9,623 research outputs found
Spatial and spin symmetry breaking in semidefinite-programming-based Hartree-Fock theory
The Hartree-Fock problem was recently recast as a semidefinite optimization
over the space of rank-constrained two-body reduced-density matrices (RDMs)
[Phys. Rev. A 89, 010502(R) (2014)]. This formulation of the problem transfers
the non-convexity of the Hartree-Fock energy functional to the rank constraint
on the two-body RDM. We consider an equivalent optimization over the space of
positive semidefinite one-electron RDMs (1-RDMs) that retains the non-convexity
of the Hartree-Fock energy expression. The optimized 1-RDM satisfies ensemble
-representability conditions, and ensemble spin-state conditions may be
imposed as well. The spin-state conditions place additional linear and
nonlinear constraints on the 1-RDM. We apply this RDM-based approach to several
molecular systems and explore its spatial (point group) and spin ( and
) symmetry breaking properties. When imposing and symmetry but
relaxing point group symmetry, the procedure often locates
spatial-symmetry-broken solutions that are difficult to identify using standard
algorithms. For example, the RDM-based approach yields a smooth,
spatial-symmetry-broken potential energy curve for the well-known Be--H
insertion pathway. We also demonstrate numerically that, upon relaxation of
and symmetry constraints, the RDM-based approach is equivalent to
real-valued generalized Hartree-Fock theory.Comment: 9 pages, 6 figure
A coherent state approach to effective potential in noncommutative D=(2+1) models
In this work we study the effective potential in noncommutative
three-dimensional models where the noncommutativity is introduced through the
coherent state approach. We discuss some important characteristics that seem to
be typical to this approach, specially the behavior of the quantum corrections
in the small noncommutativity limit.Comment: revtex4, 8 pages, 2 figures
On the Adler-Bell-Jackiw anomaly in a Horava-Lifshitz-like QED
We show the absence of the ABJ anomaly for the Horava-Lifshitz-like QED with
any even . Besides of this, we study the graph contributing to the ABJ
anomaly at non-zero temperature and extend the Fujikawa's methodology of
studying the integral measure for our model.Comment: 9 pages, version accepted to EP
On the perturbative generation of the higher-derivative Lorentz-breaking terms
In this paper, we describe the perturbative generation of the
higher-derivative Lorentz-breaking terms for the gauge field, that is, the
Myers-Pospelov term and the higher-derivative Carroll-Field-Jackiw term. These
terms are explicitly calculated in the one-loop approximation and shown to be
finite and ambiguous.Comment: 12 pages, version accepted to PR
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