1,185 research outputs found
Better Higgs-CP Tests Through Information Geometry
Measuring the CP symmetry in the Higgs sector is one of the key tasks of the
LHC and a crucial ingredient for precision studies, for example in the language
of effective Lagrangians. We systematically analyze which LHC signatures offer
dedicated CP measurements in the Higgs-gauge sector, and discuss the nature of
the information they provide. Based on the Fisher information measure, we
compare the maximal reach for CP-violating effects in weak boson fusion,
associated ZH production, and Higgs decays into four leptons. We find a subtle
balance between more theory-independent approaches and more powerful analysis
channels, indicating that rigorous evidence for CP violation in the Higgs-gauge
sector will likely require a multi-step process.Comment: 27 pages, 8 figure
Heavy metals tolerance limits : terminal progress report
The toxicity of .metal ions Lo fresh-water organisms has received considerable attention but little is known regarding their effects on estuarine and marine forms. These studies were initiated to aid in the evaluation of marine pollution problems
Phase diagram of an exactly solvable t-J ladder model
We study a system of one-dimensional t-J models coupled to a ladder system. A
special choice of the interaction between neighbouring rungs leads to an
integrable model with supersymmetry, which is broken by the presence of rung
interactions. We analyze the spectrum of low-lying excitations and ground state
phase diagram at zero temperature.Comment: LaTeX, 8 pp. incl. 1 figur
An Exactly Solvable Model of Generalized Spin Ladder
A detailed study of an spin ladder model is given. The ladder
consists of plaquettes formed by nearest neighbor rungs with all possible
SU(2)-invariant interactions. For properly chosen coupling constants, the model
is shown to be integrable in the sense that the quantum Yang-Baxter equation
holds and one has an infinite number of conserved quantities. The R-matrix and
L-operator associated with the model Hamiltonian are given in a limiting case.
It is shown that after a simple transformation, the model can be solved via a
Bethe ansatz. The phase diagram of the ground state is exactly derived using
the Bethe ansatz equation
On the dynamics of coupled S=1/2 antiferromagnetic zig-zag chains
We investigate the elementary excitations of quasi one-dimensional S=1/2
systems built up from zig-zag chains with general isotropic exchange constants,
using exact (Lanczos) diagonalization for 24 spins and series expansions
starting from the decoupled dimer limit. For the ideal one-dimensional zig-zag
chain we discuss the systematic variation of the basic (magnon) triplet
excitation with general exchange parameters and in particular the presence of
practically flat dispersions in certain regions of phase space. We extend the
dimer expansion in order to include the effects of 3D interactions on the
spectra of weakly interacting zig-zag chains. In an application to KCuCl_3 we
show that this approach allows to determine the exchange interactions between
individual pairs of spins from the spectra as determined in recent neutron
scattering experiments.Comment: 8 pages, 9 figures; some changes, figure added; final versio
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