From: Matthew Davis <mdavis_at_physics.uq.edu.au>

Date: Fri, 3 Feb 2006 16:47:46 +1000 (EST)

Date: Fri, 3 Feb 2006 16:47:46 +1000 (EST)

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-- ------------------------------------------------------------------------- Dr M. J. Davis, Senior Lecturer in Physics School of Physical Sciences, email: mdavis_at_physics.uq.edu.au University of Queensland, ph : +61 7 334 69824 Brisbane, QLD 4072, fax : +61 7 336 51242 Australia. http://www.physics.uq.edu.au/people/mdavis/ ------------------------------------------------------------------------- ------------------------------------------------------------------------------ \\ Paper: cond-mat/0601628 Date: Fri, 27 Jan 2006 07:25:28 GMT (21kb) Title: Entanglement properties of degenerate four-wave mixing of matter-waves in a periodic potential Authors: M.K. Olsen and M.J. Davis Comments: 4 pages, 3 figures Subj-class: Other \\ In a recent experiment Campbell et al. [Phys. Rev. Lett. 96, 020406 (2006)] observed degenerate four-wave mixing of matter-waves in a one-dimensional optical lattice, a process with potential for generating entanglement among atoms. We analyse the essential quantum features of the experiment to show that entanglement is created between the quadratures of the two scattered atomic clouds and is a true many-body (rather than two-body) effect. We demonstrate a significant violation of entanglement inequalities that is robust to a moderate level of coherent seeding. The system is thus a promising candididate for generating macroscopically entangled atomic samples. \\ ( http://arXiv.org/abs/cond-mat/0601628 , 21kb) ------------------------------------------------------------------------------ \\ Paper: cond-mat/0601633 Date: Fri, 27 Jan 2006 13:25:58 GMT (644kb) Title: Fabrication of magnetic atom chips based on FePt Authors: Y. T. Xing, I. Barb, R. Gerritsma, R. J. C. Spreeuw, H. Luigjes, Q. F. Xiao, C. Retif, and J. B. Goedkoop Comments: 5 pages, 5 figures Subj-class: Materials Science \\ We describe the design and fabrication of novel all-magnetic atom chips for use in ultracold atom trapping. The considerations leading to the choice of nanocrystalline exchange coupled FePt as best material are discussed. Using stray field calculations, we designed patterns that function as magnetic atom traps. These patterns were realized by spark erosion of FePt foil and e-beam lithography of FePt film. A mirror magneto-optical trap (MMOT) was obtained using the stray field of the foil chip. \\ ( http://arXiv.org/abs/cond-mat/0601633 , 644kb) ------------------------------------------------------------------------------ \\ Paper: cond-mat/0412549 replaced with revised version Fri, 27 Jan 2006 11:14:22 GMT (539kb) Title: Emergence of superfluidity in a dynamical system of ultracold atoms Authors: Joachim Brand and Andrey R. Kolovsky Subj-class: Other \\ ( http://arXiv.org/abs/cond-mat/0412549 , 539kb) ------------------------------------------------------------------------------ \\ Paper: quant-ph/0601180 Date: Fri, 27 Jan 2006 07:10:04 GMT (437kb) Title: Analysis of photon-atom entanglement generated by Faraday rotation in a cavity Authors: S. K. Y. Lee and C. K. Law Comments: 6 pages, 3 figures \\ Faraday rotation based on AC Stark shifts is a mechanism that can entangle the polarization variables of photons and atoms. We analyze the structure of such entanglement by using the Schmidt decomposition method. The time-dependence of entanglement entropy and the effective Schmidt number are derived for Gaussian amplitudes. In particular we show how the entanglement is controlled by the initial fluctuations of atoms and photons. \\ ( http://arXiv.org/abs/quant-ph/0601180 , 437kb) ------------------------------------------------------------------------------ \\ Paper: quant-ph/0601184 Date: Fri, 27 Jan 2006 10:46:49 GMT (319kb) Title: A deterministic cavity-QED source of polarization entangled photon pairs Authors: R. Garcia-Maraver, K. Eckert, R. Corbalan, and J. Mompart Comments: 5 pages, 5 figures \\ We present two cavity quantum electrodynamics proposals that, sharing the same basic elements, allow for the deterministic generation of entangled photons pairs by means of a three-level atom successively coupled to two single longitudinal mode high-Q optical resonators presenting polarization degeneracy. In the faster proposal, the three-level atom yields a polarization entangled photon pair via two truncated Rabi oscillations, whereas in the adiabatic proposal a counterintuitive Stimulated Raman Adiabatic Passage process is considered. Although slower than the former process, this second method is very efficient and robust under fluctuations of the experimental parameters and, particularly interesting, almost completely insensitive to atomic decay. \\ ( http://arXiv.org/abs/quant-ph/0601184 , 319kb) ------------------------------------------------------------------------------ \\ Paper: quant-ph/0601186 Date: Fri, 27 Jan 2006 15:14:12 GMT (572kb) Title: Deterministic atom-light quantum interface Authors: Jacob Sherson, Brian Julsgaard, and E. S. Polzik Comments: 50 pages (bookstyle) 15 graphs, to be published in "Advances in Atomic, Molecular, and Optical Physics" Vol. 54. (2006)(Some of the graphs here have lower resolution than in the version to be published) \\ The notion of an atom-light quantum interface has been developed in the past decade, to a large extent due to demands within the new field of quantum information processing and communication. A promising type of such interface using large atomic ensembles has emerged in the past several years. In this article we review this area of research with a special emphasis on deterministic high fidelity quantum information protocols. Two recent experiments, entanglement of distant atomic objects and quantum memory for light are described in detail. \\ ( http://arXiv.org/abs/quant-ph/0601186 , 572kb) ------------------------------------------------------------------------------ \\ Paper: quant-ph/0601187 Date: Fri, 27 Jan 2006 16:39:41 GMT (136kb) Title: Entangled photons on-demand from single quantum dots Authors: Robert J. Young, R. Mark Stevenson, Paola Atkinson, Ken Cooper, David A. Ritchie, Andrew J. Shields Comments: 9 pages \\ We demonstrate the on-demand emission of polarisation-entangled photon pairs from the biexciton cascade of a single InAs quantum dot embedded in a GaAs/AlAs planar microcavity. Improvements in the sample design blue shifts the wetting layer to reduce the contribution of background light in the measurements. Results presented show that >70% of the detected photon pairs are entangled. The high fidelity of the (|HxxHx>+|VxxVx>)/2^0.5 state that we determine is sufficient to satisfy numerous tests for entanglement. The improved quality of entanglement represents a significant step towards the realisation of a practical quantum dot source compatible with applications in quantum information. \\ ( http://arXiv.org/abs/quant-ph/0601187 , 136kb) ------------------------------------------------------------------------------ \\ Paper: physics/0512016 replaced with revised version Fri, 27 Jan 2006 20:26:14 GMT (86kb) Title: Direct Imaging of Periodic Sub-wavelength Patterns of Total Atomic Density Authors: Alexei Tonyushkin and Tycho Sleator Comments: 4 pages, 4 figures, to be submitted to Phys. Rev. A; order rearranged, references replaced and added, corrected typos Subj-class: Atomic Physics; Optics \\ ( http://arXiv.org/abs/physics/0512016 , 86kb) ------------------------------------------------------------------------------ \\ Paper: cond-mat/0601650 Date: Sun, 29 Jan 2006 08:36:10 GMT (36kb) Title: Dynamics of the Bose-Hubbard model: from Mott insulator to superfluid phase Authors: Fernando M. Cucchietti, Bodgan Damski, Jacek Dziarmaga, Wojciech H. Zurek Comments: 4 pages & 3 figures Report-no: LAUR-06-0477 Subj-class: Other \\ We study dynamics of the one dimensional Bose-Hubbard model. To this aim we change the tunneling frequency at a finite rate driving the system from Mott insulator to superfluid regime. We