863 research outputs found
On the Corner Elements of the CKM and PMNS Matrices
Recent experiments show that the top-right corner element () of the
PMNS, like that () of the CKM, matrix is small but nonzero, and suggest
further via unitarity that it is smaller than the bottom-left corner element
(), again as in the CKM case (). An attempt in
explaining these facts would seem an excellent test for any model of the mixing
phenomenon. Here, it is shown that if to the assumption of a universal rank-one
mass matrix, long favoured by phenomenologists, one adds that this matrix
rotates with scale, then it follows that (A) by inputting the mass ratios
, and , (i) the corner elements are
small but nonzero, (ii) , , (iii)
estimates result for the ratios and , and
(B) by inputting further the experimental values of and
, (iv) estimates result for the values of the corner elements
themselves. All the inequalities and estimates obtained are consistent with
present data to within expectation for the approximations made.Comment: 9 pages, 2 figures, updated with new experimental data and more
detail
N-String Vertices in String Field Theory
We give the general form of the vertex corresponding to the interaction of an
arbitrary number of strings. The technique employed relies on the ``comma"
representation of String Field Theory where string fields and interactions are
represented as matrices and operations between them such as multiplication and
trace. The general formulation presented here shows that the interaction vertex
of N strings, for any arbitrary N, is given as a function of particular
combinations of matrices corresponding to the change of representation between
the full string and the half string degrees of freedom.Comment: 22 pages, A4-Latex (latex twice), FTUV IFI
Usefulness of routine preoperative testing in a developing country: a prospective study
Introduction: The assessment of anesthetic risks is an essential component of preoperative evaluation. In developing world, preanesthesia evaluation may be challenging because patient's medical history and records are scare, and language barrier limits physical examination. Our objective was to evaluate the impact of routine preoperative testing in a low-resources setting. Methods: Prospective observational study performed in a French forward surgical unit in Abidjan, Ivory Coast. 201 patients who were scheduled for non urgent surgery were screened with routine laboratory exams during preoperative evaluation. Changes in surgery were assessed (delayed or scheduled). Results: Abnormal hemoglobin findings were reported in 35% of patients, abnormal WBC count in 11,1% of patients, abnormal platelets in 15,3% of patients. Positive HIV results were found in 8,3% of cases. Routine tests represented 43,6% of changes causes. Conclusion: Our study showed that in a developing country, routine preoperative tests showed abnormal results up to 35% of cases, and represented 43,6% of delayed surgery causes. The rate of tests leading to management changes varied widely, from 0% to 8,3%. These results suggested that selected tests would be useful to diagnose diseases that required treatment before non urgent surgery. However, larger studies are needeed to evaluate the cost/benefit ratio and the clinical impact of such a strategy
Impact of water saturation on seismoelectric transfer functions: a laboratory study of coseismic phenomenon
Seismic waves propagating in a porous medium, under favourable conditions, generate measurable electromagnetic fields due to electrokinetic effects. It has been proposed, following experimental and numerical studies, that these so-called ‘seismoelectromagnetic' couplings depend on pore fluid properties. The theoretical frame describing these phenomena are based on the original Biot's theory, assuming that pores are fluid-filled. We study here the impact of a partially saturated medium on amplitudes of those seismoelectric couplings by comparing experimental data to an effective fluid model. We have built a 1-m-length-scale experiment designed for imbibition and drainage of an homogeneous silica sand; the experimental set-up includes a seismic source, accelerometers, electric dipoles and capacitance probes in order to monitor seismic and seismoelectric fields during water saturation. Apparent velocities and frequency spectra (in the kiloHertz range) are derived from seismic and electrical measurements during experiments in varying saturation conditions. Amplitudes of seismic and seismoelectric waves and their ratios (i.e. transfer functions) are discussed using a spectral analysis performed by continuous wavelet transform. The experiments reveal that amplitude ratios of seismic to coseismic electric signals remain rather constant as a function of the water saturation in the Sw=[0.2-0.9] range, consistently with theoretically predicted transfer function
A Comprehensive Mechanism Reproducing the Mass and Mixing Parameters of Quarks and Leptons
