Vortex macroscopic superpositions in ultracold bosons in a double-well potential

We study macroscopic superpositions in the orbital rather than the spatial degrees of freedom, in a three-dimensional double-well system. We show that the ensuing dynamics of $N$ interacting excited ultracold bosons, which in general requires at least eight single-particle modes and ${N+7 \choose N}$ Fock vectors, is described by a surprisingly small set of many-body states. An initial state with half the atoms in each well, and purposely excited in one of them, gives rise to the tunneling of axisymmetric and transverse vortex structures. We show that transverse vortices tunnel orders of magnitude faster than axisymmetric ones and are therefore more experimentally accessible. The tunneling process generates macroscopic superpositions only distinguishable by their orbital properties and within experimentally realistic times.Comment: 9 pages, 6 figure

Particle density and non-local kinetic energy density functional for two-dimensional harmonically confined Fermi vapors

We evaluate analytically some ground state properties of two-dimensional harmonically confined Fermi vapors with isotropy and for an arbitrary number of closed shells. We first derive a differential form of the virial theorem and an expression for the kinetic energy density in terms of the fermion particle density and its low-order derivatives. These results allow an explicit differential equation to be obtained for the particle density. The equation is third-order, linear and homogeneous. We also obtain a relation between the turning points of kinetic energy and particle densities, and an expression of the non-local kinetic energy density functional.Comment: 7 pages, 2 figure

A Unified Theory of Matter Genesis: Asymmetric Freeze-In

We propose a unified theory of dark matter (DM) genesis and baryogenesis. It explains the observed link between the DM density and the baryon density, and is fully testable by a combination of collider experiments and precision tests. Our theory utilises the "thermal freeze-in" mechanism of DM production, generating particle anti-particle asymmetries in decays from visible to hidden sectors. Calculable, linked, asymmetries in baryon number and DM number are produced by the feeble interaction mediating between the two sectors, while the out-of-equilibrium condition necessary for baryogenesis is provided by the different temperatures of the visible and hidden sectors. An illustrative model is presented where the visible sector is the MSSM, with the relevant CP violation arising from phases in the gaugino and Higgsino masses, and both asymmetries are generated at temperatures of order 100 GeV. Experimental signals of this mechanism can be spectacular, including: long-lived metastable states late decaying at the LHC; apparent baryon-number or lepton-number violating signatures associated with these highly displaced vertices; EDM signals correlated with the observed decay lifetimes and within reach of planned experiments; and a prediction for the mass of the dark matter particle that is sensitive to the spectrum of the visible sector and the nature of the electroweak phase transition.Comment: LaTeX, 22 pages, 6 figure

Volume change of bulk metals and metal clusters due to spin-polarization

The stabilized jellium model (SJM) provides us a method to calculate the volume changes of different simple metals as a function of the spin polarization, $\zeta$, of the delocalized valence electrons. Our calculations show that for bulk metals, the equilibrium Wigner-Seitz (WS) radius, $\bar r_s(\zeta)$, is always a n increasing function of the polarization i.e., the volume of a bulk metal always increases as $\zeta$ increases, and the rate of increasing is higher for higher electron density metals. Using the SJM along with the local spin density approximation, we have also calculated the equilibrium WS radius, $\bar r_s(N,\zeta)$, of spherical jellium clusters, at which the pressure on the cluster with given numbers of total electrons, $N$, and their spin configuration $\zeta$ vanishes. Our calculations f or Cs, Na, and Al clusters show that $\bar r_s(N,\zeta)$ as a function of $\zeta$ behaves differently depending on whether $N$ corresponds to a closed-shell or an open-shell cluster. For a closed-shell cluster, it is an increasing function of $\zeta$ over the whole range $0\le\zeta\le 1$, whereas in open-shell clusters it has a decreasing behavior over the range $0\le\zeta\le\zeta_0$, where $\zeta_0$ is a polarization that the cluster has a configuration consistent with Hund's first rule. The resu lts show that for all neutral clusters with ground state spin configuration, $\zeta_0$, the inequality $\bar r_s(N,\zeta_0)\le\bar r_s(0)$ always holds (self-compression) but, at some polarization $\zeta_1>\zeta_0$, the inequality changes the direction (self-expansion). However, the inequality $\bar r_s(N,\zeta)\le\bar r_s(\zeta)$ always holds and the equality is achieved in the limit $N\to\infty$.Comment: 7 pages, RevTex, 10 figure

Big Bang Synthesis of Nuclear Dark Matter

We investigate the physics of dark matter models featuring composite bound states carrying a large conserved dark "nucleon" number. The properties of sufficiently large dark nuclei may obey simple scaling laws, and we find that this scaling can determine the number distribution of nuclei resulting from Big Bang Dark Nucleosynthesis. For plausible models of asymmetric dark matter, dark nuclei of large nucleon number, e.g. > 10^8, may be synthesised, with the number distribution taking one of two characteristic forms. If small-nucleon-number fusions are sufficiently fast, the distribution of dark nuclei takes on a logarithmically-peaked, universal form, independent of many details of the initial conditions and small-number interactions. In the case of a substantial bottleneck to nucleosynthesis for small dark nuclei, we find the surprising result that even larger nuclei, with size >> 10^8, are often finally synthesised, again with a simple number distribution. We briefly discuss the constraints arising from the novel dark sector energetics, and the extended set of (often parametrically light) dark sector states that can occur in complete models of nuclear dark matter. The physics of the coherent enhancement of direct detection signals, the nature of the accompanying dark-sector form factors, and the possible modifications to astrophysical processes are discussed in detail in a companion paper.Comment: 27 pages, 5 figures, v3; minor additional comments - matches published versio

Tunneling, self-trapping and manipulation of higher modes of a BEC in a double well

We consider an atomic Bose-Einstein condensate trapped in a symmetric one-dimensional double well potential in the four-mode approximation and show that the semiclassical dynamics of the two ground state modes can be strongly influenced by a macroscopic occupation of the two excited modes. In particular, the addition of the two excited modes already unveils features related to the effect of dissipation on the condensate. In general, we find a rich dynamics that includes Rabi oscillations, a mixed Josephson-Rabi regime, self-trapping, chaotic behavior, and the existence of fixed points. We investigate how the dynamics of the atoms in the excited modes can be manipulated by controlling the atomic populations of the ground states.Comment: 12 pages, 5 figure