75 research outputs found
Application of EFT at Thermal Energies
We have been evaluated some observables of n-d systems by using pionless
Effective Field Theory(\EFTNoPion) and insertion of the three-body force up to
next-to-next to leading order(NLO). The evaluated data has been compared
with experimental and the three-nucleon calculation of the total cross section
with modern realistic two- and three-nucleon forces AV18/UrbIX potential models
calculations.Comment: 3 pages, 1 figure and 1 table. Talk given at 20th European Conference
on Few-Body Problems in Physics (EFB 20), Pisa, Italy, 10-14 Sep 200
Coulomb interactions within Halo Effective Field Theory
I present preliminary results of effective field theory applied to nuclear
cluster systems, where Coulomb interactions play a significant role.Comment: Talk given at the 20th European Conference on Few-Body Problems in
Physics, Pisa, Italy, September 10-14, 200
Effective Field Theory for Few-Nucleon Systems
We review the effective field theories (EFTs) developed for few-nucleon
systems. These EFTs are controlled expansions in momenta, where certain
(leading-order) interactions are summed to all orders. At low energies, an EFT
with only contact interactions allows a detailed analysis of renormalization in
a non-perturbative context and uncovers novel asymptotic behavior. Manifestly
model-independent calculations can be carried out to high orders, leading to
high precision. At higher energies, an EFT that includes pion fields justifies
and extends the traditional framework of phenomenological potentials. The
correct treatment of QCD symmetries ensures a connection with lattice QCD.
Several tests and prospects of these EFTs are discussed.Comment: 55 pages, 18 figures, to appear in Ann. Rev. Nucl. Part. Sci. 52
(2002
Renormalization of minimally doubled fermions
We investigate the renormalization properties of minimally doubled fermions,
at one loop in perturbation theory. Our study is based on the two particular
realizations of Borici-Creutz and Karsten-Wilczek. A common feature of both
formulations is the breaking of hyper-cubic symmetry, which requires that the
lattice actions are supplemented by suitable counterterms. We show that three
counterterms are required in each case and determine their coefficients to one
loop in perturbation theory. For both actions we compute the vacuum
polarization of the gluon. It is shown that no power divergences appear and
that all contributions which arise from the breaking of Lorentz symmetry are
cancelled by the counterterms. We also derive the conserved vector and
axial-vector currents for Karsten-Wilczek fermions. Like in the case of the
previously studied Borici-Creutz action, one obtains simple expressions,
involving only nearest-neighbour sites. We suggest methods how to fix the
coefficients of the counterterms non-perturbatively and discuss the
implications of our findings for practical simulations.Comment: 23 pages, 1 figur
Strange two-baryon interactions using chiral effective field theory
We have constructed the leading order strangeness S=-1,-2 baryon-baryon
potential in a chiral effective field theory approach. The chiral potential
consists of one-pseudoscalar-meson exchanges and non-derivative four-baryon
contact terms. The potential, derived using SU(3)_f symmetry constraints,
contains six independent low-energy coefficients. We have solved a regularized
Lippmann-Schwinger equation and achieved a good description of the available
scattering data. Furthermore a correctly bound hypertriton has been obtained.Comment: 3 pages, 2 PostScript figures, talk to appear in the proceedings of
the "20th European Conference on Few-Body Problems in Physics (EFB20), Pisa,
Italy, 10-14 September 2007
Universality in Few-Body Systems
Low-energy universality in atomic few-body systems as a result of a large
two-body scattering length has gained a lot of attention recently. Here, I
discuss recent progress in describing the three-body recombination of cold
atoms in terms of a finite set of universal scaling functions and review
results for the recombination length of cesium-133 atoms obtained with these
functions. Furthermore, I will consider the inclusion of effective range
corrections and the relevance for further calculations in atomic and nuclear
physics.Comment: Plenary talk at 20th European Conference on Few-Body Problems in
Physics (EFB 20), Pisa, Italy, 10-14 Sep 2007, FBS style, 2 figue
Index Theorem and Overlap Formalism with Naive and Minimally Doubled Fermions
We present a theoretical foundation for the Index theorem in naive and
minimally doubled lattice fermions by studying the spectral flow of a Hermitean
version of Dirac operators. We utilize the point splitting method to implement
flavored mass terms, which play an important role in constructing proper
Hermitean operators. We show the spectral flow correctly detects the index of
the would-be zero modes which is determined by gauge field topology. Using the
flavored mass terms, we present new types of overlap fermions from the naive
fermion kernels, with a number of flavors that depends on the choice of the
mass terms. We succeed to obtain a single-flavor naive overlap fermion which
maintains hypercubic symmetry.Comment: 27 pages, 17 figures; references added, version accepted in JHE
The large N limit of four dimensional Yang-Mills field coupled to adjoint fermions on a single site lattice
We consider the large N limit of four dimensional SU(N) Yang-Mills field
coupled to adjoint fermions on a single site lattice. We use perturbative
techniques to show that the Z^4_N center-symmetries are broken with naive
fermions but they are not broken with overlap fermions. We use numerical
techniques to support this result. Furthermore, we present evidence for a
non-zero chiral condensate for one and two Majorana flavors at one value of the
lattice gauge coupling.Comment: 21 pages, 13 figures; a reference added; version to be published in
JHEP, small clarifications and references adde
Three-Body Halo States in Effective Field Theory: Renormalization and Three-Body Interactions in the Helium-6 System
In this paper we study the renormalization of Halo effective field theory applied to the Helium-6 halo nucleus seen as an alpha-neutron-neutron three-body state. We include the 0(+) dineutron channel together with both the 3/2(-) and 1/2(-) neutron-alpha channels into the field theory and study all of the six lowest-order three-body interactions that are present. Furthermore, we discuss three different prescriptions to handle the unphysical poles in the P-wave two-body sector. In the simpler field theory without the 1/2(-) channel present we find that the bound-state spectrum of the field theory is renormalized by the inclusion of a single three-body interaction. However, in the field theory with both the 3/2(-) and 1/2(-) included, the system can not be renormalized by only one three-body operator
The phases of deuterium at extreme densities
We consider deuterium compressed to higher than atomic, but lower than
nuclear densities. At such densities deuterium is a superconducting quantum
liquid. Generically, two superconducting phases compete, a "ferromagnetic" and
a "nematic" one. We provide a power counting argument suggesting that the
dominant interactions in the deuteron liquid are perturbative (but screened)
Coulomb interactions. At very high densities the ground state is determined by
very small nuclear interaction effects that probably favor the ferromagnetic
phase. At lower densities the symmetry of the theory is effectively enhanced to
SU(3), and the quantum liquid enters a novel phase, neither ferromagnetic nor
nematic. Our results can serve as a starting point for investigations of the
phase dynamics of deuteron liquids, as well as exploration of the stability and
dynamics of the rich variety of topological objects that may occur in phases of
the deuteron quantum liquid, which range from Alice strings to spin skyrmions
to Z_2 vortices.Comment: 9 pages, 6 figures; v2: fixed typo
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