Vacancy supersolid of hard-core bosons on the square lattice

The ground state of hard-core bosons on the square lattice with nearest and next-nearest neighbor repulsion is studied by Quantum Monte Carlo simulations. A supersolid phase with vacancy condensation and 'star' diagonal ordering is found for filling less than a quarter. At fillings above one quarter, a supersolid phase exists between the star and the stripe crystal at half-filling. No supersolid phase occurs above quarter-filling, if the ground state at half-filling is either a checkerboard crystal or a superfluid. No commensurate supersolid phase is observed.Comment: Replaced with published versio

Unitarisation of EFT Amplitudes for Dark Matter Searches at the LHC

We propose a new approach to the LHC dark matter search analysis within the effective field theory (EFT) framework by utilising the K-matrix unitarisation formalism. This approach provides a reasonable estimate of the dark matter production cross section at high energies, and hence allows reliable bounds to be placed on the cut-off scale of relevant operators without running into the problem of perturbative unitarity violation. We exemplify this procedure for the effective operator D5 in monojet dark matter searches in the collinear approximation. We compare our bounds to those obtained using the truncation method and identify a parameter region where the unitarisation prescription leads to more stringent bounds.Comment: 20 pages, 7 figures. References added and minor corrections made to match published versio

Catching VY Sculptoris in a low state

Context. In the context of a large campaign to determine the system parameters of high mass transfer cataclysmic variables, we found VY Scl in a low state in 2008. Aims. Making use of this low state, we study the stellar components of the binary with little influence of the normally dominating accretion disc. Methods. Time-resolved spectroscopy and photometry of VY Scl taken during the low state are presented. We analysed the light-curve and radial velocity curve and use time-resolved spectroscopy to calculate Doppler maps of the dominant emission lines. Results. The spectra show narrow emission lines of Halpha, Hbeta, HeI, NaID, and FeII, as well as faint TiO absorption bands that trace the motion of the irradiated secondary star, and Halpha and HeI emission line wings that trace the motion of the white dwarf. From these radial velocities, we find an orbital period of 3.84 h, and put constraints on binary parameters such as the mass ratio M2/M1 of 0.43 and the inclination of 15 deg. With a secondary's mass between 0.3 and 0.35 Msol, we derive the mass for the white dwarf as M1 = 0.6-0.1 Msol.Comment: 8 pages, 9 figures, accepted for publication in A&

Stranger than fiction : the case histories of Sigmund Freud

Bibliography: leaves 201-209.The general aim of this study is to arrive at a critical assessment of the cultural-historical significance of Freud' s major case histories, through a close examination of three of the most famous: the cases of "Dora", "Schreber" and the "WolfMan". My investigation of the case histories themselves is prefaced, in Chapter One, by a selective review of some major strands in the recent critical tradition

Self-interacting dark matter and Higgs bosons in the SU(3)_C x SU(3)_L x U(1)_N model with right-handed neutrinos

We investigate the possibility that dark matter could be made from CP-even and CP- odd Higgs bosons in the SU(3)_C X SU(3)_L X U(1)_N (3-3-1) model with right-handed neutrinos. This self-interacting dark matters are stable without imposing of new symmetry and should be weak-interacting.Comment: 7 pages, Latex, To appear in Europhys. Let

Spin-orbit-enhanced Wigner localization in quantum dots

We investigate quantum dots with Rashba spin-orbit coupling in the strongly-correlated regime. We show that the presence of the Rashba interaction enhances the Wigner localization in these systems, making it achievable for higher densities than those at which it is observed in Rashba-free quantum dots. Recurring shapes in the pair-correlated densities of the yrast spectrum, which might be associated with rotational and vibrational modes, are also reported.Comment: 5 pages, 4 figure

Vibrational Satellites of C2_2S, C3_3S, and C4_4S: Microwave Spectral Taxonomy as a Stepping Stone to the Millimeter-Wave Band

We present a microwave spectral taxonomy study of several hydrocarbon/CS$_2$ discharge mixtures in which more than 60 distinct chemical species, their more abundant isotopic species, and/or their vibrationally excited states were detected using chirped-pulse and cavity Fourier-transform microwave spectroscopies. Taken together, in excess of 85 unique variants were detected, including several new isotopic species and more than 25 new vibrationally excited states of C$_2$S, C$_3$S, and C$_4$S, which have been assigned on the basis of published vibration-rotation interaction constants for C$_3$S, or newly calculated ones for C$_2$S and C$_4$S. On the basis of these precise, low-frequency measurements, several vibrationally exited states of C$_2$S and C$_3$S were subsequently identified in archival millimeter-wave data in the 253--280 GHz frequency range, ultimately providing highly accurate catalogs for astronomical searches. As part of this work, formation pathways of the two smaller carbon-sulfur chains were investigated using $^{13}$C isotopic spectroscopy, as was their vibrational excitation. The present study illustrates the utility of microwave spectral taxonomy as a tool for complex mixture analysis, and as a powerful and convenient `stepping stone' to higher frequency measurements in the millimeter and submillimeter bands.Comment: Accepted in PCC

Higgs-gauge boson interactions in the economical 3-3-1 model

Interactions among the standard model gauge bosons and scalar fields in the framework of SU(3)_C X SU(3)_L X U(1)_X gauge model with minimal (economical) Higgs content are presented. From these couplings, all scalar fields including the neutral scalar $h$ and the Goldstone bosons can be identified and their couplings with the usual gauge bosons such as the photon, the charged $W^\pm$ and the neutral $Z$, without any additional condition, are recovered. In the effective approximation, full content of scalar sector can be recognized. The CP-odd part of Goldstone associated with the neutral non-Hermitian bilepton gauge boson $G_{X^0}$ is decouple, while its CP-even counterpart has the mixing by the same way in the gauge boson sector. Masses of the new neutral Higgs boson $H^0_1$ and the neutral non-Hermitian bilepton $X^0$ are dependent on a coefficient of Higgs self-coupling ($\lambda_1$). Similarly, masses of the singly-charged Higgs boson $H_2^\pm$ and of the charged bilepton $Y^\pm$ are proportional through a coefficient of Higgs self-interaction ($\lambda_4$). The hadronic cross section for production of this Higgs boson at the LHC in the effective vector boson approximation is calculated. Numerical evaluation shows that the cross section can exceed 260 $fb$.Comment: 22 pages, 1 figure, submitted to Phys. Rev.