39,011 research outputs found
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 CS, CS, and CS: Microwave Spectral Taxonomy as a Stepping Stone to the Millimeter-Wave Band
We present a microwave spectral taxonomy study of several hydrocarbon/CS
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 CS, CS, and CS, which have been assigned on the
basis of published vibration-rotation interaction constants for CS, or
newly calculated ones for CS and CS. On the basis of these precise,
low-frequency measurements, several vibrationally exited states of CS and
CS 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 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 and the Goldstone bosons can be identified and their
couplings with the usual gauge bosons such as the photon, the charged
and the neutral , 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 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 and the neutral non-Hermitian bilepton are dependent on a
coefficient of Higgs self-coupling (). Similarly, masses of the
singly-charged Higgs boson and of the charged bilepton are
proportional through a coefficient of Higgs self-interaction (). 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 .Comment: 22 pages, 1 figure, submitted to Phys. Rev.
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