15,679 research outputs found
Stress Response in Confined Arrays of Frictional and Frictionless Particles
Stress transmission inside three dimensional granular packings is
investigated using computer simulations. Localized force perturbation
techniques are implemented for frictionless and frictional shallow, ordered,
granular arrays confined by solid boundaries for a range of system sizes.
Stress response profiles for frictional packings agree well with the
predictions for the semi-infinite half plane of classical isotropic elasticity
theory down to boxes of linear dimensions of approximately forty particle
diameters and over several orders of magnitude in the applied force. The
response profiles for frictionless packings exhibit a transitional regime to
strongly anisotropic features with increasing box size. The differences between
the nature of the stress response are shown to be characterized by very
different particle displacement fields.Comment: To appear in J. Sta
Dual Bosonic Thermal Green Function and Fermion Correlators of the Massive Thirring Model at a Finite Temperature
The Euclidian thermal Green function of the two-dimensional (2D) free
massless scalar field in coordinate space is written as the real part of a
complex analytic function of a variable that conformally maps the infinite
strip () of the (: imaginary
time) plane into the upper-half-plane. Using this fact and the Cauchy-Riemann
conditions, we identify the dual thermal Green function as the imaginary part
of that function. Using both the thermal Green function and its dual, we obtain
an explicit series expression for the fermionic correlation functions of the
massive Thirring model (MTM) at a finite temperature.Comment: To appear in Mod. Phys. Lett. A, 8 page
Modal logic S4 as a paraconsistent logic with a topological semantics
In this paper the propositional logic LTop is introduced, as an extension of classical propositional logic by adding a paraconsistent negation. This logic has a very natural interpretation in terms of topological models. The logic LTop is nothing more than an alternative presentation of modal logic S4, but in the language of a paraconsistent logic. Moreover, LTop is a logic of formal inconsistency in which the consistency and inconsistency operators have a nice topological interpretation. This constitutes a new proof of S4 as being "the logic of topological spaces", but now under the perspective of paraconsistency
Elastic Moduli and Vibrational Modes in Jammed Particulate Packings
When we elastically impose a homogeneous, affine deformation on amorphous
solids, they also undergo an inhomogeneous, non-affine deformation, which can
have a crucial impact on the overall elastic response. To correctly understand
the elastic modulus , it is therefore necessary to take into account not
only the affine modulus , but also the non-affine modulus that
arises from the non-affine deformation. In the present work, we study the bulk
() and shear () moduli in static jammed particulate packings over a
range of packing fractions . One novelty of this work is to elucidate
the contribution of each vibrational mode to the non-affine through a
modal decomposition of the displacement and force fields. In the vicinity of
the (un)jamming transition, , the vibrational density of states,
, shows a plateau in the intermediate frequency regime above a
characteristic frequency . We illustrate that this unusual feature
apparent in is reflected in the behavior of : As , where , those modes for
contribute less and less, while contributions from those
for approach a constant value which results in to
approach a critical value , as . At
itself, the bulk modulus attains a finite value , such that has a value that remains below . In contrast,
for the critical shear modulus , and approach the same
value so that the total value becomes exactly zero, .
We explore what features of the configurational and vibrational properties
cause such the distinction between and , allowing us to validate
analytical expressions for their critical values.Comment: 23 pages, 13 figure
Comparative Enumeration Gene Expression
This paper is about differential gene expression measured by transcript counting methods such as SAGE or MPSS. It introduces two significance tests for detection of differential expressed tags: frequentist and Bayesian. Under the frequentist view, it is proposed a test that computes the critical level as a function of each tag total frequency. Under the Bayesian view the Full Bayesian Significance Test is used considering the logistic normal distribution. The two proposed significance levels, the frequentist and the Bayesian, are compared for a data set with four libraries. The linking function between them is a Beta distribution function with mean 0.39 and standard deviation 0.30
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