118434734
Dissolved deconfinement: Phase structure of large N gauge theories with fundamental matter
A class of large N U(N) gauge theories on a compact manifold S{sup 3}xR (with possible inclusion of adjoint matter) is known to show first-order deconfinement transition at the deconfinement temperature. This includes the familiar example of pure YM theory and N=4 Supersymmetric Yang-Mills theory. Here we study the effect of introduction of N{sub f} fundamental matter fields in the phase diagram of the above mentioned gauge theories at small coupling and in the limit of large N and finite N{sub f}/N. We find some interesting features like the termination of the line of first-order deconfinement phase transition at a critical point as the ratio N{sub f}/N is increased and absence of deconfinement transition thereafter (there is only a smooth crossover). This result may have some implication for QCD, which unlike a pure gauge theory does not show a first-order deconfinement transition and only displays a smooth crossover at the transition temperature.
119256345
The many phases of holographic superfluids
We investigate holographic superfluids in AdSd+1 with d =3, 4 in the nonbackreacted approximation for various masses of the scalar field. In d =3 the phase structure is universal for all the masses that we consider: the critical temperature decreases as the superfluid velocity increases, and as it is cranked high enough, the order of the phase transition changes from second to first. Surprisingly, in d = 4 we find that the phase structure is more intricate. For sufficiently high mass, there is always a second order phase transition to the normal phase, no matter how high the superfluid velocity. For some parameters, as we lower the temperature, this transition happens before a first order transition to a new super conducting phase. Across this first order transition, the gap in the transverse conductivity jumps from almost zero to about half its maximum value. We also introduce a double scaling limit where we can study the phase transitions(semi-)analytically in the large velocity limit. The results corroborate and complement our numerical results. In d =4, this approach has the virtue of being fully analytically tractable.
119212250
Analytic approaches to anisotropic holographic superfluids
A bstractWe construct an analytic solution of the Einstein-SU(2)-Yang-Mills system as the holographic dual of an anisotropic superfluid near its critical point, up to leading corrections in both the inverse Yang-Mills coupling and a symmetry breaking order parameter. We have also calculated the ratio of shear viscosity to entropy density in this background, and shown that the universality of this ratio is lost in the broken symmetry direction. The ratio displays a scaling behavior near the critical point with critical exponent β = 1, at the leading order in the double expansion.
119299572
Dissipative Nonlinear Dynamics in Holography
We look at the response of a nonlinearly coupled scalar eld in an asymptotically AdS black brane geometry and nd a behavior very similar to that of known dissipative nonlinear systems like the chaotic pendulum. Transition to chaos proceeds through a series of period-doubling bifurcations. The presence of dissipation, crucial to this behavior, arises naturally in a black hole background from the ingoing conditions imposed at the horizon. AdS/CFT translates our solution to a chaotic response ofO, the operator dual to the scalar eld. Our setup can also be used to study quenchlike behavior in strongly coupled nonlinear systems.
3995010
Superconductivity from D3/D7: holographic pion superfluid
We show that a D3/D7 system (in the limit of zero quark mass) at finite isospin chemical potential goes through a superconductor (superfluid) like phase transition. This is similar to a flavored superfluid phase studied in the QCD literature, where mesonic operators condense. We have studied the frequency dependent conductivity of the condensate and found a delta function peak in the zero frequency limit. This is an example of superconductivity in a string theory context. Consequently we have found a superfluid/supercurrent type solution and studied the associated phase diagram. The superconducting transition changes from second order to first order at a critical superfluid velocity. We have studied various properties of the superconducting system like superfluid density, energy gap, second sound etc. We investigate the possibility of the isospin chemical potential modifying the embedding of the flavor branes by checking whether the transverse scalars also condense at low temperatures. This however does not seem to be the case.
118578316
Chaos around holographic Regge trajectories
A bstractUsing methods of Hamiltonian dynamical systems, we show analytically that a dynamical system connected to the classical spinning string solution holographically dual to the principal Regge trajectory is non-integrable. The Regge trajectories themselves form an integrable island in the total phase space of the dynamical system. Our argument applies to any gravity background dual to confining field theories and we verify it explicitly in various supergravity backgrounds: Klebanov-Strassler, Maldacena-Núñez, Witten QCD and the AdS soliton. Having established non-integrability for this general class of supergravity backgrounds, we show explicitly by direct computation of the Poincaré sections and the largest Lyapunov exponent, that such strings have chaotic motion.
120204081
Statistical model analysis of fission fragment angular distributions for the system 16 O+ 181 Ta
Fission fragment angular distributions have been measured for the fusion of ${}^{16}\mathrm{O}$ with deformed ${}^{181}\mathrm{Ta}$ target, in the energy range 90 MeV to 110 MeV. Combining with the existing data of evaporation residue and fission cross sections in the literature, the fusion cross sections have been determined in the range $1.1l~{E/V}_{B}l~1.6.$ Detailed statistical model analysis of the entire data set has been performed and it has been shown that fission fragment anisotropies calculated are in good agreement with the experimental data. Even at the lowest energy studied, ${(E=1.1V}_{B})$ as there is good agreement between the data and the calculation, it can be concluded that the quasifission effect is negligible at this energy.
120752932
Elastic scattering and fusion cross sections for Be7,Li7+Al27 systems
Quasi-elastic-scattering and transfer reaction cross-section measurements were made for the {sup 7}Be+{sup 27}Al system at E{sub lab}=17, 19, and 21 MeV in the angular range {theta}{sub c.m.}=12 deg. An optical model (OM) analysis of the quasi-elastic scattering data was carried out. The fusion cross sections were derived at these energies by subtraction of the integrated transfer cross sections from the reaction cross sections obtained from the fits to quasi-elastic-scattering data. These fusion cross sections were found to be consistent with those obtained from the coupled-channels calculations. Elastic scattering and fusion cross sections were measured for the {sup 7}Li+{sup 27}Al system at E{sub lab}=10, 13, 16, 19, and 24 MeV. For elastic scattering the angular coverages were in the {theta}{sub lab}=12 deg. - 72 deg. range and for fusion the {alpha}-evaporation spectra from the compound nucleus were measured in the angular range {theta}{sub lab}=52 deg. - 132 deg. (142 deg. at 10 MeV). The elastic-scattering angular distributions were subjected to OM analysis. The {alpha}-evaporation spectra were reproduced with the statistical model calculations, and the fusion cross sections were extracted from them. The fusion cross sections were also extracted by subtraction of the integrated inelastic-scattering cross sections from the reaction cross sectionsmore » obtained from the OM fits to the elastic-scattering data, and these fusion data were found to be consistent. The CCDEF calculations describe these data quite well. A comparison of the fusion data for the {sup 7}Be+{sup 27}Al and {sup 7}Li+{sup 27}Al systems shows a similar and consistent behavior.« less
6716809
Performance of an Axial Gas Ionization Detector
An axial gas ionization chamber has been fabricated for use as a DeltaE detector in heavy ion induced nuclear reactions. Different operating parameters such as gas type, pressure, anode voltage, and anode structures have been optimized. The transparency of the anode structure is observed to play an important role in improving the energy resolution of the detector