33,260 research outputs found
University Scholar Series: Jonathan Roth
Roman Warfare
On April 13, 2011 Jonathan Roth spoke in the University Scholar Series hosted by Provost Gerry Selter at the Dr. Martin Luther King, Jr. Library. Jonathan Roth is a Professor in the History Department at SJSU. In this seminar, he examines the evolution of Roman war over its thousand-year history. He highlights the changing arms and equipment of the soldiers, unit organization and command structure, and the wars and battles of each era.https://scholarworks.sjsu.edu/uss/1008/thumbnail.jp
Large-scale second RPA calculations with finite-range interactions
Second RPA (SRPA) calculations of nuclear response are performed and
analyzed. Unlike in most other SRPA applications, the ground state,
approximated by the Hartree-Fock (HF) ground state, and the residual couplings
are described by the same Hamiltonian and no arbitrary truncations are imposed
on the model space. Finite-range interactions are used and thus divergence
problems are not present. We employ a realistic interaction, derived from the
Argonne V18 potenial using the unitary correlation operator method (UCOM), as
well as the simple Brink-Boeker interaction. Representative results are
discussed, mainly on giant resonances and low-lying collective states. The
focus of the present work is not on the comparison with data, but rather on
technical and physical aspects of the method. We present how the large-scale
eigenvalue problem that SRPA entails can be treated, and demonstrate how the
method operates in producing self-energy corrections and fragmentation. The
so-called diagonal approximation is conditionally validated. Stability problems
are traced back to missing ground-state correlations.Comment: 13 pages, incl. 9 figures, 1 tabl
Reply to Comment on ``Ab Initio Study of 40-Ca with an Importance Truncated No-Core Shell Model''
We respond to Comment on our recent letter (Phys.Rev.Lett.99:092501,2007) by
Dean et al (arXiv:0709.0449).Comment: 2 page
Giant Resonances using Correlated Realistic Interactions: The Case for Second RPA
Lately we have been tackling the problem of describing nuclear collective
excitations starting from correlated realistic nucleon-nucleon (NN)
interactions. The latter are constructed within the Unitary Correlation
Operator Method (UCOM), starting from realistic NN potentials. It has been
concluded that first-order RPA with a two-body UCOM interaction is not capable,
in general, of reproducing quantitatively the properties of giant resonances
(GRs), due to missing higher-order configurations and long-range correlations
as well as neglected three-body terms in the Hamiltonian.
Here we report results on GRs obtained by employing a UCOM interaction based
on the Argonne V18 potential in Second RPA (SRPA) calculations. The same
interaction is used to describe the Hartree-Fock (HF) ground state and the
residual interactions. We find that the inclusion of second-order
configurations -- which effectively dress the underlying HF single-particle
states with self-energy insertions -- produces sizable corrections. The effect
appears essential for a realistic description of GRs when using the UCOM. We
argue that effects of higher than second order should be negligible. Therefore,
the UCOM-SRPA emerges as a promising tool for consistent calculations of
collective states in closed-shell nuclei. This is an interesting development,
given that SRPA can accommodate more physics than RPA (e.g., fragmentation).
Remaining discrepancies due to the missing three-body terms and
self-consistency issues of the present SRPA model are pointed out.Comment: 6 pages, incl. 1 figure; Proc. 26th Int. Workshop on Nuclear Theory,
June 2007, Rila mountains, Bulgari
Theory of cubical complexes with applications to diagnosis and algorithmic description Quarterly report, 26 May - 10 Aug. 1970
Cubical complex theory with applications to diagnosis and algorithmic descriptio
Nuclear Structure in the UCOM Framework: From Realistic Interactions to Collective Excitations
The Unitary Correlation Operator Method (UCOM) provides a means for nuclear
structure calculations starting from realistic NN potentials. The dominant
short-range central and tensor correlations are described explicitly by a
unitary transformation. The application of UCOM in the context of the no-core
shell model provides insight into the interplay between dominant short-range
and residual long-range correlations in the nuclear many-body problem. The use
of the correlated interaction within Hartree-Fock, many-body perturbation
theory, and Random Phase Approximation gives access to various nuclear
structure observables throughout the nuclear chart.Comment: 9 pages, 3 figures, invited talk at the 2nd Int. Conf. on "Collective
Motion in Nuclei under Extreme Conditions" (COMEX 2), Sankt Goar, German
Quasiparticle Random Phase Approximation with Interactions from the Similarity Renormalization Group
We have developed a fully consistent framework for calculations in the
Quasiparticle Random Phase Approximation (QRPA) with interactions from the
Similarity Renormalization Group (SRG) and other unitary transformations of
realistic interactions. The consistency of our calculations, which use the same
Hamiltonian to determine the Hartree-Fock-Bogoliubov (HFB) ground states and
the residual interaction for QRPA, guarantees an excellent decoupling of
spurious strength, without the need for empirical corrections. While work is
under way to include SRG-evolved 3N interactions, we presently account for some
3N effects by means of a linearly density-dependent interaction, whose strength
is adjusted to reproduce the charge radii of closed-shell nuclei across the
whole nuclear chart. As a first application, we perform a survey of the
monopole, dipole, and quadrupole response of the calcium isotopic chain and of
the underlying single-particle spectra, focusing on how their properties depend
on the SRG parameter . Unrealistic spin-orbit splittings suggest that
spin-orbit terms from the 3N interaction are called for. Nevertheless, our
general findings are comparable to results from phenomenological QRPA
calculations using Skyrme or Gogny energy density functionals. Potentially
interesting phenomena related to low-lying strength warrant more systematic
investigations in the future.Comment: 18 pages, 17 figures, 3 tables (RevTeX 4.1), v2: fixed typos &
figures, as publishe
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