117755860
A new approach for studying large numbers of fermions in the unitary regime
A novel lattice approach is presented for studying systems comprising a large number of interacting nonrelativistic fermions. The construction is ideally suited for numerical study of fermions near unitarity--a strongly coupled regime corresponding to the two-particle s-wave scattering phase shift delta_0 = pi/2. Such systems may be achieved experimentally with trapped atoms, and provide a starting point for an effective field theory description of nuclear physics. We discuss the construction of our lattice theory, which allows us to study systems of up to (but by no means limited to) 38 fermions with high accuracy and modest computational resources, and offer an overview of several applications of the technique. A more detailed discussion of applications and simulation results will be described in companion proceedings by A. N. N. and J-W. L.
118691248
Background electromagnetic fields and nonrelativistic QED matching: Scalar case
The low-energy structure of hadrons can be described systematically using effective field theory, and the parameters of the effective theory can be determined from lattice QCD computations. Recent work, however, points to inconsistencies between the background field method in lattice QCD and effective field theory matching conditions. We show that the background field problem necessitates inclusion of operators related by equations of motion. In the presence of time-dependent electromagnetic fields, for example, such operators modify Green's functions, thereby complicating the isolation of hadronic parameters which enter on-shell scattering amplitudes. The particularly simple case of a scalar hadron coupled to uniform electromagnetic fields is investigated in detail. At the level of the relativistic effective theory, operators related by equations of motion are demonstrated to be innocuous. The same result does not hold in the non-relativistic effective theory, and inconsistencies in matching are resolved by carefully treating operators related by equations of motion. As uniform external fields potentially allow for surface terms, the problem is additionally analyzed on a torus where such terms are absent. Finite-size corrections are derived for charged scalar correlation functions in uniform electric fields as a useful byproduct.
119253557
Listening to Noise
We show how sign problems in simulations of many-body systems can manifest themselves in the form of heavy-tailed correlator distributions, similar to what is seen in electron propagation through disordered media. We propose an alternative statistical approach for extracting ground state energies in such systems, illustrating the method with a toy model and with lattice data for unitary fermions and for baryons in QCD.
119116117
Large Nc volume reduction and chiral random matrix theory
Motivated by recent progress on the understanding of the Eguchi-Kawai (EK) volume equivalence and growing interest in conformal window, we simultaneously use the large-Nc volume reduction and Chiral Random Matrix Theory (chRMT) to study the chiral symmetry breaking of four dimensional SU(Nc) gauge theory with adjoint fermions in the large Nc limit. Although some cares are required because the chRMT limit and 't Hooft limit are not compatible in general, we show that the breakdown of the chiral symmetry can be detected in large-Nc gauge theories. As a first step, we mainly focus on the quenched approximation to establish the methodology. We first confirm that heavy adjoint fermions, introduced as the center symmetry preserver, work as expected and thanks to them the volume reduction holds. Using massless overlap fermion as a probe, we then calculate the low-lying Dirac spectrum for fermion in the adjoint representation to compare to that of chRMT, and find that chiral symmetry is indeed broken in the quenched theory.
54711211
Extended study for unitary fermions on a lattice using the cumulant expansion technique
A recently developed lattice method for large numbers of strongly interacting nonrelativistic fermions exhibits a heavy tail in the distributions of correlators for large Euclidean time {\tau} and large number of fermions N, which only allows the measurement of ground state energies for a limited number of fermions using standard techniques. In such cases, it is suggested that measuring the log of the correlator is more efficient, and a cumulant expansion of this quantity can be exactly related to the correlation function. The cumulant expansion technique allows us to determine the ground state energies of up to 66 unpolarized unitary fermions on lattices as large as 72$\times$14^3, and up to 70 unpolarized unitary fermions trapped in a harmonic potential on lattices as large as 72$\times$64^3. We have also improved our lattice action with a Galilean invariant form for the four-fermion interaction, which results in predictive volume scaling of the lowest energy of three fermions in a periodic box and in good agreement of our results for N \leq 6 trapped unitary fermions with those from other benchmark calculations.
