374 research outputs found
Coupled channel description of 16O+142,144,146Nd scattering around the Coulomb barrier using a complex microscopic potential
Angular distributions of elastic scattering and inelastic scattering from 2+ 1 state are measured for 16O+142,144,146Nd systems at several energies in the vicinity of the Coulomb barrier. The angular distributions are systematically analyzed in coupled channel framework. Renormalized double folded real optical and coupling potentials with DDM3Y interaction have been used in the calculation. Relevant nuclear densities needed to generate the potentials are derived from shell model wavefunctions. A truncated shell model calculation has been performed and the calculated energy levels are compared with the experimental ones. To simulate the absorption, a 'hybrid' approach is adopted. The contribution to the imaginary potential of couplings to the inelastic channels, other than the 2+ 1 target excitation channel, is calculated in the Feshbach formalism. This calculated imaginary potential along with a short ranged volume Woods-Saxon potential to simulate the absorption in fusion channel reproduces the angular distributions for 16O+146Nd quite well. But for 16O+142,144Nd systems additional surface absorption is found to be necessary to fit the angular distribution data. The variations of this additional absorption term with incident energy and the mass of the target are explored. © 2003 Elsevier Science B.V. All rights reserved
Extraction of Scandium (III) from acidic solutions using organo-phosphoric acid reagents: A comparative study
Comparative and synergistic solvent extraction of Sc(III) using two phosphoric acidic reagents such as di-(2-ethyhexyl) phosphoric acid and 2,4,4,tri-methyl,pentyl-phosphinic acid was investigated. Slope analysis method suggests a cation exchange reaction of Sc(III) with both extractants at a molar ratio of extractant: Sc(III) = 2.5:1 at equilibrium pH< 1.5. The plot of log D vs. log [Extractant] yield the slope (n) value as low as 1.2-1.3 and as high as n=7 at low and high extrcatant concentration level, respectively. Extraction isotherm study predicted the need of 2 stages at A: O=1:4 and A: O=1:3 using 0.1 M D2EHPA and 0.1 M Cyanex 272, respectively. Stripping of Sc (III) was carried out at varied NaOH concentration to ascertain the optimum stripping condition for effective enrichment of metal. The predicted stripping condition (2)-stages with A: O=1:3 and 1:4 for D2EHPA and Cyanex 272, respectively) obtained from Mc-Cabe Thiele plot was further validated by 6-cycles CCS study. An actual leach solution of Mg-Sc alloy bearing 1.0 g/L of Sc (III), 2.5 g/L of Mg and 0.2 M HCl was subjected for selective separation of Sc at the optimum condition. The counter current simulation (CCS) study for both extraction and stripping of actual solution resulted quantitative separation of Sc with ∼12 fold enrichment. The organic phase before and after loading of Sc (III) along with the diluents was characterized by FTIR to ascertain the phase transportation of Sc (III)
Partially spin polarized quantum Hall effect in the filling factor range 1/3 < nu < 2/5
The residual interaction between composite fermions (CFs) can express itself
through higher order fractional Hall effect. With the help of diagonalization
in a truncated composite fermion basis of low-energy many-body states, we
predict that quantum Hall effect with partial spin polarization is possible at
several fractions between and . The estimated excitation
gaps are approximately two orders of magnitude smaller than the gap at
, confirming that the inter-CF interaction is extremely weak in higher
CF levels.Comment: 4 pages, 3 figure
Spinning Pulsating String Solitons in AdS_5 x S^5
We point out the existence of some simple string solitons in AdS_5 x S^5,
which at the same time are spinning in AdS_5 and pulsating in S^5, or
vice-versa. This introduces an additional arbitrary constant into the scaling
relations between energy and spin or R-charge. The arbitrary constant is not an
angular momentum, but can be related to the amplitude of the pulsation. We
discuss the solutions in detail and consider the scaling relations. Pulsating
multi spin or multi R-charge solutions can also be constructed.Comment: 15 pages, Late
Greybody Factors of Charged Dilaton Black Holes in 2 + 1 Dimensions
We have studied scalar perturbations of charged dilaton black holes in 2+1
dimensions. The black hole considered here is a solution to the low-energy
string theory in 2+1 dimensions. The exact decay rates and the grey body
factors for the massless minimally coupled scalar is computed for both the
charged and the uncharged dilaton black holes. The charged and the uncharged
black hole show similar behavior for grey body factors, reflection coefficients
and decay rates.Comment: The equation for the potential and figure:1 are changed. The changes
does not effect the result
Open String Fluctuations in AdS with and without Torsion