describe build up of correlations during such transitions using variational wave functions, dynamical BCS-Bogoliubov theory, estimates based on the Kibble-Zurek mechanism, and numerical simulations. We show that time-dependent correlations satisfy characteristic scaling relations being directly experimentally measurable, e.g., in a ring-shaped optical lattice filled with ultracold atoms. \\ ( http://arXiv.org/abs/cond-mat/0601650 , 36kb) ------------------------------------------------------------------------------ \\ Paper: cond-mat/0601664 Date: Mon, 30 Jan 2006 13:53:46 GMT (76kb) Title: Formation of bright matter-wave solitons during the collapse of Bose-Einstein condensates Authors: Simon L. Cornish, Sarah T. Thompson and Carl E. Wieman Comments: 4 pages, 4 figures Subj-class: Other \\ We observe bright matter-wave solitons form during the collapse of 85Rb condensates in a three-dimensional magnetic trap. The collapse is induced by using a Feshbach resonance to suddenly switch the atomic interactions from repulsive to attractive. Remnant condensates containing several times the critical number of atoms for the onset of instability are observed to survive the collapse. Under these conditions a highly robust configuration of solitons forms such that each soliton satisfies the condition for stability and neighboring solitons exhibit repulsive interactions. \\ ( http://arXiv.org/abs/cond-mat/0601664 , 76kb) ------------------------------------------------------------------------------ \\ Paper: quant-ph/0601202 Date: Mon, 30 Jan 2006 17:07:11 GMT (367kb) Title: Probing BEC phase fluctuations with atomic quantum dots Authors: M. Bruderer, D. Jaksch Comments: 11 pages, 3 figures \\ We consider the dephasing of two internal states |0> and |1> of a trapped impurity atom, a so-called atomic quantum dot (AQD), where only state |1> couples to a Bose-Einstein condensate (BEC). A direct relation between the dephasing of the internal states of the AQD and the temporal phase fluctuations of the BEC is established. Based on this relation we suggest a scheme to probe BEC phase fluctuations nondestructively via dephasing measurements of the AQD. In particular, the scheme allows to trace the dependence of the phase fluctuations on the trapping geometry of the BEC. \\ ( http://arXiv.org/abs/quant-ph/0601202 , 367kb) ------------------------------------------------------------------------------ \\ Paper: cond-mat/0601542 replaced with revised version Mon, 30 Jan 2006 11:38:20 GMT (51kb) Title: A two-channel R-matrix analysis of magnetic field induced Feshbach resonances Authors: Nicolai Nygaard, Barry I. Schneider and Paul S. Julienne Comments: Added references. 11 pages, 6 figures. For additional information see http://www.phys.au.dk/quantop/Feshbach/Feshbach.shtm Subj-class: Other; Atomic Physics \\ ( http://arXiv.org/abs/cond-mat/0601542 , 51kb) ------------------------------------------------------------------------------ \\ Paper: cond-mat/0601681 Date: Mon, 30 Jan 2006 21:18:20 GMT (220kb) Title: Exact Study of the 1D Boson Hubbard Model with a Superlattice Potential Authors: V.G. Rousseau, M. Rigol, F. H\'ebert, D.P. Arovas, G.G. Batrouni, R.T. Scalettar Comments: 12 pages, 22 figures Subj-class: Other; Strongly Correlated Electrons \\ We use Quantum Monte Carlo simulations and exact diagonalization to explore the phase diagram of the Bose-Hubbard model with an additional superlattice potential. We first analyze the properties of superfluid and insulating phases present in the hard-core limit where an exact analytic treatment is possible via the Jordan-Wigner transformation. The extension to finite on-site interaction is achieved by means of quantum Monte Carlo simulations. We determine insulator/superfluid phase diagrams as functions of the on-site repulsive interaction, superlattice potential strength, and filling, finding that insulators with fractional occupation numbers, which are present in the hard-core case, extend deep into the soft-core region. Furthermore, at integer fillings, we find