119295378
Conformality Lost
Abstract We consider zero-temperature transitions from conformal to non-conformal phases in quantum theories. We argue that there are three generic mechanisms for the loss of conformality in any number of dimensions: (i) fixed point goes to zero coupling, (ii) fixed point runs off to infinite coupling, or (iii) an IR fixed point annihilates with a UV fixed point and they both disappear into the complex plane. We give both relativistic and non-relativistic examples of the last case in various dimensions and show that the critical behavior of the mass gap behaves similarly to the correlation length in the finite temperature Berezinskii-Kosterlitz-Thouless (BKT) phase transition in two dimensions, ξ ∼ exp(c/|T − Tc|). We speculate that the chiral phase transition in QCD at large number of fermion flavors belongs to this universality class, and attempt to identify the UV fixed point that annihilates with the Banks-Zaks fixed point at the lower end of the conformal window.
15708185
COMPOSITE OPERATORS AND TOPOLOGICAL CONTRIBUTIONS IN GAUGE THEORY
In D-dimensional gauge theory with a kinetic term based on p-form tensor gauge field, we introduce a gauge-invariant operator associated with the composite form from an electric (p - 1)-brane and a magnetic (q - 1)-brane in D = p + q + 1 space–time dimensions. By evaluating the partition function of this operator, we show that the expectation value of this operator gives rise to the topological contributions identical to those in gauge theory with a topological Chern–Simons BF term.
3289948
Flavour geometry and effective Yukawa couplings in the MSSM
We present a new geometric approach to the flavour decomposition of an arbitrary soft supersymmetry-breaking sector in the MSSM. Our approach is based on the geometry that results from the quark and lepton Yukawa couplings, and enables us to derive the necessary and sufficient conditions for a linearly-independent basis of matrices related to the completeness of the internal [SU(3)⊗U(1)]5 flavour space. In a second step, we calculate the effective Yukawa couplings that are enhanced at large values of tan β for general soft supersymmetry-breaking mass parameters. We highlight the contributions due to non-universal terms in the flavour decompositions of the sfermion mass matrices. We present numerical examples illustrating how such terms are induced by renormalization-group evolution starting from universal input boundary conditions, and demonstrate their importance for the flavour-violating effective Yukawa couplings of quarks.
206997496
CPsuperH2.3: An updated tool for phenomenology in the MSSM with explicit CP violation
Abstract We describe the Fortran code CPsuperH2.3 , which incorporates the following updates compared with its predecessor CPsuperH2.0 . It implements improved calculations of the Higgs-boson masses and mixing including stau contributions and finite threshold effects on the tau-lepton Yukawa coupling. It incorporates the LEP limits on the processes e + e − → H i Z , H i H j and the CMS limits on H i → τ τ obtained from 4.6 fb − 1 of data at a center-of-mass energy of 7 TeV. It also includes the decay mode H i → Z γ and the Schiff-moment contributions to the electric dipole moments of Mercury and Radium 225, with several calculational options for the case of Mercury. These additions make CPsuperH2.3 a suitable tool for analyzing possible CP-violating effects in the MSSM in the era of the LHC and a new generation of EDM experiments. 1 Program summary Program title: CPsuperH2.3 Catalogue identifier: ADSR_v3_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADSR_v3_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 24058 No. of bytes in distributed program, including test data, etc.: 158721 Distribution format: tar.gz Programming language: Fortran77. Computer: PC running under Linux and computers in Unix environment. Operating system: Linux. RAM: 32 MB Classification: 11.1. Does the new version supersede the previous version?: Yes Catalogue identifier of previous version: ADSR_v2_0 Journal reference of previous version: Comput. Phys. Comm. 180(2009)312 Nature of problem: The calculations of mass spectrum, decay widths and branching ratios of the neutral and charged Higgs bosons in the Minimal Supersymmetric Standard Model with explicit CP violation have been