Andrea De Luca

Stationary states in a free fermionic chain from the quench action method

We employ the Quench Action Method (QAM) for a recently considered geometrical quantum quench: two free fermionic chains initially at different temperatures are joined together in the middle and let evolve unitarily with a translation invariant Hamiltonian. We show that two different stationary regimes are reached at long times, depending on the interplay between the observation time scale T and the total length L of the system. We show the emergence of a non-equilibrium steady state (NESS) supporting an energy current for observation time T much smaller than the system size L. We then identify a longer time-scale for which thermalization occurs in a Generalized Gibbs Ensemble (GGE).

Energy transport in Heisenberg chains beyond the Luttinger liquid paradigm

We study the energy transport between two interacting spin chains which are initially separated, held at different temperatures and subsequently put in contact. We consider the spin-1/2 XXZ model in the gapless regime and exploit its integrability properties to formulate an analytical Ansatz for the non-equilibrium steady state even at temperatures where the low-energy Luttinger liquid description is not accurate. We apply our method to compute the steady energy current and benchmark it both with the known low-energy limit and at higher temperatures with numerical simulations. We find an excellent agreement even at high temperatures, where the Luttinger liquid prediction is shown to fail.

Nonequilibrium thermal transport in the quantum Ising chain

We consider two quantum Ising chains initially prepared at thermal equilibrium but with different temperatures and coupled at a given time through one of their end points. In the long-time limit the system reaches a non-equilibrium steady state. We discuss properties of this non-equilibrium steady state, and characterize the convergence to the steady regime. We compute the mean energy flux through the chain and the large deviation function for the quantum and thermal fluctuations of this energy transfer.

1E 161348–5055 in the Supernova Remnant RCW 103: A Magnetar in a Young Low-Mass Binary System?

We suggest that the unique X-ray source 1E 161348?5055 at the center of the supernova remnant RCW 103 consists of a neutron star in close orbit with a low-mass main-sequence star. The time signature of 6.67 hr is interpreted as the neutron stars spin period. This requires the neutron star to be endowed with a high surface magnetic field of ~1015 G. Magnetic or/and material (propeller) torques are able to rapidly spin the young neutron star down to an asymptotic, equilibrium spin period in close synchronism with the orbital period, similar to what happens in the Polar cataclysmic variables. 1E 161348?5055 could be the first case of a magnetar born in a young low-mass binary system.

Hubble Space Telescope Proper Motion Confirms the Optical Identification of the Nearby Pulsar PSR 1929+10

We report on the proper-motion measurement of the proposed optical counterpart of the X-ray/radio pulsar PSR 1929+10. Using images obtained with the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS; average epoch 2001.73), we computed a yearly displacement of +97 ? 1 mas yr-1 in right ascension and +46 ? 1 mas yr-1 in declination since the epoch (1994.52) of the original HST Faint Object Camera (FOC) detection. Both the magnitude and direction of the optical proper-motion components are found to be fully consistent with the most recent Very Long Baseline Array radio measurements. This result provides an unambiguous confirmation of the pulsar optical identification. In addition, we have used the combined STIS/FOC data sets to derive information on the pulsar spectrum, which seems characterized by a power-law component, apparently unrelated to the X-ray emission.

Nonequilibrium spin transport in integrable spin chains: Persistent currents and emergence of magnetic domains

We construct exact steady states of unitary nonequilibrium time evolution in the gapless XXZ spin-1/2 chain where integrability preserves ballistic spin transport at long times. We characterize the quasilocal conserved quantities responsible for this feature and introduce a computationally effective way to evaluate their expectation values on generic matrix product initial states. We employ this approach to reproduce the long-time limit of local observables in all quantum quenches which explicitly break particle-hole or time-reversal symmetry. We focus on a class of initial states supporting persistent spin currents and our predictions remarkably agree with numerical simulations at long times. Furthermore, we propose a protocol for this model where interactions, even when antiferromagnetic, are responsible for the unbounded growth of a macroscopic magnetic domain.

Energy transport between two integrable spin chains

We study the energy transport in a system of two half-infinite XXZ chains initially kept separated at different temperatures, and later connected and let free to evolve unitarily. By changing independently the parameters of the two halves, we highlight, through bosonisation and time-dependent matrix-product-state simulations, the different contributions of low-lying bosonic modes and of fermionic quasi-particles to the energy transport. In the simulations we also observe that the energy current reaches a finite value which only slowly decays to zero. The general pictures that emerges is the following. Since integrability is only locally broken in this model, a pre-equilibration behaviour may appear. In particular, when the sound velocities of the bosonic modes of the two halves match, the low-temperature energy current is almost stationary and described by a formula with a non-universal prefactor interpreted as a transmission coefficient. Thermalisation, characterized by the absence of any energy flow, occurs only on longer time-scales which are not accessible with our numerics.

Equilibration properties of classical integrable field theories

We study the equilibration properties of classical integrable field theories at a finite energy density, with a time evolution that starts from initial conditions far from equilibrium. These classical field theories may be regarded as quantum field theories in the regime of high occupation numbers. This observation permits to recover the classical quantities from the quantum ones by taking a proper

Thermalization and many-body localization in systems under dynamic nuclear polarization

\hbar \rightarrow 0

Stellar Encounter Driven Red-giant Star Mass Loss in Globular Clusters

limit. In particular, the time averages of the classical theories can be expressed in terms of a suitable version of the LeClair-Mussardo formula relative to the Generalized Gibbs Ensemble. For the purposes of handling time averages, our approach provides a solution of the problem of the {\em infinite gap solutions} of the Inverse Scattering Method.