884 research outputs found
Quantization on Curves
Deformation quantization on varieties with singularities offers perspectives
that are not found on manifolds. Essential deformations are classified by the
Harrison component of Hochschild cohomology, that vanishes on smooth manifolds
and reflects information about singularities. The Harrison 2-cochains are
symmetric and are interpreted in terms of abelian -products. This paper
begins a study of abelian quantization on plane curves over \Crm, being
algebraic varieties of the form R2/I where I is a polynomial in two variables;
that is, abelian deformations of the coordinate algebra C[x,y]/(I).
To understand the connection between the singularities of a variety and
cohomology we determine the algebraic Hochschild (co-)homology and its
Barr-Gerstenhaber-Schack decomposition. Homology is the same for all plane
curves C[x,y]/(I), but the cohomology depends on the local algebra of the
singularity of I at the origin.Comment: 21 pages, LaTex format. To appear in Letters Mathematical Physic
Effective String Theory of Vortices and Regge Trajectories
Starting from a field theory containing classical vortex solutions, we obtain
an effective string theory of these vortices as a path integral over the two
transverse degrees of freedom of the string. We carry out a semiclassical
expansion of this effective theory, and use it to obtain corrections to Regge
trajectories due to string fluctuations.Comment: 27 pages, revtex, 3 figures, corrected an error with the cutoff in
appendix E (was previously D), added more discussion of Fig. 3, moved some
material in section 9 to a new appendi
Supersymmetry and a rationale for small CP violating phases
We analyse the CP problem in the context of a supersymmetric extension of the
standard model with universal strength of Yukawa couplings. A salient feature
of these models is that the CP phases are constrained to be very small by the
hierarchy of the quark masses, and the pattern of CKM mixing angles. This leads
to a small amount of CP violation from the usual KM mechanism and a significant
contribution from supersymmetry is required. Due to the large generation mixing
in some of the supersymmetric interactions, the electric dipole moments impose
severe constraints on the parameter space, forcing the trilinear couplings to
be factorizable in matrix form. We find that the LL mass insertions give the
dominant gluino contribution to saturate epsilon_K. The chargino contributions
to epsilon'/epsilon are significant and can accommodate the experimental
results. In this framework, the standard model gives a negligible contribution
to the CP asymmetry in B-meson decay, a_{J/\psi K_s}. However, due to
supersymmetric contributions to B_d-\bar{B}_d mixing, the recent large value of
a_{J/\psi K_s} can be accommodated.Comment: 30 pages, 5 figures. Version to appear in Nucl. Phys.
Effective field theory
I give a brief review of effective field theory, disscussing the contribution
of Feza G\"ursey in particular and focusing on the literature I am most
familiar with.Comment: 17 pages, no figs, macros appended, plain te
Worldwide experience with a totally subcutaneous implantable defibrillator: Early results from the EFFORTLESS S-ICD registry
Aims The totally subcutaneous implantable-defibrillator (S-ICD) is a new alternative to the conventional transveno
Measuring Black Hole Spin using X-ray Reflection Spectroscopy
I review the current status of X-ray reflection (a.k.a. broad iron line)
based black hole spin measurements. This is a powerful technique that allows us
to measure robust black hole spins across the mass range, from the stellar-mass
black holes in X-ray binaries to the supermassive black holes in active
galactic nuclei. After describing the basic assumptions of this approach, I lay
out the detailed methodology focusing on "best practices" that have been found
necessary to obtain robust results. Reflecting my own biases, this review is
slanted towards a discussion of supermassive black hole (SMBH) spin in active
galactic nuclei (AGN). Pulling together all of the available XMM-Newton and
Suzaku results from the literature that satisfy objective quality control
criteria, it is clear that a large fraction of SMBHs are rapidly-spinning,
although there are tentative hints of a more slowly spinning population at high
(M>5*10^7Msun) and low (M<2*10^6Msun) mass. I also engage in a brief review of
the spins of stellar-mass black holes in X-ray binaries. In general,
reflection-based and continuum-fitting based spin measures are in agreement,
although there remain two objects (GROJ1655-40 and 4U1543-475) for which that
is not true. I end this review by discussing the exciting frontier of
relativistic reverberation, particularly the discovery of broad iron line
reverberation in XMM-Newton data for the Seyfert galaxies NGC4151, NGC7314 and
MCG-5-23-16. As well as confirming the basic paradigm of relativistic disk
reflection, this detection of reverberation demonstrates that future large-area
X-ray observatories such as LOFT will make tremendous progress in studies of
