Veneziano like amplitude as a test for AdS/QCD models

The high energy asymptotics of QCD correlation functions is often used as a test for bottom-up holographic models. Since QCD is not strongly coupled in the ultraviolet domain, such a test may look questionable. We propose that the sum over resonance poles emerging in correlators of a bottom-up model should reproduce the structure of a Veneziano like amplitude at zero momentum transfer assuming equivalence of spin and radial states in the latter. This requires a five-dimensional background that suppresses the ultraviolet part in the effective action of a model. We give examples of emerging low-energy holographic models.Comment: 9 pages, accepted by the European Physical Journal C. arXiv admin note: substantial text overlap with arXiv:1102.274

The effect of spring burning on competitive ranking of prairie species

A common explanation for the changes in species abundance following a fire is a shift in competitive ranking. However, experimental tests have been inconsistent and generally do not support this explanation. I examined the competitive ability of an abundant C 4 grass, Andropogon gerardii , and a C 3 forb, Ratibida pinnata , in a prairie remnant in northern Ohio, USA, for each of three years following a spring burn in 1996. While the abiotic environment directly influenced both species similarly, relative competitive abilities in terms of growth changed markedly: in 1996 Andropogon was less inhibited by neighbors; in 1997 both Andropogon and Ratibida had similar competitive abilities; and in 1998 Ratibida was less inhibited by neighbors. This shift in competitive response ranking paralleled the changes in relative abundance for the two species. In contrast, the effect of neighbors on survival changed markedly over time but did not differ among the two species. Thus, fire may influence species abundance through changing species competitive response ranking, at least in terms of growth.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72362/1/3236873.pd

Selection of single blastocysts for fresh transfer via standard morphology assessment alone and with array CGH for good prognosis IVF patients: results from a randomized pilot study

Background Single embryo transfer (SET) remains underutilized as a strategy to reduce multiple gestation risk in IVF, and its overall lower pregnancy rate underscores the need for improved techniques to select one embryo for fresh transfer. This study explored use of comprehensive chromosomal screening by array CGH (aCGH) to provide this advantage and improve pregnancy rate from SET. Methods First-time IVF patients with a good prognosis (age <35, no prior miscarriage) and normal karyotype seeking elective SET were prospectively randomized into two groups: In Group A, embryos were selected on the basis of morphology and comprehensive chromosomal screening via aCGH (from d5 trophectoderm biopsy) while Group B embryos were assessed by morphology only. All patients had a single fresh blastocyst transferred on d6. Laboratory parameters and clinical pregnancy rates were compared between the two groups. Results For patients in Group A (n=55), 425 blastocysts were biopsied and analyzed via aCGH (7.7 blastocysts/patient). Aneuploidy was detected in 191/425 (44.9%) of blastocysts in this group. For patients in Group B (n=48), 389 blastocysts were microscopically examined (8.1 blastocysts/patient). Clinical pregnancy rate was significantly higher in the morphology+aCGH group compared to the morphology-only group (70.9 and 45.8%, respectively; p=0.017); ongoing pregnancy rate for Groups A and B were 69.1 vs. 41.7%, respectively (p=0.009). There were no twin pregnancies. Conclusion Although aCGH followed by frozen embryo transfer has been used to screen at risk embryos (e.g., known parental chromosomal translocation or history of recurrent pregnancy loss), this is the first description of aCGH fully integrated with a clinical IVF program to select single blastocysts for fresh SET in good prognosis patients. The observed aneuploidy rate (44.9%) among biopsied blastocysts highlights the inherent imprecision of SET when conventional morphology is used alone. Embryos randomized to the aCGH group implanted with greater efficiency, resulted in clinical pregnancy more often, and yielded a lower miscarriage rate than those selected without aCGH. Additional studies are needed to verify our pilot data and confirm a role for on-site, rapid aCGH for IVF patients contemplating fresh SET

Spin Two Glueball Mass and Glueball Regge Trajectory from Supergravity

We calculate the mass of the lowest lying spin two glueball in N=1 super Yang-Mills from the dual Klebanov-Strassler background. We show that the Regge trajectory obtained is linear; the 0++, 1-- and 2++ states lie on a line of slope 0.23 -measured in units of the conifold deformation. We also compare mass ratios with lattice data and find agreement within one standard deviation.Comment: 17 pages, 2 figure

