374 research outputs found
Chirally motivated K^- nuclear potentials
In-medium subthreshold KbarN scattering amplitudes calculated within a
chirally motivated meson-baryon coupled-channel model are used self
consistently to confront K^- atom data across the periodic table. Substantially
deeper K^- nuclear potentials are obtained compared to the shallow potentials
derived in some approaches from threshold amplitudes, with Re V_{chiral} =
-(85+/-5) MeV at nuclear matter density. When KbarNN contributions are
incorporated phenomenologically, a very deep K^- nuclear potential results, Re
V_{chiral+phen.} = -(180+/-5) MeV, in agreement with density dependent
potentials obtained in purely phenomenological fits to the data. Self
consistent dynamical calculations of K^- nuclear quasibound states are reported
and discussed.Comment: extended discussion, unchanged results and conclusions, accepted by
PL
No-Core Shell Model for Nuclear Systems with Strangeness
We report on a novel ab initio approach for nuclear few- and many-body
systems with strangeness. Recently, we developed a relevant no-core shell model
technique which we successfully applied in first calculations of lightest
hypernuclei. The use of a translationally invariant finite harmonic
oscillator basis allows us to employ large model spaces, compared to
traditional shell model calculations, and use realistic nucleon-nucleon and
nucleon-hyperon interactions (such as those derived from EFT). We discuss
formal aspects of the methodology, show first demonstrative results for
H, H and He, and give outlook.Comment: 4 pages, 3 figures; Proceedings of the 22nd European Conference on
Few Body Problems in Physics, 9 - 13 September, 2013, Cracow, Polan
Multi- nuclei and kaon condensation
We extend previous relativistic mean-field (RMF) calculations of multi- nuclei, using vector boson fields with SU(3) PPV coupling constants and
scalar boson fields constrained phenomenologically. For a given core nucleus,
the resulting separation energy , as well as the
associated nuclear and -meson densities, saturate with the number
of mesons for . Saturation
appears robust against a wide range of variations, including the RMF nuclear
model used and the type of boson fields mediating the strong interactions.
Because generally does not exceed 200 MeV, it is argued that
multi- nuclei do not compete with multihyperonic nuclei in providing
the ground state of strange hadronic configurations and that kaon condensation
is unlikely to occur in strong-interaction self-bound strange hadronic matter.
Last, we explore possibly self-bound strange systems made of neutrons and
mesons, or protons and mesons, and study their properties.Comment: 21 pages, 8 figures, revised text and reference
Nuclear physics uncertainties in light hypernuclei
The energy levels of light hypernuclei are experimentally accessible
observables that contain valuable information about the interaction between
hyperons and nucleons. In this work we study strangeness systems
H and He using the ab initio no-core shell
model (NCSM) with realistic interactions obtained from chiral effective field
theory (EFT). In particular, we quantify the finite precision of
theoretical predictions that can be attributed to nuclear physics
uncertainties. We study both the convergence of the solution of the many-body
problem (method uncertainty) and the regulator- and calibration data-dependence
of the nuclear EFT Hamiltonian (model uncertainty). For the former, we
implement infrared correction formulas and extrapolate finite-space NCSM
results to infinite model space. We then use Bayesian parameter estimation to
quantify the resulting method uncertainties. For the latter, we employ a family
of 42 realistic Hamiltonians and measure the standard deviation of predictions
while keeping the leading-order hyperon-nucleon interaction fixed. Following
this procedure we find that model uncertainties of ground-state
separation energies amount to keV in
H(H,He) and keV in He. Method
uncertainties are comparable in magnitude for the H,He
excited states and He, which are computed in limited model spaces,
but otherwise much smaller. This knowledge of expected theoretical precision is
crucial for the use of binding energies of light hypernuclei to infer the
elusive hyperon-nucleon interaction.Comment: 16 pages with 8 figure
Effects of Spreading Sequences on the Performance of MC-CDMA System with Nonlinear Models of HPA
Performance evaluation and comparison of multi-carrier code division multiple access (MC-CDMA) system model for different spreading sequences at the presence of Saleh and Rapp model of high power amplifier (HPA) is investigated. Nonlinear amplification introduces degradation of bit error performance and destroys the orthogonality among subcarriers. In order to avoid performance degradation without requiring extremely large backoffs in the transmitter amplifier, it becomes convenient to use nonlinear multi-user detection techniques at the receiver side. In order to illustrate this fact, microstatistic multi-user receiver (MSF-MUD) and conventional minimum mean square error receiver (MMSE-MUD) are considered and mutually compared. The results of our analyses based on computer simulations will show very clearly, that the application of nonlinear MSF-MUD in combination with Golay codes can provide significantly better results than the other tested spreading codes and receivers. Besides this fact, a failure of Walsh codes especially at the Saleh model of HPA will be outlined by using constellation diagram
The methodology and model for in-process inventories calculation in the conditions of metallurgy production
In the paper a methodology and model for “In-process inventories calculation“ in the metallurgy production conditions is described. The model was designed based on the factors affecting the in-process inventories levels. The inprocess inventories levels have to respect different efficiency of the aggregates in sequence, idle times, technological safety and the production continuity. For the calculation of the in-production inventories levels a dynamic model was designed. In the paper the results are compared from the analyses of real metallurgical production division and this model too
Application of balance models in metallurgy
In general, management is the planning and coordination of all processes and their elements in enterprises in order to achieve the objectives with the highest efficiency. The basic management tools, especially in companies with complex production processes with high inertia and long production time, include balance models. The paper points out the methodology, principles and importance of balance models in metallurgy and describes the methodology for material-energy, capacity and economic balance of this process
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