19,185 research outputs found
Interplay between nanometer-scale strain variations and externally applied strain in graphene
We present a molecular modeling study analyzing nanometer-scale strain
variations in graphene as a function of externally applied tensile strain. We
consider two different mechanisms that could underlie nanometer-scale strain
variations: static perturbations from lattice imperfections of an underlying
substrate and thermal fluctuations. For both cases we observe a decrease in the
out-of-plane atomic displacements with increasing strain, which is accompanied
by an increase in the in-plane displacements. Reflecting the non-linear elastic
properties of graphene, both trends together yield a non-monotonic variation of
the total displacements with increasing tensile strain. This variation allows
to test the role of nanometer-scale strain variations in limiting the carrier
mobility of high-quality graphene samples
Echoes of the electroweak phase transition: discovering a second Higgs doublet through A0 â ZH0
The existence of a second Higgs doublet in nature could lead to a cosmological first-order electroweak
phase transition and explain the origin of the matter-antimatter asymmetry in the Universe. We obtain the
spectrum and properties of the new scalars H0, A0, and Hïżœ that signal such a phase transition and show that
the observation of the decay A0 â ZH0 at LHC would be a âsmoking gunâ signature of these scenarios. We
analyze the LHC search prospects for this decay in the llbbÂŻ and llWĂŸWâ final states, arguing that current
data may be sensitive to this signature in the former channel as well as there being great potential for a
discovery in either channel at the very early stages of the 14 TeV run
Is U3Ni3Sn4 best described as near a quantum critical point?
Although most known non-Fermi liquid (NFL) materials are structurally or
chemically disordered, the role of this disorder remains unclear. In
particular, very few systems have been discovered that may be stoichiometric
and well ordered. To test whether U3Ni3Sn4 belongs in this latter class, we
present measurements of the x-ray absorption fine structure (XAFS) of
polycrystalline and single-crystal U3Ni3Sn4 samples that are consistent with no
measurable local structural disorder. We also present temperature-dependent
specific heat data in applied magnetic fields as high as 8 T that show features
that are inconsistent with the antiferromagnetic Griffiths' phase model, but do
support the conclusion that a Fermi liquid/NFL crossover temperature increases
with applied field. These results are inconsistent with theoretical
explanations that require strong disorder effects, but do support the view that
U3Ni3Sn4 is a stoichiometric, ordered material that exhibits NFL behavior, and
is best described as being near an antiferromagnetic quantum critical point.Comment: 9 pages, 8 figures, in press with PR
R2D2 - a symmetric measurement of reactor neutrinos free of systematical errors
We discuss a symmetric setup for a reactor neutrino oscillation experiment
consisting of two reactors separated by about 1 km, and two symmetrically
placed detectors, one close to each reactor. We show that such a configuration
allows a determination of which is essentially free of
systematical errors, if it is possible to separate the contributions of the two
reactors in each detector sufficiently. This can be achieved either by
considering data when in an alternating way only one reactor is running or by
directional sensitivity obtained from the neutron displacement in the detector.Comment: 11 pages, 3 figures, clarifications added, some numbers in relation
with the neutron displacement corrected, version to appear in JHE
Composite MFV and Beyond
We revisit and extend realizations of Minimal Flavor Violation (MFV) in
theories with strongly coupled electro-weak symmetry breaking. MFV requires
that some chiralities of light SM quarks are strongly composite leading,
depending on the scenario, to bounds from compositeness searches, precision
electro-weak tests or even flavor physics. Within the framework of partial
compositeness we show how to extend the MFV paradigm allowing the treat the top
quark differently. This can be realized if for example the strong sector has an
U(2) symmetry. In this case the light generations can be mostly elementary and
all the bounds are easily satisfied.Comment: 16 pages. v2) estimates improved, conclusions unchange
Neutron star properties with relativistic equations of state
We study the properties of neutron stars adopting relativistic equations of
state of neutron star matter, calculated in the framework of the relativistic
Brueckner-Hartree-Fock approximation for electrically charge neutral neutron
star matter in beta-equilibrium. For higher densities more baryons (hyperons
etc.) are included by means of the relativistic Hartree- or Hartree-Fock
approximation. The special features of the different approximations and
compositions are discussed in detail. Besides standard neutron star properties
special emphasis is put on the limiting periods of neutron stars, for which the
Kepler criterion and gravitation-reaction instabilities are considered.
Furthermore the cooling behaviour of neutron stars is investigated, too. For
comparison we give also the outcome for some nonrelativistic equations of
state.Comment: 43 pages, 22 ps-figures, to be published in the International Journal
of Modern Physics
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