7,977 research outputs found
Mu-tau neutrino refraction and collective three-flavor transformations in supernovae
We study three-flavor collective neutrino transformations in the
dense-neutrino region above the neutrino sphere of a supernova core. We find
that two-flavor conversions driven by the atmospheric mass difference and the
13-mixing angle capture the full effect if one neglects the second-order
difference between the muon and tau neutrino refractive index. Including this
"mu-tau matter term" provides a resonance at a density of approximately 3 x
10^7 g cm^-3 that typically causes significant modifications of the overall
electron neutrino and antineutrino survival probabilities. This effect is
surprisingly sensitive to deviations from maximal 23-mixing, being different
for each octant.Comment: 9 pages, 7 figures. New presentation of results, version to be
published in PR
The tidally disturbed luminous compact blue galaxy Mkn 1087 and its surroundings
We present new broad-band optical and near-infrared CCD imaging together with
deep optical intermediate-resolution spectroscopy of Mkn 1087 and its
surrounding objects. We analyze the morphology and colors of the stellar
populations of the brightest objects, some of them star-formation areas, as
well as the kinematics, physical conditions and chemical composition of the
ionized gas associated with them. Mkn 1087 does not host an Active Galactic
Nucleus, but it could be a Luminous Compact Blue Galaxy. Although it was
classified as a suspected Wolf-Rayet galaxy, we do not detect the spectral
features of these sort of massive stars. Mkn 1087 shows morphological and
kinematical features that can be explained assuming that it is in interaction
with two nearby galaxies: the bright KPG 103a and a dwarf ()
star-forming companion. We argue that this dwarf companion is not a tidal
object but an external galaxy because of its low metallicity [12+log(O/H) =
8.24] with respect to the one derived for Mkn 1087 [12+log(O/H) = 8.57] and its
kinematics. Some of the non-stellar objects surrounding Mkn 1087 are connected
by bridges of matter with the main body, host star-formation events and show
similar abundances despite their different angular distances. These facts,
together their kinematics, suggest that they are tidal dwarf galaxies formed
from material stripped from Mkn 1087. A bright star-forming region at the south
of Mkn 1087 (knot #7) does not show indications of being a tidal galaxy or the
product of a merging process as suggested in previous works. We argue that Mkn
1087 and its surroundings should be considered a group of galaxies.Comment: Accepted by A&A, 21 pages, 13 figures, 8 table
Bragg spectroscopy for measuring Casimir-Polder interactions with Bose-Einstein condensates above corrugated surfaces
We propose a method to probe dispersive atom-surface interactions by measuring via two-photon Bragg spectroscopy the dynamic structure factor of a Bose-Einstein condensate above corrugated surfaces. This method takes advantage of the condensate coherence to reveal the spatial Fourier components of the lateral Casimir-Polder interaction energy.Fil: Moreno, Gustavo Ariel. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Ciudad Universitaria. Instituto de FĂsica de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de FĂsica de Buenos Aires; ArgentinaFil: Dalvit, Diego A. R.. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Calzetta, Esteban Adolfo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Ciudad Universitaria. Instituto de FĂsica de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de FĂsica de Buenos Aires; Argentin
Recommended from our members
Regional index of sustainable economic well-being development project: final report
This report presents results from a development project carried out by nef (the new economics foundation) on behalf of emda (the East Midlands Development Agency) and Natural England, to improve the methodologies used in the calculation of the R-ISEW (Regional Index of Sustainable Economic Well-Being)
Quantum optimal control of photoelectron spectra and angular distributions
Photoelectron spectra and photoelectron angular distributions obtained in
photoionization reveal important information on e.g. charge transfer or hole
coherence in the parent ion. Here we show that optimal control of the
underlying quantum dynamics can be used to enhance desired features in the
photoelectron spectra and angular distributions. To this end, we combine
Krotov's method for optimal control theory with the time-dependent
configuration interaction singles formalism and a splitting approach to
calculate photoelectron spectra and angular distributions. The optimization
target can account for specific desired properties in the photoelectron angular
distribution alone, in the photoelectron spectrum, or in both. We demonstrate
the method for hydrogen and then apply it to argon under strong XUV radiation,
maximizing the difference of emission into the upper and lower hemispheres, in
order to realize directed electron emission in the XUV regime
Capital Inflows, Exchange Rate Flexibility, and Credit Booms
The prospects of expansionary monetary policies in the advanced countries for the foreseeable future have renewed the debate over policy options to cope with large capital inflows that are, at least partly, driven by low interest rates in the financial centers. Historically, capital flow bonanzas have often fueled sharp credit expansions in advanced and emerging market economies alike. Focusing primarily on emerging markets, we analyze the impact of exchange rate flexibility on credit markets during periods of large capital inflows. We show that credit grows more rapidly and its composition tilts to foreign currency in economies with less flexible exchange rate regimes, and that these results are not explained entirely by the fact that the latter attract more capital inflows than economies with more flexible regimes. Our findings thus suggest countries with less flexible exchange rate regimes may stand to benefit the most from regulatory policies that reduce banksâ incentives to tap external markets and to lend/borrow in foreign currency; these policies include marginal reserve requirements on foreign lending, currency-dependent liquidity requirements, and higher capital requirement and/or dynamic provisioning on foreign exchange loans.
Stochastic vortex dynamics in two-dimensional easy-plane ferromagnets: Multiplicative versus additive noise
We study how thermal fluctuations affect the dynamics of vortices in the
two-dimensional classical, ferromagnetic, anisotropic Heisenberg model
depending on their additive or multiplicative character. Using a collective
coordinate theory, we analytically show that multiplicative noise, arising from
fluctuations in the local field term of the Landau-Lifshitz equations, and
Langevin-like additive noise both have the same effect on vortex dynamics
(within a very plausible assumption consistent with the collective coordinate
approach). This is a non-trivial result, as multiplicative and additive noises
usually modify the dynamics quite differently. We also carry out numerical
simulations of both versions of the model finding that they indeed give rise to
very similar vortex dynamics.Comment: 10 pages, 6 figure
- âŠ