usual one. We also show that in our
model the Dirac brackets of the phase space variables in the original second
class constraint system are exactly the same as the Poisson brackets of the
corresponding modified fields in the extended phase space due to the linear
character of the constraints comparing the Dirac or Faddeev-Jackiw formalisms.
Then, according to the BFV formalism we obtain that the desired resulting
Lagrangian preserving BRST symmetry in the standard local gauge fixing
procedure naturally includes the St\"uckelberg scalar related to the explicit
gauge symmetry breaking effect due to the presence of the mass term. We also
analyze the nonstandard nonlocal gauge fixing procedure.Comment: 29 pages, plain Latex, To be published in Int. J. Mod. Phys.
The quantization of the chiral Schwinger model based on the BFT-BFV formalism II
We apply an improved version of Batalin-Fradkin-Tyutin (BFT) Hamiltonian
method to the a=1 chiral Schwinger Model, which is much more nontrivial than
the a>1.\delta\xi$ in the measure. As a result, we explicitly
obtain the fully gauge invariant partition function, which includes a new type
of Wess-Zumino (WZ) term irrelevant to the gauge symmetry as well as usual WZ
action.Comment: 17 pages, To be published in J. Phys.
XTE J1739-302: An Unusual New X-ray Transient
A new x-ray transient, designated XTE J1739-302, was discovered with the
Proportional Counter Array (PCA) on the Rossi X-ray Timing Explorer (RXTE) in
data from 12 August 1997. Although it was the brightest source in the Galactic
Center region while active (about 3.0 x 10^-9 ergs/cm2/s from 2 to 25 keV), it
was only observed on that one day; it was not detectable nine days earlier or
two days later. There is no known counterpart at other wavelengths, and its
proximity to the Galactic Center will make such an identification difficult due
to source confusion and extinction. The x-ray spectrum and intensity suggest a
giant outburst of a Be/neutron star binary, although no pulsations were
observed and the outburst was shorter than is usual from these systems.Comment: 11 pages incorporating 6 figures, AAStex; accepted for The
Astrophysical Journal, Part 2 (Letters
Analysis of Density Matrix reconstruction in NMR Quantum Computing
Reconstruction of density matrices is important in NMR quantum computing. An
analysis is made for a 2-qubit system by using the error matrix method. It is
found that the state tomography method determines well the parameters that are
necessary for reconstructing the density matrix in NMR quantum computations.
Analysis is also made for a simplified state tomography procedure that uses
fewer read-outs. The result of this analysis with the error matrix method
demonstrates that a satisfactory accuracy in density matrix reconstruction can
be achieved even in a measurement with the number of read-outs being largely
reduced.Comment: 7 pages, title slightly changed and references adde
Globular Cluster Distance Determinations
The present status of the distance scale to Galactic globular clusters is
reviewed. Six distance determination techniques which are deemed to be most
reliable are discussed in depth. These different techniques are used to
calibrate the absolute magnitude of the RR Lyrae stars. The various
calibrations fall into three groups. Main sequence fitting using Hipparcos
parallaxes, theoretical HB models and the RR Lyrae in the LMC all favor a
bright calibration, implying a `long' globular cluster distance scale. White
dwarf fitting and the astrometric distances yield a somewhat fainter RR Lyrae
calibration, while the statistical parallax solution yields faint RR Lyrae
stars implying a `short' distance scale to globular clusters. Various secondary
distance indicators discussed all favor the long distance scale. The `long' and
`short' distance scales differ by (0.31+/-0.16) mag. Averaging together all of
the different distance determinations yields Mv(RR) = (0.23+/-0.04)([Fe/H] +
1.6) + (0.56+/-0.12) mag.Comment: Invited review article to appear in: `Post-Hipparcos Cosmic Candles',
A. Heck & F. Caputo (Eds), Kluwer Academic Publ., Dordrecht, in pres
The Orbit of the Eclipsing X-ray Pulsar EXO 1722-363
With recent and archival Rossi X-Ray Timing Explorer (RXTE) X-ray
measurements of the heavily obscured X-ray pulsar EXO 1722-363 (IGR
J17252-3616), we carried out a pulse timing analysis to determine the orbital
solution for the first time. The binary system is characterized by a_x sin(i) =
