10,608 research outputs found
Reflection positive doubles
Here we introduce reflection positive doubles, a general framework for reflection positivity, covering a wide variety of systems in statistical physics and quantum field theory. These systems may be bosonic, fermionic, or parafermionic in nature. Within the framework of reflection positive doubles, we give necessary and sufficient conditions for reflection positivity. We use a reflection-invariant cone to implement our construction. Our characterization allows for a direct interpretation in terms of coupling constants, making it easy to check in concrete situations. We illustrate our methods with numerous examples
Nano-scale oxygen octahedral tilting in 0.90(Bi1/2Na1/2)TiO3-0.05(Bi1/2K1/2)TiO3-0.05BaTiO3 lead-free perovskite piezoelectric ceramics
The oxygen octahedral tilted domains in
0.90(Bi1/2Na1/2)TiO3-0.5(Bi1/2K1/2)TiO3-0.5BaTiO3 lead-free perovskite
piezoelectric ceramic have been studied by transmission electron microscopy
(TEM). Selected-area electron diffraction patterns shows the 1/2ooo and 1/2ooe
reflections, indicating the presence of antiphase (a-a-a-) and in-phase
(aoaoc+) octahedral tilting, respectively. The morphology and distributions of
these tilted domains are shown in the centered dark-field images. Further, the
Bragg-filtered high-resolution TEM image reveals that the size of the in-phase
tilted domains varies from 1 to 8 nm across. The ceramic contains the mixture
of non-tilted and variants of the antiphase and in-phase tilted domains.Comment: 12 pages, 3 figure
Ex-ante measure of patent quality reveals intrinsic fitness for citation-network growth
We have constructed a fitness parameter, characterizing the intrinsic
attractiveness for patents to be cited, from attributes of the associated
inventions known at the time a patent is granted. This exogenously obtained
fitness is shown to determine the temporal growth of the citation network in
conjunction with mechanisms of preferential attachment and obsolescence-induced
ageing that operate without reference to characteristics of individual patents.
Our study opens a window on understanding quantitatively the interplay of the
rich-gets-richer and fit-gets-richer paradigms that have been suggested to
govern the growth dynamics of real-world complex networks.Comment: 6 pages, 3 figures, RevTex4.1, v2: minor changes, version to appear
as a Rapid Communication in Phys. Rev.
Unraveling the dynamics of growth, aging and inflation for citations to scientific articles from specific research fields
We analyze the time evolution of citations acquired by articles from journals
of the American Physical Society (PRA, PRB, PRC, PRD, PRE and PRL). The
observed change over time in the number of papers published in each journal is
considered an exogenously caused variation in citability that is accounted for
by a normalization. The appropriately inflation-adjusted citation rates are
found to be separable into a preferential-attachment-type growth kernel and a
purely obsolescence-related (i.e., monotonously decreasing as a function of
time since publication) aging function. Variations in the empirically extracted
parameters of the growth kernels and aging functions associated with different
journals point to research-field-specific characteristics of citation intensity
and knowledge flow. Comparison with analogous results for the citation dynamics
of technology-disaggregated cohorts of patents provides deeper insight into the
basic principles of information propagation as indicated by citing behavior.Comment: 13 pages, 6 figures, Elsevier style, v2: revised version to appear in
J. Informetric
Effect of magnetic field and temperature on the ferroelectric loop in MnWO4
The ferroelectric properties of MnWO4 single crystal have been investigated.
