3,872 research outputs found
Read-Green resonances in a topological superconductor coupled to a bath
We study a topological superconductor capable of exchanging particles with an
environment. This additional interaction breaks particle-number symmetry and
can be modelled by means of an integrable Hamiltonian, building on the class of
Richardson-Gaudin pairing models. The isolated system supports zero-energy
modes at a topological phase transition, which disappear when allowing for
particle exchange with an environment. However, it is shown from the exact
solution that these still play an important role in system-environment particle
exchange, which can be observed through resonances in low-energy and -momentum
level occupations. These fluctuations signal topologically protected Read-Green
points and cannot be observed within traditional mean-field theory.Comment: 7 pages, 4 figure
Inner products in integrable Richardson-Gaudin models
We present the inner products of eigenstates in integrable Richardson-Gaudin
models from two different perspectives and derive two classes of Gaudin-like
determinant expressions for such inner products. The requirement that one of
the states is on-shell arises naturally by demanding that a state has a dual
representation. By implicitly combining these different representations, inner
products can be recast as domain wall boundary partition functions. The
structure of all involved matrices in terms of Cauchy matrices is made explicit
and used to show how one of the classes returns the Slavnov determinant
formula. This framework provides a further connection between two different
approaches for integrable models, one in which everything is expressed in terms
of rapidities satisfying Bethe equations, and one in which everything is
expressed in terms of the eigenvalues of conserved charges, satisfying
quadratic equations.Comment: 21+16 pages, minor revisions compared to the previous versio
CheMPS2: a free open-source spin-adapted implementation of the density matrix renormalization group for ab initio quantum chemistry
The density matrix renormalization group (DMRG) has become an indispensable
numerical tool to find exact eigenstates of finite-size quantum systems with
strong correlation. In the fields of condensed matter, nuclear structure and
molecular electronic structure, it has significantly extended the system sizes
that can be handled compared to full configuration interaction, without losing
numerical accuracy. For quantum chemistry (QC), the most efficient
implementations of DMRG require the incorporation of particle number, spin and
point group symmetries in the underlying matrix product state (MPS) ansatz, as
well as the use of so-called complementary operators. The symmetries introduce
a sparse block structure in the MPS ansatz and in the intermediary contracted
tensors. If a symmetry is non-abelian, the Wigner-Eckart theorem allows to
factorize a tensor into a Clebsch-Gordan coefficient and a reduced tensor. In
addition, the fermion signs have to be carefully tracked. Because of these
challenges, implementing DMRG efficiently for QC is not straightforward.
Efficient and freely available implementations are therefore highly desired. In
this work we present CheMPS2, our free open-source spin-adapted implementation
of DMRG for ab initio QC. Around CheMPS2, we have implemented the augmented
Hessian Newton-Raphson complete active space self-consistent field method, with
exact Hessian. The bond dissociation curves of the 12 lowest states of the
carbon dimer were obtained at the DMRG(28 orbitals, 12 electrons,
D=2500)/cc-pVDZ level of theory. The contribution of
core correlation to the bond dissociation curve of the carbon
dimer was estimated by comparing energies at the DMRG(36o, 12e,
D=2500)/cc-pCVDZ and DMRG-SCF(34o, 8e,
D=2500)/cc-pCVDZ levels of theory.Comment: 16 pages, 13 figure
A 125.5 GeV Higgs Boson in F-SU(5): Imminently Observable Proton Decay, A 130 GeV Gamma-ray Line, and SUSY Multijets & Light Stops at the LHC8
We establish that the light Higgs boson mass in the context of the No-Scale
Flipped SU(5) GUT with TeV scale vector-like matter multiplets (flippons) is
consistent with m_h = 125.5+-0.5 GeV in the region of the best supersymmetry
(SUSY) spectrum fit to low statistics data excesses observed by ATLAS in
multijet and light stop 5/fb SUSY searches at the LHC7. Simultaneous
satisfaction of these disparate goals is achieved by employing a minor decrease
in the SU(5) partial unification scale M_{32} to lower the flippon mass,
inducing a larger Higgs boson mass shift from the flippon loops. The reduction
in M_{32}, which is facilitated by a phenomenologically favorable reduction of
the low-energy strong coupling constant, moreover suggests an imminently
observable (e|mu)^+ pi^0 proton decay with a central value time scale of
1.7x10^34 years. At the same point in the model space, we find a lightest
neutralino mass of m_{\chi} = 145 GeV, which is suitable for the production of
130 GeV monochromatic gamma-rays through annihilations yielding associated
Z-bosons; a signal with this energy signature has been identified within
observations of the galactic center by the FERMI-LAT Space Telescope. In
conjunction with direct correlations to the fate of the ATLAS multijet and
light stop production channels presently being tested at the LHC8, we suggest
that the reality of a 125.5 GeV Higgs boson affords a particularly rich company
of specific and imminently testable associated observables.Comment: European Physical Journal C Version; 10 Pages, 2 Figures, 2 Table
Non-trivial Supersymmetry Correlations between ATLAS and CMS Observations
We present definite correlations between the CMS 5 \fb all-hadronic search
employing the stransverse mass variable and the ATLAS 5 \fb
all-hadronic and multijet supersymmetry (SUSY) searches, suggesting the
possibility that both the ATLAS and CMS experiments are already registering a
faint but legitimate SUSY signal at the LHC. We isolate this prospective mutual
productivity beyond the Standard Model in the framework of the supersymmetric
No-Scale Flipped (5) grand unified theory, supplemented with extra
vector-like matter (flippons). Evident overproduction is observed in three CMS
\mt2 and four ATLAS hadronic and multijet signal regions, where a \x2 fitting
procedure of the CMS 5 \fb \mt2 search establishes a best fit SUSY mass in
sharp agreement with corresponding ATLAS searches of equivalently heightened
signal significance. We believe this correlated behavior across two distinct
experiments at precisely the same SUSY mass scale to be highly non-trivial, and
potentially indicative of an existing 5 \fb LHC reach into a pervasive physical
supersymmetry framework.Comment: 6 Pages, 2 Figure
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