Quantum Impurity Models coupled to Markovian and Non Markovian Baths

We develop a method to study quantum impurity models, small interacting quantum systems linearly coupled to an environment, in presence of an additional Markovian quantum bath, with a generic non-linear coupling to the impurity. We aim at computing the evolution operator of the reduced density matrix of the impurity, obtained after tracing out all the environmental degrees of freedom. First, we derive an exact real-time hybridization expansion for this quantity, which generalizes the result obtained in absence of the additional Markovian dissipation, and which could be amenable to stochastic sampling through diagrammatic Monte Carlo. Then, we obtain a Dyson equation for this quantity and we evaluate its self-energy with a resummation technique known as the Non-Crossing-Approximation. We apply this novel approach to a simple fermionic impurity coupled to a zero temperature fermionic bath and in presence of Markovian pump, losses and dephasing.Comment: Accepted for publication in the special issue on "Dynamics of Open Quantum Systems" of the AIP Journal of Chemical Physics (JCP

Hybrid light-matter states in topological superconductors coupled to cavity photons

We consider a one-dimensional topological superconductor hosting Majorana bound states at its ends coupled to a single mode cavity. In the strong light-matter coupling regime, electronic and photonic degrees of freedom hybridize resulting in the formation of polaritons. We find the polariton spectrum by calculating the cavity photon spectral function of the coupled electron-photon system. In the topological phase the lower in energy polariton modes are formed by the bulk-Majorana transitions coupled to cavity photons and are also sensitive to the Majorana parity. In the trivial phase the lower polariton modes emerge due to the coupling of the bulk-bulk transitions across the gap to photons. Our work demonstrates the formation of polaritons in topological superconductors coupled to photons that contain information on the features of the Majorana bound states.Comment: 9 pages, 5 figures; references adde

Anharmonic activations in proteins and peptide model systems and their connection with supercooled water thermodynamics

Proteins, the nano-machines of living systems, are highly dynamic molecules. The time-scale of functionally relevant motions spans over a very broad range, from femtoseconds to several seconds. In particular, the pico- to nanoseconds region is characterized by side-chain and backbone anharmonic fluctuations that are responsible for many biological tasks like ligand binding, substrate recognition and enzymatic activity. Neutron scattering on hydrated protein powders reveals two main activations of anharmonic dynamics, characterized by different onset temperature and amplitude. Here we review our work on synthetic polypeptides, native proteins, and single amino acids to identify the physical origin of the two onsets—one involving water-independent local dynamics of methyl groups and, to a minor extent, of aromatic side-chains, and the other one, known as “protein dynamical transition”, concerning large scale functional protein fluctuations, most likely induced by a crossover in the structure and dynamics of hydration water connected with the second critical point hypothesis

Dissipative Dynamics of a Fermionic Superfluid with Two-Body Losses

We study the dissipative dynamics of a fermionic superfluid in presence of two-body losses. We use a variational approach for the Lindblad dynamics and obtain dynamical equations for Anderson's pseudo-spins where dissipation enters as a complex pairing interaction as well as effective, density-dependent, single particle losses which break the conservation of the pseudo-spin norm. We show that this latter has key consequences on the dynamical behavior of the system. In the case of a sudden switching of the two-body losses we show that the superfluid order parameter decays much faster than then particle density at short times and eventually slows-down, setting into a power-law decay at longer time scales driven by the depletion of the system. We then consider a quench of pairing interaction, leading to coherent oscillations in the unitary case, followed by the switching of the dissipation. We show that losses wash away the dynamical BCS synchronization by introducing not only damping but also a renormalization of the frequency of coherent oscillations, which depends strongly from the rate of two-body losses.Comment: 5 pages, 3 figure

Protein dynamical transition vs. liquid-liquid phase transition in protein hydration water

In this work, we compare experimental data on myoglobin hydrated powders from elastic neutron scattering, broadband dielectric spectroscopy, and differential scanning calorimetry. Our aim is to obtain new insights on the connection between the protein dynamical transition, a fundamental phenomenon observed in proteins whose physical origin is highly debated, and the liquid-liquid phase transition (LLPT) possibly occurring in protein hydration water and related to the existence of a low temperature critical point in supercooled water. Our results provide a consistent thermodynamic/dynamic description which gives experimental support to the LLPT hypothesis and further reveals how fundamental properties of water and proteins are tightly related

