12,755 research outputs found
Non-perturbative unification in the light of LEP results
We consider an alternative to conventional GUTs originally proposed by
Maiani, Parisi and Petronzio, where owing to the existence of extra fermion
generations at some intermediate scale, the gauge couplings become large at
high energies. We first comment on how the non- supersymmetric version of this
scenario is ruled out; we then consider the two-loop evolution of the couplings
in the supersymmetric extension of this scenario, and check whether such a
scenario is feasible in the light of the precies values of couplings now
available from LEP.Comment: Latex file 7 pages+1 fig. (ps file appended after the latex file),
CERN-TH.6913/9
Chemical reactivity of the compressed noble gas atoms and their reactivity dynamics during collisions with protons
Attempts are made to gain insights into the effect of confinement of noble gas atoms on their various reactivity indices. Systems become harder, less polarizable and difficult to excite as the compression increases. Ionization also causes similar effects. A quantum fluid density functional technique is adopted in order to study the dynamics of reactivity parameters during a collision between protons and He atoms in different electronic states for various projectile velocities and impact parameters. Dynamical variants of the principles of maximum hardness, minimum polarizability and maximum entropy are found to be operative
Quantum analogue of the Kolmogorov-Arnold-Moser transition in the field induced barrier penetration in a quartic potential
Quantum signatures of the Kolmogorov-Arnold-Moser (KAM) transition from the regular to chaotic classical dynamics of a double-well oscillator in the presence of an external monochromatic field of different amplitudes are analysed in terms of the corresponding Bohmian trajectories. It is observed that the classical chaos generally enhances the quantum fluctuations, while the quantum nonclassical effects try to suppress classical stochasticity
High-spin structure and Band Termination in Cd
Excited states of the neutron deficient Cd nucleus have been
investigated via the Ge(Cl, p3n) reaction at beam energy of 135
MeV by use of in-beam spectroscopic methods. Gamma rays depopulating the
excited states were detected using the Gammasphere spectrometer with high-fold
-ray coincidences. A quadrupole -ray coincidence analysis
() has been used to extend the known level scheme. The positive
parity levels have been established up to and
MeV. In addition to the observation of highly-fragmented level scheme belonging
to the positive-parity sequences at E 5 MeV, the termination of a
negative-parity sequence connected by transitions has been established at
and MeV. The experimental results
corresponding to both the positive- and negative-parity sequences have been
theoretically interpreted in the framework of the core particle coupling model.
Evidence is presented for a shape change from collective prolate to
non-collective oblate above the (8011 keV) level and for a
smooth termination of the negative-parity band.Comment: 19 pages, 8 figures. Submitted to Phys. Rev.
Identification of the slow E3 transition 136mCs -> 136Cs with conversion electrons
We performed at ISOLDE the spectroscopy of the decay of the 8- isomer in
136Cs by and conversion-electron detection. For the first time the excitation
energy of the isomer and the multipolarity of its decay have been measured. The
half-life of the isomeric state was remeasured to T1/2 = 17.5(2) s. This isomer
decays via a very slow 518 keV E3 transition to the ground state. In addition
to this, a much weaker decay branch via a 413 keV M4 and a subsequent 105 keV
E2 transition has been found. Thus we have found a new level at 105 keV with
spin 4+ between the isomeric and the ground state. The results are discussed in
comparison to shell model calculations.Comment: Phys. Rev. C accepted for publicatio
The joint application of a metaheuristic algorithm and a Bayesian statistics approach for uncertainty and stability assessment of nonlinear magnetotelluric data
In this paper, we have developed three algorithms, namely hybrid weighted
particle swarm optimization (wPSO) with the gravitational search algorithm (GSA),
known as wPSOGSA; GSA; and PSO in MATLAB to interpret one-dimensional
magnetotelluric (MT) data for some corrupted and non-corrupted synthetic
data, as well as two examples of MT field data over different geological
terrains: (i) geothermally rich area, island of Milos, Greece, and (ii) southern Scotland due to the occurrence of a significantly high electrical
conductivity anomaly under crust and upper mantle, extending from the Midland
Valley across the Southern Uplands into northern England. Even though the
fact that many models provide a good fit in a large predefined search space,
specific models do not fit well. As a result, we used a Bayesian statistical
technique to construct and assess the posterior probability density function
(PDF) rather than picking the global model based on the lowest misfit error.
