120306861
Nuclear Level Densities and Partition Functions with Interactions
A general theory, based on central limit theorems and unitary-group decompositions of the microscopic H, is given for the nuclear level density. The density appears in terms of convolutions of noninteracting-particle densities with easily calculable interaction functions given explicitly in terms of the Hamiltonian matrix elements.
28323659
Symmetries and quantum chaos: Time-reversal invariance in the nucleon-nucleon interaction.
Let \ensuremath{\alpha} be the relative norm of a symmetry-breaking term in the Hamiltonian of a many-particle system, and \ensuremath{\Lambda} the energy-dependent transition parameter which charcterizes the quantum chaos via spectral and strength fluctuations. Combining a compact theory for \ensuremath{\Lambda}/${\mathrm{\ensuremath{\alpha}}}^{2}$ with fluctuation theories by which \ensuremath{\Lambda} can be deduced from (neutron-resonance) data gives, for the time-reversal-noninvariant nucleon-nucleon interaction, \ensuremath{\alpha}\ensuremath{\le}(1\char21{}2)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}3}$, which would improve with better small-strength data in nuclei with dense spectra. Diffusion equations involving \ensuremath{\Lambda} as the ``time'' variable are also discussed.
123029512
Statistical properties of many-particle spectra V. Fluctuations and symmetries
Abstract The manner in which energy-level and strength fluctuations change as a good symmetry is gradually broken is studied for a wide variety of chaotic systems describable in terms of random-matrix models. The local parameter Λ which governs the transition is identified as the mean-square symmetry-breaking matrix element in units of the local average spacing; its basic significance is clarified by exhibiting it as the “time” variable in a hierarchic set of diffusion equations. While many transitions, including Poisson → GOE, are considered, the transition GOE → GUE, from Gaussian orthogonal to Gaussian unitary ensembles, is studied in particular detail because of its connection with the breaking of time-reversal invariance (TRI), especially in complex nuclei for which the relevance of the GOE has been experimentally confirmed (GOE → GUE enters also into the study of chaotic magnetic systems). It is shown that the ensemble theory is directly applicable to real systems so that the transition equations derived for various spectral and strength measures can be applied to fluctuation data to give multiparticle bounds on the TRI-breaking part of the Hamiltonian. Analyses of spectral and strength fluctuations in the nuclear neutron-resonance and proton-resonance regions give bounds on the symmetry-breaking matrix elements as approximately one-tenth of the local average spacing. The analysis however must not stop with determining a bound on Λ; although the mere existence of a nonzero Λ could be of interest, indicating the occurrence of a symmetry breaking, the significance, if any, of an upper bound will usually not be obvious. It is therefore essential to determine, from the local multibody parameter Λ, the global (two-body) quantity α, the relative norm of the time-reversal noninvariant (TRNI) part of the nucleon-nucleon interaction. We do that in the following paper.
122129897
Angular Momentum Coupling and the Internucleon Interaction in the Calcium Isotopes
11400551
Bound on time-reversal noninvariance in the nuclear Hamiltonian.
Energy-level fluctuations are calculated by random-matrix methods, for time-reversal noninvariant (TRNI) Hamiltonians. The theory, applied to the data, shows that in the neutron and proton resonance regions, for heavy and intermediate nuclei (i.e., respectively), the local rms off-diagonal multiparticle H(TRNI) matrix element < or approx. = D/10, with D the level spacing. Spectral averaging methods reduce this to a bound on the nucleon-nucleon TRNI vs TRI interactions. First calculations, for /sup 169/Er, give a 1% upper bound.
121854499
Random-matrix physics: spectrum and strength fluctuations
It now appears that the general nature of the deviations from uniformity in the spectrum of a complicated nucleus is essentially the same in all regions of the spectrum and over the entire Periodic Table. This behavior, moreover, is describable in terms of standard Hamiltonian ensembles which could be generated on the basis of simple information-theory concepts, and which give also a good account of fluctuation phenomena of other kinds and, apparently, in other many-body systems besides nuclei. The main departures from simple behavior are ascribable to the moderation of the level repulsion by effects due to symmetries and collectivities, for the description of which more complicated ensembles are called for. One purpose of this review is to give a self-contained account of the theory, using methods: sometimes approximate: which are consonant with the usual theory of stochastic processes. Another purpose is to give a proper foundation for the use of ensemble theory, to make clear the origin of the simplicities in the observable fluctuations, and to derive other general fluctuation results. In comparing theory and experiment, the authors give an analysis of much of the nuclear-energy-level data, as well as an extended discussion of observable effects in nuclear transitionsmore » and reactions and in the low-temperature thermodynamics of aggregates of small metallic particles.« less
118419469
Inflation from Strongly Coupled Gauge Dynamics
We argue, using a phenomenological holographic approach, that walking, strongly coupled gauge theories generate a suitable potential for a small field inflation model. We show that the effective description is a model of a single inflaton. We determine the tunings necessary in the gauge sector to generate inflation and overcome the \eta problem.
119206061
Hadronization at the AdS wall
We describe hadronization events, using the AdS/CFT Correspondence, which display many of the qualitative features expected in QCD. In particular we study the motion of strings with separating end points in a back-reacted hard wall geometry. The solutions show the development of a linear QCD-like string. The end points oscillate in the absence of string breaking. We introduce string breaking by hand and evolve the new state forward in time to observe the separation of two string segments. A kink associated with this breaking evolves to the end points of the string inducing rho meson production. We explicitly compute the rho meson production at the end point.
119255085
Holography of a composite inflaton
We study the time evolution of a brane construction that is holographically dual to a strongly coupled gauge theory that dynamically breaks a global symmetry through the generation of an effective composite Higgs vev. The D3/D7 system with a background magnetic field or non-trivial gauge coupling (dilaton) profile displays the symmetry breaking. We study motion of the D7 brane in the background of the D3 branes. For small field inflation in the field theory the effective Higgs vev rolls from zero to the true vacuum value. We study what phenomenological dilaton profile generates the slow rolling needed, hence learning how the strongly coupled gauge theory’s coupling must run. We note that evolution of our configuration in the holographic direction, representing the phyiscs of the strong interactions, can provide additional slowing of the roll time. Inflation seems to be favoured if the coupling changes by only a small amount or very gently. We speculate on how such a scenario could be realized away from N=4 gauge theory, for example, in a walking gauge theory.