Soliton attenuation and emergent hydrodynamics in fragile matter

Disordered packings of soft grains are fragile mechanical systems that loose rigidity upon lowering the external pressure towards zero. At zero pressure, we find that any infinitesimal strain-impulse propagates initially as a non-linear solitary wave progressively attenuated by disorder. We demonstrate that the particle fluctuations generated by the solitary-wave decay, can be viewed as a granular analogue of temperature. Their presence is manifested by two emergent macroscopic properties absent in the unperturbed granular packing: a finite pressure that scales with the injected energy (akin to a granular temperature) and an anomalous viscosity that arises even when the microscopic mechanisms of energy dissipation are negligible. Consistent with the interpretation of this state as a fluid-like thermalized state, the shear modulus remains zero. Further, we follow in detail the attenuation of the initial solitary wave identifying two distinct regimes : an initial exponential decay, followed by a longer power law decay and suggest simple models to explain these two regimes.Comment: 8 pages, 3 Figure

Crystallography on Curved Surfaces

We study static and dynamical properties that distinguish two dimensional crystals constrained to lie on a curved substrate from their flat space counterparts. A generic mechanism of dislocation unbinding in the presence of varying Gaussian curvature is presented in the context of a model surface amenable to full analytical treatment. We find that glide diffusion of isolated dislocations is suppressed by a binding potential of purely geometrical origin. Finally, the energetics and biased diffusion dynamics of point defects such as vacancies and interstitials is explained in terms of their geometric potential.Comment: 12 Pages, 8 Figure

Shocks near Jamming

Non-linear sound is an extreme phenomenon typically observed in solids after violent explosions. But granular media are different. Right when they jam, these fragile and disordered solids exhibit a vanishing rigidity and sound speed, so that even tiny mechanical perturbations form supersonic shocks. Here, we perform simulations in which two-dimensional jammed granular packings are dynamically compressed, and demonstrate that the elementary excitations are strongly non-linear shocks, rather than ordinary phonons. We capture the full dependence of the shock speed on pressure and impact intensity by a surprisingly simple analytical model.Comment: Revised version. Accepted for publication in Phys. Rev. Let

Anomalous coupling between topological defects and curvature

We investigate a counterintuitive geometric interaction between defects and curvature in thin layers of superfluids, superconductors and liquid crystals deposited on curved surfaces. Each defect feels a geometric potential whose functional form is determined only by the shape of the surface, but whose sign and strength depend on the transformation properties of the order parameter. For superfluids and superconductors, the strength of this interaction is proportional to the square of the charge and causes all defects to be repelled (attracted) by regions of positive (negative) Gaussian curvature. For liquid crystals in the one elastic constant approximation, charges between 0 and $4\pi$ are attracted by regions of positive curvature while all other charges are repelled.Comment: 5 pages, 4 figures, minor changes, accepted for publication in Phys. Rev. Let

General rules for bosonic bunching in multimode interferometers

We perform a comprehensive set of experiments that characterize bosonic bunching of up to 3 photons in interferometers of up to 16 modes. Our experiments verify two rules that govern bosonic bunching. The first rule, obtained recently in [1,2], predicts the average behavior of the bunching probability and is known as the bosonic birthday paradox. The second rule is new, and establishes a n!-factor quantum enhancement for the probability that all n bosons bunch in a single output mode, with respect to the case of distinguishable bosons. Besides its fundamental importance in phenomena such as Bose-Einstein condensation, bosonic bunching can be exploited in applications such as linear optical quantum computing and quantum-enhanced metrology.Comment: 6 pages, 4 figures, and supplementary material (4 pages, 1 figure

Health of Non-binary and Genderqueer People: A Systematic Review

Background: Non-binary and genderqueer (NBGQ) people are those who do not identify within the gender binary system (male vs. female), not falling exclusively in man/male or woman/female normative categories. A higher proportion of NBGQ people is usually found within young persons. This population is marginalized and, as such, is at risk of stigmatization and of developing negative health outcomes. As literature on the health of NBGQ people is sparse, this study aims at systematically review the limited studies on this field. Methods: The research questions which guided the systematic review were: (1) What are the differences in the health levels between NBGQ and binary transgender (BT) individuals? (2) What are the differences in the health levels between NBGQ and cisgender individuals? (3) Which medical and psychological interventions are most suitable for improving NBGQ health? According to PRISMA guidelines, a systematic search was conducted in PubMed, PsycInfo, Web of Science, and Google Scholar. Results: Eleven studies met the inclusion criteria for the current systematic review. Among them, 9 were focused on the health differences between NBGQ and BT individuals, 4 of the latter and 1 individually were focused on the health differences between NBGQ and cisgender individuals, and 1 was focused on the evaluation of health outcomes related to medical procedures. No studies assessed psychological interventions aimed at improving health in NBGQ individuals. All studies were cross-sectional, did not generally recruit a large sample of NBGQ individuals, and used non-probability sample design. Results related to the difference in health between NBGQ and BT were mixed; indeed, some found a better health status while others a worse one. Results related to the differences in health between NBGQ and cisgender highlighted higher health needs in NBGQ than in BT individuals. The only study analyzing the effects of medical interventions on health found that NBGQ female-assigned at birth individuals improved their quality of life after chest surgery. Conclusions: Although scholars are starting to pay attention to the NBGQ health, research needs to be expanded both in terms of methodology and research contents. Clinical, health-related social policies, and research recommendations in this field are reported

A qualitative study on minority stress subjectively experienced by transgender and gender nonconforming people in Italy

A great amount of quantitative research has largely demonstrated that transgender and gender nonconforming (TGNC) people experience high rates of minority stress, against which they are able to exercise resilience and to use adaptive strategies buffering the negative effects of stress on health. Notwithstanding, qualitative investigations on how TGNC people subjectively experience minority stress are still scarce. This study aims at exploring the subjective experiences of minority stress through a focus group with 8 Italian TGNC individuals (5 male-to-female, 2 female-to-male, and 1 genderqueer; M = 25; SD = 5). Narratives were analyzed through the deductive thematic analysis. The analysis generated four main categories: (1) family rejection; (2) visibility of the body; (3) negative effects of family violence on health; and (4) integration of TGNC identity. Results offer an in-depth exploration of minority stress processes in TGNC people, as well as the impact of stress on health and adaptive strategies to face with stigma. Suggestions for clinical practice are discussed