Perturbative QCD Fragmentation Functions for BcB_c and Bc∗B_c^* Production

The dominant production mechanism for ${\bar b} c$ bound states in high energy processes is the production of a high energy ${\bar b}$ or $c$ quark, followed by its fragmentation into the ${\bar b} c$ state. We calculate the fragmentation functions for the production of the S-wave states $B_c$ and $B_c^*$ to leading order in the QCD coupling constant. The fragmentation probabilities for ${\bar b} \rightarrow B_c$ and ${\bar b} \rightarrow B_c^*$ are approximately $2.2 \times 10^{-4}$ and $3.1 \times 10^{-4}$, while those for $c \rightarrow B_c$ and $c \rightarrow B_c^*$ are smaller by almost two orders of magnitude.Comment: Latex, 12 pages, 3 figures available upon request, NUHEP-TH-93-

No-Go Theorem for Horizon-Shielded Self-Tuning Singularities

We derive a simple no-go theorem relating to self-tuning solutions to the cosmological constant for observers on a brane, which rely on a singularity in an extra dimension. The theorem shows that it is impossible to shield the singularity from the brane by a horizon, unless the positive energy condition (rho+p >= 0) is violated in the bulk or on the brane. The result holds regardless of the kinds of fields which are introduced in the bulk or on the brane, whether Z_2 symmetry is imposed at the brane, or whether higher derivative terms of the Gauss-Bonnet form are added to the gravitational part of the action. However, the no-go theorem can be evaded if the three-brane has spatial curvature. We discuss explicit realizations of such solutions which have both self-tuning and a horizon shielding the singularity.Comment: 7 pages, 4 figures, revtex; added reference and minor correction

Single-Inclusive Jet Production in Polarized pp Collisions at O(alpha_s^3)

We present a next-to-leading order QCD calculation for single-inclusive high-p_T jet production in longitudinally polarized pp collisions within the ``small-cone'' approximation. The fully analytical expressions obtained for the underlying partonic hard-scattering cross sections greatly facilitate the analysis of upcoming BNL-RHIC data on the double-spin asymmetry A_{LL}^{jet} for this process in terms of the unknown polarization of gluons in the nucleon. We simultaneously rederive the corresponding QCD corrections to unpolarized scattering and confirm the results existing in the literature. We also numerically compare to results obtained with Monte-Carlo methods and assess the range of validity of the ``small-cone'' approximation for the kinematics relevant at BNL-RHIC.Comment: 23 pages, 8 eps-figure

Ab initio study of charge doping effect on 1D polymerization of C60

We study the interplay between charge doping and intermolecular distance in the polymerization of C60 fullerene chains by means of density functional theory (DFT)-based first principle calculations. The potential energy surface analysis shows that both the equilibrium intermolecular distance of the unpolymerized system and the polymerization energy barrier are inversely proportional to the electron doping of the system. We analyze the origin of this charge-induced polymerization effect by studying the behavior of the system's wavefunctions around the Fermi level and the structural modifications of the molecules as a function of two variables: the distance between the centers of the molecules and the number of electrons added to the system

Photoproduction of J/psi mesons at high energies in parton model and k_t-faktorization approach

We consider J/psi meson photoproduction on protons at high energies at the leading order in alpha_s using conventional parton model and k_t-factorization approach of QCD. It is shown that in the both cases the colour singlet mechanism gives correct description for experimental data from HERA for the total cross section and for the J/psi meson z-spectrum at realistic values of a c-quark mass and meson wave function at the origin Psi (0). At the same time our predictions for p_t-spectrum of J/psi meson and for p_t dependence of the spin parameter alpha obtained in k_t-factorization approach are very different from the results obtained in conventional parton model. Such a way the experimental study of a polarized J/psi meson production at the large p_t should be a direct test of BFKL gluons.Comment: LaTeX2e, 11 pages plus 8 fig. using epsfig.st