6,057 research outputs found
Using baryon octet magnetic moments and masses to fix the pion cloud contribution
Using SU(3) symmetry to constrain the pion BB' couplings, assuming SU(3)
breaking comes only from one-loop pion cloud contributions, and using the the
covariant spectator theory to describe the photon coupling to the quark core,
we show how the experimental masses and magnetic moments of the baryon octet
can be used to set a model independent constraint on the strength of the pion
cloud contributions to the octet, and hence the nucleon, form factors at Q2=0.Comment: 7 pages, 1 figur
Gauging the three-nucleon spectator equation
We derive relativistic three-dimensional integral equations describing the
interaction of the three-nucleon system with an external electromagnetic field.
Our equations are unitary, gauge invariant, and they conserve charge. This has
been achieved by applying the recently introduced gauging of equations method
to the three-nucleon spectator equations where spectator nucleons are always on
mass shell. As a result, the external photon is attached to all possible places
in the strong interaction model, so that current and charge conservation are
implemented in the theoretically correct fashion. Explicit expressions are
given for the three-nucleon bound state electromagnetic current, as well as the
transition currents for the scattering processes
\gamma He3 -> NNN, Nd -> \gamma Nd, and \gamma He3 -> Nd. As a result, a
unified covariant three-dimensional description of the NNN-\gamma NNN system is
achieved.Comment: 23 pages, REVTeX, epsf, 4 Postscript figure
Children's Oncology Group's 2013 blueprint for research: NonâHodgkin lymphoma
NonâHodgkin lymphomas account for approximately 7% of cancers diagnosed in patients less than 20 years of age, with approximately 800 cases diagnosed annually at COG institutions. With current therapies, cure rates range from 70% to over 90%, even for children with disseminated disease. However, two major challenges need to be overcome: (i) to optimize upfront treatment to prevent relapse since prognosis for patients with relapsed disease remains poor and (ii) minimize longâterm side effects in survivors. Hence, the future initiatives for the treatment of pediatric NHL are to utilize novel targeted therapies to not only improve outcomes but to decrease bystander organ toxicities and late effects. Pediatr Blood Cancer 2013; 60: 979â984. © 2012 Wiley Periodicals, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97477/1/24416_ftp.pd
Multi-phonon scattering and Ti-induced hydrogen dynamics in sodium alanate
We use ab initio methods and neutron inelastic scattering (NIS) to study the
structure, energetics, and dynamics of pure and Ti-doped sodium alanate
(NaAlH_4), focusing on the possibility of substitutional Ti doping. The NIS
spectrum is found to exhibit surprisingly strong and sharp two-phonon features.
The calculations reveal that substitutional Ti doping is energetically
possible. Ti prefers to substitute for Na and is a powerful hydrogen attractor
that facilitates multiple Al--H bond breaking. Our results hint at new ways of
improving the hydrogen dynamics and storage capacity of the alanates.Comment: 5 pages, with 4 postscript figures embedded. Uses REVTEX4 and
graphicx macro
Mathematics and Morphogenesis of the City: A Geometrical Approach
Cities are living organisms. They are out of equilibrium, open systems that
never stop developing and sometimes die. The local geography can be compared to
a shell constraining its development. In brief, a city's current layout is a
step in a running morphogenesis process. Thus cities display a huge diversity
of shapes and none of traditional models from random graphs, complex networks
theory or stochastic geometry takes into account geometrical, functional and
dynamical aspects of a city in the same framework. We present here a global
mathematical model dedicated to cities that permits describing, manipulating
and explaining cities' overall shape and layout of their street systems. This
street-based framework conciliates the topological and geometrical sides of the
problem. From the static analysis of several French towns (topology of first
and second order, anisotropy, streets scaling) we make the hypothesis that the
development of a city follows a logic of division / extension of space. We
propose a dynamical model that mimics this logic and which from simple general
rules and a few parameters succeeds in generating a large diversity of cities
and in reproducing the general features the static analysis has pointed out.Comment: 13 pages, 13 figure
Conference Discussion of the Nuclear Force
Discussion of the nuclear force, lead by a round table consisting of T.
Cohen, E. Epelbaum, R. Machleidt, and F. Gross (chair). After an invited talk
by Machleidt, published elsewhere in these proceedings, brief remarks are made
by Epelbaum, Cohen, and Gross, followed by discussion from the floor moderated
by the chair. The chair asked the round table and the participants to focus on
the following issues: (i) What does each approach (chiral effective field
theory, large Nc, and relativistic phenomenology) contribute to our knowledge
of the nuclear force? Do we need them all? Is any one transcendent? (ii) How
important for applications (few body, nuclear structure, EMC effect, for
example) are precise fits to the NN data below 350 MeV? How precise do these
fits have to be? (iii) Can we learn anything about nonperturbative QCD from
these studies of the nuclear force? The discussion presented here is based on a
video recording made at the conference and transcribed afterward.Comment: Discussion at the 21st European Conference on Few Body Problems
(EFP21) held at Salamanca, Spain, 30 Aug - 3 Sept 201
Higher-Loop Corrections to the Infrared Evolution of a Gauge Theory with Fermions
We consider a vectorial, asymptotically free gauge theory and analyze the
effect of higher-loop corrections to the beta function on the evolution of the
theory from the ultraviolet to the infrared. We study the case in which the
theory contains copies of a fermion transforming according to the
fundamental representation and several higher-dimensional representations of
the gauge group. We also calculate higher-loop values of the anomalous
dimension of the mass, of at the infrared zero of the
beta function. We find that for a given theory, the values of
calculated to three- and four-loop order, and evaluated at the infrared zero
computed to the same order, tend to be somewhat smaller than the value
calculated to two-loop order. The results are compared with recent lattice
simulations.Comment: 22 pages, latex, matches Phys. Rev. D publicatio
Gauging the spectator equations
We show how to derive relativistic, unitary, gauge invariant, and charge
conserving three-dimensional scattering equations for a system of hadrons
interacting with an electromagnetic field. In the method proposed, the
spectator equations describing the strong interactions of the hadrons are
gauged using our recently introduced gauging of equations method. A key
ingredient in our model is the on-mass-shell particle propagator. We discuss
how to gauge this on-mass-shell propagator so that both the Ward-Takahashi and
Ward identities are satisfied. We then demonstrate our gauging procedure by
deriving the gauge-invariant three-dimensional expression for the deuteron
photodisintegration amplitude within the spectator approach.Comment: 17 pages, REVTeX, epsf, 1 Postscript figur
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