17,121 research outputs found
Universality of TMD distribution functions of definite rank
Transverse momentum dependent (TMD) distribution and fragmentation functions
are described as Fourier transforms of matrix elementscontaining nonlocal
combinations of quark and gluon fields. These matrix elements also contain a
gauge link operator with a process dependent path, of which the process
dependence that can be traced back to the color flow in the process. Expanding
into irreducible tensors built from the transverse momenta p_\st, we can
define a universal set of TMD correlators of definite rank with a well-defined
operator structure.Comment: 6 pages, to be published in proceedings of the Third Worshop on the
QCD Structure of the Nucleon (QCD N'12), Bilbao, Spain, 22-26 October 201
Universality of TMD correlators
In a high-energy scattering process with hadrons in the initial state, color
is involved. Transverse momentum dependent distribution functions (TMDs)
describe the quark and gluon distributions in these hadrons in momentum space
with the inclusion of transverse directions. Apart from the (anti)-quarks and
gluons that are involved in the hard scattering process, additional gluon
emissions by the hadrons have to be taken into account as well, giving rise to
Wilson lines or gauge links. The TMDs involved are sensitive to the process
under consideration and hence potentially nonuniversal due to these Wilson line
interactions with the hard process; different hard processes give rise to
different Wilson line structures. We will show that in practice only a finite
number of universal TMDs have to be considered, which come in different linear
combinations depending on the hard process under consideration, ensuring a
generalized universality. For quarks this gives rise to three Pretzelocity
functions, whereas for gluons a richer structure of functions arises.Comment: 6 pages, presented by the first author at the 4th International
Workshop on Transverse Polarization Phenomena in Hard Processes (Transversity
2014), June 9-13, 2014, Chia, Italy. To appear in EPJ Web of Conference
Suppression of complete fusion due to breakup in the reactions B + Bi
Above-barrier cross sections of -active heavy reaction products, as
well as fission, were measured for the reactions of B with
Bi. Detailed analysis showed that the heavy products include components
from incomplete fusion as well as complete fusion (CF), but fission originates
almost exclusively from CF. Compared with fusion calculations without breakup,
the CF cross sections are suppressed by 15% for B and 7% for B. A
consistent and systematic variation of the suppression of CF for reactions of
the weakly bound nuclei Li, Be, B on targets of
Pb and Bi is found as a function of the breakup threshold
energy
Detecting Singleton Review Spammers Using Semantic Similarity
Online reviews have increasingly become a very important resource for
consumers when making purchases. Though it is becoming more and more difficult
for people to make well-informed buying decisions without being deceived by
fake reviews. Prior works on the opinion spam problem mostly considered
classifying fake reviews using behavioral user patterns. They focused on
prolific users who write more than a couple of reviews, discarding one-time
reviewers. The number of singleton reviewers however is expected to be high for
many review websites. While behavioral patterns are effective when dealing with
elite users, for one-time reviewers, the review text needs to be exploited. In
this paper we tackle the problem of detecting fake reviews written by the same
person using multiple names, posting each review under a different name. We
propose two methods to detect similar reviews and show the results generally
outperform the vectorial similarity measures used in prior works. The first
method extends the semantic similarity between words to the reviews level. The
second method is based on topic modeling and exploits the similarity of the
reviews topic distributions using two models: bag-of-words and
bag-of-opinion-phrases. The experiments were conducted on reviews from three
different datasets: Yelp (57K reviews), Trustpilot (9K reviews) and Ott dataset
(800 reviews).Comment: 6 pages, WWW 201
On the dyon partition function in N=2 theories
We study the entropy function of two N =2 string compactifications obtained
as freely acting orbifolds of N=4 theories : the STU model and the FHSV model.
The Gauss-Bonnet term for these compactifications is known precisely. We apply
the entropy function formalism including the contribution of this four
derivative term and evaluate the entropy of dyons to the first subleading order
in charges for these models. We then propose a partition function involving the
product of three Siegel modular forms of weight zero which reproduces the
degeneracy of dyonic black holes in the STU model to the first subleading order
in charges. The proposal is invariant under all the duality symmetries of the
STU model. For the FHSV model we write down an approximate partition function
involving a Siegel modular form of weight four which captures the entropy of
dyons in the FHSV model in the limit when electric charges are much larger than
magnetic charges.Comment: 48 page
Evolutionary flexibility in routes to mat formation by Pseudomonas
Abstract Many bacteria form mats at the air-liquid interface of static microcosms. These structures typically involve the secretion of exopolysaccharides, the production of which is often controlled by the secondary messenger c-di-GMP. Mechanisms of mat formation have been particularly well characterized in Pseudomonas fluorescens SBW25; stimuli or mutations that increase c-di-GMP production by diguanylate cyclases (WspR, AwsR, and MwsR) result in the secretion of cellulose and mat formation. Here, we characterize and compare mat formation in two close relatives of SBW25: Pseudomonas simiae PICF7 and P. fluorescens A506. We find that PICF7?the strain more closely related to SBW25?can form mats through mutations affecting the activity of the same three diguanylate cyclases as SBW25. However, instead of cellulose, these mutations activate production of the exopolysaccharide Pel. We also provide evidence for at least two further?as yet uncharacterized?routes to mat formation by PICF7. P. fluorescens A506, while retaining the same mutational routes to mat formation as SBW25 and PICF7, preferentially forms mats by a semi-heritable mechanism that culminates in Psl and Pga over-production. Our results demonstrate a high level of evolutionary flexibility in the molecular and structural routes to mat formation, even among close relatives
Emergent Universe with Exotic Matter
A general framework for an emergent universe scenario has been given which
makes use of an equation of state. The general features of the model have also
been studied and possible primordial composition of the universe have been
suggested.Comment: 11 pages, no fi
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