1,522 research outputs found
Typical Gibbs configurations for the 1d Random Field Ising Model with long range interaction
We study a one--dimensional Ising spin systems with ferromagnetic,
long--range interaction decaying as n^{-2+\a}, \a \in [0,\frac 12], in the
presence of external random fields. We assume that the random fields are given
by a collection of symmetric, independent, identically distributed real random
variables, gaussian or subgaussian with variance . We show that for
temperature and variance of the randomness small enough, with an overwhelming
probability with respect to the random fields, the typical configurations,
within volumes centered at the origin whose size grow faster than any power of
, % {\bf around the origin} are intervals of spins followed by
intervals of spins whose typical length is \simeq
\th^{-\frac{2}{(1-2\a)}} for 0\le \a<1/2 and
for \a=1/2
Partially observed Markov random fields are variable neighborhood random fields
The present paper has two goals. First to present a natural example of a new
class of random fields which are the variable neighborhood random fields. The
example we consider is a partially observed nearest neighbor binary Markov
random field. The second goal is to establish sufficient conditions ensuring
that the variable neighborhoods are almost surely finite. We discuss the
relationship between the almost sure finiteness of the interaction
neighborhoods and the presence/absence of phase transition of the underlying
Markov random field. In the case where the underlying random field has no phase
transition we show that the finiteness of neighborhoods depends on a specific
relation between the noise level and the minimum values of the one-point
specification of the Markov random field. The case in which there is phase
transition is addressed in the frame of the ferromagnetic Ising model. We prove
that the existence of infinite interaction neighborhoods depends on the phase.Comment: To appear in Journal of Statistical Physic
DNA barcoding as a molecular tool to track down mislabeling and food piracy
DNA barcoding is a molecular technology that allows the identification of any biological species by amplifying, sequencing and querying the information from genic and/or intergenic standardized target regions belonging to the extranuclear genomes. Although these sequences represent a small fraction of the total DNA of a cell, both chloroplast and mitochondrial barcodes chosen for identifying plant and animal species, respectively, have shown sufficient nucleotide diversity to assess the taxonomic identity of the vast majority of organisms used in agriculture. Consequently, cpDNA and mtDNA barcoding protocols are being used more and more in the food industry and food supply chains for food labeling, not only to support food safety but also to uncover food piracy in freshly commercialized and technologically processed products. Since the extranuclear genomes are present in many copies within each cell, this technology is being more easily exploited to recover information even in degraded samples or transformed materials deriving from crop varieties and livestock species. The strong standardization that characterizes protocols used worldwide for DNA barcoding makes this technology particularly suitable for routine analyses required by agencies to safeguard food safety and quality. Here we conduct a critical review of the potentials of DNA barcoding for food labeling along with the main findings in the area of food piracy, with particular reference to agrifood and livestock foodstuffs
Phase Transitions in Ferromagnetic Ising Models with spatially dependent magnetic fields
In this paper we study the nearest neighbor Ising model with ferromagnetic
interactions in the presence of a space dependent magnetic field which vanishes
as , , as . We prove that in
dimensions for all large enough if there is a phase
transition while if there is a unique DLR state.Comment: to appear in Communications in Mathematical Physic
Geometry of contours and Peierls estimates in d=1 Ising models
Following Fr\"ohlich and Spencer, we study one dimensional Ising spin systems
with ferromagnetic, long range interactions which decay as ,
. We introduce a geometric description of the spin
configurations in terms of triangles which play the role of contours and for
which we establish Peierls bounds. This in particular yields a direct proof of
the well known result by Dyson about phase transitions at low temperatures.Comment: 28 pages, 3 figure
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