54,131 research outputs found
Neutrino Masses and GUT Baryogenesis
We reconsider the GUT-baryogenesis mechanism for generating the baryon
asymmetry of the Universe. The baryon asymmetry is produced by the out of
equilibrium decay of coloured Higgs bosons at the GUT scale, conserving B-L. If
neutrinos are Majorana particles, lepton number violating interactions erase
the lepton number excess, but part of the baryon asymmetry may be preserved,
provided those interactions are not in thermal equilibrium when the sphaleron
processes become effective, at . We analyse whether this
mechanism for baryogenesis is feasible in a variety of GUT models of fermion
masses proposed in the literature, based on horizontal symmetries.Comment: Talk presented at AHEP2003, Valencia, Spain, October 200
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Synthesis of molybdenum oxide nanoparticles by nanosecond laser ablation
Phothermal therapy (PTT) is one of the most promising techniques to treat cancer. Finding the ideal PTT agent nanomaterial has remained a challenge and has brought the interest of several researchers. In this work, we report the synthesis of molybdenum oxide (MoOx) nanoparticles (NPs), which exhibit absorption in the biological optical window ~840 nm, by using the laser ablation of solids in liquids (LASL) technique with nanosecond (ns) pulses. A Nd:YAG laser was used to synthesize the NPs in deionized (DI) water, free of surfactants or additives, which were optically characterized by absorption spectroscopy and TEM-EDX microscopy. Semi spherical NPs with a suitable average size and shape for potential use as PTT agents were obtained by laser ablation and ablation + fragmentation. The calculated band gap is 3.1 eV, which corresponds to MoO3. Micro-Raman spectroscopy studies determined that these NPs are composed of amorphous molybdenum oxide hydrates (MoO3 · xH2O)
Gauge field theory approach to spin transport in a 2D electron gas
We discuss the Pauli Hamiltonian including the spin-orbit interaction within
an U(1) x SU(2) gauge theory interpretation, where the gauge symmetry appears
to be broken. This interpretation offers new insight into the problem of spin
currents in the condensed matter environment, and can be extended to Rashba and
Dresselhaus spin-orbit interactions. We present a few outcomes of the present
formulation: i) it automatically leads to zero spin conductivity, in contrast
to predictions of Gauge symmetric treatments, ii) a topological quantization
condition leading to voltage quantization follows, and iii) spin
interferometers can be conceived in which, starting from a arbitrary incoming
unpolarized spinor, it is always possible to construct a perfect spin filtering
condition.Comment: Invited contribution to Statphys conference, June 2009, Lviv
(Ukraine
An ab-initio converse NMR approach for pseudopotentials
We extend the recently developed converse NMR approach [T. Thonhauser, D.
Ceresoli, A. Mostofi, N. Marzari, R. Resta, and D. Vanderbilt, J. Chem. Phys.
\textbf{131}, 101101 (2009)] such that it can be used in conjunction with
norm-conserving, non-local pseudopotentials. This extension permits the
efficient ab-initio calculation of NMR chemical shifts for elements other than
hydrogen within the convenience of a plane-wave pseudopotential approach. We
have tested our approach on several finite and periodic systems, finding very
good agreement with established methods and experimental results.Comment: 11 pages, 2 figures, 4 tables; references expande
Direct and Inverse Results for Multipoint Hermite-Pade Approximants
Given a system of functions f = (f1, . . . , fd) analytic on a neighborhood
of some compact subset E of the complex plane, we give necessary and sufficient
conditions for the convergence with geometric rate of the common denominators
of multipoint Hermite-Pade approximants. The exact rate of convergence of these
denominators and of the approximants themselves is given in terms of the
analytic properties of the system of functions. These results allow to detect
the location of the poles of the system of functions which are in some sense
closest to E.Comment: 18 pages. arXiv admin note: text overlap with arXiv:1606.07920,
arXiv:1801.03004, arXiv:1203.494
New solution to Airy's equation for modeling beams near turning points
Here I present a summarised description of the general behavior of waves near
turning points. I show that when asymptotic matching to a prescribed incident
wavefield is performed, the solution changes from being the Airy function to
being more generally the hyperbolic umbilic function. This solution accounts
for (de-)focusing of the incident wavefield due to gradient-index lensing in
addition to the familiar Airy physics, which importantly do not superimpose.
Possible applications to fusion research are discussed.Comment: Proceeding for 2023 EPS plasma physics conferenc
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