6,015 research outputs found
Addendum to "Travelling waves for a non-local Korteweg-de Vries-Burgers equation" [J. Differential Equations 257 (2014), no. 3, 720--758]
We add a theorem to [J. Differential Equations 257 (2014), no. 3, 720--758]
by F. Achleitner, C.M. Cuesta and S. Hittmeir. In that paper we studied
travelling wave solutions of a Korteweg-de Vries-Burgers type equation with a
non-local diffusion term. In particular, the proof of existence and uniqueness
of these waves relies on the assumption that the exponentially decaying
functions are the only bounded solutions of the linearised equation. In this
addendum we prove this assumption and thus close the existence and uniqueness
proof of travelling wave solutions
WP 37 - Search, mismatch and unemployment
This paper explores the efficiency of the equilibrium allocation in a matching model with heterogeneous workers and jobs. In the basic setup the labor force is divided in two groups. The high-skill workers are qualified for all jobs, while low-skill workers can perform unskilled jobs but not the more attractive skilled jobs. We demonstrate that the equilibrium with random search and ex post bargaining is never efficient. Under Hosios’ condition the average wage is correct, but bargaining compresses the wage distribution relative to workers’ shadow values. The wage compression distorts the relative profits of jobs making it too attractive to create skilled jobs. Furthermore, the low skill premium may prevent that the two types of workers efficiently sort in different jobs. In the first case we show that the market offers too few job opportunities for low-skill workers. On the contrary, when mismatch is socially wasteful, we find that low-skill workers experience shorter unemployment spells than in the efficient allocation. Finally, we show that our results generalize to environments with many types of agents and less stringent restrictions on the production technology.
Experimental and theoretical studies of sequence effects on the fluctuation and melting of short DNA molecules
Understanding the melting of short DNA sequences probes DNA at the scale of
the genetic code and raises questions which are very different from those posed
by very long sequences, which have been extensively studied. We investigate
this problem by combining experiments and theory. A new experimental method
allows us to make a mapping of the opening of the guanines along the sequence
as a function of temperature. The results indicate that non-local effects may
be important in DNA because an AT-rich region is able to influence the opening
of a base pair which is about 10 base pairs away. An earlier mesoscopic model
of DNA is modified to correctly describe the time scales associated to the
opening of individual base pairs well below melting, and to properly take into
account the sequence. Using this model to analyze some characteristic sequences
for which detailed experimental data on the melting is available [Montrichok et
al. 2003 Europhys. Lett. {\bf 62} 452], we show that we have to introduce
non-local effects of AT-rich regions to get acceptable results. This brings a
second indication that the influence of these highly fluctuating regions of DNA
on their neighborhood can extend to some distance.Comment: To be published in J. Phys. Condensed Matte
Nonlinear electrodynamics and the gravitational redshift of highly magnetised neutron stars
The idea that the nonlinear electromagnetic interaction, i. e., light
propagation in vacuum, can be geometrized was developed by Novello et al.
(2000) and Novello & Salim (2001). Since then a number of physical consequences
for the dynamics of a variety of systems have been explored. In a recent paper
Mosquera Cuesta & Salim (2003) presented the first astrophysical study where
such nonlinear electrodynamics (NLEDs) effects were accounted for in the case
of a highly magnetized neutron star or pulsar. In that paper the NLEDs was
invoked {\it a l\`a} Euler-Heisenberg, which is an infinite series expansion of
which only the first term was used for the analisys. The immediate consequence
of that study was an overall modification of the space-time geometry around the
pulsar, which is ``perceived'', in principle, only by light propagating out of
the star. This translates into an significant change in the surface redshift,
as inferred from absorption (emission) lines observed from a super magnetized
pulsar. The result proves to be even more dramatic for the so-called magnetars,
pulsars endowed with magnetic () fields higher then the Schafroth quantum
electrodynamics critical -field. Here we demonstrate that the same effect
still appears if one calls for the NLEDs in the form of the one rigorously
derived by Born & Infeld (1934) based on the special relativistic limit for the
velocity of approaching of an elementary particle to a pointlike electron [From
the mathematical point of view, the Born & Infeld (1934) NLEDs is described by
an exact Lagrangean, whose dynamics has been successfully studied in a wide set
of physical systems.].Comment: Accepted for publication in Month. Not. Roy. Ast. Soc. latex file,
mn-1.4.sty, 5 pages, 2 figure
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