The equations of motion and boundary conditions for the fluctuations around a
classical open string, in a curved space-time with torsion, are considered in
compact and world-sheet covariant form. The rigidly rotating open strings in
Anti de Sitter space with and without torsion are investigated in detail. By
carefully analyzing the tangential fluctuations at the boundary, we show
explicitly that the physical fluctuations (which at the boundary are
combinations of normal and tangential fluctuations) are finite, even though the
world-sheet is singular there. The divergent 2-curvature thus seems less
dangerous than expected, in these cases. The general formalism can be
straightforwardly used also to study the (bosonic part of the) fluctuations
around the closed strings, recently considered in connection with the AdS/CFT
duality, on AdS_5 \times S^5 and AdS_3 \times S^3 \times T^4.Comment: 19 pages, Late
Precision Spectroscopy of AdS/CFT
We extend recent remarkable progress in the comparison of the dynamical
energy spectrum of rotating closed strings in AdS_5xS^5 and the scaling weights
of the corresponding non-near-BPS operators in planar N=4 supersymmetric gauge
theory. On the string side the computations are feasible, using semiclassical
methods, if angular momentum quantum numbers are large. This results in a
prediction of gauge theory anomalous dimensions to all orders in the `t Hooft
coupling lambda. On the gauge side the direct computation of these dimensions
is feasible, using a recently discovered relation to integrable (super) spin
chains, provided one considers the lowest order in lambda. This one-loop
computation then predicts the small-tension limit of the string spectrum for
all (i.e. small or large) quantum numbers. In the overlapping window of large
quantum numbers and small effective string tension, the string theory and gauge
theory results are found to match in a mathematically highly non-trivial
fashion. In particular, we compare energies of states with (i) two large
angular momenta in S^5, and (ii) one large angular momentum in AdS_5 and S^5
each, and show that the solutions are related by an analytic continuation.
Finally, numerical evidence is presented on the gauge side that the agreement
persists also at higher (two) loop order.Comment: 26 pages, 1 figure, v2: typos correcte
Singularities and closed time-like curves in type IIB 1/2 BPS geometries
We study in detail the moduli space of solutions discovered in LLM relaxing
the constraint that guarantees the absence of singularities. The solutions fall
into three classes, non-singular, null-singular and time machines with a
time-like naked singularity. We study the general features of these metrics and
prove that there are actually just two generic classes of space-times - those
with null singularities are in the same class as the non-singular metrics.
AdS/CFT seems to provide a dual description only for the first of these two
types of space-time in terms of a unitary CFT indicating the possible existence
of a chronology protection mechanism for this class of geometries.Comment: 34 pages, 7 figures, LaTeX. References adde
Yang-Mills Duals for Semiclassical Strings
We consider a semiclassical multiwrapped circular string pulsating on S_5,
whose center of mass has angular momentum J on an S_3 subspace. Using the
AdS/CFT correspondence we argue that the one-loop anomalous dimension of the
dual operator is a simple rational function of J/L, where J is the R-charge and
L is the bare dimension of the operator. We then reproduce this result directly
from a super Yang-Mills computation, where we make use of the integrability of
the one-loop system to set up an integral equation that we solve. We then
verify the results of Frolov and Tseytlin for circular rotating strings with
R-charge assignment (J',J',J). In this case we solve for an integral equation
found in the O(-1) matrix model when J' J.
The latter region starts at J'=L/2 and continues down, but an apparent critical
point is reached at J'=4J. We argue that the critical point is just an artifact
of the Bethe ansatz and that the conserved charges of the underlying integrable
model are analytic for all J' and that the results from the O(-1) model
continue onto the results of the O(+1) model.Comment: 26 Pages, LaTeX; v2 Typos corrected, reference update
On the Classical String Solutions and String/Field Theory Duality
We classify almost all classical string configurations, considered in the
framework of the semi-classical limit of the string/gauge theory duality. Then,
we describe a procedure for obtaining the conserved quantities and the exact
classical string solutions in general string theory backgrounds, when the
string embedding coordinates depend non-linearly on the worldsheet time
parameter.Comment: LaTeX, 15 pages, no figures; V2: some typos corrected; V3: no
corrections, to appear in JHE
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