From pregnancy to motherhood among adolescents : a longitudinal study on factors associated with mother-infant interaction in Brazil

Nesta tese investigaram-se características psicossociais associadas à qualidade dos comportamentos maternos de adolescentes e seus filhos na gravidez, 3, 6 e 12 meses pós-parto. Apoio social, depressão materna e comportamentos mãe-bebé foram analisados no pré e pós-parto. O primeiro estudo investigou a associação entre apoio social e depressão com apego materno-fetal. O apoio social moderou esta associação no grupo com mais depressão. No segundo estudo, examinou-se a relação entre apoio social e depressão durante gravidez e 3 meses pós-parto com comportamento materno. Sobressaiu a importância do apoio social e depressão no pós-parto em detrimento da gravidez. O terceiro estudo avaliou se o comportamento do bebé era mediado pelo apoio social recebido pela mãe. Comprovou-se essa mediação. Por fim, examinou-se a relação entre os comportamentos mãe-criança e as variáveis psicossociais ao longo dos quatro tempos. Destaca-se a influência das variáveis psicossociais na qualidade dos comportamentos da mãe-bebé no decorrer do tempo.This doctoral dissertation aimed to investigate longitudinally social and personal factors associated with mother-infant behaviors, at pregnancy, 3, 6, and 12 months postpartum. Self-reported measures of social support and depression were applied and mother-infant behaviors observed at postpartum. The first one examined the association between social support, depression with maternal-fetal attachment. Social support moderated the effect of maternal depression on maternal-fetal attachment. The second study explored how variables measured during pregnancy predicted postpartum maternal behaviors, as well as its concurrent reports. Just postpartum measures of social support and maternal depression were associated with maternal behaviors at 3 months. Study 3 accessed if infant behaviors were mediated social support received by mother. This mediation model was found. The last study analyzed the correlation between social support, depression, mother and infant behaviors across the four time-points. Results revealed how mother-infant behaviors are affected by personal and contextual variables over time

Signatures of Self-Trapping in the Driven-Dissipative Bose-Hubbard Dimer

We investigate signatures of a self-trapping transition in the driven-dissipative Bose Hubbard dimer, in presence of incoherent pump and single-particle losses. For fully symmetric couplings the stationary state density matrix is independent of any Hamiltonian parameter, and cannot therefore capture the competition between hopping-induced delocalization and the interaction-dominated self-trapping regime. We focus instead on the exact quantum dynamics of the particle imbalance after the system is prepared in a variety of initial states, and on the frequency-resolved spectral properties of the steady state, as encoded in the single-particle Green's functions. We find clear signatures of a localization-delocalization crossover as a function of hopping to interaction ratio. We further show that a finite a pump-loss asymmetry restores a delocalization crossover in the steady-state imbalance and leads to a finite intra-dimer dissipation

Medicina e diritto nell’Ottocento attraverso l’opera di Lorenzo Tenchini (1852-1906).La Scuola medica positiva

This article analyses the figure of the Brescian doctor Lorenzo Tenchini (1852-1906),famous for creating wax masks to reproduce the faces of criminals in order to showthe link between the shape of the face and the predisposition to crime

Volume-to-Area Law Entanglement Transition in a non-Hermitian Free Fermionic Chain

We consider the dynamics of the non-Hermitian Su-Schrieffer-Heeger model arising as the no-click limit of a continuously monitored free fermion chain where particles and holes are measured on two sublattices. The model has $\mathcal{PT}$-symmetry, which we show to spontaneously break as a function of the strength of measurement backaction, resulting in a spectral transition where quasiparticles acquire a finite lifetime in patches of the Brillouin zone. We compute the entanglement entropy's dynamics in the thermodynamic limit and demonstrate an entanglement transition between volume-law and area-law scaling, which we characterize analytically. Interestingly we show that the entanglement transition and the $\mathcal{PT}$-symmetry breaking do not coincide, the former occurring when the entire decay spectrum of the quasiparticle becomes gapped.Comment: version 2 , 4 figures, minor adjustments and clarifications in section I