2967918
Radiative capture reactions in lattice effective field theory.
We outline a general method for computing nuclear capture reactions on the lattice. The method consists of two major parts. In this study we detail the second part which consists of calculating an effective two-body capture reaction on the lattice at finite volume. We solve this problem by calculating the two-point Green's function using an infrared regulator and the capture amplitude to a two-body bound state. We demonstrate the details of this method by calculating on the lattice the leading M1 contribution to the radiative neutron capture on proton at low energies using pionless effective field theory. We find good agreement with exact continuum results. The approach we outline here can be used in a wide range of applications including few-body reactions in cold atomic systems and hadronic reactions in lattice quantum chromodynamics.
125749692
Nuclear lattice simulations
We review recent progress on nuclear lattice simulations using chiral effective field theory. We discuss lattice results for dilute neutron matter at next-to-leading order, three-body forces at next-to-next-to- leading order, isospin-breaking and Coulomb effects, and the binding energy of light nuclei.
13972554
A non-perturbative analysis of symmetry breaking in two-dimensional φ4 theory using periodic field methods
Abstract We describe the generalization of spherical field theory to other modal expansion methods. The main approach remains the same, to reduce a d -dimensional field theory into a set of coupled one-dimensional systems. The method we discuss here uses an expansion with respect to periodic-box modes. We apply the method to φ 4 theory in two dimensions and compute the critical coupling and critical exponents. We compare with lattice results and predictions via universality and the two-dimensional Ising model.
119868800
Ab initio lattice results for Fermi polarons in two and three dimensions
We investigate the attractive Fermi polaron problem in two and three dimensions using non-perturbative Monte Carlo simulations. We introduce a new Monte Carlo algorithm called the impurity lattice Monte Carlo method. This algorithm samples the path integral in a computationally efficient manner and has only small sign oscillations for systems with a single impurity. To benchmark the method, we calculate the universal polaron energy in three dimensions in the scale-invariant unitarity limit and find agreement with published results. We then present the first fully non-perturbative calculations of the polaron energy in two dimensions in the limit of zero range interactions. We find evidence for a smooth crossover transition from a fermionic quasiparticle to a molecular state as a function of interaction strength with significant mixing between the two descriptions in the crossover region.
15307965
The role of Monte Carlo within a diagonalization/Monte Carlo scheme
Abstract We review the method of stochastic error correction which eliminates the truncation error associated with any subspace diagonalization. Monte Carlo sampling is used to compute the contribution of the remaining basis vectors not included in the initial diagonalization. The method is part of a new approach to computational quantum physics which combines both diagonalization and Monte Carlo techniques.
118374917
Lattice calculations for A = 3 , 4, 6, 12 nuclei using chiral effective field theory
Abstract.We present lattice calculations for the ground-state energies of tritium, helium-3, helium-4, lithium-6, and carbon-12 nuclei. Our results were previously summarized in a letter publication. This paper provides full details of the calculations. We include isospin-breaking, Coulomb effects, and interactions up to next-to-next-to-leading order in chiral effective field theory.
125435973
Reaction Ni-58 (pi+, p p) at T(pi+) = 160-MeV
89609083
Evidence for a New Phase of Solid He-3
)Permanent address: Faculte des Sciences, Orsay, France. See, for exaxnple, I. Prigogine, Non Equi/ibrinm Statistica/ Mechanics (Wiley, New York, 1962); P. Resibois, in-Many Pmticle Physics, edited by K. Meeron (Gordon and Breach, New York, 1966). J. Van der Waals, Dissertation, University of Leiden, 1873 (unpublished) . See M. Kac, G. Uhlenbeck, and P. Hemmer, J. Math. Phys. 4, 216, 229 (1963), and 5, 60 (1964); J. Lebowitz, G. Steli, and S. Baer, J. Math. Phys. (N.Y.) 4, 1282 (1965). See K. Kawasaki, Progr. Theor. Phys. 41, 1190 (1969), snd references quoted therein. ~H. Mori, Progr. Theor. Phys. 28, 763 (1962}. P. Resibois, J. Chem. Phys. 41, 2979 (1964). P. Resibois, J. Stat. Phys. 2, 21 (1970). J. Dorfman and E. Cohen, Phys. Rev. Lett. 25, 1257 (1970). L. Kadanoff and J. Swift, Phys. Rev. 166, 89 (1968). M. Ernst, E. Hauge, and J. Van Leeuwen, Phys. Rev. Lett. 25, 1254 (1970), and Phys. Rev. A 4, 2055 (1971). "B.Alder and T. Wainwright, Phys. Rev. A 1, 18 (1970); see also Refs. 8 and 10; and Y. Pomeau, to be published.
2385881
The Coincidence of Nuclear Star Clusters and Active Galactic Nuclei
We study galaxies that host both nuclear star clusters and AGNs, implying the presence of a massive black hole. We select a sample of 176 galaxies with previously detected nuclear star clusters that range from ellipticals to late-type spirals. We search for AGNs in this sample using optical spectroscopy and archival radio and X-ray data. We find galaxies of all Hubble types and with a wide range of masses (109-1011 M☉) hosting both AGNs and nuclear star clusters. From the optical spectra, we classify 10% of the galaxies as AGN and an additional 15% as composite, indicating a mix of AGN and star formation spectra. The fraction of nucleated galaxies with AGNs increases strongly as a function of galaxy and nuclear star cluster mass. For galaxies with both a nuclear star cluster and a black hole, we find that the masses of these two objects are quite similar. However, nondetections of black holes in Local Group nuclear star clusters show that not all clusters host black holes of similar masses. We discuss the implications of our results for the formation of nuclear star clusters and massive black holes.
120849057
Design and performance of an 8 cm thick intrinsic germanium detector telescope
Abstract A detector telescope consisting of eight 1 cm thick intrinsic Ge diodes is described. The diodes have thin dead layer Li junctions (∼15 ωm ) and are mounted in interchangeable holders. Designs of the holders and the mounting assembly are presented. The major problem in using stopping detectors at medium energies is the tail of low pulse height events produced by nuclear reactions and scattering out. A technique for rejecting these events is described and the results obtained with deuterons from p-d elastic scattering of 800 MeV protons are presented. Analysis of the nuclear reaction tail for 120, 220, and 250 MeV deutrons yields an average total reaction cross section for deuterons on Ge of σ R = (1490±130) mb.
121136564
Proportional chambers with monofilar helical cathodes for high spatial resolution
Abstract Multiware proportional chambers with monofilar helical delay line cathodes have been developed. Spatial resolutions better than 0.33 mm fwhm have been achieved. Such chambers are easily constructed and read out and can be adapted to a large variety of geometries. The properties of monofilar helical delay lines are analyzed in detail.