COMPARING APPLES TO APPLES
Does an apple dropped in the summer fall at the same rate
as an apple dropped in the winter? The answer could be no,
according to this Letter.
The work presents a new class of possible violations of
Einstein's theory of relativity that are detectable only
when gravity is involved. The intrinsic size of the new
relativity violations could be large because the weak
gravity force suppresses effects.
The new violations change the gravitational properties of
objects depending on their motion and composition. Objects
on the Earth move differently in different seasons because
the Earth moves around the Sun, so apples could fall faster
in some seasons than others.
The new violations affect matter and antimatter differently,
so an apple and an anti-apple could fall at different rates
too. Objects with different compositions like apples and
oranges may also fall differently.
***
BV10489
Heat transport in nanodevices: a road to nonequilibrium temperature.
The recent surge of interest in nanotechnology, in miniaturized systems with internal degrees of freedom, or in high-frequency short wavelength perturbations,has opened new frontiers in the analysis of heat transport.
Several experiments or simulations along nanoscale devices led to results significantly different from those of the classical Fourier law since, at the lenght scale of the mean free path of heat carriers, small temperature differences may produce very high temperature gradients.
In this paper a new dynamical temperature has been used to model hyperbolic heat transport in nanosystems. It is related to the absolute one by a partial differential equation and at the equilibrium reduces to a suitable regular function of the local-equilibrium temperature.
By using such a temperature We have studied the different speed of propagation of thermal signals along or against the average heat flux. The result indicates that perturbations of the hotter temperature or of the lower temperature in a nanosystem will not propagate at the same speed inside the system.
This work may have important technological applications since it can be useful in the dynamical studies of heat transfer in nanosystems. From the theoretical point of view, the paper may open a new road to the definiton of nonequilibrium temperature in the presence of fast phenomena.
***
BU10577
PROBING METALLIC SURFACES WITH ELECTRONS - A NEW THEORY
Electron energy-loss spectroscopy is a technique in which solid surfaces are bombarded with electrons and the scattering intensity is recorded as a function of the energy lost by the incident electrons to the solid, as a means of getting information about the electronic structure of solid surfaces. A new theoretical model has been formulated that accounts successfully for such measurements made on the transition metals Scandium, Titanium, Vanadium, Chromium, Manganese, Iron, Cobalt and Nickel. This is to appear soon in the journal Physical Review B (Condensed Matter and Materials Physics). Until now, experimentalists have relied mainly on theories based on light/lasers/photons as probes for solids to support their electron energy-loss measurements -and these involve considerable amount of computational effort to do so. The final results of the new theoretical model require only few adjustable parameters to fit theory to measurements, and can be performed even on scientific calculators. Perhaps the scope and possible impact of the new theoretical model is best summed up by a remark in the report of one of the referees: "...The theoretical results will have an impact on future experiments and their interpretation..."
***
LU12103 and LU12107
Fracture in slow motion: Observations of a crack’s singular region yield
a new theory of fracture
A detailed view of precisely how things break is achieved by using soft
materials to slow down fracture dynamics by a factor of a thousand,
while still faithfully mirroring all of the complicated dynamics of the
fracture process. This enables first-time high resolution measurements
of the deformation fields surrounding the near-singular tip of rapid
cracks. The measurements show that the canonical theory of fracture
fails to provide a consistent description of the experimental data, with
elastic nonlinearities near the singular region the culprit. This, by
itself, is not surprising since the theory is based on a key assumption
of linear elastic behavior – which is an excellent assumption except at
the smallest scales near a crack’s tip. On the other hand, as fracture
occurs precisely /at/ the smallest scales, a description of this
near-tip region is important. In an accompanying Letter we develop a
weakly nonlinear theory of the dynamic fracture of a single crack that
provides excellent quantitative agreement with the experiments. The
theory, which is based on a controlled expansion of the nonlinearly
elastic stress-strain relation for highly stretched material, is
expected to be generally applicable to any brittle material.
