40,032 research outputs found
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
Renormalization of the Sigma-Omega model within the framework of U(1) gauge symmetry
It is shown that the Sigma-Omega model which is widely used in the study of
nuclear relativistic many-body problem can exactly be treated as an Abelian
massive gauge field theory. The quantization of this theory can perfectly be
performed by means of the general methods described in the quantum gauge field
theory. Especially, the local U(1) gauge symmetry of the theory leads to a
series of Ward-Takahashi identities satisfied by Green's functions and proper
vertices. These identities form an uniquely correct basis for the
renormalization of the theory. The renormalization is carried out in the
mass-dependent momentum space subtraction scheme and by the renormalization
group approach. With the aid of the renormalization boundary conditions, the
solutions to the renormalization group equations are given in definite
expressions without any ambiguity and renormalized S-matrix elememts are
exactly formulated in forms as given in a series of tree diagrams provided that
the physical parameters are replaced by the running ones. As an illustration of
the renormalization procedure, the one-loop renormalization is concretely
carried out and the results are given in rigorous forms which are suitable in
the whole energy region. The effect of the one-loop renormalization is examined
by the two-nucleon elastic scattering.Comment: 32 pages, 17 figure
Does the 2D Hubbard Model Really Show d-Wave Superconductivity?
Some issues concerning the question if the two-dimensional Hubbard model
really show d-wave superconductivity are briefly discussed.Comment: Revtex, no figure
Compensation of compliance errors in parallel manipulators composed of non-perfect kinematic chains
The paper is devoted to the compliance errors compensation for parallel
manipulators under external loading. Proposed approach is based on the
non-linear stiffness modeling and reduces to a proper adjusting of a target
trajectory. In contrast to previous works, in addition to compliance errors
caused by machining forces, the problem of assembling errors caused by
inaccuracy in the kinematic chains is considered. The advantages and practical
significance of the proposed approach are illustrated by examples that deal
with groove milling with Orthoglide manipulator.Comment: Advances in Robot Kinematics, France (2012
Aharonov-Casher phase and persistent current in a polyacetylene ring
We investigate a polyacetylene ring in an axially symmetric, static electric
field with a modified SSH Hamiltonian of a polyacetylene chain. An effective
gauge potential of the single electron Hamiltonian due to spin-field
interaction is obtained and it results in a Fr\"{o}hlich's type of
superconductivity equivalent to the effect of travelling lattice wave. The
total energy as well as the persistent current density are shown to be a
periodic function of the flux of the gauge field embraced by the polyacetylene
ring.Comment: 12 pages, 5 figure
Fermi gas in harmonic oscillator potentials
Assuming the validity of grand canonical statistics, we study the properties
of a spin-polarized Fermi gas in harmonic traps. Universal forms of Fermi
temperature , internal energy and the specific heat per particle of
the trapped Fermi gas are calculated as a {\it function} of particle number,
and the results compared with those of infinite number particles.Comment: 8 pages, 1 figure, LATE
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Palladium-Catalyzed Oxidation of β-C(sp3)-H Bonds of Primary Alkylamines through a Rare Four-Membered Palladacycle Intermediate.
Site-selective functionalizations of C-H bonds are often achieved with a directing group that leads to five- or six-membered metallacyclic intermediates. Analogous reactions that occur through four-membered metallacycles are rare. We report a challenging palladium-catalyzed oxidation of primary C-H bonds β to nitrogen in an imine of an aliphatic amine, a process that occurs through a four-membered palladacyclc intermediate. The success of the reaction relies on the identification, by H/D exchange, of a simple directing group (salicylaldehyde) capable of inducing the formation of this small ring. To gain insight into the steps of the catalytic cycle of this unusual oxidation reaction, a series of mechanistic experiments and density functional theory (DFT) calculations were conducted. The experimental studies showed that cleavage of the C-H bond is rate-limiting and formation of the strained four-membered palladacycle is thermodynamically uphill. DFT calculations corroborated these conclusions and suggested that the presence of an intramolecular hydrogen bond between the oxygen of the directing group and hydroxyl group of the ligating acetic acid is crucial for stabilization of the palladacyclic intermediate
Symmetry restrictions in chirality dependence of physical properties of single wall nanotubes
We investigate the chirality dependence of physical properties of nanotubes
which are wrapped by the planar hexagonal lattice including graphite and boron
nitride sheet, and reveal its symmetry origin. The observables under
consideration are of scalar, vector and tensor types. These exact chirality
dependence obtained are useful to verify the experimental and numerical results
and propose accurate empirical formulas. Some important features of physical
quantities can also be extracted by only considering the symmetry restrictions
without complicated calculations.Comment: 5 pages, 1 figure
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