Scaling of v2v_2 in heavy ion collisions

We interpret the scaling of the corrected elliptic flow parameter w.r.t. the corrected multiplicity, observed to hold in heavy ion collisions for a wide variety of energies and system sizes. We use dimensional analysis and power-counting arguments to place constraints on the changes of initial conditions in systems with different center of mass energy $\sqrt{s}$. Specifically, we show that a large class of changes in the (initial) equation of state, mean free path, and longitudinal geometry over the observed $\sqrt{s}$ are likely to spoil the scaling in $v_2$ observed experimentally. We therefore argue that the system produced at most Super Proton Synchrotron (SPS) and Relativistic Heavy Ion Collider (RHIC) energies is fundamentally the same as far as the soft and approximately thermalized degrees of freedom are considered. The ``sQGP'' (Strongly interacting Quark-Gluon Plasma) phase, if it is there, is therefore not exclusive to RHIC. We suggest, as a goal for further low-energy heavy ion experiments, to search for a ``transition'' $\sqrt{s}$ where the observed scaling breaks.Comment: Accepted for publication by Phys. Rev. C Based on presentation in mini-symposium on QGP collective properties, Frankfurt. Discussion expanded, results adde

3+1D hydrodynamic simulation of relativistic heavy-ion collisions

We present MUSIC, an implementation of the Kurganov-Tadmor algorithm for relativistic 3+1 dimensional fluid dynamics in heavy-ion collision scenarios. This Riemann-solver-free, second-order, high-resolution scheme is characterized by a very small numerical viscosity and its ability to treat shocks and discontinuities very well. We also incorporate a sophisticated algorithm for the determination of the freeze-out surface using a three dimensional triangulation of the hyper-surface. Implementing a recent lattice based equation of state, we compute p_T-spectra and pseudorapidity distributions for Au+Au collisions at root s = 200 GeV and present results for the anisotropic flow coefficients v_2 and v_4 as a function of both p_T and pseudorapidity. We were able to determine v_4 with high numerical precision, finding that it does not strongly depend on the choice of initial condition or equation of state.Comment: 16 pages, 11 figures, version accepted for publication in PRC, references added, minor typos corrected, more detailed discussion of freeze-out routine adde

Macroscopic Aharonov--Bohm Effect in Type-I Superconductors

In type-I superconducting cylinders bulk superconductivity is destroyed above the first critical current. Below the second critical current the `type-I mixed state' displays fluctuation superconductivity which contributes to the total current. A magnetic flux on the axis of the cylinder can change the second critical current by as much as 50 percent so that half a flux quantum can switch the cylinder from normal conduction to superconductivity: the Aharonov--Bohm effect manifests itself in macroscopically large resistance changes of the cylinder.Comment: five pages, one figur

Shear viscosity to entropy density ratio in nuclear multifragmentation

Nuclear multifragmentation in intermediate energy heavy ion collisions has long been associated with liquid-gas phase transition. We calculate the shear viscosity to entropy density ratio eta/s for an equilibrated system of nucleons and fragments produced in multifragmentation within an extended statistical multifragmentation model. The temperature dependence of eta/s exhibits surprisingly similar behavior as that for water. In the coexistence phase of fragments and light particles, the ratio eta/s reaches a minimum of comparable depth as that for water in the vicinity of the critical temperature for liquid-gas phase transition. The effects of freeze-out volume and surface symmetry energy on eta/s in multifragmentation are studied.Comment: 5 pages, 5 figures, to appear in PR

Partial Dynamical Symmetry at Critical-Points of Quantum Phase Transitions

We show that partial dynamical symmetries (PDS) can occur at critical-points of quantum phase transitions, in which case, underlying competing symmetries are conserved exactly by a subset of states, and mix strongly in other states. Several types of PDS are demonstrated with the example of critical-point Hamiltonians for first- and second-order transitions in the framework of the interacting boson model, whose dynamical symmetries correspond to different shape-phases in nuclei.Comment: 4 pages, 5 figures, minor adjustments to PRL requirements. PRL in pres

Crossover from Fermi-Pasta-Ulam to normal diffusive behaviour in heat conduction through open anharmonic lattices

We study heat conduction in one, two and three dimensional anharmonic lattices connected to stochastic Langevin heat baths. The inter-atomic potential of the lattices is double-well type, i.e., $V_{\rm DW}(x)=k_2x^2/2+k_4 x^4/4$ with $k_20$. We observe two different temperature regimes of transport: a high-temperature regime where asymptotic length dependence of nonequilibrium steady state heat current is similar to the well-known Fermi-Pasta-Ulam lattices with an inter-atomic potential, $V_{\rm FPU}(x)=k_2x^2/2+k_4 x^4/4$ with $k_2,k_4>0$. A low temperature regime where heat conduction is diffusive normal satisfying Fourier's law. We present our simulation results at different temperature regimes in all dimensions.Comment: 5 pages, 7 figure

Analytic description of atomic interaction at ultracold temperatures II: Scattering around a magnetic Feshbach resonance

Starting from a multichannel quantum-defect theory, we derive analytic descriptions of a magnetic Feshbach resonance in an arbitrary partial wave $l$, and the atomic interactions around it. An analytic formula, applicable to both broad and narrow resonances of arbitrary $l$, is presented for ultracold atomic scattering around a Feshbach resonance. Other related issues addressed include (a) the parametrization of a magnetic Feshbach resonance of arbitrary $l$, (b) rigorous definitions of "broad" and "narrow" resonances of arbitrary $l$ and their different scattering characteristics, and (c) the tuning of the effective range and the generalized effective range by a magnetic field.Comment: 13 pages, 4 figure

Consistency of a Causal Theory of Radiative Reaction with the Optical Theorem

The Abraham-Lorentz-Dirac equation for a point electron, while suffering from runaway solutions and an acausal response to external forces, is compatible with the optical theorem. We show that a theory of radiative reaction that allows for a finite charge distribution is not only causal and free of runaway solutions, but is also consistent with the optical theorem and the standard formula for the Rayleigh scattering cross section.Comment: 4 pages, 2 figure

Tight binding formulation of the dielectric response in semiconductor nanocrystals

We report on a theoretical derivation of the electronic dielectric response of semiconductor nanocrystals using a tight-binding framework. Extending to the nanoscale the Hanke and Sham approach [Phys. Rev. B 12, 4501 (1975)] developed for bulk semiconductors, we show how local field effects can be included in the study of confined systems. A great advantage of this scheme is that of being formulated in terms of localized orbitals and thus it requires very few computational resources and times. Applications to the optical and screening properties of semiconductor nanocrystals are presented here and discussed. Results concerning the absorption cross section, the static polarizability and the screening function of InAs (direct gap) and Si (indirect gap) nanocrystals compare well to both first principles results and experimental data. We also show that the present scheme allows us to easily go beyond the continuum dielectric model, based on the Clausius-Mossotti equation, which is frequently used to include the nanocrystal surface polarization. Our calculations indicate that the continuum dielectric model, used in conjunction with a size dependent dielectric constant, underestimates the nanocrystal polarizability, leading to exceedingly strong surface polarization fields.Comment: 9 pages, 5 figures; corrected typos, added reference

Covariant form of the ideal magnetohydrodynamic "connection theorem" in a relativistic plasma

The magnetic connection theorem of ideal Magnetohydrodynamics by Newcomb [Newcomb W.A., Ann. Phys., 3, 347 (1958)] and its covariant formulation are rederived and reinterpreted in terms of a "time resetting" projection that accounts for the loss of simultaneity in different reference frames between spatially separated events.Comment: 3 pages- 0 figures EPL, accepted in pres