It is shown that if, from the starting point of a universal rank-one mass
matrix long favoured by phenomenologists, one adds the assumption that it
rotates (changes its orientation in generation space) with changing scale, one
can reproduce, in terms of only 6 real parameters, all the 16 mass ratios and
mixing parameters of quarks and leptons. Of these 16 quantities so reproduced,
10 for which data exist for direct comparison (i.e. the CKM elements including
the CP-violating phase, the angles in
-oscillation, and the masses ) agree well with
experiment, mostly to within experimental errors; 4 others (), the experimental values for which can only be inferred, agree
reasonably well; while 2 others ( for leptons), not yet
measured experimentally, remain as predictions. In addition, one gets as
bonuses, estimates for (i) the right-handed neutrino mass and (ii)
the strong CP angle inherent in QCD. One notes in particular that the
output value for from the fit agrees very well with
recent experiments. By inputting the current experimental value with its error,
one obtains further from the fit 2 new testable constraints: (i) that
must depart from its "maximal" value: , (ii) that the CP-violating (Dirac) phase in the PMNS would be
smaller than in the CKM matrix: of order only if
not vanishing altogether.Comment: 37 pages, 1 figur
Computing in String Field Theory Using the Moyal Star Product
Using the Moyal star product, we define open bosonic string field theory
carefully, with a cutoff, for any number of string oscillators and any
oscillator frequencies. Through detailed computations, such as Neumann
coefficients for all string vertices, we show that the Moyal star product is
all that is needed to give a precise definition of string field theory. The
formulation of the theory as well as the computation techniques are
considerably simpler in the Moyal formulation. After identifying a monoid
algebra as a fundamental mathematical structure in string field theory, we use
it as a tool to compute with ease the field configurations for wedge, sliver,
and generalized projectors, as well as all the string interaction vertices for
perturbative as well as monoid-type nonperturbative states. Finally, in the
context of VSFT we analyze the small fluctuations around any D-brane vacuum. We
show quite generally that to obtain nontrivial mass and coupling, as well as a
closed strings, there must be an associativity anomaly. We identify the
detailed source of the anomaly, but leave its study for future work.Comment: 77 pages, LaTeX. v3: corrections of signs or factors (for a list of
corrections see beginning of source file
Measuring effective electroweak couplings in single top production at the LHC
We study the mechanism of single top production at the LHC in the framework
of an effective electroweak Lagrangian, analyzing the sensitivity of different
observables to the magnitude of the effective couplings that parametrize new
physics beyond the Standard Model. The observables relevant to the distinction
between left and right effective couplings involve in practice the measurement
of the spin of the top and this can be achieved only indirectly by measuring
the angular distribution of its decay products. We show that the presence of
effective right-handed couplings implies that the top is not in a pure spin
state. A unique spin basis is singled out which allows one to connect top decay
products angular distribution with the polarized top differential cross
section. We present a complete analytical expression of the differential
polarized cross section of the relevant perturbative subprocess including
general effective couplings. The mass of the bottom quark, which actually turns
out to be more relevant than naively expected, is retained. Finally we analyze
different aspects the total cross section relevant to the measurement of new
physics through the effective couplings. The above analysis also applies to
anti-top production in a straightforward way.Comment: 38 pages, 17 figure
Neural Networks for Information Retrieval
Machine learning plays a role in many aspects of modern IR systems, and deep
learning is applied in all of them. The fast pace of modern-day research has
given rise to many different approaches for many different IR problems. The
amount of information available can be overwhelming both for junior students
and for experienced researchers looking for new research topics and directions.
Additionally, it is interesting to see what key insights into IR problems the
new technologies are able to give us. The aim of this full-day tutorial is to
give a clear overview of current tried-and-trusted neural methods in IR and how
they benefit IR research. It covers key architectures, as well as the most
promising future directions.Comment: Overview of full-day tutorial at SIGIR 201
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