Dual Formulation and Phase Diagram of Lattice QCD in the Strong Coupling Regime

We present the computation of invariants that arise in the strong coupling expansion of lattice QCD. These invariants are needed for Monte Carlo simulations of Lattice QCD with staggered fermions in a dual, color singlet representation. This formulation is in particular useful to tame the finite density sign problem. The gauge integrals in this limiting case $\beta\rightarrow 0$ are well known, but the gauge integrals needed to study the gauge corrections are more involved. We discuss a method to evaluate such integrals. The phase boundary of lattice QCD for staggered fermions in the $\mu_B-T$ plane has been established in the strong coupling limit. We present numerical simulations away from the strong coupling limit, taking into account the higher order gauge corrections via plaquette occupation numbers. This allows to study the nuclear and chiral transition as a function of $\beta$.Comment: 16 pages, 10 figures, Proceedings of the 35th International Symposium on Lattice Field Theory, Granada, Spai

The QCD Phase Diagram from Strong Coupling Expansion

Gagliardi G. The QCD Phase Diagram from Strong Coupling Expansion. Bielefeld: Universität Bielefeld; 2020

A 1-year follow-up study with C-VEMPs, O-VEMPs and video head impulse testing in vestibular neuritis

The aim of this paper was to evaluate prospectively, in a group of patients affected by VN, a diagnostic protocol employing C-VEMPs, O-VEMPs and vHIT together. The diagnosis of vestibular neurolabyrinthitis was based on the clinical history, absence of associated auditory or neurological symptoms, and a neuro-otological examination with an evaluation of lateral semicircular canal function using the Fitzgerald-Hallpike caloric vestibular test and ice test. Our series revealed an incidence of 55 % of superior and inferior vestibular neurolabyrinthitis, 40 % of superior vestibular neurolabyrinthitis and 5 % of inferior vestibular neurolabyrinthitis. These data, however, comprised different degrees of vestibular involvement considering the evaluation of each single vestibular end-organ with potential different prognosis. Four patients had only deficits of the horizontal and superior semicircular canals or their ampullary nerves. The implementation of C-VEMPs, O-VEMPs and vHIT in a vestibular diagnostic protocol has made possible to observe patients with ampullary VN, unidentifiable with other types of vestibular exams. The effect of age seems to have some impact on the recovery. When recovery firstly involves the utricular and saccular nerves and subsequently the ampullary nerves, it may be reasonable to expect a more favorable and successful outcome

New dual representation for staggered lattice QCD

Gagliardi G, Unger W. New dual representation for staggered lattice QCD. PHYSICAL REVIEW D. 2020;101(3): 034509.We propose a new strategy to evaluate the partition function of lattice QCD with Wilson gauge action coupled to staggered fermions, based on a strong coupling expansion in the inverse bare gauge coupling beta = 2N/g(2). Our method makes use of the recently developed formalism to evaluate the SU(N) 1-link integrals and consists in an exact rewriting of the partition function in terms of a set of additional dual degrees of freedom which we call "decoupling operator indices" (DOI). The method is not limited to any particular number of dimensions or gauge group U(N), SU(N). In terms of the DOI, the system takes the form of a tensor network which can be simulated using wormlike algorithms. Higher order beta-corrections to strong coupling lattice QCD can be, in principle, systematically evaluated, helping to answer the question whether the finite density sign problem remains mild when plaquette contributions are included. Issues related to the complexity of the description and strategies for the stochastic evaluation of the partition function are discussed

Towards a Dual Representation of Lattice QCD

Our knowledge about the QCD phase diagram at finite baryon chemical potential $\mu_{B}$ is limited by the well known sign problem. The path integral measure, in the standard determinantal approach, becomes complex at finite $\mu_{B}$ so that standard Monte Carlo techniques cannot be directly applied. As the sign problem is representation dependent, by a suitable choice of the fundamental degrees of freedom that parameterize the partition function, it can get mild enough so that reweighting techniques can be used. A successful formulation, capable to tame the sign problem, is known since decades in the limiting case $\beta\to 0$, where performing the gauge integration first, gives rise to a dual formulation in terms of color singlets (MDP formulation). Going beyond the strong coupling limit represents a serious challenge as the gauge integrals involved in the computation are only partially known analytically and become strongly coupled for $\beta>0$. We will present explict formulae for all the integral relevant for ${\rm SU}(N)$ gauge theories discretised \`a la Wilson, and will discuss how they can be used to obtain a positive dual formulation, valid for all $\beta$, for pure Yang Mills theory.Comment: 7 pages, 1 figure, proceedings to talk presented at 36th annual International Symposium on Lattice Field Theory, 22-28 July 2018, East Lansing, MI, US

