2,987,052 research outputs found
Photon-Photon Correlations as a Probe of Vacuum Induced Coherence Effects
We present new experimental implications of the effects of vacuum induced
coherence on the photon -photon correlation in the pi-polarized fluorescence in
j = 1/2 to j = 1/2 transition. These effects should be thus observable in
measurements of photon statistics in for example Hg and Ba ion traps.Comment: 7 pages, 6 figures, submitted to Physical Review
Comments to On the Accuracy of Lamb Shift Measurements in Hydrogen (Physica Scripta, 55 (1997) 33-40) by V. G. Pal'chikov, Yu. L. Sokolov, and V. P. Yakovlev
The work is a comments on the article of V. G. Pal'chikov, Yu. L. Sokolov,
and V. P. Yakovlev, devoted to the measurement of the Lamb shift in the
hydrogen atom and published in Physica Scripta, 55 (1997) 33-40.Comment: 4 pages; [email protected]
Study of quadrupole polarizabilities with combined configuration interaction and coupled-cluster method
The recently developed method combining the configuration interaction and the
coupled-cluster method was demonstrated to provide accurate treatment of
correlation corrections in divalent atomic systems [M.S.Safronova, M.G.Kozlov,
and C.W.Clark, Phys. Rev. Lett. 107, 143006 (2011)]. We have extended this
approach to the calculation of quadrupole polarizabilities alpha_2 and applied
it to evaluate alpha_2 for the ground state of Mg and Mg-like Si^{2+}.
Performing the calculations in three different approximations of increasing
accuracy allowed us to place the upper bounds on the uncertainty of the final
results. The recommended values alpha_2(3s^2 1S0)= 35.86(13) a.u. for Si^{2+}
and alpha_2(3s^2 1S0)= 814(3) a.u. for Mg are estimated to be accurate to
0.37%. Differences in quadrupole polarizability contributions in neutral Mg and
Si^{2+} ion are discussed.Comment: 6 pages, submitted to Phys. Rev.
Measure valued solutions of sub-linear diffusion equations with a drift term
In this paper we study nonnegative, measure valued solutions of the initial
value problem for one-dimensional drift-diffusion equations when the nonlinear
diffusion is governed by an increasing function with . By using tools of optimal transport, we will show
that this kind of problems is well posed in the class of nonnegative Borel
measures with finite mass and finite quadratic momentum and it is the
gradient flow of a suitable entropy functional with respect to the so called
-Wasserstein distance. Due to the degeneracy of diffusion for large
densities, concentration of masses can occur, whose support is transported by
the drift. We shall show that the large-time behavior of solutions depends on a
critical mass , which can be explicitely characterized in terms of
and of the drift term. If the initial mass is less then ,
the entropy has a unique minimizer which is absolutely continuous with respect
to the Lebesgue measure. Conversely, when the total mass of the solutions
is greater than the critical one, the steady state has a singular part in which
the exceeding mass is accumulated.Comment: 30 page
Extracting the Omega- electric quadrupole moment from lattice QCD data
The Omega- has an extremely long lifetime, and is the most stable of the
baryons with spin 3/2. Therefore the Omega- magnetic moment is very accurately
known. Nevertheless, its electric quadrupole moment was never measured,
although estimates exist in different formalisms. In principle, lattice QCD
simulations provide at present the most appropriate way to estimate the Omega-
form factors, as function of the square of the transferred four-momentum, Q2,
since it describes baryon systems at the physical mass for the strange quark.
However, lattice QCD form factors, and in particular GE2, are determined at
finite Q2 only, and the extraction of the electric quadrupole moment, Q_Omega=
GE2(0) e/(2 M_Omega), involves an extrapolation of the numerical lattice
results. In this work we reproduce the lattice QCD data with a covariant
spectator quark model for Omega- which includes a mixture of S and two D states
for the relative quark-diquark motion. Once the model is calibrated, it is used
to determine Q_Omega. Our prediction is Q_Omega= (0.96 +/- 0.02)*10^(-2) efm2
[GE2(0)=0.680 +/- 0.012].Comment: To appear in Phys. Rev. D. Version with small modifications. 8 pages,
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Chaotic behavior of the Compound Nucleus, open Quantum Dots and other nanostructures
It is well established that physical systems exhibit both ordered and chaotic
behavior. The chaotic behavior of nanostructure such as open quantum dots has
been confirmed experimentally and discussed exhaustively theoretically. This is
manifested through random fluctuations in the electronic conductance. What
useful information can be extracted from this noise in the conductance? In this
contribution we shall address this question. In particular, we will show that
the average maxima density in the conductance is directly related to the
correlation function whose characteristic width is a measure of energy- or
applied magnetic field- correlation length. The idea behind the above has been
originally discovered in the context of the atomic nucleus, a mesoscopic
system. Our findings are directly applicable to graphene.Comment: 10 pages, 5 figures. Contribution to: "4th International Workshop on
Compound-Nuclear Reactions and Related Topics (CNR*13)", October 7-11, 2013,
Maresias, Brazil. To appear in the proceeding
The on-axis view of GRB 170817A
The peculiar short gamma-ray burst GRB 170817A has been firmly associated to
the gravitational wave event GW170817, which has been unaninmously interpreted
as due to the coalescence of a double neutron star binary. The unprecedented
behaviour of the non-thermal afterglow led to a debate about its nature, which
was eventually settled by high-resolution VLBI observations, which strongly
support the off-axis structured jet scenario. Using information on the jet
structure derived from multi-wavelength fitting of the afterglow emission and
of the apparent VLBI image centroid motion, we compute the appearance of a GRB
170817A-like jet as seen by an on-axis observer and we compare it to the
previously observed population of SGRB afterglows and prompt emission events.
We find that the intrinsic properties of the GRB 170817A jet are representative
of a typical event in the SGRB population, hinting at a quasi-universal jet
structure. The diversity in the SGRB afterglow population could therefore be
ascribed in large part to extrinsic (redshift, density of the surrounding
medium, viewing angle) rather than intrinsic properties. Although more
uncertain, the comparison can be extended to the prompt emission properties,
leading to similar conclusions.Comment: 9 pages, 3 figures, submitted to A&A. Comments and suggestions are
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