15,078 research outputs found
Quasi Periodic Oscillations (QPOs) and frequencies in an accretion disk and comparison with the numerical results from non-rotating black hole computed by the GRH code
The shocked wave created on the accretion disk after different physical
phenomena (accretion flows with pressure gradients, star-disk interaction etc.)
may be responsible observed Quasi Periodic Oscillations (QPOs) in ray
binaries. We present the set of characteristics frequencies associated with
accretion disk around the rotating and non-rotating black holes for one
particle case. These persistent frequencies are results of the rotating pattern
in an accretion disk. We compare the frequency's from two different numerical
results for fluid flow around the non-rotating black hole with one particle
case. The numerical results are taken from our papers Refs.\refcite{Donmez2}
and \refcite{Donmez3} using fully general relativistic hydrodynamical code with
non-selfgravitating disk. While the first numerical result has a relativistic
tori around the black hole, the second one includes one-armed spiral shock wave
produced from star-disk interaction. Some physical modes presented in the QPOs
can be excited in numerical simulation of relativistic tori and spiral waves on
the accretion disk. The results of these different dynamical structures on the
accretion disk responsible for QPOs are discussed in detail.Comment: 13 figures, added reference, accepted for publication in Modern
Physics Letters
The GL_2 main conjecture for elliptic curves without complex multiplication
The main conjectures of Iwasawa theory provide the only general method known
at present for studying the mysterious relationship between purely arithmetic
problems and the special values of complex L-functions, typified by the
conjecture of Birch and Swinnerton-Dyer and its generalizations. Our goal in
the present paper is to develop algebraic techniques which enable us to
formulate a precise version of such a main conjecture for motives over a large
class of p-adic Lie extensions of number fields. The paper ends by formulating
and briefly discussing the main conjecture for an elliptic curve E over the
rationals Q over the field generated by the coordinates of its p-power division
points, where p is a prime greater than 3 of good ordinary reduction for E.Comment: 39 page
Two-spin subsystem entanglement in spin 1/2 rings with long range interactions
We consider the two-spin subsystem entanglement for eigenstates of the
Hamiltonian
for a ring of spins 1/2 with
asssociated spin vector operator for the -th
spin. Here is the chord-distance betwen sites and . The case
corresponds to the solvable Haldane-Shastry model whose spectrum
has very high degeneracies not present for . Two spin subsystem
entanglement shows high sensistivity and distinguishes from . There is no entanglement beyond nearest neighbors for all eigenstates
when . Whereas for one has selective entanglement at
any distance for eigenstates of sufficiently high energy in a certain interval
of which depends on the energy. The ground state (which is a singlet
only for even ) does not have entanglement beyond nearest neighbors, and the
nearest neighbor entanglement is virtually independent of the range of the
interaction controlled by .Comment: 16 figure
Avaliação de cultivares de mandioca em Altamira - Pará.
bitstream/item/64570/1/Altamira-PA8.pd
Preparo de área sem queima, uma alternativa para a agricultura de derruba e queima da Amazônia Oriental: aspectos agroecologicos.
Mandioca: resultados preliminares de pesquisa na Transamazônica - PA.
bitstream/item/66788/1/Altamira-Doc3.pd
Comportamento de cultivares de mandioca em Altamira - Pará.
bitstream/item/67229/1/Altamira-PA9.PD
Superconductivity in Boron under pressure - why are the measured T's so low?
Using the full potential linear muffin-tin orbitals (FP-LMTO) method we
examine the pressure-dependence of superconductivity in the two metallic phases
of Boron: bct and fcc. Linear response calculations are carried out to examine
the phonon frequencies and electron-phonon coupling for various lattice
parameters, and superconducting transition temperatures are obtained from the
Eliashberg equation. In both bct and fcc phases the superconducting transition
temperature T is found to decrease with increasing pressure, due to
stiffening of phonons with an accompanying decrease in electron-phonon
coupling. This is in contrast to a recent report, where T is found to
increase with pressure. Even more drastic is the difference between the
measured T, in the range 4-11 K, and the calculated values for both bct and
fcc phases, in the range 60-100 K. The calculation reveals that the transition
from the fcc to bct phase, as a result of increasing volume or decreasing
pressure, is caused by the softening of the X-point transverse phonons. This
phonon softening also causes large electron-phonon coupling for high volumes in
the fcc phase, resulting in coupling constants in excess of 2.5 and T
nearing 100 K. We discuss possible causes as to why the experiment might have
revealed T's much lower than what is suggested by the present study. The
main assertion of this paper is that the possibility of high T, in excess
of 50 K, in high pressure pure metallic phases of boron cannot be ruled out,
thus substantiating the need for further experimental investigations of the
superconducting properties of high pressure pure phases of boron.Comment: 16 pages, 8 figures, 1 Tabl
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>
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