17,183 research outputs found
Screening in three-dimensional QED with arbitrary fermion mass
We compute the quark--antiquark potential in three dimensional massive
Quantum Electrodynamics for arbitrary fermion mass. The result indicates that
screening prevails for any quark masses, contrary to the classical
expectations, generalizing our previous result obtained for large masses. We
also test the validity of several approximation schemes using a detailed
numerical analysis. The classical result is still reproduced for small
separation of the quarks.Comment: latex, 10 pages, 4 figures (6 ps-files
Inter- and intra-layer excitons in MoS/WS and MoSe/WSe heterobilayers
Accurately described excitonic properties of transition metal dichalcogenide
heterobilayers (HBLs) are crucial to comprehend the optical response and the
charge carrier dynamics of them. Excitons in multilayer systems posses inter or
intralayer character whose spectral positions depend on their binding energy
and the band alignment of the constituent single-layers. In this study, we
report the electronic structure and the absorption spectra of MoS/WS
and MoSe/WSe HBLs from first-principles calculations. We explore the
spectral positions, binding energies and the origins of inter and intralayer
excitons and compare our results with experimental observations. The absorption
spectra of the systems are obtained by solving the Bethe-Salpeter equation on
top of a GW calculation which corrects the independent particle
eigenvalues obtained from density functional theory calculations. Our
calculations reveal that the lowest energy exciton in both HBLs possesses
interlayer character which is decisive regarding their possible device
applications. Due to the spatially separated nature of the charge carriers, the
binding energy of inter-layer excitons might be expected to be considerably
smaller than that of intra-layer ones. However, according to our calculations
the binding energy of lowest energy interlayer excitons is only 20\%
lower due to the weaker screening of the Coulomb interaction between layers of
the HBLs. Therefore, it can be deduced that the spectral positions of the
interlayer excitons with respect to intralayer ones are mostly determined by
the band offset of the constituent single-layers. By comparing oscillator
strengths and thermal occupation factors, we show that in luminescence at low
temperature, the interlayer exciton peak becomes dominant, while in absorption
it is almost invisible.Comment: 17 pages, 4 figure
The \rho\rho interaction in the hidden gauge formalism and the f_0(1370) and f_2(1270) resonances
We have studied the interaction of vectors mesons within the hidden gauge
formalism and applied it to the particular case of the interaction.
We find a strong attraction in the isospin, spin channels I,S=0,0 and 0,2,
which is enough to bind the system. We also find that the
attraction in the I,S=0,2 channel is much stronger than in the 0,0 case. The
states develop a width when the mass distribution is considered, and
particularly when the decay channel is turned on. Using a
regularization scheme with cut offs of natural size, we obtain results in fair
agreement with the mass and the width of the and meson
states, providing a natural explanation of why the tensor state is more bound
than the scalar and offering a new picture for these states, which would be
dynamically generated from the interaction or, in simpler words,
molecular states.Comment: Version accepted for publicatio
Charmed hadrons in nuclear medium
We study the properties of charmed hadrons in dense matter within a
coupled-channel approach which accounts for Pauli blocking effects and meson
self-energies in a self-consistent manner. We analyze the behaviour in this
dense environment of dynamically-generated baryonic resonances as well as the
open-charm meson spectral functions. We discuss the implications of the
in-medium properties of open-charm mesons on the and the
predicted X(3700) scalar resonances.Comment: 4 pages, 5 figures, invited parallel talk in the 5th International
Conference on Quarks and Nuclear Physics (QNP09), Beijing, September 21-26,
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Scalar field evolution in Gauss-Bonnet black holes
It is presented a thorough analysis of scalar perturbations in the background
of Gauss-Bonnet, Gauss-Bonnet-de Sitter and Gauss-Bonnet-anti-de Sitter black
hole spacetimes. The perturbations are considered both in frequency and time
domain. The dependence of the scalar field evolution on the values of the
cosmological constant and the Gauss-Bonnet coupling is
investigated. For Gauss-Bonnet and Gauss-Bonnet-de Sitter black holes, at
asymptotically late times either power-law or exponential tails dominate, while
for Gauss-Bonnet-anti-de Sitter black hole, the quasinormal modes govern the
scalar field decay at all times. The power-law tails at asymptotically late
times for odd-dimensional Gauss-Bonnet black holes does not depend on ,
even though the black hole metric contains as a new parameter. The
corrections to quasinormal spectrum due to Gauss-Bonnet coupling is not small
and should not be neglected. For the limit of near extremal value of the
(positive) cosmological constant and pure de Sitter and anti-de Sitter modes in
Gauss-Bonnet gravity we have found analytical expressions.Comment: 10 pages, to be published in Phys. Rev.
Microwave-assisted synthesis of 3-aminobenzo[b]thiophene scaffolds for the preparation of kinase inhibitors
Microwave irradiation of 2-halobenzonitriles and methyl thioglycolate in the presence of triethylamine in DMSO at 130 °C provides rapid access to 3-aminobenzo[b]thiophenes in 58–96% yield. This transformation has been applied in the synthesis of the thieno[2,3-b]pyridine core motif of LIMK1 inhibitors, the benzo[4,5]thieno[3,2-e][1,4]diazepin-5(2H)-one scaffold of MK2 inhibitors and a benzo[4,5]thieno[3,2-d]pyrimidin-4-one inhibitor of the PIM kinases
Strange and charm mesons at FAIR
We study the properties of strange and charm mesons in hot and dense matter
within a self-consistent coupled-channel approach for the experimental
conditions of density and temperature expected for the CBM experiment at
FAIR/GSI. The in-medium solution at finite temperature accounts for Pauli
blocking effects, mean-field binding of all the baryons involved, and meson
self-energies. We analyze the behaviour in this hot and dense environment of
dynamically-generated baryonic resonances together with the evolution with
density and temperature of the strange and open-charm meson spectral functions.
We test the spectral functions for strange mesons using energy-weighted sum
rules and finally discuss the implications of the properties of charm mesons on
the D_{s0}(2317) and the predicted X(3700) scalar resonances.Comment: 12 pages, 9 figures, invited talk at XXXI Mazurian Lakes Conference
on Physics: Nuclear Physics and the Road to FAIR, August 30-September 6,
2009, Piaski, Polan
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