35,394 research outputs found
String tension and glueball masses of SU(2) QCD from perfect action for monopoles and strings
We study the perfect monopole action as an infrared effective theory of SU(2)
QCD. It is transformed exactly into a lattice string model. Since the monopole
interactions are weak in the infrared SU(2) QCD, the string interactions become
strong. The strong coupling expansion of string model shows the quantum
fluctuation is small. The classical string tension is estimated analytically,
and we see it is very close to the quantum one in the SU(2) QCD. We also
discuss how to calculate the glueball mass in our model.Comment: LATTICE99(Confinement), 3 pages and 1 EPS figure
The X-ray Outburst of H1743-322: High-Frequency QPOs with a 3:2 Frequency Ratio
We observed the 2003 X-ray outburst of H1743-322 in a series of 130 pointed
observation with RXTE. We searched individual observations for high-frequency
QPOs (HFQPOs) and found only weak or marginal detections near 240 and 160 Hz.
We next grouped the observations in several different ways and computed the
average power-density spectra (PDS) in a search for further evidence of HFQPOs.
This effort yielded two significant results for those observations defined by
the presence of low-frequency QPOs (0.1-20 Hz) and an absence of
``band-limited'' power continua: (1) The 9 time intervals with the highest 7-35
keV count rates yielded an average PDS with a QPO at Hz. (; 3--35 keV); and (2) a second group with lower 7-35 keV count rates (26
intervals) produced an average PDS with a QPO at Hz (;
7--35 keV). The ratio of these two frequencies is . This finding
is consistent with results obtained for three other black hole systems that
exhibit commensurate HFQPOs in a 3:2 ratio. Furthermore, the occurrence of
H1743-322's slower HFQPO at times of higher X-ray luminosity closely resembles
the behavior of XTE J1550-564 and GRO J1655-40. We discuss our results in terms
of a resonance model that invokes frequencies set by general relativity for
orbital motions near a black-hole event horizon.Comment: 12 pages, 3 figures, submitted to Ap
On the perfect lattice actions of abelian-projected SU(2) QCD
We study the perfect lattice actions of abelian-projected SU(2) gluodynamics.
Using the BKT and duality transformations on the lattice, an effective string
model is derived from the direction-dependent quadratic monopole action,
obtained numerically from SU(2) gluodynamics in maximally abelian gauge. The
string tension and the restoration of continuum rotational invariance are
investigated using strong coupling expansion of lattice string model
analytically. We also found that the block spin transformation can be performed
analytically for the quadratic monopole action.Comment: 3 pages, Latex, 1 figures; talk presented at LATTICE9
Relativistic Diskoseismology. I. Analytical Results for 'Gravity Modes'
We generalize previous calculations to a fully relativistic treatment of
adiabatic oscillations which are trapped in the inner regions of accretion
disks by non-Newtonian gravitational effects of a black hole. We employ the
Kerr geometry within the scalar potential formalism of Ipser and Lindblom,
neglecting the gravitational field of the disk. This approach treats
perturbations of arbitrary stationary, axisymmetric, perfect fluid models. It
is applied here to thin accretion disks. Approximate analytic eigenfunctions
and eigenfrequencies are obtained for the most robust and observable class of
modes, which corresponds roughly to the gravity (internal) oscillations of
stars. The dependence of the oscillation frequencies on the mass and angular
momentum of the black hole is exhibited. These trapped modes do not exist in
Newtonian gravity, and thus provide a signature and probe of the strong-field
structure of black holes. Our predictions are relevant to observations which
could detect modulation of the X-ray luminosity from stellar mass black holes
in our galaxy and the UV and optical luminosity from supermassive black holes
in active galactic nuclei.Comment: 31 pages, 6 figures, uses style file aaspp4.sty, prepared with the
AAS LATEX macros v4.0, significant revision of earlier submission to include
modes with axial index m>
Three Disk Oscillation Modes of Rotating Magnetized Neutron Stars
We discuss three specific modes of accretion disks around rotating magnetized
neutron stars which may explain the separations of the kilo Hertz quasi
periodic oscillations (QPO) seen in low mass X-ray binaries. The existence of
