1,542 research outputs found
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 studyâs hypotheses. Results. The perceived denial of the victimsâ human uniqueness was not associated with the dependent variables, whereas the perceived denial of the victimsâ 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 victimsâ 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 machinesâ 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
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