119491644
Cold dilute neutron matter on the lattice. II. Results in the unitary limit
This is the second of two articles that investigate cold dilute neutron matter on the lattice using pionless effective field theory. In the unitary limit, where the effective range is zero and scattering length is infinite, simple scaling relations relate thermodynamic functions at different temperatures. When the second virial coefficient is properly tuned, we find that the lattice results obey these scaling relations. We compute the energy per particle, pressure, spin susceptibility, dineutron correlation function, and an upper bound for the superfluid critical temperature.
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.
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.
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.
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.
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.
118608523
MEASURING TRANSVERSE MOTIONS FOR NEARBY GALAXY CLUSTERS
Measuring the full three-dimensional motions of extragalactic objects in the universe presents a seemingly insurmountable challenge. In this Letter, we investigate the application of a technique to measure tangential motion that has previously only been applied nearby within the Local Group of galaxies, to clusters of galaxies far beyond its borders. We show that mapping the mean line-of-sight motion throughout a galaxy cluster could in principle be used to detect the perspective rotation induced by the projection of the cluster's tangential motion into the line of sight. The signal will be most prominent for clusters of the largest angular extent, most symmetric intrinsic velocity distribution and surveyed with the largest number of pointings possible. We investigate the feasibility of detecting this signal using three different approaches: measuring line-of-sight motions of individual cluster members, taking spectra of intracluster gas, and mapping distortions of the cosmic microwave background radiation. We conclude that future spectroscopic surveys of thousands of members of nearby galaxy clusters hold the most promise of measuring cluster tangential motions using this technique.
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.
53708822
A MASS-DEPENDENT YIELD ORIGIN OF NEUTRON-CAPTURE ELEMENT ABUNDANCE DISTRIBUTIONS IN ULTRA-FAINT DWARFS
One way to constrain the nature of the high-redshift progenitors of the Milky Way (MW) is to look at the low-metallicity stellar populations of the different Galactic components today. For example, high-resolution spectroscopy of very metal poor (VMP) stars demonstrates remarkable agreement between the distribution of [Ti/Fe] in the stellar populations of the MW halo and ultra-faint dwarf (UFD) galaxies. In contrast, for the neutron-capture (nc) abundance ratio distributions [(Sr, Ba)/Fe], the peak of the small UFD sample (6 stars) exhibits a significant under-abundance relative to the VMP stars in the larger MW halo sample (~300 stars). We present a simple scenario that can simultaneously explain these similarities and differences by assuming: (1) that the MW VMP stars were predominately enriched by a prior generation of stars which possessed a higher total mass than the prior generation of stars that enriched the UFD VMP stars; and (2) a much stronger mass-dependent yield (MDY) for nc-elements than for the (known) MDY for Ti. Simple statistical tests demonstrate that conditions (1) and (2) are consistent with the observed abundance distributions, albeit without strong constraints on model parameters. A comparison of the broad constraints for these nc-MDY with those derived in the literature seems to rule out Ba production from low-mass supernovae (SNe) and affirms models that primarily generate yields from high-mass SNe. Our scenario can be confirmed by a relatively modest (factor of ~3-4) increase in the number of high-resolution spectra of VMP stars in UFDs.
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.
118591353
A prediction of the neutron and charged particle backgrounds in the L detector
Monte Carlo calculations have been made of the neutron flux and activation in the forward and barrel calorimeters in the L* detector and of the neutron flux in the central detector volume. In addition estimates of the charged particle and neutron background rates in the vicinity of the muon chambers has been determined. The Los Alamos National Laboratory code system LAHET and CINDER, 90 along with ISAJET and GEANT were used in these studies. The results indicate that neutron fluences as low as 2 {times} 10{sup 12} per SSC year can be achieved in the central volume. 6 refs., 3 figs., 2 tabs.