1,337 research outputs found
Chiral Suppression of Scalar Glueball Decay
Because glueballs are SU(3)_{Flavor} singlets, they are expected to couple
equally to u,d, and s quarks, so that equal coupling strengths to \pi^+\pi^-
and K^+K^- are predicted. However, we show that chiral symmetry implies the
scalar glueball amplitude for G_0 \to \qbq is proportional to the quark mass,
so that mixing with \sbs mesons is enhanced and decays to K^+K^- are favored
over \pi^+\pi^-. Together with evidence from lattice calculations and from
experiment, this supports the hypothesis that f_0(1710) is the ground state
scalar glueball.Comment: 9 pages; This revision reconciles posting (approximately) with
published version. Posting contains figures that are omitted in the
publicatio
transition form factor within Light Front Quark Model
We study the transition form factor of as a
function of the momentum transfer within the light-front quark model
(LFQM). We compare our result with the experimental data by BaBar as well as
other calculations based on the LFQM in the literature. We show that our
predicted form factor fits well with the experimental data, particularly those
at the large region.Comment: 11 pages, 4 figures, accepted for publication in PR
The Resolved Asteroid Program - Size, shape, and pole of (52) Europa
With the adaptive optics (AO) system on the 10 m Keck-II telescope, we
acquired a high quality set of 84 images at 14 epochs of asteroid (52) Europa
on 2005 January 20. The epochs covered its rotation period and, by following
its changing shape and orientation on the plane of sky, we obtained its
triaxial ellipsoid dimensions and spin pole location. An independent
determination from images at three epochs obtained in 2007 is in good agreement
with these results. By combining these two data sets, along with a single epoch
data set obtained in 2003, we have derived a global fit for (52) Europa of
diameters (379x330x249) +/- (16x8x10) km, yielding a volume-equivalent
spherical-diameter of 315 +/- 7 km, and a rotational pole within 7 deg of [RA;
Dec] = [257,+12] in an Equatorial J2000 reference frame (ECJ2000: 255,+35).
Using the average of all mass determinations available forEuropa, we derive a
density of 1.5 +/- 0.4, typical of C-type asteroids. Comparing our images with
the shape model of Michalowski et al. (A&A 416, 2004), derived from optical
lightcurves, illustrates excellent agreement, although several edge features
visible in the images are not rendered by the model. We therefore derived a
complete 3-D description of Europa's shape using the KOALA algorithm by
combining our imaging epochs with 4 stellar occultations and 49 lightcurves. We
use this 3-D shape model to assess these departures from ellipsoidal shape.
Flat facets (possible giant craters) appear to be less distinct on (52) Europa
than on other C-types that have been imaged in detail. We show that fewer giant
craters, or smaller craters, is consistent with its expected impact history.
Overall, asteroid (52) Europa is still well modeled as a smooth triaxial
ellipsoid with dimensions constrained by observations obtained over several
apparitions.Comment: Accepted for publication in Icaru
Photon-meson transition form factors of light pseudoscalar mesons
The photon-meson transition form factors of light pseudoscalar mesons , , and are systematically calculated in a
light-cone framework, which is applicable as a light-cone quark model at low
and is also physically in accordance with the light-cone pQCD approach
at large . The calculated results agree with the available experimental
data at high energy scale. We also predict the low behaviors of the
photon-meson transition form factors of , and , which are measurable in process via Primakoff
effect at JLab and DESY.Comment: 22 Latex pages, 7 figures, Version to appear in PR
Curve counting via stable pairs in the derived category
For a nonsingular projective 3-fold , we define integer invariants
virtually enumerating pairs where is an embedded curve and
is a divisor. A virtual class is constructed on the associated
moduli space by viewing a pair as an object in the derived category of . The
resulting invariants are conjecturally equivalent, after universal
transformations, to both the Gromov-Witten and DT theories of . For
Calabi-Yau 3-folds, the latter equivalence should be viewed as a wall-crossing
formula in the derived category.
Several calculations of the new invariants are carried out. In the Fano case,
the local contributions of nonsingular embedded curves are found. In the local
toric Calabi-Yau case, a completely new form of the topological vertex is
described.