that the competition between the on-site repulsion and the superlattice potential can produce a phase transition between a Mott insulator and a charge density wave insulator, with an intermediate superfluid phase. Our results are relevant to the behavior of ultracold atoms in optical superlattices which are beginning to be studied experimentally. \\ ( http://arXiv.org/abs/cond-mat/0601681 , 220kb) ------------------------------------------------------------------------------ \\ Paper: cond-mat/0601690 Date: Tue, 31 Jan 2006 07:19:56 GMT (811kb) Title: Fringe spacing and phase of interfering matter waves Authors: O. Vainio, C. J. Vale, M. J. Davis, N. R. Heckenberg, and H. Rubinsztein-Dunlop Comments: 4 pages, 3 figures Subj-class: Other \\ We experimentally investigate the outcoupling of atoms from Bose-Einstein condensates using two radio-frequency (rf) fields in the presence of gravity. We show that the fringe separation in the resulting interference pattern derives entirely from the energy difference between the two rf fields and not the gravitational potential difference. We subsequently demonstrate how the phase and polarisation of the rf radiation directly control the phase of the matter wave interference and provide a semi-classical interpretation of the results. \\ ( http://arXiv.org/abs/cond-mat/0601690 , 811kb) ------------------------------------------------------------------------------ \\ Paper: cond-mat/0601695 Date: Tue, 31 Jan 2006 11:38:27 GMT (55kb) Title: Vortex-lattice melting in a one-dimensional optical lattice Authors: Michiel Snoek and H.T.C. Stoof Comments: 4 pages, 4 figures Report-no: ITP-UU-06/04 Subj-class: Mesoscopic Systems and Quantum Hall Effect \\ We investigate quantum fluctuations of a vortex lattice in a one-dimensional optical lattice. Our method gives full access to all the modes of the vortex lattice and we discuss in particular the Bloch bands of the Tkachenko modes. Because of the small number of particles in the pancake Bose-Einstein condensates at every site of the optical lattice, finite-size effects become very important. Therefore, the fluctuations in the vortex positions are inhomogeneous and the melting of the lattice occurs from the outside inwards. Tunneling between neighbouring pancakes substantially reduces the inhomogeneity as well as the size of the fluctuations. \\ ( http://arXiv.org/abs/cond-mat/0601695 , 55kb) ------------------------------------------------------------------------------ \\ Paper: cond-mat/0601714 Date: Tue, 31 Jan 2006 18:22:16 GMT (875kb) Title: Spatial effects in superradiant Rayleigh scattering from Bose-Einstein condensates Authors: O. Zobay and Georgios M. Nikolopoulos Comments: 14 pages, 13 figures Subj-class: Other Journal-ref: Phys. Rev. A 73, 013620 (2006) DOI: 10.1103/PhysRevA.73.013620 \\ We present a detailed theoretical analysis of superradiant Rayleigh scattering from atomic Bose-Einstein condensates. A thorough investigation of the spatially resolved time-evolution of optical and matter-wave fields is performed in the framework of the semiclassical Maxwell-Schroedinger equations. Our theory is not only able to explain many of the known experimental observations, e.g., the behavior of the atomic side-mode distributions, but also provides further detailed insights into the coupled dynamics of optical and matter-wave fields. To work out the significance of propagation effects, we compare our results to other theoretical models in which these effects are neglected. \\ ( http://arXiv.org/abs/cond-mat/0601714 , 875kb) ------------------------------------------------------------------------------ \\ Paper: cond-mat/0511113 replaced with revised version Tue, 31 Jan 2006 11:57:08 GMT (511kb) Title: Intense slow beams of bosonic potassium isotopes Authors: J. Catani, P. Maioli, L. De Sarlo, F. Minardi, and M. Inguscio Comments: Updated references, 1 figure added, 10 pages, 9 figures Subj-class: Other \\ ( http://arXiv.org/abs/cond-mat/0511113 , 511kb) ------------------------------------------------------------------------------ \\ Paper: quant-ph/0601208 Date: Tue, 31 Jan 2006 14:13:47 GMT (215kb) Title: Entanglement And Cross-Correlations In Cavity QED Authors: P. R. Rice, J. Gea-Banacloche, M. L. Terraciano, D. L. Freimund, L. A. Orozco Comments: 13 pages, 3 figures \\ We investigate entanglement in an open quantum system, specifically a single atom in a driven optical cavity with cavity loss and spontaneous emission. In the weak driving limit, the system reaches a pure state in the steady state. We find that any normalized cross-correlation function, of the type historically considered in quantum optics, is an indicator of the entanglement in a system. In particular we find that the zero delay intensity-field cross correlation is proportional to the entanglement of formation for weak driving fields. Other correlation functions are considered as indicators, or witnesses, of entanglement. \\ ( http://arXiv.org/abs/quant-ph/0601208 , 215kb) ------------------------------------------------------------------------------ \\ Paper: quant-ph/0602006 Date: Wed, 1 Feb 2006 13:26:23 GMT (527kb) Title: A cavity-QED scheme for Heisenberg-limited interferometry Authors: David Vitali, Stefan Kuhr, Michel Brune, Jean-Michel Raimond Comments: 13 pages, 7 figures \\ We propose a Ramsey interferometry experiment using an entangled state of N atoms to reach the Heisenberg limit for the estimation of an atomic phase shift if the atom number parity is perfectly determined. In a more realistic situation, due to statistical fluctuations of the atom source and the finite detection efficiency, the parity is unknown. We then achieve about half the Heisenberg limit. The scheme involves an ensemble of circular Rydberg atoms which dispersively interact successively with two initially empty microwave cavities. The scheme does not require very high-Q cavities. An experimental realization with about ten entangled Rydberg atoms is achievable with state of art apparatuses. \\ ( http://arXiv.org/abs/quant-ph/0602006 , 527kb) ------------------------------------------------------------------------------ \\ Paper: quant-ph/0602010 Date: Wed, 1 Feb 2006 13:57:20 GMT (158kb) Title: Optimized production of large Bose Einstein Condensates Authors: D. Comparat (LAC), A. Fioretti (LAC), G. Stern (LAC), E. Dimova (LAC), B. Laburthe Tolra (LPL), P. Pillet (LAC) Comments: 14 pages Proxy: ccsd ccsd-00018383 \\ We suggest different simple schemes to efficiently load and evaporate a ''dimple'' crossed dipolar trap. The collisional processes between atoms which are trapped in a reservoir load in a non adiabatic way the dimple. The reservoir trap can be provided either by a dark SPOT Magneto Optical Trap, the (aberrated) laser beam itself or by a quadrupolar or quadratic magnetic trap. Optimal parameters for the dimple are derived from thermodynamical equations and from loading time, including possible inelastic and Majorana losses. We suggest to load at relatively high temperature a tight optical trap. Simple evaporative cooling equations, taking into account gravity, the possible occurrence of hydrodynamical regime, Feshbach resonance processes and three body recombination events are given. To have an efficient evaporation the elastic collisional rate (in s$^{-1}$) is found to be on the order of the trapping frequency and lower than one hundred times the temperature in micro-Kelvin. Bose Einstein condensates with more than $10^7$ atoms should be obtained in much less than one second starting from an usual MOT setup. \\ ( http://arXiv.org/abs/quant-ph/0602010 , 158kb) ------------------------------------------------------------------------------ \\ Paper: quant-ph/0602013 Date: Wed, 1 Feb 2006 16:17:27 GMT (217kb) Title: Transversal laser excitation of atoms in a waveguide Authors: I. Lizuain, A. Ruschhaupt, J. G. Muga Comments: 10 pages, 9 figures \\ We investigate the effect of a laser shining perpendicularly to a waveguide channeling two-level atoms. For weak transversal coupling the excitation of transverse atomic levels occurs at avoided