strong gravity using relativistic reverberation in AGN.Comment: 19 pages. To appear in proceedings of the ISSI-Bern workshop on "The
Physics of Accretion onto Black Holes" (8-12 Oct 2012). Revised version adds
a missing source to Table 1 and Fig.6 (IRAS13224-3809) and corrects the
referencing of the discovery of soft lags in 1H0707-495 (which were in fact
first reported in Fabian et al. 2009
Product-Group Unification in Type IIB String Thoery
The product-group unification is a model of unified theories, in which
masslessness of the two Higgs doublets and absence of dimension-five proton
decay are guaranteed by a symmetry. It is based on SU(5) x U(N) (N=2,3) gauge
group. It is known that various features of the model are explained naturally,
when it is embedded in a brane world. This article describes an idea of how to
accommodate all the particles of the model in Type IIB brane world. The
GUT-breaking sector is realized by a D3--D7 system, and chiral quarks and
leptons arise from intersection of D7-branes. The D-brane configuration can be
a geometric realization of the non-parallel family structure of quarks and
leptons, an idea proposed to explain the large mixing angles observed in the
neutrino oscillation. The tri-linear interaction of the next-to-minimal
supersymmetric standard model is obtained naturally in some cases.Comment: 33 pages, 5 figure
Constraining neutrino oscillation parameters with current solar and atmospheric data
We analyze the impact of recent solar, atmospheric and reactor data in the
determination of the neutrino oscillation parameters, taking into account that
both the solar nu_e and the atmospheric nu_mu may convert to a mixture of
active and sterile neutrinos. We use the most recent global solar neutrino
data, including the 1496-day Super-K neutrino data sample, and we investigate
in detail the impact of the SNO neutral current, spectral and day/night data by
performing also an analysis using only the charged current rate from SNO. The
implications of the first 145.1 days of KamLAND data on the determination of
the solar neutrino parameters are also discussed in detail. We confirm the
clear preference of solar+reactor data for the pure active LMA-MSW solution of
the solar neutrino problem, and obtain that the LOW, VAC, SMA and Just-So^2
solutions are disfavored with a Delta_chi^2 = 22, 22, 36, 44, respectively.
Furthermore, we find that the global solar data constrains the admixture of a
sterile neutrino to be less than 43% at 99% CL. By performing an improved fit
of the atmospheric data, we also update the corresponding regions of
oscillation parameters. We find that the recent atmospheric Super-K (1489-day)
and MACRO data have a strong impact on constraining a sterile component in
atmospheric oscillations: if the nu_mu is restricted to the atmospheric mass
states only a sterile admixture of 16% is allowed at 99% CL, while a bound of
35% is obtained in the unconstrained case. Pure sterile oscillations are
disfavored with a Delta_chi^2 = 34.6 compared to the pure active case.Comment: 28 pages, LaTeX file using RevTEX4, 12 figures and 3 tables included.
Improved version including the new KamLAND dat
The learning curve associated with the introduction of the subcutaneous implantable defibrillator
Aims: The subcutaneous implantable cardioverter defibrillator (S-ICD) was introduced to overcome complications related to transvenous leads. Adoption of the S-ICD requires implanters to learn a new implantation technique. The aim of this study was to assess the learning curve for S-ICD implanters with respect to implant-related complications, procedure time, and inappropriate shocks (IASs). Methods and results: In a pooled cohort from two clinical S-ICD databases, the IDE Trial and the EFFORTLESS Registry, complications, IASs at 180 days follow-up and implant procedure duration were assessed. Patients were grouped in quartiles based on experience of the implanter and Kaplan-Meier estimates of complication and IAS rates were calculated. A total of 882 patients implanted in 61 centres by 107 implanters with a median of 4 implants (IQR 1,8) were analysed. There were a total of 59 patients with complications and 48 patients with IAS. The complication rate decreased significantly from 9.8% in Quartile 1 (least experience) to 5.4% in Quartile 4 (most experience) (P = 0.02) and non-significantly for IAS from 7.9 to 4.8% (P = 0.10). Multivariable analysis demonstrated a hazard ratio of 0.78 (P = 0.045) for complications and 1.01 (P = 0.958) for IAS. Dual-zone programming increased with experience of the individual implanter (P 13 implants). Conclusion: There is a short and significant learning curve associated with physicians adopting the S-ICD. Performance stab
The status of GEO 600
The GEO 600 laser interferometer with 600m armlength is part of a worldwide network of gravitational wave detectors. GEO 600 is unique in having advanced multiple pendulum suspensions with a monolithic last stage and in employing a signal recycled optical design. This paper describes the recent commissioning of the interferometer and its operation in signal recycled mode
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