101 +/- 3 lt-s and P_orb = 9.7403 +/- 0.0004 days (90% confidence), with the
precision of the orbital period being obtained by connecting datasets separated
by more than 7 years (272 orbital cycles). The orbit is consistent with
circular, and e < 0.19 at the 90% confidence level. The mass function is 11.7
+/- 1.2 M_sun and confirms that this source is a High Mass X-ray Binary (HMXB)
system. The orbital period, along with the previously known ~414 s pulse
period, places this system in the part of the Corbet diagram populated by
supergiant wind accretors. Using previous eclipse time measurements by Corbet
et al. and our orbital solution, combined with the assumption that the primary
underfills its Roche lobe, we find i > 61 degrees at the 99% confidence level,
the radius of the primary is between 21 R_sun and 37 R_sun, and its mass is
less than about 22 M_sun. The acceptable range of radius and mass shows that
the primary is probably a supergiant of spectral type B0I-B5I. Photometric
measurements of its likely counterpart are consistent with the spectral type
and luminosity if the distance to the system is between 5.3 kpc and 8.7 kpc.
Spectral analysis of the pulsar as a function of orbital phase reveals an
evolution of the hydrogen column density suggestive of dense filaments of gas
in the downstream wake of the pulsar, with higher levels of absorption seen at
orbital phases 0.5-1.0, as well as a variable Fe K_alpha line.Comment: Submitted to ApJ, 11 pages, 11 figure
Study of the neutron star structure in strong magnetic fields including the anomalous magnetic moments
We study the effects of strong magnetic fields on the neutron star structure.
If the interior field of a star is on the same order of the surface field
currently observed, the influences of the magnetic field on the star mass and
radius are negligible. If one assumes that the internal magnetic field can be
as large as that estimated from the scalar virial theorem, considerable effects
can be induced. The maximum mass of stars is arisen substantially while the
central density is largely suppressed. For two equal-mass stars the radius of
the magnetic star can be larger by about 10% 20% than the nonmagnetic
star.Comment: 26 pages, 5 postscript figures; replaced by the revised version,
Chin. J. Astron. Astrophys., accepte
Existence of maximal hypersurfaces in some spherically symmetric spacetimes
We prove that the maximal development of any spherically symmetric spacetime
with collisionless matter (obeying the Vlasov equation) or a massless scalar
field (obeying the massless wave equation) and possessing a constant mean
curvature Cauchy surface also contains a maximal Cauchy
surface. Combining this with previous results establishes that the spacetime
can be foliated by constant mean curvature Cauchy surfaces with the mean
curvature taking on all real values, thereby showing that these spacetimes
satisfy the closed-universe recollapse conjecture. A key element of the proof,
of interest in itself, is a bound for the volume of any Cauchy surface
in any spacetime satisfying the timelike convergence condition in terms of the
volume and mean curvature of a fixed Cauchy surface and the maximal
distance between and . In particular, this shows that any
globally hyperbolic spacetime having a finite lifetime and obeying the
timelike-convergence condition cannot attain an arbitrarily large spatial
volume.Comment: 8 pages, REVTeX 3.
Band gap opening by two-dimensional manifestation of Peierls instability in graphene
Using first-principles calculations of graphene having high-symmetry
distortion or defects, we investigate band gap opening by chiral symmetry
breaking, or intervalley mixing, in graphene and show an intuitive picture of
understanding the gap opening in terms of local bonding and antibonding
hybridizations. We identify that the gap opening by chiral symmetry breaking in
honeycomb lattices is an ideal two-dimensional (2D) extension of the Peierls
metal-insulator transition in 1D linear lattices. We show that the spontaneous
Kekule distortion, a 2D version of the Peierls distortion, takes place in
biaxially strained graphene, leading to structural failure. We also show that
the gap opening in graphene antidots and armchair nanoribbons, which has been
attributed usually to quantum confinement effects, can be understood with the
chiral symmetry breaking
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