15,106 research outputs found
Coexistence of strong nematic and superconducting correlations in a two-dimensional Hubbard model
Using a dynamic cluster quantum Monte Carlo approximation, we study a
two-dimensional Hubbard model with a small orthorhombic distortion in the
nearest neighbor hopping integrals. We find a large nematic response in the
low-frequency single-particle scattering rate which develops with decreasing
temperature and doping as the pseudogap region is entered. At the same time,
the d-wave superconducting gap function develops an s-wave component and its
amplitude becomes anisotropic. The strength of the pairing correlations,
however, is found to be unaffected by the strong anisotropy, indicating that
d-wave superconductivity can coexist with strong nematicity in the system.Comment: 4 pages, 4 figures, published as PRB 84, 220506(R) (2011
Distinguishing Dynamical Dark Matter at the LHC
Dynamical dark matter (DDM) is a new framework for dark-matter physics in
which the dark sector comprises an ensemble of individual component fields
which collectively conspire to act in ways that transcend those normally
associated with dark matter. Because of its non-trivial structure, this DDM
ensemble --- unlike most traditional dark-matter candidates --- cannot be
characterized in terms of a single mass, decay width, or set of scattering
cross-sections, but must instead be described by parameters which describe the
collective behavior of its constituents. Likewise, the components of such an
ensemble need not be stable so long as lifetimes are balanced against
cosmological abundances across the ensemble as a whole. In this paper, we
investigate the prospects for identifying a DDM ensemble at the LHC and for
distinguishing such a dark-matter candidate from the candidates characteristic
of traditional dark-matter models. In particular, we focus on DDM scenarios in
which the component fields of the ensemble are produced at colliders alongside
some number of Standard-Model particles via the decays of additional heavy
fields. The invariant-mass distributions of these Standard-Model particles turn
out to possess several unique features that cannot be replicated in most
traditional dark-matter models. We demonstrate that in many situations it is
possible to differentiate between a DDM ensemble and a traditional dark-matter
candidate on the basis of such distributions. Moreover, many of our results
also apply more generally to a variety of other extensions of the Standard
Model which involve multiple stable or metastable neutral particles.Comment: 17 pages, LaTeX, 10 figure
Trilepton Signals in the Inert Doublet Model
In this work, we investigate the prospects for detecting the Inert Doublet
Model via the trilepton channel at the LHC. We present a set of representative
benchmark scenarios in which all applicable constraints are satisfied, and show
that in some of these scenarios, it is possible to obtain a signal at the 5
sigma significance level or better with integrated luminosity of 300 fb^{-1}.Comment: 15 pages, ReVTeX, 3 figures, 5 tables
Dynamical Dark Matter from Strongly-Coupled Dark Sectors
Dynamical Dark Matter (DDM) is an alternative framework for dark-matter
physics in which the dark sector comprises a vast ensemble of particle species
whose decay widths are balanced against their cosmological abundances. Previous
studies of this framework have focused on a particular class of DDM ensembles
--- motivated primarily by KK towers in theories with extra dimensions --- in
which the density of states scales roughly as a polynomial of mass. In this
paper, by contrast, we study the properties of a different class of DDM
ensembles in which the density of states grows exponentially with mass.
Ensembles with this Hagedorn-like property arise naturally as the "hadrons"
associated with the confining phase of a strongly-coupled dark sector; they
also arise naturally as the gauge-neutral bulk states of Type I string
theories. We study the dynamical properties of such ensembles, and demonstrate
that an appropriate DDM-like balancing between decay widths and abundances can
emerge naturally --- even with an exponentially rising density of states. We
also study the effective equations of state for such ensembles, and investigate
some of the model-independent observational constraints on such ensembles that
follow directly from these equations of state. In general, we find that such
constraints tend to introduce correlations between various properties of these
DDM ensembles such as their associated mass scales, lifetimes, and abundance
distributions. For example, we find that these constraints allow DDM ensembles
with energy scales ranging from the GeV scale all the way to the Planck scale,
but the total present-day cosmological abundance of the dark sector must be
spread across an increasing number of different states in the ensemble as these
energy scales are dialed from the Planck scale down to the GeV scale. Numerous
other correlations and constraints are also discussed.Comment: 29 pages, LaTeX, 10 figure
The LHC Discovery Potential of a Leptophilic Higgs
In this work, we examine a two-Higgs-doublet extension of the Standard Model
in which one Higgs doublet is responsible for giving mass to both up- and
down-type quarks, while a separate doublet is responsible for giving mass to
leptons. We examine both the theoretical and experimental constraints on the
model and show that large regions of parameter space are allowed by these
constraints in which the effective couplings between the lightest neutral Higgs
scalar and the Standard-Model leptons are substantially enhanced. We
investigate the collider phenomenology of such a "leptophilic"
two-Higgs-doublet model and show that in cases where the low-energy spectrum
contains only one light, CP-even scalar, a variety of collider processes
essentially irrelevant for the discovery of a Standard Model Higgs boson
(specifically those in which the Higgs boson decays directly into a
charged-lepton pair) can contribute significantly to the discovery potential of
a light-to-intermediate-mass (m_h < 140 GeV) Higgs boson at the LHC.Comment: 25 pages, LaVTeX, 11 figures, 1 tabl
Uniaxial and hydrostatic pressure effects in alpha-RuCl3 single crystals via thermal-expansion measurements
We present high-resolution thermal-expansion and specific-heat measurements
of single crystalline alpha-RuCl3. An extremely hysteretic structural
transition expanding over 100 K is observed by thermal- expansion along both
crystallographic axes, which we attribute to a change of stacking sequence of
the RuCl3 layers. Three magnetic transitions are observed, which we link to the
different stacking sequences. Using our data and thermodynamic relations, we
derive the uniaxial and hydrostatic pressure derivatives of all three magnetic
transitions. Our results demonstrate that magnetic order should be totally
suppressed by very moderate pressures of 0.3 GPa to 0.9 GPa. Finally, we
discuss why our results differ from recent hydrostatic pressure measurements
and suggest a possible route to reaching the spin-liquid state in alpha-RuCl3.Comment: 6 pages, 3 figure
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