The 4-spinon dynamical structure factor of the Heisenberg chain

We compute the exact 4-spinon contribution to the zero-temperature dynamical structure factor of the spin-1/2 Heisenberg isotropic antiferromagnet in zero magnetic field, directly in the thermodynamic limit. We make use of the expressions for matrix elements of local spin operators obtained by Jimbo and Miwa using the quantum affine symmetry of the model, and of their adaptation to the isotropic case by Abada, Bougourzi and Si-Lakhal (correcting some overall factors). The 4-spinon contribution to the first frequency moment sum rule at fixed momentum is calculated. This shows, as expected, that most of the remaining correlation weight above the known 2-spinon part is carried by 4-spinon states. Our results therefore provide an extremely accurate description of the exact structure factor.Comment: 13 page

Finite temperature correlations in the Lieb-Liniger 1D Bose gas

We address the problem of calculating finite-temperature response functions of an experimentally relevant low-dimensional strongly-correlated system: the integrable 1D Bose gas with repulsive \delta-function interaction (Lieb-Liniger model). Focusing on the observable dynamical density-density function, we present a Bethe Ansatz-based method allowing for its accurate evaluation over a broad range of momenta, frequencies, temperatures and interaction parameters, in finite but large systems. We show how thermal fluctuations smoothen the zero temperature critical behavior and present explicit quantitative results in experimentally accessible regimes.Comment: 5 page

Generalized TBA and generalized Gibbs

We consider the extension of the thermodynamic Bethe Ansatz (TBA) to cases in which additional terms involving higher conserved charges are added to the Hamiltonian, or in which a distinction is made between the Hamiltonian used for time evolution and that used for defining the density matrix. Writing down equations describing the saddle-point (pseudo-equilibrium) state of the infinite system, we prove the existence and uniqueness of solutions for Lieb-Liniger provided simple requirements are met. We show how a knowledge of the saddle-point rapidity distribution is equivalent to that of all generalized chemical potentials, and how the standard equilibrium equations for e.g. excitations are simply generalized.Comment: 9 pages, no figure

Survey of the galactic disk from 1 = -150 deg to 1 = 82 deg in the submillimeter range

The first almost complete survey of the galactic disk from 1 = -150 deg to 1 = 82 deg in the submillimeter range (effective wavelength = 380 microns), performed with the AGLAE balloon-borne instrument modified to include a submillimeter channel, is reported. The instrumentation and observational procedures are described, as are the signal processing and calibration. The results are presented as a profile of the submillimeter brightness of the galactic disk displayed as a function of the galactic longitude. This profile exhibits diffuse emission all along the disk with bright peaks associated with resolved sources. The averaged galactic spectrum is in agreement with a temperature distribution of the interstellar cold dust

Analytical expression for a post-quench time evolution of the one-body density matrix of one-dimensional hard-core bosons

We apply the logic of the quench action to give an exact analytical expression for the time evolution of the one-body density matrix after an interaction quench in the Lieb-Liniger model from the ground state of the free theory (BEC state) to the infinitely repulsive regime. In this limit there exists a mapping between the bosonic wavefuntions and the free fermionic ones but this does not help the computation of the one-body density matrix which is sensitive to particle statistics. The final expression, given in terms of the difference of the square root of two Fredholm determinants, can be numerically evaluated and is valid in the thermodynamic limit and for all times after the quench.Comment: 24 pages, 2 figur

Celebrating Haldane's `Luttinger liquid theory'

This short piece celebrates Haldane's seminal J. Phys. C 14, 2585 (1981) paper laying the foundations of the modern theory of Luttinger liquids in one-dimensional systems.Comment: Viewpoint for Journal of Physics: Condensed Matte