The virtual enumeration of pairs is closely related to the geometry
underlying the BPS state counts of Gopakumar and Vafa. We prove that our
integrality predictions for Gromov-Witten invariants agree with the BPS
integrality. Conversely, the BPS geometry imposes strong conditions on the
enumeration of pairs.Comment: Corrected typos and duality error in Proposition 4.6. 47 page
The Boundary Conformal Field Theories of the 2D Ising critical points
We present a new method to identify the Boundary Conformal Field Theories
(BCFTs) describing the critical points of the Ising model on the strip. It
consists in measuring the low-lying excitation energies spectra of its quantum
spin chain for different boundary conditions and then to compare them with
those of the different boundary conformal field theories of the
minimal model.Comment: 7 pages, no figures. Talk given at the XXth International Conference
on Integrable Systems and Quantum Symmetries (ISQS-20). Prague, June 201
Ground State of the Quantum Symmetric Finite Size XXZ Spin Chain with Anisotropy Parameter
We find an analytic solution of the Bethe Ansatz equations (BAE) for the
special case of a finite XXZ spin chain with free boundary conditions and with
a complex surface field which provides for symmetry of the
Hamiltonian. More precisely, we find one nontrivial solution, corresponding to
the ground state of the system with anisotropy parameter
corresponding to .Comment: 6 page
Holomorphic anomaly equations and the Igusa cusp form conjecture
Let be a K3 surface and let be an elliptic curve. We solve the
reduced Gromov-Witten theory of the Calabi-Yau threefold for all
curve classes which are primitive in the K3 factor. In particular, we deduce
the Igusa cusp form conjecture.
The proof relies on new results in the Gromov-Witten theory of elliptic
curves and K3 surfaces. We show the generating series of Gromov-Witten classes
of an elliptic curve are cycle-valued quasimodular forms and satisfy a
holomorphic anomaly equation. The quasimodularity generalizes a result by
Okounkov and Pandharipande, and the holomorphic anomaly equation proves a
conjecture of Milanov, Ruan and Shen. We further conjecture quasimodularity and
holomorphic anomaly equations for the cycle-valued Gromov-Witten theory of
every elliptic fibration with section. The conjecture generalizes the
holomorphic anomaly equations for ellliptic Calabi-Yau threefolds predicted by
Bershadsky, Cecotti, Ooguri, and Vafa. We show a modified conjecture holds
numerically for the reduced Gromov-Witten theory of K3 surfaces in primitive
classes.Comment: 68 page
On certain other sets of integers
We show that if A is a subset of {1,...,N} containing no non-trivial
three-term arithmetic progressions then |A|=O(N/ log^{3/4-o(1)} N).Comment: 29 pp. Corrected typos. Added definitions for some non-standard
notation and remarks on lower bound
SOPHIE velocimetry of Kepler transit candidates XII. KOI-1257 b: a highly eccentric three-month period transiting exoplanet
In this paper we report a new transiting warm giant planet: KOI-1257 b. It
was first detected in photometry as a planet-candidate by the
space telescope and then validated thanks to a radial velocity follow-up with
the SOPHIE spectrograph. It orbits its host star with a period of 86.647661 d
3 s and a high eccentricity of 0.772 0.045. The planet transits the
main star of a metal-rich, relatively old binary system with stars of mass of
0.99 0.05 Msun and 0.70 0.07 Msun for the primary and secondary,
respectively. This binary system is constrained thanks to a self-consistent
modelling of the transit light curve, the SOPHIE radial
velocities, line bisector and full-width half maximum (FWHM) variations, and
the spectral energy distribution. However, future observations are needed to
confirm it. The PASTIS fully-Bayesian software was used to validate the nature
of the planet and to determine which star of the binary system is the transit
host. By accounting for the dilution from the binary both in photometry and in
radial velocity, we find that the planet has a mass of 1.45 0.35 Mjup,
and a radius of 0.94 0.12 Rjup, and thus a bulk density of 2.1
1.2 g.cm. The planet has an equilibrium temperature of 511 50 K,
making it one of the few known members of the warm-jupiter population. The
HARPS-N spectrograph was also used to observe a transit of KOI-1257 b,
simultaneously with a joint amateur and professional photometric follow-up,
with the aim of constraining the orbital obliquity of the planet. However, the
Rossiter-McLaughlin effect was not clearly detected, resulting in poor
constraints on the orbital obliquity of the planet.Comment: 39 pages, 17 figures, accepted for publication in Astronomy &
Astrophysic
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