these modes requires that there be a maximum in the angular velocity of the
accreting material, and that the fluid is in stable, nearly circular motion
near this maximum rather than moving rapidly towards the star or out of the
disk plane into funnel flows. It is presently not known if these conditions
occur, but we are exploring this with 3D magnetohydrodynamic simulations and
will report the results elsewhere. The first mode is a corotation mode which is
radially trapped in the vicinity of the maximum of the disk rotation rate and
is unstable. The second mode, relevant to relatively slowly rotating stars, is
a magnetically driven eccentric () oscillation of the disk excited at a
Lindblad radius in the vicinity of the maximum of the disk rotation. The third
mode, relevant to rapidly rotating stars, is a magnetically coupled eccentric
() and an axisymmetric () radial disk perturbation which has an inner
Lindblad radius also in the vicinity of the maximum of the disk rotation. We
suggest that the first mode is associated with the upper QPO frequency,
, the second with the lower QPO frequency, , and
the third with the lower QPO frequency, , where
is the star's rotation rate.Comment: 6 pages, 2 figure
Epicyclic oscillations of non-slender fluid tori around Kerr black holes
Considering epicyclic oscillations of pressure-supported perfect fluid tori
orbiting Kerr black holes we examine non-geodesic (pressure) effects on the
epicyclic modes properties. Using a perturbation method we derive fully general
relativistic formulas for eigenfunctions and eigenfrequencies of the radial and
vertical epicyclic modes of a slightly non-slender, constant specific angular
momentum torus up to second-order accuracy with respect to the torus thickness.
The behaviour of the axisymmetric and lowest-order () non-axisymmetric
epicyclic modes is investigated. For an arbitrary black hole spin we find that,
in comparison with the (axisymmetric) epicyclic frequencies of free test
particles, non-slender tori receive negative pressure corrections and exhibit
thus lower frequencies. Our findings are in qualitative agreement with the
results of a recent pseudo-Newtonian study of analogous problem defined within
the Paczy{\'n}ski-Wiita potential. Implications of our results on the
high-frequency QPO models dealing with epicyclic oscillations are addressed.Comment: 24 pages, 8 figure
A Theoretical Light-Curve Model for the 1999 Outburst of U Scorpii
A theoretical light curve for the 1999 outburst of U Scorpii is presented in
order to obtain various physical parameters of the recurrent nova. Our U Sco
model consists of a very massive white dwarf (WD) with an accretion disk and a
lobe-filling, slightly evolved, main-sequence star (MS). The model includes a
reflection effect by the companion and the accretion disk together with a
shadowing effect on the companion by the accretion disk. The early visual light
curve (t ~ 1-15 days after maximum) is well reproduced by a thermonuclear
runaway model on a very massive WD close to the Chandrasekhar limit (M_{WD}=
1.37 \pm 0.01 M_\odot), in which optically thick winds blowing from the WD play
a key role in determining the nova duration. The duration of the strong wind
phase (t~0-17 days) is very consistent with the BeppoSAX supersoft X-ray
detection at t~19-20 days because supersoft X-rays are self-absorbed by the
massive wind. The envelope mass at the peak is estimated to be ~3x10^{-6}
M_\odot, which is indicating an average mass accretion rate ~2.5x10^{-7}
M_\odot yr^{-1} during the quiescent phase between 1987 and 1999. These
quantities are exactly the same as those predicted in a new progenitor model of
Type Ia supernovae.Comment: 7 pages, 3 figures, to appear in ApJL, vol. 52
Wind and waves in the middle atmosphere observed with the MU radar
The VHF band MU radar at Shigaraki, Japan, has been in full operation successfully since April 1985. Dynamical features found primarily in the data obtained by the radar during a one year period from December 1985 to November 1986 are examined. These include: basic wind observations, quasi-monochromatic gravity waves generated by the jet stream or through a geostrophic adjustment process, seasonal variation of the mesoscale wind variability, the momentum flux due to gravity wave motions, and saturated gravity wave spectrum. A short discussion is added to the relationship between turbulent layers and ambient wind field in the mesosphere
- …