6,008 research outputs found
Deconfinement vs. chiral symmetry and higher representation matter
The interplay of deconfinement and chiral symmetry restoration are considered
in terms of effective theories. We generalize the earlier model studies by
considering fermions in higher representations, and study the finite
temperature phase diagrams of SU(2) and SU(3) gauge theories with two fermion
flavors in fundamental, adjoint or two-index symmetric representations. We
discuss our results in relation to recent lattice simulations on these theories
and outline possible applications in the context of dynamical electroweak
symmetry breaking.Comment: 13 pages, 6 figure
Discriminating between technicolor and warped extra dimensional model via pp ZZ channel
We explore the possibility to discriminate between certain strongly-coupled
technicolor (TC) models and warped extra-dimensional models where the Standard
Model fields are propagating in the extra dimension. We consider a generic
QCD-like TC model with running coupling as well as two TC models with walking
dynamics. We argue that due to the different production mechanisms for the
lowest-lying composite tensor state in these TC theories compared to the first
Kaluza-Klein graviton mode of warped extra-dimensional case, it is possible to
distinguish between these models based on the angular analysis of the
reconstructed longitudinal Z bosons in the four charged
leptons channel.Comment: 16 pages, 3 figures, 1 tabl
On finite-temperature holographic QCD in the Veneziano limit
Holographic models in the T=0 universality class of QCD in the limit of large
number N_c of colors and N_f massless fermion flavors, but constant ratio
x_f=N_f/N_c, are analyzed at finite temperature. The models contain a
5-dimensional metric and two scalars, a dilaton sourcing TrF^2 and a tachyon
dual to \bar qq. The phase structure on the T,x_f plane is computed and various
1st order, 2nd order transitions and crossovers with their chiral symmetry
properties are identified. For each x_f, the temperature dependence of p/T^4
and the quark-antiquark -condensate is computed. In the simplest case, we find
that for x_f up to the critical x_c\sim 4 there is a 1st order transition on
which chiral symmetry is broken and the energy density jumps. In the conformal
window x_c<x_f<11/2, there is only a continuous crossover between two conformal
phases. When approaching x_c from below, x_f\to x_c, temperature scales
approach zero as specified by Miransky scaling.Comment: 66 pages, 29 figure
Confinement and Chiral Symmetry
We illustrate why color deconfines when chiral symmetry is restored in gauge
theories with quarks in the fundamental representation, and while these
transitions do not need to coincide when quarks are in the adjoint
representation, entanglement between them is still present.Comment: 4 pages, 1 figure, proceedings of Quark Matter 200
Measurement of Magnetization Dynamics in Single-Molecule Magnets Induced by Pulsed Millimeter-Wave Radiation
We describe an experiment aimed at measuring the spin dynamics of the Fe8
single-molecule magnet in the presence of pulsed microwave radiation. In
earlier work, heating was observed after a 0.2-ms pulse of intense radiation,
indicating that the spin system and the lattice were out of thermal equilibrium
at millisecond time scale [Bal et al., Europhys. Lett. 71, 110 (2005)]. In the
current work, an inductive pick-up loop is used to probe the photon-induced
magnetization dynamics between only two levels of the spin system at much
shorter time scales (from ns to us). The relaxation time for the magnetization,
induced by a pulse of radiation, is found to be on the order of 10 us.Comment: 3 RevTeX pages, including 3 eps figures. The paper will appear in the
Journal of Applied Physics as MMM'05 conference proceeding
Optical quality assurance of GEM foils
An analysis software was developed for the high aspect ratio optical scanning
system in the Detec- tor Laboratory of the University of Helsinki and the
Helsinki Institute of Physics. The system is used e.g. in the quality assurance
of the GEM-TPC detectors being developed for the beam diagnostics system of the
SuperFRS at future FAIR facility. The software was tested by analyzing five
CERN standard GEM foils scanned with the optical scanning system. The
measurement uncertainty of the diameter of the GEM holes and the pitch of the
hole pattern was found to be 0.5 {\mu}m and 0.3 {\mu}m, respectively. The
software design and the performance are discussed. The correlation between the
GEM hole size distribution and the corresponding gain variation was studied by
comparing them against a detailed gain mapping of a foil and a set of six lower
precision control measurements. It can be seen that a qualitative estimation of
the behavior of the local variation in gain across the GEM foil can be made
based on the measured sizes of the outer and inner holes.Comment: 12 pages, 29 figure
Switching of +/-360deg domain wall states in a nanoring by an azimuthal Oersted field
We demonstrate magnetic switching between two domain wall vortex
states in cobalt nanorings, which are candidate magnetic states for robust and
low power MRAM devices. These domain wall (DW) or "twisted onion"
states can have clockwise or counterclockwise circulation, the two states for
data storage. Reliable switching between the states is necessary for any
realistic device. We accomplish this switching by applying a circular Oersted
field created by passing current through a metal atomic force microscope tip
placed at the center of the ring. After initializing in an onion state, we
rotate the DWs to one side of the ring by passing a current through the center,
and can switch between the two twisted states by reversing the current, causing
the DWs to split and meet again on the opposite side of the ring. A larger
current will annihilate the DWs and create a perfect vortex state in the rings.Comment: 5 pages, 5 figure
- âŠ