Are polymer melts "ideal"?

It is commonly accepted that in concentrated solutions or melts high-molecular weight polymers display random-walk conformational properties without long-range correlations between subsequent bonds. This absence of memory means, for instance, that the bond-bond correlation function, $P(s)$, of two bonds separated by $s$ monomers along the chain should exponentially decay with $s$. Presenting numerical results and theoretical arguments for both monodisperse chains and self-assembled (essentially Flory size-distributed) equilibrium polymers we demonstrate that some long-range correlations remain due to self-interactions of the chains caused by the chain connectivity and the incompressibility of the melt. Suggesting a profound analogy with the well-known long-range velocity correlations in liquids we find, for instance, $P(s)$ to decay algebraically as $s^{-3/2}$. Our study suggests a precise method for obtaining the statistical segment length \bstar in a computer experiment.Comment: 4 pages, 3 figure

Scale Dependence of Twist-3 Quark-Gluon Operators for Single Spin Asymmetries

We derive the scale dependence of twist-3 quark-gluon operators, or ETQS matrix elements, at one-loop. These operators are used to factorize transverse single spin asymmetries, which are studied intensively both in experiment and theory. The scale dependence of two special cases are particularly interesting. One is of soft-gluon-pole matrix elements, another is of soft-quark-pole matrix elements. From our results the evolutions in the two cases can be obtained. A comparison with existing results of soft-gluon-pole matrix elements is made.Comment: typo in Eq.(10) corrected, references adde

Revisiting spin alignment of heavy mesons in its inclusive production

In the heavy quark limit inclusive production rate of a heavy meson can be factorized, in which the nonperturbative effect related to the heavy meson can be characterized by matrix elements defined in the heavy quark effective theory. Using this factorization, predictions for the full spin density matrix of a spin-1 and spin-2 meson can be obtained and they are characterized only by one coefficient representing the nonperturbative effect. Predictions for spin-1 heavy meson are compared with experiment performed at $e^+e^-$ colliders in the energy range from $\sqrt{s}=10.5$GeV to $\sqrt{s}=91$GeV, a complete agreement is found for $D^*$- and $B^*$-meson. For $D^{**}$ meson, our prediction suffers a large correction, as indicated by experimental data. There exists another approach by taking heavy mesons as bound systems, in which the total angular momentum of the light degrees of freedom is 1/2 and 3/2 for spin-1 and spin-2 meson respectively, then the diagonal parts of spin density matrices can be obtained. However, there are distinct differences in the predictions from the two approaches and they are discussed in detail.Comment: 14 pages with one figur

An SU(5)×A5 golden ratio flavour model

In this paper we study an SU(5)×A5 flavour model which exhibits a neutrino mass sum rule and golden ratio mixing in the neutrino sector which is corrected from the charged lepton Yukawa couplings. We give the full renormalisable superpotential for the model which breaks SU(5) and A5 after integrating out heavy messenger fields and minimising the scalar potential. The mass sum rule allows for both mass orderings but we will show that inverted ordering is not valid in this setup. For normal ordering we find the lightest neutrino to have a mass of about 10-50 meV, and all leptonic mixing angles in agreement with experiment

Supersymmetric IIB Solutions with Schr\"{o}dinger Symmetry

We find a class of non-relativistic supersymmetric solutions of IIB supergravity with non-trivial B-field that have dynamical exponent n=2 and are invariant under the Schrodinger group. For a general Sasaki-Einstein internal manifold with U(1)^3 isometry, the solutions have two real supercharges. When the internal manifold is S^5, the number of supercharges can be four. We also find a large class of non-relativistic scale invariant type IIB solutions with dynamical exponents different from two. The explicit solutions and the values of the dynamical exponents are determined by vector eigenfunctions and eigenvalues of the Laplacian on an Einstein manifold.Comment: 28 pages, LaTe

Variability of an early developmental cell population underlies stochastic laterality defects

