6,121 research outputs found
Global Disk Oscillation Modes in Cataclysmic Variables and Other Newtonian Accretors
Diskoseismology, the theoretical study of small adiabatic hydrodynamical
global perturbations of geometrically thin, optically thick accretion disks
around black holes (and other compact objects), is a potentially powerful probe
of the gravitational field. For instance, the frequencies of the normal mode
oscillations can be used to determine the elusive angular momentum parameter of
the black hole. The general formalism developed by diskoseismologists for
relativistic systems can be readily applied to the Newtonian case of
cataclysmic variables (CVs). Some of these systems (e.g., the dwarf nova SS
Cygni) show rapid oscillations in the UV with periods of tens of seconds and
high coherence. In this paper, we assess the possibility that these dwarf nova
oscillations (DNOs) are diskoseismic modes. Besides its importance in
investigating the physical origin of DNOs, the present work could help us to
answer the following question. To what extent are the similarities in the
oscillation phenomenology of CVs and X-ray binaries (XRBs) indicative of a
common physical mechanism?Comment: 1 figur
The non-perturbative unquenched quark model
In recent years states in the quarkonium spectrum not expected in the naive quark model have appeared and created a lot of interest. In the theoretical side the study of the effect of meson-meson thresholds in the spectrum have been performed in different approximations. In a quark model framework, and in the spirit of the Cornell model, when a meson-meson threshold is included, the coupling to all the quark-antiquark states have to be considered. In practice only the closest states are included perturbatively. In this contribution we will present a framework in which we couple quark-antiquark states with meson-meson states non-perturbatively, taking into account effectively the coupling to all quark-antiquark states. The method will be applied to the study of the X(3872) and a comparison with the perturbative calculation will be performed
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Quasi-normal modes, area spectra and multi-horizon spacetimes
We suggest an interpretation for the highly damped QNM frequencies of the
spherically symmetric multi-horizon spacetimes (Reissner-Nordstrom,
Schwarzschild-deSitter, Reissner-Nordstrom-deSitter) following Maggiore's
proposal about the link between the asymptotic QNM frequencies and the black
hole thermodynamics. We show that the behavior of the asymptotic frequencies is
easy to understand if one assumes that all of the horizons have the same
equispaced area spectra. The QNM analysis is then consistent with the choice of
the area spectra to be the one originally proposed for the black hole's horizon
by Bekenstein: A=8\pi n (in Planck units). The interpretation of the highly
damped QNM frequencies in the multi-horizon case is based on the similar
grounds as in the single horizon (Schwarzschild) case, but it has some new
features that are discussed in the paper.Comment: 8 pages, v2: no physics changed, some references added, few sentences
added in the discussion part
Trigonometry of 'complex Hermitian' type homogeneous symmetric spaces
This paper contains a thorough study of the trigonometry of the homogeneous
symmetric spaces in the Cayley-Klein-Dickson family of spaces of 'complex
Hermitian' type and rank-one. The complex Hermitian elliptic CP^N and
hyperbolic CH^N spaces, their analogues with indefinite Hermitian metric and
some non-compact symmetric spaces associated to SL(N+1,R) are the generic
members in this family. The method encapsulates trigonometry for this whole
family of spaces into a single "basic trigonometric group equation", and has
'universality' and '(self)-duality' as its distinctive traits. All previously
known results on the trigonometry of CP^N and CH^N follow as particular cases
of our general equations. The physical Quantum Space of States of any quantum
system belongs, as the complex Hermitian space member, to this parametrised
family; hence its trigonometry appears as a rather particular case of the
equations we obtain.Comment: 46 pages, LaTe
Theory for Spin-Polarized Oscillations in Nonlinear Magneto-Optics due to Quantum Well States
Using an electronic tight-binding theory we calculate the nonlinear
magneto-optical response from an x-Cu/1Fe/Cu(001) film as a function of
frequency and Cu overlayer thickness (x=3 ... 25). We find very strong
spin-polarized quantum well oscillations in the nonlinear magneto-optical Kerr
effect (NOLIMOKE). These are enhanced by the large density of Fe states
close to the Fermi level acting as intermediate states for frequency doubling.
In good agreement with experiment we find two oscillation periods of 6-7 and 11
monolayers the latter being more pronounced.Comment: 12 pages, Revtex, 3 postscript figure
Measuring the mixing efficiency in a simple model of stirring:some analytical results and a quantitative study via Frequency Map Analysis
We prove the existence of invariant curves for a --periodic Hamiltonian
system which models a fluid stirring in a cylindrical tank, when is small
and the assigned stirring protocol is piecewise constant. Furthermore, using
the Numerical Analysis of the Fundamental Frequency of Laskar, we investigate
numerically the break down of invariant curves as increases and we give a
quantitative estimate of the efficiency of the mixing.Comment: 10 figure
Quasinormal modes from potentials surrounding the charged dilaton black hole
We clarify the purely imaginary quasinormal frequencies of a massless scalar
perturbation on the 3D charged-dilaton black holes. This case is quite
interesting because the potential-step appears outside the event horizon
similar to the case of the electromagnetic perturbations on the large
Schwarzschild-AdS black holes. It turns out that the potential-step type
provides the purely imaginary quasinormal frequencies, while the
potential-barrier type gives the complex quasinormal modes.Comment: 19 pages, 8 figure
Spin-orbit splitting of image states
We quantify the effect of the spin-orbit interaction on the Rydberg-like
series of image state electrons at the (111) and (001) surface of Ir, Pt and
Au. Using relativistic multiple-scattering methods we find Rashba-like
dispersions with Delta E(K)=gamma K with values of gamma for n=1 states in the
range 38-88 meV Angstrom. Extending the phase-accumulation model to include
spin-orbit scattering we find that the splittings vary like 1/(n+a)^3 where a
is the quantum defect and that they are related to the probability of spin-flip
scattering at the surface. The splittings should be observable experimentally
being larger in magnitude than some exchange-splittings that have been resolved
by inverse photoemission, and are comparable to linewidths from inelastic
lifetimes.Comment: 10 pages, 4 figure
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