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 $NN$ 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 $\lambda$. 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