crossings associated with "Rabi resonances" in which the Rabi frequency coincides with the transition frequency between the transverse levels. \\ ( http://arXiv.org/abs/quant-ph/0602013 , 217kb) ------------------------------------------------------------------------------ \\ Paper: quant-ph/0602017 Date: Wed, 1 Feb 2006 20:16:20 GMT (156kb) Title: Controlling Polar Molecules in Optical Lattices Authors: S. Kotochigova, E. Tiesinga \\ We investigate theoretically the interaction of polar molecules with optical lattices and microwave fields. We demonstrate the existence of frequency windows in the optical domain where the complex internal structure of the molecule does not influence the trapping potential of the lattice. In such frequency windows the Franck-Condon factors are so small that near-resonant interaction of vibrational levels of the molecule with the lattice fields have a negligible contribution to the polarizability and light-induced decoherences are kept to a minimum. In addition, we show that microwave fields can induce a tunable dipole-dipole interaction between ground-state rotationally symmetric (J=0) molecules. A combination of a carefully chosen lattice frequency and microwave-controlled interaction between molecules will enable trapping of polar molecules in a lattice and possibly realize molecular quantum logic gates. Our results are based on ab initio relativistic electronic structure calculations of the polar KRb and RbCs molecules combined with calculations of their rovibrational motion. \\ ( http://arXiv.org/abs/quant-ph/0602017 , 156kb) ------------------------------------------------------------------------------ \\ Paper: physics/0602011 Date: Wed, 1 Feb 2006 19:20:19 GMT (108kb) Title: Demonstration of an Electron Electric Dipole Moment Experiment Using Electric-Field Quantization in a Cesium Cold Atom Fountain Authors: Jason M. Amini, Charles T. Munger Jr., Harvey Gould Comments: 4 pages, 4 figures plus bibtex Subj-class: Atomic Physics \\ A Cs fountain electron electric dipole moment (EDM) experiment using electric-field quantization is demonstrated. With magnetic fields reduced to 200 pT or less, the electric field lifts the degeneracy between hyperfine levels of different|mF| and, along with the slow beam and fountain geometry, suppresses systematics from motional magnetic fields. Transitions are induced and the atoms polarized and analyzed in field-free regions. The feasibility of reaching a sensitivity to an electron EDM of 2 x 10 exp(-50) C-m [1.3 x 10 exp(-29) e-cm] in a cesium fountain experiment is discussed. \\ ( http://arXiv.org/abs/physics/0602011 , 108kb) ------------------------------------------------------------------------------ \\ Paper: cond-mat/0602032 Date: Wed, 1 Feb 2006 21:01:57 GMT (23kb) Title: Fermi surfaces and Luttinger's theorem in paired fermion systems Authors: Subir Sachdev and Kun Yang Comments: 7 pages with one figure embedded Subj-class: Superconductivity \\ We discuss ground state properties of a mixture of two fermion species which can bind to form a molecular boson. When the densities of the fermions are unbalanced, one or more Fermi surfaces can appear: we describe the constraints placed by Luttinger's theorem on the volumes enclosed by these surfaces in such Bose-Fermi mixtures. We also discuss the nature of the quantum phase transitions involving changes in the number of Fermi surfaces. \\ ( http://arXiv.org/abs/cond-mat/0602032 , 23kb) ------------------------------------------------------------------------------ \\ Paper: cond-mat/0602037 Date: Thu, 2 Feb 2006 20:45:05 GMT (156kb) Title: Validity of the Lowest Landau Level Approximation for Rotating Bose Gases Authors: Alexis G. Morris and David L. Feder Comments: 8 pages, 9 figures Subj-class: Mesoscopic Systems and Quantum Hall Effect \\ The energy spectra for an ultracold rotating Bose gas in a harmonic trap are calculated exactly for small systems, allowing the atoms to occupy several Landau levels. Two vortex-like states and two strongly correlated states (the