49,581 research outputs found
Presymmetry beyond the Standard Model
We go beyond the Standard Model guided by presymmetry, the discrete
electroweak quark-lepton symmetry hidden by topological effects which explain
quark fractional charges as in condense matter physics. Partners of the
particles of the Standard Model and the discrete symmetry associated with this
partnership appear as manifestations of a residual presymmetry and its
extension from matter to forces. This duplication of the spectrum of the
Standard Model keeps spin and comes nondegenerated about the TeV scale.Comment: 6 pages, 11 figures. To be published in the proceedings of DPF-2009,
Detroit, MI, July 2009, eConf C09072
Classification of finite irreducible modules over the Lie conformal superalgebra CK6
We classify all continuous degenerate irreducible modules over the
exceptional linearly compact Lie superalgebra E(1, 6), and all finite
degenerate irreducible modules over the exceptional Lie conformal superalgebra
CK6, for which E(1, 6) is the annihilation algebra
Modulation Doping near Mott-Insulator Heterojunctions
We argue that interesting strongly correlated two-dimensional electron
systems can be created by modulation doping near a heterojunction between Mott
insulators. Because the dopant atoms are remote from the carrier system, the
electronic system will be weakly disordered. We argue that the competition
between different ordered states can be engineered by choosing appropriate
values for the dopant density and the setback distance of the doping layer. In
particular larger setback distances favor two-dimensional antiferromagnetism
over ferromagnetism. We estimate some key properties of modulation-doped Mott
insulator heterojunctions by combining insights from Hartree-Fock-Theory and
Dynamical-Mean-Field-Theory descriptions and discuss potentially attractive
material combinations.Comment: 9 pages, 9 figures, submitte
Colossal negative magnetoresistance in dilute fluorinated graphene
Adatoms offer an effective route to modify and engineer the properties of
graphene. In this work, we create dilute fluorinated graphene using a clean,
controlled and reversible approach. At low carrier densities, the system is
strongly localized and exhibits an unexpected, colossal negative
magnetoresistance. The zero-field resistance is reduced by a factor of 40 at
the highest field of 9 T and shows no sign of saturation. Unusual "staircase"
field dependence is observed below 5 K. The magnetoresistance is highly
anisotropic. We discuss possible origins, considering quantum interference
effects and adatom-induced magnetism in graphene.Comment: 21 pages, 4 figures, including supplementary informatio
Matrix Norms
In many situations it is very useful to have a single nonnegative real number to be, in some sense, the measure of the size of a vector or a matrix. As a matter of fact we do a similiar thing with scalars, we let jÀj represent the familiar absolute value or modulus of À. Fora vector x e: C , one way n of assigning magnitude is the usual definition of length, Il I 1/2 2 1/2 xl= = {jxij } , which is called the euclidean norm of x. In this case, length gives an overall estimate of the size of the elements of x. If llxll is large, at least one of the elements in x is large, and vise versa. There are many ways of defining norms for vectors and matrices. We will examine some of these in this paper
Local density of states of a d-wave superconductor with inhomogeneous antiferromagnetic correlations
The tunneling spectrum of an inhomogeneously doped extended Hubbard model is
calculated at the mean field level. Self-consistent solutions admit both
superconducting and antiferromagnetic order, which coexist inhomogeneously
because of spatial randomness in the doping. The calculations find that, as a
function of doping, there is a continuous cross over from a disordered ``pinned
smectic'' state to a relatively homogeneous d-wave state with pockets of
antiferromagnetic order. The density of states has a robust d-wave gap, and
increasing antiferromagnetic correlations lead to a suppression of the
coherence peaks. The spectra of isolated nanoscale antiferromagnetic domains
are studied in detail, and are found to be very different from those of
macroscopic antiferromagnets. Although no single set of model parameters
reproduces all details of the experimental spectrum in BSCCO, many features,
notably the collapse of the coherence peaks and the occurence of a low-energy
shoulder in the local spectrum, occur naturally in these calculations.Comment: 9 pages, 5 figure
Measuring Invisible Particle Masses Using a Single Short Decay Chain
We consider the mass measurement at hadron colliders for a decay chain of two
steps, which ends with a missing particle. Such a topology appears as a
subprocess of signal events of many new physics models which contain a dark
matter candidate. From the two visible particles coming from the decay chain,
only one invariant mass combination can be formed and hence it is na\"ively
expected that the masses of the three invisible particles in the decay chain
cannot be determined from a single end point of the invariant mass
distribution. We show that the event distribution in the
vs. invariant mass-squared plane, where , are the transverse
energies of the two visible particles, contains the information of all three
invisible particle masses and allows them to be extracted individually. The
experimental smearing and combinatorial issues pose challenges to the mass
measurements. However, in many cases the three invisible particle masses in the
decay chain can be determined with reasonable accuracies.Comment: 45 pages, 32 figure
Viscous Effects on Elliptic Flow and Shock Waves
Fast thermalization and a strong buildup of elliptic flow of QCD matter as
found at RHIC are understood as the consequence of perturbative QCD (pQCD)
interactions within the 3+1 dimensional parton cascade BAMPS. The main
contributions stem from pQCD bremsstrahlung processes.
By comparing to Au+Au data of the flow parameter as a function of
participation number the shear viscosity to entropy ratio is dynamically
extracted, which lies in the range of 0.08 and 0.2, depending on the chosen
coupling constant and freeze out condition. Furthermore, first simulations on
the temporal propagation of dissipative shock waves are given. The cascade can
either simulate true ideal shocks as well as initially diluted, truely viscous
shocks, depending on the employed cross sections or mean free path,
respectively.Comment: 7 pages, 8 figures, to appear in the proceedings of the 2008 Erice
School on Nuclear Physics, Sicil
- …