Bose Einstein Condensation of incommensurate solid 4He

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.Comment: 5 pages, 2 figure

Supersolid of Hardcore Bosons on the Face Centered Cubic Lattice

We investigate a supersolid state in hardcore boson models on the face-centered-cubic (FCC) lattice. The supersolid state is characterized by a coexistence of crystalline order and superfluidity. Using a quantum Monte Carlo method based on the directed-loop algorithm, we calculate static structure factors and superfluid density at finite temperature, from which we obtain the phase diagram. The supersolid phase exists at intermediate fillings between a three-quarter-filled solid phase and a half-filled solid phase. We also discuss the mechanism of the supersolid state on the FCC lattice.Comment: 5pages, 6figure

Measurement of the electron electric dipole moment using GdIG

A new method for the detection of the electron edm using a solid is described. The method involves the measurement of a voltage induced across the solid by the alignment of the samples magnetic dipoles in an applied magnetic field, H. A first application of the method to GdIG has resulted in a limit on the electron edm of 5E-24 e-cm, which is a factor of 40 below the limit obtained from the only previous solid-state edm experiment. The result is limited by the imperfect discrimination of an unexpectedly large voltage that is even upon the reversal of the sample magnetization.Comment: 10 pages, 5 figures, v2:references corrected, submitted to PRL, v3:added labels to figure

Thoriated nickel bonded by solid-state diffusion method

Solid-state diffusion bonding in an inert-gas atmosphere forms high-strength joints between butting or overlapping surfaces of thoriated nickel. This method eliminates inert-phase agglomeration

Rates of Nuclear Reactions in Solid-Like Stars

In stellar matter as cool and dense as the interior of a white dwarf, the Coulomb energies between neighboring nuclei are large compared to the kinetic energies of the nuclei. Each nucleus is constrained to vibrate about an equilibrium position, and the motion of the nuclei in the interior of a white dwarf is similar to the motion of the atoms in a solid or liquid. We propose a solid-state method for calculating the rate at which a nuclear reaction proceeds between two identical nuclei oscillating about adjacent lattice sites. An effective potential U(r) derived by analyzing small lattice vibrations is used to represent the influence of the Coulomb fields of the lattice on the motion of the two reacting nuclei. The wave function describing the relative motion of the two reacting particles is obtained by solving the Schrödinger equation containing the effective potential U(r). From this wave function, we derive an expression for the reaction rate. The rates of the p+p and C^(12)+C^(12) reactions calculated using this solid-state method are typically 1 to 10 orders of magnitude smaller than those calculated by the method previously suggested by Cameron