534 research outputs found
f [N pi N]: from quarks to the pion derivative coupling
We study the N pi N coupling, in the framework of a QCD-inspired confining
Nambu-Jona-Lasinio model. A simple relativistic confining and instantaneous
quark model is reviewed. The Salpeter equation for the nucleon and the boosted
pion is solved. The f [n pi n] and f[n pi Delta] couplings are calculated and
they turn out to be reasonably good. The sensibility of f[n pi n] and f[n pi
Delta] to confinement, chiral symmetry breaking and Lorentz invariance is
briefly discussed.Comment: 30 pages in LaTex RevTex, 6 postscript figure
Analytical approach to chiral symmetry breaking in Minkowsky space
The mass gap equation for spontaneous chiral symmetry breaking is studied
directly in Minkowsky space. In hadronic physics, spontaneous chiral symmetry
breaking is crucial to generate a constituent mass for the quarks, and to
produce the Partially Conserved Axial Current theorems, including a small mass
for the pion. Here a class of finite kernels is used, expanded in Yukawa
interactions. The Schwinger-Dyson equation is solved with an analytical
approach. This improves the state of the art of solving the mass gap equation,
which is usually solved with the equal-time approximation or with the Euclidean
approximation. The mapping from the Euclidean space to the Minkowsky space is
also illustrated.Comment: 7 pages, 3 figure
Field theory description of vacuum replicas
In this paper we develop a systematic quantum field theory based approach to
the vacuum replica recently found to exist in effective low energy models in
hadronic physics. A local operator creating the replica state is constructed
explicitly. We show that a new effective quark-quark force arises in result of
replica existence. Phenomenological implications of such a force are also
briefly discussed.Comment: RevTeX4, 23 pages, 4 Postscript figures, uses epsfig.sty, to appear
in Phys.Rev.
Confinement and chiral symmetry breaking in heavy-light quark systems
Assuming a Gaussian approximation for the QCD gluodynamics, all the
nonperturbative physics can be encoded into two parameters: the gluon
correlation length and the gluon condensate . These parameters are
sufficient in order to describe the heavy-heavy quark nonperturbative
interaction. In this work we adopt the same framework in order to study
heavy-light bound states in the non-recoil limit. Spontaneous chiral symmetry
breaking and a confining chiral non-invariant interaction emerge quite
naturally. The gap equation is solved and discussed. In particular a relation
between the light quark condensate and is derived. The energy spectrum
for the bound state equation is evaluated and commented.Comment: 15 pages, 2 figures, elsart.st
Chiral corrections to baryon properties with composite pions
A calculational scheme is developed to evaluate chiral corrections to
properties of composite baryons with composite pions. The composite baryons and
pions are bound states derived from a microscopic chiral quark model. The model
is amenable to standard many-body techniques such as the BCS and RPA
formalisms. An effective chiral model involving only hadronic degrees of
freedom is derived from the macroscopic quark model by projection onto hadron
states. Chiral loops are calculated using the effective hadronic Hamiltonian. A
simple microscopic confining interaction is used to illustrate the derivation
of the pion-nucleon form factor and the calculation of pionic self-energy
corrections to the nucleon and Delta(1232) masses.Comment: 29 pages, Revtex, 4 ps figure
Advanced therapies and the Brexit process: emerging geographies of legal responsibilities and market opportunities
This paper analyses how so-called Brexit, that is the United Kingdom’s departure from the European Union (EU), has modified the regional geography of Advanced Therapy Medicinal Products (ATMPs). The latter are therapies deriving from cell manipulation, gene editing, tissue engineering, or a combination of these techniques. Their development and delivery have been realised through research collaborations and commercial relations of international scope. In the EU, this has happened by means of a complex distribution of commercial activities and legal responsibilities. With Brexit, three main kinds of reconfigurations have occurred: the relocation of research and manufacturing activities; the reorganisation of quality control tests aimed to manage clinical risks; and the redistribution of legal responsibilities and representatives. This technical and legal reconfiguration is captured here by means of theoretical insights from the emerging domain of legal geography. Drawing on interviews conducted with both EU and UK professionals involved in ATMP development, this paper reveals the main challenges brought by Brexit to the current and future configuration of the ATMP landscape in the EU and the UK. Furthermore, it demonstrates how shifts in legal arrangements impact on science-intensive domains
Two-meson cloud contribution to the baryon antidecuplet self-energy
We study the self-energy of the SU(3) antidecuplet coming from two-meson
virtual clouds. Assuming that the exotic Theta+ belongs to an antidecuplet
representation with N(1710) as nucleon partner, we derive effective Lagrangians
that describe the decay of N(1710) into N pi pi with two pions in s- or p-wave.
It is found that the self-energies for all members of the antidecuplet are
attractive, and the larger strangeness particle is more bound. From two-meson
cloud, we obtain about 20 % of the empirical mass splitting between states with
different strangeness.Comment: 4 pages, 2 figures, 1 table, Talk given at the 10th International
Conference on Baryons (Baryons04), Palaiseau (France), October 25-29, 200
Repulsive Core of NN S-Wave Scattering in a Quark Model with a Condensed Vacuum
We work in a chiral invariant quark model, with a condensed vacuum,
characterized by only one parameter. Bound state equations for the nucleon and
Delta are solved in order to obtain an updated value of their radii and masses.
Nucleon-nucleon S-Wave scattering is studied in the RGM framework both for
isospin T=1 and T=0. The phase shifts are calculated and an equivalent local
potential, which is consistent with K-N scattering, is derived. The result is a
reasonable microscopic short range repulsion in the nucleon-nucleon
interaction.Comment: 23 pages in latex revtex, 4 Postscript figure
- …