19,515 research outputs found
Chiral Perturbation Theory and U(3)_L\times U(3)_R Chiral Theory of Mesons
We examine low energy limit of chiral theory of mesons
through integrating out fields of vector and axial-vector mesons. The effective
lagrangian for pseudoscalar mesons at has been obtained, and five low
energy coupling constants have been revealed. They are in
good agreement with the results of CHPT's at .Comment: 20 pages, Standard LaTex file, no finger
Multi-keyword multi-click advertisement option contracts for sponsored search
In sponsored search, advertisement (abbreviated ad) slots are usually sold by
a search engine to an advertiser through an auction mechanism in which
advertisers bid on keywords. In theory, auction mechanisms have many desirable
economic properties. However, keyword auctions have a number of limitations
including: the uncertainty in payment prices for advertisers; the volatility in
the search engine's revenue; and the weak loyalty between advertiser and search
engine. In this paper we propose a special ad option that alleviates these
problems. In our proposal, an advertiser can purchase an option from a search
engine in advance by paying an upfront fee, known as the option price. He then
has the right, but no obligation, to purchase among the pre-specified set of
keywords at the fixed cost-per-clicks (CPCs) for a specified number of clicks
in a specified period of time. The proposed option is closely related to a
special exotic option in finance that contains multiple underlying assets
(multi-keyword) and is also multi-exercisable (multi-click). This novel
structure has many benefits: advertisers can have reduced uncertainty in
advertising; the search engine can improve the advertisers' loyalty as well as
obtain a stable and increased expected revenue over time. Since the proposed ad
option can be implemented in conjunction with the existing keyword auctions,
the option price and corresponding fixed CPCs must be set such that there is no
arbitrage between the two markets. Option pricing methods are discussed and our
experimental results validate the development. Compared to keyword auctions, a
search engine can have an increased expected revenue by selling an ad option.Comment: Chen, Bowei and Wang, Jun and Cox, Ingemar J. and Kankanhalli, Mohan
S. (2015) Multi-keyword multi-click advertisement option contracts for
sponsored search. ACM Transactions on Intelligent Systems and Technology, 7
(1). pp. 1-29. ISSN: 2157-690
The long-range interactions between branes in diverse dimensions
We calculate the long-range interactions between two simple branes placed
parallel at a separation in diverse dimensions via an effective field theory
approach. We also compute for the first time the explicit long-range
interaction between two D-branes with each carrying a world-volume non-abelian
magnetic flux in three special cases, respectively. In particular, we
demonstrate that the half-string creation between a D-brane and a
D-brane continues to hold even in the present context, therefore lending
further support to the previous assertion of this. Our computations re-raise
also the issue in one case on whether so constructed (D, D) bound state
is actually a marginal one.Comment: 28 pages, various discussions expanded and references adde
Comparison of Magnetic Flux Distribution between a Coronal Hole and a Quiet Region
Employing Big Bear Solar Observatory (BBSO) deep magnetograms and H
images in a quiet region and a coronal hole, observed on September 14 and 16,
2004, respectively, we have explored the magnetic flux emergence, disappearance
and distribution in the two regions. The following results are obtained: (1)
The evolution of magnetic flux in the quiet region is much faster than that in
the coronal hole, as the flux appeared in the form of ephemeral regions in the
quiet region is 4.3 times as large as that in the coronal hole, and the flux
disappeared in the form of flux cancellation, 2.9 times as fast as in the
coronal hole. (2) More magnetic elements with opposite polarities in the quiet
region are connected by arch filaments, estimating from magnetograms and
H images. (3) We measured the magnetic flux of about 1000 magnetic
elements in each observing region. The flux distribution of network and
intranetwork (IN) elements is similar in both polarities in the quiet region.
For network fields in the coronal hole, the number of negative elements is much
more than that of positive elements. However for the IN fields, the number of
positive elements is much more than that of negative elements. (4) In the
coronal hole, the fraction of negative flux change obviously with different
threshold flux density. 73% of the magnetic fields with flux density larger
than 2 Gauss is negative polarity, and 95% of the magnetic fields is negative,
if we only measure the fields with their flux density larger than 20 Gauss. Our
results display that in a coronal hole, stronger fields is occupied by one
predominant polarity; however the majority of weaker fields, occupied by the
other polarity
Neutrino oscillations in de Sitter space-time
We try to understand flavor oscillations and to develop the formulae for
describing neutrino oscillations in de Sitter space-time. First, the covariant
Dirac equation is investigated under the conformally flat coordinates of de
Sitter geometry. Then, we obtain the exact solutions of the Dirac equation and
indicate the explicit form of the phase of wave function. Next, the concise
formulae for calculating the neutrino oscillation probabilities in de Sitter
space-time are given. Finally, The difference between our formulae and the
standard result in Minkowski space-time is pointed out.Comment: 13 pages, no figure
Next-to-leading order QCD predictions for graviton and photon associated production in the Large Extra Dimensions model at the LHC
We present the calculations of the complete next-to-leading order(NLO) QCD
corrections to the inclusive total cross sections for the Kaluza-Klein(KK)
graviton and photon associated production process in
the large extra dimensions(LED) model at the LHC. We show that the NLO QCD
corrections in general enhance the total cross sections and reduce the
dependence of the total cross sections on the factorization and renormalization
scales. When jet veto is considered, the NLO corrections reduce the total cross
sections. We also calculate some important differential cross sections for this
process at NLO: the missing transverse momentum distribution, the transverse
momentum distribution and the pseudorapidity distribution of photon.Comment: 28 pages, 14 figures; minor changes, version published in Phys.Rev.
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