The study proceeds using a 68.27 % confidence interval for selecting a region
where the PDF is more prevalent to estimate the mean model which is more
accurate and close to the true model. For illustration, correlation matrices
show a significant relationship among layer parameters. The findings
indicate that wPSOGSA is less sensitive to model parameters and produces
more stable and reliable results with the least uncertainty in the
model, compatible with existing borehole samples. Furthermore, the
present methods resolve two additional geologically significant layers, one
highly conductive (less than 1.0 Ωm) and another resistive (300.0 Ωm), over the island of Milos, Greece, characterized by alluvium and
volcanic deposits, respectively, as corroborated by borehole stratigraphy.</p
High-spin structure and Band Termination in Cd
Excited states of the neutron deficient Cd nucleus have been
investigated via the Ge(Cl, p3n) reaction at beam energy of 135
MeV by use of in-beam spectroscopic methods. Gamma rays depopulating the
excited states were detected using the Gammasphere spectrometer with high-fold
-ray coincidences. A quadrupole -ray coincidence analysis
() has been used to extend the known level scheme. The positive
parity levels have been established up to and
MeV. In addition to the observation of highly-fragmented level scheme belonging
to the positive-parity sequences at E 5 MeV, the termination of a
negative-parity sequence connected by transitions has been established at
and MeV. The experimental results
corresponding to both the positive- and negative-parity sequences have been
theoretically interpreted in the framework of the core particle coupling model.
Evidence is presented for a shape change from collective prolate to
non-collective oblate above the (8011 keV) level and for a
smooth termination of the negative-parity band.Comment: 19 pages, 8 figures. Submitted to Phys. Rev.
Ferromagnetic Ordering in CeIr2B2: Transport, magnetization, specific heat and NMR studies
We present a complete characterization of ferromagnetic system CeIr2B2 using
powder x-ray diffraction XRD, magnetic susceptibility chi(T), isothermal
magnetization M(H), specific heat C(T), electrical resistivity rho(T,H), and
thermoelectric power S(T) measurements. Furthermore 11B NMR study was performed
to probe the magnetism on a microscopic scale. The chi(T), C(T) and rho(T) data
confirm bulk ferromagnetic ordering with Tc = 5.1 K. Ce ions in CeIr2B2 are in
stable trivalent state. Our low-temperature C(T) data measured down to 0.4 K
yield Sommerfeld coefficient gamma = 73(4) mJ/molK2 which is much smaller than
the previously reported value of gamma = 180 mJ/molK2 deduced from the specific
heat measurement down to 2.5 K. For LaIr2B2 gamma = 6(1) mJ/molK2 which implies
the density of states at the Fermi level D(EF) = 2.54 states/(eV f.u.) for both
spin directions. The renormalization factor for quasi-particle density of
states and hence for quasi-particle mass due to 4f correlations in CeIr2B2 is
12. The Kondo temperature TK ~ 4 K is estimated from the jump in specific heat
of CeIr2B2 at Tc. Both C(T) and rho(T) data exhibit gapped-magnon behavior in
magnetically ordered state with an energy gap Eg ~ 3.5 K. The rho data as a
function of magnetic field H indicate a large negative magnetoresistance (MR)
which is highest for T = 5 K.While at 5 K the negative MR keeps on increasing
up to 10 T, at 2 K an upturn is observed near H = 3.5 T. On the other hand, the
thermoelectric power data have small absolute values (S ~ 7 {\mu}V/K)
indicating a weak Kondo interaction. A shoulder in S(T) at about 30 K followed
by a minimum at ~ 10 K is attributed to crystal electric field (CEF) effects
and the onset of magnetic ordering. 11B NMR line broadening provides strong
evidence of ferromagnetic correlations below 40 K.Comment: 10 pages, 11 figure
Analysis of the washability characteristics of low-volatile Indian coking coal with crushing at different top sizes - a case study
The effect of comminution on liberation characteristics has been studied for a low volatile coking coal of Indian origin through washability studies. Two parameters, namely "Index of Washability" (IW) and "Near Gravity Material Index" (NGMI), are used to describe the ease of washability. The ROM Coal is crushed to four different top sizes namely, 75 mm,
25 mm, 13 mm and 6mm. On the basis of calculated IW it is observed that relative ease of washabiltiy increases with decrease in top size. The value of IW at -6 mm crushing size is 41.4 which confirm the ease of washing of this coal at this feed size. From the calculated NGMI values the critical specific gravities have bee n estimated. Critical specific gravity suggests that the separation at this specific gravity range is most difficult task using gravity methods. NGMI analysis reveals that the critical specific gravities for crushing to -75 mm, -25 mm, -13 mm and -6mm are 1.65, 1.68, 1.53 and 1.58 respectively
- …