Search results for "Tensor"

Bi-color spatial solitons in linearly uncoupled planar waveguides

2004

We report on the observation of spatial optical simultons in a novel geometry consisting of two partially overlapped, linearly uncoupled planar waveguides in lithium niobate obtained by reverse proton exchange. Two orthogonally polarized modes are coupled through an off-diagonal tensor element of the quadratic nonlinearity, giving rise to second harmonic generation and mutual trapping via cascading. This phenomenon demonstrates a balance between diffraction and self-focusing for two orthogonal modes of different waveguides, and occurs at room temperature in longitudinally uniform waveguides.

Broken symmetry states of metallacrowns: Distribution of spins and the g tensor

2019

Infinite matter properties and zero-range limit of nonrelativistic finite-range interactions

2016

We discuss some infinite matter properties of two finite-range interactions widely used for nuclear structure calculations, namely Gogny and M3Y interactions. We show that some useful informations can be deduced for the central, tensor and spin-orbit terms from the spin-isospin channels and the partial wave decomposition of the symmetric nuclear matter equation of state. We show in particular that the central part of the Gogny interaction should benefit from the introduction of a third Gaussian and the tensor parameters of both interactions can be deduced from special combinations of partial waves. We also discuss the fact that the spin-orbit of the M3Y interaction is not compatible with lo…

Partial wave decomposition of the N3LO equation of state

2014

By means of a partial wave decomposition, we separate their contributions to the equation of state of symmetric nuclear matter for the N3LO pseudo-potential. In particular, we show that although both the tensor and the spin-orbit terms do not contribute to the equation of state, they give a non-vanishing contribution to the separate (JLS) channels.

Partial wave decomposition of finite-range effective tensor interaction

2016

We perform a detailed analysis of the properties of the finite-range tensor term associated with the Gogny and M3Y effective interactions. In particular, by using a partial-wave decomposition of the equation of state of symmetric nuclear matter, we show how we can extract their tensor parameters directly from microscopic results based on bare nucleon-nucleon interactions. Furthermore, we show that the zero-range limit of both finite-range interactions has the form of the next-to-next-to-next-leading-order (N3LO) Skyrme pseudopotential, which thus constitutes a reliable approximation in the density range relevant for finite nuclei. Finally, we use Brueckner-Hartree-Fock results to fix the te…

A programming guide for tensor networks with global SU(2) symmetry

2020

Abstract This paper is a manual with tips and tricks for programming tensor network algorithms with global S U ( 2 ) symmetry. We focus on practical details that are many times overlooked when it comes to implementing the basic building blocks of codes, such as useful data structures to store the tensors, practical ways of manipulating them, and adapting typical functions for symmetric tensors. Here we do not restrict ourselves to any specific tensor network method, but keep always in mind that the implementation should scale well for simulations of higher-dimensional systems using, e.g., Projected Entangled Pair States, where tensors with many indices may show up. To this end, the structur…

Thermal field theories and shifted boundary Conditions

2014

The analytic continuation to an imaginary velocity of the canonical partition function of a thermal system expressed in a moving frame has a natural implementation in the Euclidean path-integral formulation in terms of shifted boundary conditions. The Poincare' invariance underlying a relativistic theory implies a dependence of the free-energy on the compact length L_0 and the shift xi only through the combination beta=L_0(1+xi^2)^(1/2). This in turn implies that the energy and the momentum distributions of the thermal theory are related, a fact which is encoded in a set of Ward identities among the correlators of the energy-momentum tensor. The latter have interesting applications in latti…

Infinite projected entangled pair states algorithm improved: Fast full update and gauge fixing

2015

© 2015 American Physical Society. ©2015 American Physical Society. The infinite projected entangled pair states (iPEPS) algorithm [J. Jordan, Phys. Rev. Lett. 101, 250602 (2008)PRLTAO0031-900710.1103/PhysRevLett.101.250602] has become a useful tool in the calculation of ground-state properties of two-dimensional quantum lattice systems in the thermodynamic limit. Despite its many successful implementations, the method has some limitations in its present formulation which hinder its application to some highly entangled systems. The purpose of this paper is to unravel some of these issues, in turn enhancing the stability and efficiency of iPEPS methods. For this, we first introduce the fast f…

Parameterized nonrelativistic limit of stellar structure equations in Ricci-based gravity theories

2021

We present the non-relativistic limit of the stellar structure equations of Ricci-based gravities, a family of metric-affine theories whose Lagrangian is built via contractions of the metric with the Ricci tensor of an a priori independent connection. We find that this limit is characterized by four parameters that arise in the expansion of several geometric quantities in powers of the stress-energy tensor of the matter fields. We discuss the relevance of this result for the phenomenology of non-relativistic stars, such as main-sequence stars as well as several substellar objects.

Junction conditions in Palatinif(R) gravity

2020

We work out the junction conditions for $f(R)$ gravity formulated in metric-affine (Palatini) spaces using a tensor distributional approach. These conditions are needed for building consistent models of gravitating bodies with an interior and exterior regions matched at some hypersurface. Some of these conditions depart from the standard Darmois-Israel ones of General Relativity and from their metric $f(R)$ counterparts. In particular, we find that the trace of the stress-energy momentum tensor in the bulk must be continuous across the matching hypersurface, though its normal derivative need not to. We illustrate the relevance of these conditions by considering the properties of stellar sur…