Single-molecule Electronics: Cooling Individual Vibrational Modes by the Tunneling Current

Electronic devices composed of single molecules constitute the ultimate limit in the continued downscaling of electronic components. A key challenge for single-molecule electronics is to control the temperature of these junctions. Controlling heating and cooling effects in individual vibrational modes, can in principle, be utilized to increase stability of single-molecule junctions under bias, to pump energy into particular vibrational modes to perform current-induced reactions or to increase the resolution in inelastic electron tunneling spectroscopy by controlling the life-times of phonons in a molecule by suppressing absorption and external dissipation processes. Under bias the current and the molecule exchange energy, which typically results in heating of the molecule. However, the opposite process is also possible, where energy is extracted from the molecule by the tunneling current. Designing a molecular 'heat sink' where a particular vibrational mode funnels heat out of the molecule and into the leads would be very desirable. It is even possible to imagine how the vibrational energy of the other vibrational modes could be funneled into the 'cooling mode', given the right molecular design. Previous efforts to understand heating and cooling mechanisms in single molecule junctions, have primarily been concerned with small models, where it is unclear which molecular systems they correspond to. In this paper, our focus is on suppressing heating and obtaining current-induced cooling in certain vibrational modes. Strategies for cooling vibrational modes in single-molecule junctions are presented, together with atomistic calculations based on those strategies. Cooling and reduced heating are observed for two different cooling schemes in calculations of atomistic single-molecule junctions.Comment: 18 pages, 6 figure

Retinitis pigmentosa: evaluation of the vestibular system with cervical and ocular vestibular evoked myogenic potentials and the video head impulse test

OBJECTIVE: Retinitis pigmentosa (RP) represents a group of inherited disorders in which abnormalities of the photoreceptors lead to progressive visual loss. Night blindness, peripheral visual field loss, and eventual total blindness represent typical visual damage of such disease. No study has previously evaluated the presence of a "latent" vestibular deficit in patients with RP. STUDY DESIGN: Prospective study with caloric test, cervical vestibular evoked myogenic potentials (C-VEMPs), ocular vestibular evoked myogenic potentials (O-VEMPs), and video head impulse test (v-HIT). SETTING: Tertiary referral center. PATIENTS: 16 patients suffering from RP. INTERVENTION: Evaluation of vestibular dysfunction with caloric test, C-VEMPs, O-VEMPs, and the measurement of the vestibular-ocular reflex (VOR) using the v-HIT. RESULTS: Only five patients with RP showed normal values in all the vestibular tests performed. Three patients had an evident deficit at the caloric test, whereas eight (50%) of them had a normal caloric test but a pathological response in at least one of the other vestibular tests performed. No patient of the study showed a bilateral otolith or ampullary dysfunction. CONCLUSION: Our patients with RP unexpectedly showed pathological responses in at least one of the vestibular tests performed. Nowadays, in patients affected by RP, a vestibular diagnostic protocol must include VEMPs and v-HIT to confirm the vestibular damage and to identify selective damage of the vestibular nerve

Physical activity scale for the elderly: translation, cultural adaptation, and validation of the Italian version

Objective. The aim of the study was to translate and culturally adapt the Physical Activity Scale for the Elderly into Italian (PASE-I) and to evaluate its psychometric properties in the Italian older adults healthy population. Methods. For translation and cultural adaptation, the "Translation and Cultural Adaptation of Patient-Reported Outcomes Measures" guidelines have been followed. Participants included healthy individuals between 55 and 75 years old. The reliability and validity were assessed following the "Consensus-Based Standards for the Selection of Health Status Measurement Instruments" checklist. To evaluate internal consistency and test-retest reliability, Cronbach's α and Intraclass Correlation Coefficient (ICC) were, respectively, calculated. The Berg Balance Score (BBS) and the PASE-I were administered together, and Pearson's correlation coefficient was calculated for validity. Results. All the PASE-I items were identical or similar to the original version. The scale was administered twice within a week to 94 Italian healthy older people. The mean PASE-I score in this study was 159±77.88. Cronbach's α was 0.815 (p < 0.01) and ICC was 0.977 (p < 0.01). The correlation with the BBS was 0.817 (p < 0.01). Conclusions. The PASE-I showed positive results for reliability and validity. This scale will be of great use to clinicians and researchers in evaluating and managing physical activities in the Italian older adults population