improved. The program is based on renormalization-group-improved diagrammatic calculations that include dominant higher-order logarithmic and threshold corrections, b -quark and τ -lepton Yukawa-coupling resummation effects and improved treatment of Higgs-boson pole-mass shifts. The couplings of the Higgs bosons to the Standard Model gauge bosons and fermions, to their supersymmetric partners and all the trilinear and quartic Higgs-boson self-couplings are also calculated. Also included are a full treatment of the 4×4 (2×2) neutral (charged) Higgs propagator matrix together with the center-of-mass dependent Higgs-boson couplings to gluons and photons, and an integrated treatment of several B-meson observables. The new implementations include the EDMs of Thallium, neutron, Mercury, Deuteron, Radium, and muon, as well as the anomalous magnetic moment of muon, ( g μ − 2 ), the top-quark decays, improved calculations of the Higgs-boson masses and mixing including stau contributions, the LEP limits, and the CMS limits on H i → τ τ . It also implements the decay mode H i → Z γ and includes the corresponding Standard Model branching ratios of the three neutral Higgs bosons in the array GAMBRN(IM,IWB = 2,IH) . Solution method: One-dimensional numerical integration for several Higgs-decay modes and EDMs, iterative treatment of the threshold corrections and Higgs-boson pole masses, and the numerical diagonalization of the neutralino mass matrix. Reasons for new version: Mainly to provide the full calculations of the EDMs of Thallium, neutron, Mercury, Deuteron, Radium, and muon as well as ( g μ − 2 ) , improved calculations of the Higgs-boson masses and mixing including stau contributions, the LEP limits, the CMS limits on H i → τ τ , the top-quark decays, H i → Z γ decay, and the corresponding Standard Model branching ratios of the three neutral Higgs bosons. Summary of revisions: Full calculations of the EDMs of Thallium, neutron, Mercury, Deuteron, Radium, and muon as well as ( g μ − 2 ) . Improved treatment of Higgs-boson masses and mixing including stau contributions. The LEP limits. The CMS limits on H i → τ τ . The top-quark decays. The H i → Z γ decay. The corresponding Standard Model branching ratios of the three neutral Higgs bosons. Running time: Less than 1.0 s.
119214223
THE ALGOL SYSTEM SZ HERCULIS: PHYSICAL NATURE AND ORBITAL BEHAVIOR
Multiband CCD photometric observations of SZ Her were obtained between 2008 February and May. The light curve was completely covered and indicated a significant temperature difference between both components. The light-curve synthesis presented in this paper indicates that the eclipsing binary is a classical Algol-type system with parameters of q = 0.472, i = 8757, and Δ(T 1 - T 2) = 2381 K; the primary component fills approximately 77% of its limiting lobe and is slightly larger than the lobe-filling secondary component. More than 1100 times of minimum light spanning more than a century were used to study an orbital behavior of the binary system. It was found that the orbital period of SZ Her varied due to a combination of two periodic variations with cycle lengths of P 3 = 85.8 yr and P 4 = 42.5 yr and semi-amplitudes of K 3 = 0.013 days and K 4 = 0.007 days, respectively. The most reasonable explanation for these variations is a pair of light-time effects driven by the possible existence of two M-type companions with minimum masses of M 3 = 0.22 M ☉ and M 4 = 0.19 M ☉ that are located close to the 2:1 mean motion resonance. If two additional bodies exist, then the overall dynamics of the multiple system may provide a significant clue to the formation and evolution of the eclipsing pair.
465148
SUPERGRAVITY RADIATIVE EFFECTS ON SOFT TERMS AND THE MU TERM
We compute quadratically divergent supergravity one-loop effects on soft supersymmetry-breaking parameters and the $\mu$ term in generic hidden sector supergravity models. These effects can significantly modify the matching condition for soft parameters at the Planck scale and also provide several new sources of the $\mu$ term which are naturally of order the weak scale. We also discuss some phenomenological implications of these effects, particularly the violation of the scalar mass universality which may lead to dangerous FCNC phenomena, and apply the results to superstring effective supergravity models.