Synchronized oscillations and acoustic fluidization in confined granular materials

According to the acoustic fluidization hypothesis, elastic waves at a characteristic frequency form inside seismic faults even in the absence of an external perturbation. These waves are able to generate a normal stress which contrasts the confining pressure and promotes failure. Here, we study the mechanisms responsible for this wave activation via numerical simulations of a granular fault model. We observe the particles belonging to the percolating backbone, which sustains the stress, to perform synchronized oscillations over ellipticlike trajectories in the fault plane. These oscillations occur at the characteristic frequency of acoustic fluidization. As the applied shear stress increases, these oscillations become perpendicular to the fault plane just before the system fails, opposing the confining pressure, consistently with the acoustic fluidization scenario. The same change of orientation can be induced by external perturbations at the acoustic fluidization frequency

Induced and endogenous acoustic oscillations in granular faults

The frictional properties of disordered systems are affected by external perturbations. These perturbations usually weaken the system by reducing the macroscopic friction coefficient. This friction reduction is of particular interest in the case of disordered systems composed of granular particles confined between two plates, as this is a simple model of seismic fault. Indeed, in the geophysical context frictional weakening could explain the unexpected weakness of some faults, as well as earthquake remote triggering. In this manuscript we review recent results concerning the response of confined granular systems to external perturbations, considering the different mechanisms by which the perturbation could weaken a system, the relevance of the frictional reduction to earthquakes, as well as discussing the intriguing scenario whereby the weakening is not monotonic in the perturbation frequency, so that a re-entrant transition is observed, as the system first enters a fluidized state and then returns to a frictional state.Comment: 15 pages, 12 figure

Two flavor QCD and Confinement

We argue that the order of the chiral transition for N_f=2 is a sensitive probe of the QCD vacuum, in particular of the mechanism of color confinement. A strategy is developed to investigate the order of the transition by use of finite size scaling analysis. An in-depth numerical investigation is performed with staggered fermions on lattices with N_t=4 and N_s=12,16,20,24,32 and quark masses am_q ranging from 0.01335 to 0.307036. The specific heat and a number of susceptibilities are measured and compared with the expectations of an O(4) second order and of a first order phase transition. A second order transition in the O(4) and O(2) universality classes are excluded. Substantial evidence emerges for a first order transition. A detailed comparison with previous works is performed.Comment: 46 pages, 20 eps figures, 9 tables, REVTeX

'You Treated Me Like an Object, I Don't Forgive You!': The Effect of Dehumanization on Interpersonal Forgiveness from the Victim's Perspective

Introduction. There is a gap in the literature on the impact of the perceptions of a victim of an offense upon their forgiveness towards the offender, particularly when those perceptions include dehumanization. Objectives. The present cross-sectional exploratory study aimed at examining whether the perceptions of being treated in a dehumanized fashion influences interpersonal forgiveness, avoidance, and revenge intentions of dehumanized victims towards the offender. Method. We recruited 149 individuals from the general population, who took part in an online task, consisting of remembering an offense they had been victim of and of a set of self-reported measures of dehumanization (uniqueness and nature), interpersonal forgiveness, avoidance, and revenge intentions. We used multiple linear regression to test the study’s hypotheses. Results. The perceived denial of the victims’ human uniqueness was not associated with the dependent variables, whereas the perceived denial of the victims’ human nature was significantly and negatively associated with interpersonal forgiveness and positively with avoidance and revenge intentions, after controlling for the effects of a set of known covariates. Conclusions. The results revealed a role for dehumanization (nature) in predicting the victims’ interpersonal forgiveness, avoidance, and revenge intentions. Implications for further research are discussed

Improved Lattice Spectroscopy of Minimal Walking Technicolor

We present a numerical study of spectroscopic observables in the SU(2) gauge theory with two adjoint fermions using improved source and sink operators. We compare in detail our improved results with previous determinations of masses that used point sources and sinks and we investigate possible systematic effects in both cases. Such comparison enables us to clearly assess the impact of a short temporal extent on the physical picture, and to investigate some effects due to the finite spatial box. While confirming the IR-conformal behaviour of the theory, our investigation shows that in order to make firm quantitative predictions, a better handle on finite size effects is needed.Comment: 33 pages, 30 figures, 18 table

BSMBench: A flexible and scalable HPC benchmark from beyond the standard model physics

Lattice Quantum ChromoDynamics (QCD), and by extension its parent field, Lattice Gauge Theory (LGT), make up a significant fraction of supercomputing cycles worldwide. As such, it would be irresponsible not to evaluate machines’ suitability for such applications. To this end, a benchmark has been developed to assess the performance of LGT applications on modern HPC platforms. Distinct from previous QCD-based benchmarks, this allows probing the behaviour of a variety of theories, which allows varying the ratio of demands between on- node computations and inter-node communications. The results of testing this benchmark on various recent HPC platforms are presented, and directions for future development are discussed

Pseudo Goldstone Bosons Phenomenology in Minimal Walking Technicolor

We construct the non-linear realized Lagrangian for the Goldstone Bosons associated to the breaking pattern of SU(4) to SO(4). This pattern is expected to occur in any Technicolor extension of the standard model featuring two Dirac fermions transforming according to real representations of the underlying gauge group. We concentrate on the Minimal Walking Technicolor quantum number assignments with respect to the standard model symmetries. We demonstrate that for, any choice of the quantum numbers, consistent with gauge and Witten anomalies the spectrum of the pseudo Goldstone Bosons contains electrically doubly charged states which can be discovered at the Large Hadron Collider.Comment: 25 pages, 5 figure