24016762
Inequalities for light nuclei in the Wigner symmetry limit.
Using effective field theory we derive inequalities for light nuclei in the Wigner symmetry limit. This is the limit where isospin and spin degrees of freedom can be interchanged. We prove that the energy of any three-nucleon state is bounded below by the average energy of the lowest two-nucleon and four-nucleon states. We show how this is modified by lowest-order terms breaking Wigner symmetry and prove general energy convexity results for SU(N). We also discuss the inclusion of Wigner-symmetric three- and four-nucleon force terms.
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.
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.
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.
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.
123479705
Design and construction of double-sided silicon ladders for the L3 microvertex detector
Abstract The techniques used in the construction of the double-sided ladders for the L3 Silicon Microvertex Detector (SMD) are presented. The detector consists of two cylindrical layers, each of 12 ladders, with double-sided silicon detectors which provide r -phi and z coordinates measurements. This description includes ladder mechanical design and the assembly. A novel solution to readout the z -coordinates is presented. It optimizes very effectively the removal of heat generated by the readout electronics and minimizes the radiation length in the central region. Some results from the survey of the individual ladders are also discussed.
119836609
Deuterium atoms and molecules in nanoclusters of molecular deuterium
Impurity-helium solids created by injecting deuterium atoms and molecules into superfluid 4 He have been studied via x-ray-diffraction and electron-spin-resonance (ESR) techniques. X-ray-diffraction measurements show thatthese solids are highly porous gel-like structures consisting of D 2 clusters with the characteristic cluster size of 90′ 30 A. The densities of D 2 molecules in the samples are 7 × 10 2 0 -3 × 10 2 1 cm - 3 . Each of the D 2 clusters are either partially or totally surrounded by thin layers of adsorbed helium which may play an important role in preventing the coalescence of the clusters into larger crystallites of solid D 2 . Using ESR, we find that average concentrations of D atoms of order I × 10 1 8 cm - 3 can be achieved in our samples. Measurements of the ground-state spectroscopic parameters and relaxation times of atomic deuterium show that the D atoms reside in the D 2 clusters. The combined x-ray and ESR data show that local concentrations of D atoms as large as 2 × 10 1 9 cm - 3 are obtained in our experiments. The highly porous deuterium nanostructures studied in this work are promising for the production of high concentrations of ultracold neutrons and for significant nuclear polarization of D 2 molecules by the "brute force method" at low temperatures.
30885576
Wide Dynamic Range Beam Profile Monitor
An economical harp multiplexer system has been developed to achieve a wide dynamic range. The harp system incorporates a pneumatically actuated harp detector with ceramic boards and carbon wires; a high-sensitivity multiplexer packaged in a double-wide NIM module; and flat, shielded ribbon cable consisting of individual twisted pairs. The system multiplexes 30 wires in each of the x and y planes simultaneously and operates with or without computer control. The system has operated in beams of 100 nA to 1 mA, 1-to 120-Hz repetition rate, with a signal-to-noise ratio of greater than 10/1.
120631837
A bifilar helical multiware proportional chamber for position sensitive detection of minimum ionizing particles
Abstract A new type of multiware proportional chamber with a helical cathode for delay line readout has been developed and studied in detail. It gives cathode delay line pulses nearly as large as the anode pulses, and hence is well-suited for minimum ionizing particles. Measurements on such a chamber yielded spatial resolution better than 0.33 mm fwhm for 90 Sr β particles, a resolving time less than 30 ns, and maximum counting rate greater than 2 MHz. The most probable pulse height induced on the delay line by minimum ionizing particles in this chamber is approximately 8 mV.
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.