30,027 research outputs found
One-dimensional relativistic dissipative system with constant force and its quantization
For a relativistic particle under a constant force and a linear velocity
dissipation force, a constant of motion is found. Problems are shown for
getting the Hamiltoninan of this system. Thus, the quantization of this system
is carried out through the constant of motion and using the quantization of the
velocity variable. The dissipative relativistic quantum bouncer is outlined
within this quantization approach.Comment: 11 pages, no figure
Velocity quantization approach of the one-dimensional dissipative harmonic oscillator
Given a constant of motion for the one-dimensional harmonic oscillator with
linear dissipation in the velocity, the problem to get the Hamiltonian for this
system is pointed out, and the quantization up to second order in the
perturbation approach is used to determine the modification on the eigenvalues
when dissipation is taken into consideration. This quantization is realized
using the constant of motion instead of the Hamiltonian.Comment: 10 pages, 2 figure
Influence of oxygen pressure on the fs laserinduced oxidation of molybdenum thin films
We present a study of femtosecond (1028 nm, 230 fs, 54.7 MHz) laser processing on molybdenum (Mo) thin films. Irradiations were done under ambient air as well as pure oxygen (O2) at various gauge pressures (4, 8, 12 and 16 psi). Our results indicate that the high heating rates associated with laser processing allow the production of different molybdenum oxides. Raman spectroscopy and scanning electron microscopy are used to characterize the molybdenum oxidation for the different irradiation and oxygen pressures parameters chosen showing a high correlation between well-defined oxidation zones and the oxygen pressure surrounding the samples during the irradiation of the Mo thin films
On algebraic classification of quasi-exactly solvable matrix models
We suggest a generalization of the Lie algebraic approach for constructing
quasi-exactly solvable one-dimensional Schroedinger equations which is due to
Shifman and Turbiner in order to include into consideration matrix models. This
generalization is based on representations of Lie algebras by first-order
matrix differential operators. We have classified inequivalent representations
of the Lie algebras of the dimension up to three by first-order matrix
differential operators in one variable. Next we describe invariant
finite-dimensional subspaces of the representation spaces of the one-,
two-dimensional Lie algebras and of the algebra sl(2,R). These results enable
constructing multi-parameter families of first- and second-order quasi-exactly
solvable models. In particular, we have obtained two classes of quasi-exactly
solvable matrix Schroedinger equations.Comment: LaTeX-file, 16 pages, submitted to J.Phys.A: Math.Ge
Second-harmonic generation of ZnO nanoparticles synthesized by laser ablation of solids in liquids
We report the synthesis of small zinc oxide nanoparticles (ZnO NPs) based colloidal suspensions and the study of second-harmonic generation from aggregated ZnO NPs deposited on glass substrates. The colloidal suspensions were obtained using the laser ablation of solids in liquids technique, ablating a Zn solid target immersed in acetone as the liquid medium, with ns-laser pulses (1064 nm) of a Nd-YAG laser. The per pulse laser fluence, the laser repetition rate frequency and the ablation time were kept constant. The absorption evolution of the obtained suspensions was optically characterized through absorption spectroscopy until stabilization. Raman spectroscopy, SEM and HRTEM were used to provide evidence of the ZnO NPs structure. HRTEM results showed that 5–8 nm spheroids ZnO NPs were obtained. Strong second-harmonic signal is obtained from random ZnO monocrystalline NPs and from aggregated ZnO NPs, suggesting that the high efficiency of the nonlinear process may not depend on the NPs size or aggregation state
Eviction of a 125 GeV "heavy"-Higgs from the MSSM
We prove that the present experimental constraints are already enough to rule
out the possibility of the ~125 GeV Higgs found at LHC being the second
lightest Higgs in a general MSSM context, even with explicit CP violation in
the Higgs potential. Contrary to previous studies, we are able to eliminate
this possibility analytically, using simple expressions for a relatively small
number of observables. We show that the present LHC constraints on the diphoton
signal strength, tau-tau production through Higgs and BR(B -> X_s gamma) are
enough to preclude the possibility of H_2 being the observed Higgs with m_H~125
GeV within an MSSM context, without leaving room for finely tuned
cancellations. As a by-product, we also comment on the difficulties of an MSSM
interpretation of the excess in the gamma-gamma production cross section
recently found at CMS that could correspond to a second Higgs resonance at
m_H~136 GeV.Comment: 38 pages, 9 figures. Final version accepted at JHEP. Sections 2, 3
and appendices simplified. Experimental results updated, several references
added. Small typos corrected and a new comparison of approximate formulas
with full expressions include
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