Embryonic development seemingly proceeds with almost perfect precision. However, it is largely unknown how much microscopic variability is hidden beneath this macroscopic accuracy. Here, we quantified embryo-to-embryo variability in vertebrate development, by studying cell number variation in the zebrafish endoderm. We noticed that the size of a subpopulation of the endoderm, the dorsal forerunner cells (which later form the left-right organizer), is highly variable between individual embryos. We found that the frequency of left-right laterality defects is increased drastically in embryos with a low number of dorsal forerunner cells, and we observed that these fluctuations are largely nonhereditary. Hence, a stochastic variation in early development leads to a remarkably strong macroscopic phenotype. These fluctuations appear to be caused by variable deposition of maternal factors involved in specification of the dorsal forerunner cells. In summary, we here dissect cause and consequence of embryo-to-embryo variability in a vertebrate model

Variability of an early developmental cell population underlies stochastic laterality defects

Embryonic development seemingly proceeds with almost perfect precision. However, it is largely unknown how much underlying microscopic variability is compatible with normal development. Here, we quantify embryo-to-embryo variability in vertebrate development by studying cell number variation in the zebrafish endoderm. We notice that the size of a sub-population of the endoderm, the dorsal forerunner cells (DFCs, which later form the left-right organizer), exhibits significantly more embryo-to-embryo variation than the rest of the endoderm. We find that, with incubation of the embryos at elevated temperature, the frequency of left-right laterality defects is increased drastically in embryos with a low number of DFCs. Furthermore, we observe that these fluctuations have a large stochastic component among fish of the same genetic background. Hence, a stochastic variation in early development leads to a remarkably strong macroscopic phenotype. These fluctuations appear to be associated with maternal effects in the specification of the DFCs

Diffractive Photoproduction of Eta_c

Diffractive photoproduction of $\eta_c$ is an important process to study the effect of Odderon, whose existence is still not confirmed in experiment. A detailed interpretation of Odderon in QCD, i.e., in terms of gluons is also unclear.Taking charm quarks as heavy quarks, we can use NRQCD and take $\eta_c$ as a $c\bar c$ bound state. Hence, in the production of $\eta_c$a free $c\bar c$ pair is first produced and this pair is transformed into $\eta_c$ subsequently.In the forward region of the kinematics, the $c\bar c$ pair interacts with initial hadron through exchanges of soft gluons. This interaction can be studied with HQET, which provides a systematic expansion in the inverse of the $c$-quark mass $m_c$. We find that the calculation of the $S$-matrix element in the forward region can be formulated as the problem of solving a wave function of a $c$-quark propagating in a background field of soft gluons. At leading order we find that the differential cross-section can be expressed with four functions, which are defined with a twist-3 operator of gluons. The effect of exchanging a Odderon can be identified with this operator in our case. We discuss our results in detail and compare them with those obtained in previous studies. Our results and those from other studies show that the differential cross-section is very small in the forward region. We also show that the production through photon exchange is dominant in the extremely forward region, hence the effect of Odderon exchange can not be identified in this region.For completeness we also give results for diffractive photoproduction of $J/\Psi$.Comment: 20 pages with 3 figures. Text improve

Hard diffractive quarkonium hadroproduction at high energies

We present a study of heavy quarkonium production in hard diffractive process by the Pomeron exchange for Tevatron and LHC energies. The numerical results are computed using recent experimental determination of the diffractive parton density functions in Pomeron and are corrected by unitarity corrections through gap survival probability factor. We give predictions for single as well as central diffractive ratios. These processes are sensitive to the gluon content of the Pomeron at small Bjorken-x and may be particularly useful in studying the small-x physics. They may also be a good place to test the different available mechanisms for quarkonium production at hadron colliders.Comment: 7 pages, 3 figures, 1 table. Final version to be published in European Physical Journal

Some No-go Theorems for String Duals of Non-relativistic Lifshitz-like Theories

We study possibilities of string theory embeddings of the gravity duals for non-relativistic Lifshitz-like theories with anisotropic scale invariance. We search classical solutions in type IIA and eleven-dimensional supergravities which are expected to be dual to (2+1)-dimensional Lifshitz-like theories. Under reasonable ansaetze, we prove that such gravity duals in the supergravities are not possible. We also discuss a possible physical reason behind this.Comment: 18 pages, Latex, flux conditions clarified (v2), brief summary of results added (v3