Despite a relatively low remanent polarization, we show that the sample is
ferroelectric. The shape of the ferroelectric loop of MnWO4 strongly depends on
magnetic field and temperature. While its dependence does not directly
correlate with the magnetocapacitance effect before the paraelectric
transition, the effect of magnetic field on the ferroelectric polarization loop
supports magnetoelectric coupling.Comment: 3 pages, 4 figures, first report on ferroelectric loop in MnWO
Evidence from Patents and Patent Citations on the Impact of NASA and Other Federal Labs on Commercial Innovation
We explore the commercialization of government-generated technology by analyzing patents awarded to the U.S. government and the citations to those patents from subsequent patents. We use information on citations to federal patents in two ways: (1) to compare the average technological impact of NASA patents, other Federal' patents, and a random sample of all patents using measures of importance' and generality;' and (2) to trace the geographic location of commercial development by focusing on the location of inventors who cite NASA and other federal patents. We find, first, that the evidence is consistent with increased effort to commercialize federal lab technology generally and NASA specifically. The data reveal a striking NASA golden age' during the second half of the 1970s which remains a puzzle. Second, spillovers are concentrated within a federal lab complex of states representing agglomerations of labs and companies. The technology complex links five NASA states through patent citations: California, Texas, Ohio, DC/Virginia-Maryland, and Alabama. Third, qualitative evidence provides some support for the use of patent citations as proxies for both technological impact and knowledge spillovers.
On the relation between nuclear and nucleon Structure Functions and their moments
Calculations of nuclear Structure Functions (SF) F_k^A(x,Q^2) routinely
exploit a generalized convolution, involving the SF for nucleons F_k^N and the
linking SF f^{PN,A} of a fictitious nucleus, composed of point-particles, with
the latter usually expressed in terms of hadronic degrees of freedom. For
finite Q^2 the approach seemed to be lacking a solid justification and the same
is the case for recently proposed, effective nuclear parton distribution
functions (pdf), which exactly reproduce the above-mentioned hadronically
computed F_k^A. Many years ago Jaffe and West proved the above convolution in
the Plane Wave Impulse Approximation (PWIA) for the nuclear components in the
convolution. In the present note we extend the above proof to include classes
of nuclear Final State Interactions (FSI). One and the same function appears to
relate parton distribution functions (pdf) in nuclei and nucleons, and SF for
nuclear targets and for nucleons. That relation is the previously conjectured
one,with an entirely different interpretation of f^{PN,A}. We conclude with an
extensive analysis of moments of nuclear SF based on the generalized
convolution. Characteristics of those moments are shown to be quite similar to
the same for a nucleon. We conclude that the above evidences asymptotic freedom
of a nucleon in a medium and not of a composite nucleus.Comment: 18 pages, 9 figure
Einstein's mirror revisited
We describe a simple geometrical derivation of the formula for reflection of
light from a uniformly moving plane mirror directly from the postulates of
special relativity.Comment: 4 pages, 5 figures, RevTeX4, comments welcome; V2: corrected Fig. 5
and the discussion associated with it, co-author include
OPE analysis for polarized deep inelastic scattering
We present an explicit OPE analysis for the first moment of up to order
. This result allows to calculate power corrections to the Bjorken and
Ellis--Jaffe sum rules.Comment: 10 pages, minor modifications, revised version for the journa
Existence of Multiple Vortices in Supersymmetric Gauge Field Theory
Two sharp existence and uniqueness theorems are presented for solutions of
multiple vortices arising in a six-dimensional brane-world supersymmetric gauge
field theory under the general gauge symmetry group and
with Higgs scalar fields in the fundamental representation of .
Specifically, when the space of extra dimension is compact so that vortices are
hosted in a 2-torus of volume |\Om|, the existence of a unique multiple
vortex solution representing respectively prescribed vortices
arising in the species of the Higgs fields is established under the
explicitly stated necessary and sufficient condition \[ n_i<\frac{g^2v^2}{8\pi
N}|\Om|+\frac{1}{N}(1-\frac{1}{N}[\frac{g}{e}]^2)n,\quad i=1,...,N,] where
and are the U(1) electromagnetic and SU(N) chromatic coupling constants,
measures the energy scale of broken symmetry, and is
the total vortex number; when the space of extra dimension is the full plane,
the existence and uniqueness of an arbitrarily prescribed -vortex solution
of finite energy is always ensured. These vortices are governed by a system of
nonlinear elliptic equations, which may be reformulated to allow a variational
structure. Proofs of existence are then developed using the methods of calculus
of variations.Comment: 23 page
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