Pfaffian and Laughlin) are considered in detail. In particular, their critical rotation frequencies and energy gaps are determined as a function of particle number, interaction strength, and the number of Landau levels occupied (up to three). For the vortex-like states, the Lowest Landau level (LLL) approximation is justified only if the interaction strength decreases with the number of particles; nevertheless, the constant of proportionality increases rapidly with the angular momentum per particle. For the strongly correlated states, however, the interaction strength can \emph{increase} with particle number without violating the LLL condition. The results suggest that in large systems, the Pfaffian and Laughlin states might be stabilized at rotation frequencies well below the centrifugal limit for sufficiently large interaction strengths, with energy gaps a significant fraction of the trap energy. \\ ( http://arXiv.org/abs/cond-mat/0602037 , 156kb) ------------------------------------------------------------------------------ \\ Paper: cond-mat/0602048 Date: Thu, 2 Feb 2006 16:09:58 GMT (166kb) Title: Coherent transport of cold atoms in angle-tuned optical lattices Authors: Roberto Franzosi, Matteo Cristiani, Carlo Sias, Ennio Arimondo Comments: 7 pages, 5 figures Subj-class: Other \\ Optical lattices with a large spacing between the minima of the optical potential can be created using the angle-tuned geometry where the 1-D periodic potential is created by two propagating laser beams intersecting at an angle different from $\pi$. The present work analyzes the coherent transport for the case of that geometry. We show that the potential depth can be kept constant during the transport by choosing a \emph{magic} value for the laser wavelength. This value agrees with that of the counterpropagating laser case, thus resulting independent on the lattice geometry. Moreover, we find that this scheme can be used to implement controlled collision experiments under special geometrical conditions. Finally we study the transport of hyperfine-Zeeman states of rubidium 87. \\ ( http://arXiv.org/abs/cond-mat/0602048 , 166kb) ------------------------------------------------------------------------------ \\ Paper: cond-mat/0602055 Date: Thu, 2 Feb 2006 17:37:51 GMT (28kb) Title: Bose Einstein Condensation of incommensurate solid 4He Authors: D. E. Galli and L. Reatto Comments: 4 pages, 2 figures Subj-class: Other; Statistical Mechanics \\ It is pointed out that simulation computation of energy performed so far cannot be used to decide if the ground state of solid 4He has the number of lattice sites equal to the number of atoms (commensurate state) or if it is different (incommensurate state). The best variational wave function, a shadow wave function, gives an incommensurate state but the equilibrium concentration of vacancies remains to be determined. In order to investigate the presence of a supersolid phase we have computed the one--body density matrix in solid 4He for the incommensurate state by means of the exact Shadow Path Integral Ground State projector method. We find a vacancy induced Bose Einstein condensation of about 0.23 atoms per vacancy at a pressure of 54 bar. This means that bulk solid 4He is supersolid at low enough temperature if the exact ground state is incommensurate. \\ ( http://arXiv.org/abs/cond-mat/0602055 , 28kb) ------------------------------------------------------------------------------ \\ Paper: cond-mat/0512010 replaced with revised version Thu, 2 Feb 2006 12:38:18 GMT (422kb) Title: Sound velocity and dimensional crossover in a superfluid Fermi gas in an optical lattice Authors: T. Koponen, J.-P. Martikainen, J. Kinnunen, and P. Torma Comments: 16 pages, 9 figures, v2: minor corrections to the text, replaced one figure Subj-class: Superconductivity \\ ( http://arXiv.org/abs/cond-mat/0512010 , 422kb) ------------------------------------------------------------------------------Received on Fri Feb 03 2006 - 16:47:46 EST

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