3,779 research outputs found
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
Halogen bonding enhances nonlinear optical response in poled supramolecular polymers
We demonstrate that halogen bonding strongly enhances the nonlinear optical response of poled supramolecular polymer systems. We compare three nonlinear optical chromophores with similar electronic structures but different bond-donating units, and show that both the type and the strength of the noncovalent interaction between the chromophores and the polymer matrix play their own distinctive roles in the optical nonlinearity of the systems
Constraints on Conformal Windows from Holographic Duals
We analyze a beta function with the analytic form of
Novikov-Shifman-Vainshtein-Zakharov result in the five dimensional
gravity-dilaton environment. We show how dilaton inherits poles and fixed
points of such beta function through the zeros and points of extremum in its
potential. Super Yang-Mills and supersymmetric QCD are studied in detail and
Seiberg's electric-magnetic duality in the dilaton potential is explicitly
demonstrated. Non-supersymmetric proposals of similar functional form are
tested and new insights into the conformal window as well as determinations of
scheme-independent value of the anomalous dimension at the fixed point are
presented.Comment: Fig. 5b is corrected to match the discussion in the tex
Magnetic Doppler Imaging of Active Stars
We present a new implementation of the magnetic Doppler imaging technique,
which aims at self-consistent temperature and magnetic mapping of the surface
structures in cool active stars. Our magnetic imaging procedure is unique in
its capability to model individual spectral features in all four Stokes
parameters. We discuss performance and intrinsic limitations of the new
magnetic Doppler imaging method. A special emphasis is given to the
simultaneous modelling of the magnetically sensitive lines in the optical and
infrared regions and to combining information from both atomic and molecular
spectral features. These two techniques may, for the first time, give us a tool
to study magnetic fields in the starspot interiors.Comment: 4 pages, 3 figures; to appear in the proceedings of Solar
Polarization Workshop 5, ASP Conf. Se
Doppler images of II Pegasi for 2004-2010
Aims. We study the spot activity of II Peg during the years 2004-2010 to
determine long- and short-term changes in the magnetic activity. In a previous
study, we detected a persistent active longitude, as well as major changes in
the spot configuration occurring on a timescale of shorter than a year. The
main objective of this study is to determine whether the same phenomena persist
in the star during these six years of spectroscopic monitoring.
Methods. The observations were collected with the high-resolution SOFIN
spectrograph at the Nordic Optical Telescope. The temperature maps were
calculated using a Doppler imaging code based on Tikhonov regularization.
Results. We present 12 new temperature maps that show spots distributed
mainly over high and intermediate latitudes. In each image, 1-3 main active
regions can be identified. The activity level of the star is clearly lower than
during our previous study for the years 1994-2002. In contrast to the previous
observations, we detect no clear drift of the active regions with respect to
the rotation of the star.
Conclusions. Having shown a systematic longitudinal drift of the
spot-generating mechanism during 1994-2002, the star has clearly switched to a
low-activity state for 2004-2010, during which the spot locations appear more
random over phase space. It could be that the star is near to a minimum of its
activity cycle.Comment: Accepted for publication in Astron. and Astrophys., 8 pages, 5
figure
Superweakly interacting dark matter from the Minimal Walking Technicolor
We study a superweakly interacting dark matter particle motivated by minimal
walking technicolor theories. Our WIMP is a mixture of a sterile state and a
state with the charges of a standard model fourth family neutrino. We show that
the model can give the right amount of dark matter over a range of the WIMP
mass and mixing angle. We compute bounds on the model parameters from the
current accelerator data including the oblique corrections to the precision
electroweak parameters, as well as from cryogenic experiments, Super-Kamiokande
and from the IceCube experiment. We show that consistent dark matter solutions
exist which satisfy all current constraints. However, almost the entire
parameter range of the model lies within the the combined reach of the next
generation experiments.Comment: 29 pages, 6 figure
Halogen bonding enhances nonlinear optical response in poled supramolecular polymers
We demonstrate that halogen bonding strongly enhances the nonlinear optical response of poled supramolecular polymer systems. We compare three nonlinear optical chromophores with similar electronic structures but different bond-donating units, and show that both the type and the strength of the noncovalent interaction between the chromophores and the polymer matrix play their own distinctive roles in the optical nonlinearity of the systems
Critical Behavior of Non Order-Parameter Fields
We show that all of the relevant features of a phase transition can be
determined using a non order parameter field which is a physical state of the
theory. This fact allows us to understand the deconfining transition of the
pure Yang-Mills theory via the physical excitations rather than using the
Polyakov loop.Comment: RevTeX, 4-pages, 1 figur
Superconductivity in Ultrasmall Metallic Grains
We develop a theory of superconductivity in ultrasmall (nm-scale) metallic
grains having a discrete electronic eigenspectrum with a mean level spacing of
order of the bulk gap. The theory is based on calculating the eigenspectrum
using a generalized BCS variational approach, whose applicability has been
extensively demonstrated in studies of pairing correlations in nuclear physics.
We discuss how conventional mean field theory breaks down with decreasing
sample size, how the so-called blocking effect weakens pairing correlations in
states with non-zero total spin, and how this affects the discrete
eigenspectrum's behavior in a magnetic field, which favors non-zero total spin.
In ultrasmall grains, spin magnetism dominates orbital magnetism, just as in
thin films in a parallel field; but whereas in the latter the magnetic-field
induced transition to a normal state is known to be first-order, we show that
in ultrasmall grains it is softened by finite size effects. Our calculations
qualitatively reproduce the magnetic-field dependent tunneling spectra for
individual aluminum grains measured recently by Ralph, Black and Tinkham. We
argue that previously-discussed parity effects for the odd-even ground state
energy difference are presently not observable for experimental reasons, and
propose an analogous parity effect for the pair-breaking energy that should be
observable provided that the grain size can be controlled sufficiently well.
Finally, experimental evidence is pointed out that the dominant role played by
time-reversed pairs of states, well-established in bulk and in dirty
superconductors, persists also in ultrasmall grains.Comment: 21 pages RevTeX, 12 EPS figures included, uses epsf.st
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