617 research outputs found
Quantum Monte Carlo Calculations for Carbon Nanotubes
We show how lattice Quantum Monte Carlo can be applied to the electronic
properties of carbon nanotubes in the presence of strong electron-electron
correlations. We employ the path-integral formalism and use methods developed
within the lattice QCD community for our numerical work. Our lattice
Hamiltonian is closely related to the hexagonal Hubbard model augmented by a
long-range electron-electron interaction. We apply our method to the
single-quasiparticle spectrum of the (3,3) armchair nanotube configuration, and
consider the effects of strong electron-electron correlations. Our approach is
equally applicable to other nanotubes, as well as to other carbon
nanostructures. We benchmark our Monte Carlo calculations against the two- and
four-site Hubbard models, where a direct numerical solution is feasible.Comment: 54 pages, 16 figures, published in Physical Review
Energy spectra of two interacting fermions with spin-orbit coupling in a harmonic trap
We explore the two-body spectra of spin- fermions in isotropic harmonic
traps with external spin-orbit potentials and short range two-body
interactions. Using a truncated basis of total angular momentum eigenstates,
non-perturbative results are presented for experimentally realistic forms of
the spin-orbit coupling: a pure Rashba coupling, Rashba and Dresselhaus
couplings in equal parts, and a Weyl-type coupling. The technique is easily
adapted to bosonic systems and other forms of spin-orbit coupling.Comment: 12 pages, 9 figure
Hubbard-Stratonovich-like Transformations for Few-Body Interactions
Through the development of many-body methodology and algorithms, it has
become possible to describe quantum systems composed of a large number of
particles with great accuracy. Essential to all these methods is the
application of auxiliary fields via the Hubbard-Stratonovich transformation.
This transformation effectively reduces two-body interactions to interactions
of one particle with the auxiliary field, thereby improving the computational
scaling of the respective algorithms. The relevance of collective phenomena and
interactions grows with the number of particles. For many theories, e.g. Chiral
Perturbation Theory, the inclusion of three-body forces has become essential in
order to further increase the accuracy on the many-body level. In this
proceeding, the analytical framework for establishing a
Hubbard-Stratonovich-like transformation, which allows for the systematic and
controlled inclusion of contact three- and more-body interactions, is
presented.Comment: Conference proceeding, 8 pages, 4 figure
Sampling General N-Body Interactions with Auxiliary Fields
We present a general auxiliary field transformation which generates effective
interactions containing all possible N-body contact terms. The strength of the
induced terms can analytically be described in terms of general coefficients
associated with the transformation and thus are controllable. This
transformation provides a novel way for sampling 3- and 4-body (and higher)
contact interactions non-perturbatively in lattice quantum monte-carlo
simulations. We show that our method reproduces the exact solution for a
two-site quantum mechanical problem.Comment: 5 pages, 1 figure and a supplemental Mathematica noteboo
The nucleon electric dipole moment with the gradient flow: the -term contribution
We propose a new method to calculate electric dipole moments induced by the
strong QCD -term. The method is based on the gradient flow for gauge
fields and is free from renormalization ambiguities. We test our method by
computing the nucleon electric dipole moments in pure Yang-Mills theory at
several lattice spacings, enabling a first-of-its-kind continuum extrapolation.
The method is rather general and can be applied for any quantity computed in a
vacuum. This first application of the gradient flow has been
successful and demonstrates proof-of-principle, thereby providing a novel
method to obtain precise results for nucleon and light nuclear electric dipole
moments.Comment: 32 pages, 14 figures, 2 tables. v2: added 1 plot, 1 table and 1
reference. Typos corrected. Published versio
S-wave scattering of strangeness -3 baryons
We explore the interactions of two strangeness -3 baryons in multiple spin
channels with lattice QCD. This system provides an ideal laboratory for
exploring the interactions of multi-baryon systems with minimal dependence on
light quark masses. Model calculations of the two- system in two
previous works have obtained conflicting results, which can be resolved by
lattice QCD. The lattice calculations are performed using two different volumes
with and 3.9 fm on anisotropic clover lattices at
MeV with a lattice spacing of fm in the spatial direction and
in the temporal direction. Using multiple interpolating
operators from a non-displaced source, we present scattering information for
two ground state baryons in both the S=0 and S=2 channels. For S=0,
is extracted at two volumes, which lead to an extrapolated
scattering length of ,
indicating a weakly repulsive interaction. Additionally, for S=2, two separate
highly repulsive states are observed. We also present results on the
interactions of the excited strangeness -3, spin-1/2 states with the ground
spin-3/2 states for the spin-1 and spin-2 channels. Results for these
interactions are consistent with attractive behavior.Comment: 21 pages, 10 fig
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