Entangled-photon generation in nano-to-bulk crossover regime

We have theoretically investigated a generation of entangled photons from biexcitons in a semiconductor film with thickness in nano-to-bulk crossover regime. In contrast to the cases of quantum dots and bulk materials, we can highly control the generated state of entangled photons by the design of peculiar energy structure of exciton-photon coupled modes in the thickness range between nanometers and micrometers. Owing to the enhancement of radiative decay rate of excitons at this thickness range, the statistical accuracy of generated photon pairs can be increased beyond the trade-off problem with the signal intensity. Implementing an optical cavity structure, the generation efficiency can be enhanced with keeping the high statistical accuracy.Comment: 9 pages, 3 figure

Diffusion of single long polymers in fixed and low density matrix of obstacles confined to two dimensions

Diffusion properties of a self-avoiding polymer embedded in regularly distributed obstacles with spacing a=20 and confined in two dimensions is studied numerically using the extended bond fluctuation method which we have developed recently. We have observed for the first time to our knowledge, that the mean square displacement of a center monomer $\phi_{M/2}(t)$ exhibits four dynamical regimes, i.e., $\phi_{M/2}(t) \sim t^{\nu_m}$ with $\nu_m\sim 0.6$, 3/8, 3/4, and 1 from the shortest to longest time regimes. The exponents in the second and third regimes are well described by segmental diffusion in the ``self-avoiding tube''. In the fourth (free diffusion) regime, we have numerically confirmed the relation between the reptation time $\tau_d$ and the number of segments $M, \tau_d\propto M^3$.Comment: 7 pages, 11 figure

Chaos in Glassy Systems from a TAP Perspective

We discuss level crossing of the free-energy of TAP solutions under variations of external parameters such as magnetic field or temperature in mean-field spin-glass models that exhibit one-step Replica-Symmetry-Breaking (1RSB). We study the problem through a generalized complexity that describes the density of TAP solutions at a given value of the free-energy and a given value of the extensive quantity conjugate to the external parameter. We show that variations of the external parameter by any finite amount can induce level crossing between groups of TAP states whose free-energies are extensively different. In models with 1RSB, this means strong chaos with respect to the perturbation. The linear-response induced by extensive level crossing is self-averaging and its value matches precisely with the disorder-average of the non self-averaging anomaly computed from the 2nd moment of thermal fluctuations between low-lying, almost degenerate TAP states. We present an analytical recipe to compute the generalized complexity and test the scenario on the spherical multi-$p$ spin models under variation of temperature.Comment: 12 pages, 2 figure

Formation and Disruption of Cosmological Low Mass Objects

We investigate the evolution of cosmological low mass (low virial temperature) objects and the formation of the first luminous objects. First, the `cooling diagram' for low mass objects is shown. We assess the cooling rate taking into account the contribution of H_2, which is not in chemical equilibrium generally, with a simple argument of time scales. The reaction rates and the cooling rate of H_2 are taken from the recent results by Galli & Palla (1998). Using this cooling diagram, we also estimate the formation condition of luminous objects taking into account the supernova (SN) disruption of virialized clouds. We find that the mass of the first luminous object is several times 10^7 solar mass, because smaller objects may be disrupted by the SNe before they become luminous. Metal pollution of low mass (Ly-alpha) clouds also discussed. The resultant metallicity of the clouds is about 1/1000 of the solar metallicity.Comment: 11 pages, 2 figures, To appear in ApJ

SUPERMAN, a regulator of floral homeotic genes in Arabidopsis

We describe a locus, SUPERMAN, mutations in which result in extra stamens developing at the expense of the central carpels in the Arabidopsis thaliana flower. The development of superman flowers, from initial primordium to mature flower, is described by scanning electron microscopy. The development of doubly and triply mutant strains, constructed with superman alleles and previously identified homeotic mutations that cause alterations in floral organ identity, is also described. Essentially additive phenotypes are observed in superman agamous and superman apetala2 double mutants. The epistatic relationships observed between either apetala3 or pistillata and superman alleles suggest that the SUPERMAN gene product could be a regulator of these floral homeotic genes. To test this, the expression patterns of AGAMOUS and APETALA3 were examined in superman flowers. In wild-type flowers, APETALA3 expression is restricted to the second and third whorls where it is required for the specification of petals and stamens. In contrast, in superman flowers, APETALA3 expression expands to include most of the cells that would normally constitute the fourth whorl. This ectopic APETALA3 expression is proposed to be one of the causes of the development of the extra stamens in superman flowers. The spatial pattern of AGAMOUS expression remains unaltered in superman flowers as compared to wild-type flowers. Taken together these data indicate that one of the functions of the wild-type SUPERMAN gene product is to negatively regulate APETALA3 in the fourth whorl of the flower. In addition, superman mutants exhibit a loss of determinacy of the floral meristem, an effect that appears to be mediated by the APETALA3 and PISTILLATA gene products

Probing Strong-Field Scalar-Tensor Gravity with Gravitational Wave Asteroseismology

We present an alternative way of tracing the existence of a scalar field based on the analysis of the gravitational wave spectrum of a vibrating neutron star. Scalar-tensor theories in strong-field gravity can potentially introduce much greater differences in the parameters of a neutron star than the uncertainties introduced by the various equations of state. The detection of gravitational waves from neutron stars can set constraints on the existence and the strength of scalar fields. We show that the oscillation spectrum is dramatically affected by the presence of a scalar field, and can provide unique confirmation of its existence.Comment: 14 pages, 7 figure

Theoretical framework of entangled-photon generation from biexcitons in nano-to-bulk crossover regime with planar geometry

We have constructed a theoretical framework of the biexciton-resonant hyperparametric scattering for the pursuit of high-power and high-quality generation of entangled photon pairs. Our framework is applicable to nano-to-bulk crossover regime where the center-of-mass motion of excitons and biexcitons is confined. Material surroundings and the polarization correlation of generated photons can be considered. We have analyzed the entangled-photon generation from CuCl film, by which ultraviolet entangled-photon pairs are generated, and from dielectric microcavity embedding a CuCl layer. We have revealed that in the nano-to-bulk crossover regime we generally get a high performance from the viewpoint of statistical accuracy, and the generation efficiency can be enhanced by the optical cavity with maintaining the high performance. The nano-to-bulk crossover regime has a variety of degrees of freedom to tune the entangled-photon generation, and the scattering spectra explicitly reflect quantized exciton-photon coupled modes in the finite structure.Comment: 18 pages, 10 figure

Two-photon nonlinearity in general cavity QED systems

We have investigated the two-photon nonlinearity at general cavity QED systems, which covers both weak and strong coupling regimes and includes radiative loss from the atom. The one- and two-photon propagators are obtained in analytic forms. By surveying both coupling regimes, we have revealed the conditions on the photonic wavepacket for yielding large nonlinearity depending on the cavity Q-value. We have also discussed the effect of radiative loss on the nonlinearity.Comment: 8 pages, 5 figure

Confluent primary fields in the conformal field theory

For any complex simple Lie algebra, we generalize primary fileds in the Wess-Zumino-Novikov-Witten conformal field theory with respect to the case of irregular singularities and we construct integral representations of hypergeometric functions of confluent type, as expectation values of products of generalized primary fields. In the case of sl(2), these integral representations coincide with solutions to confluent KZ equations. Computing the operator product expansion of the energy-momentum tensor and the generalized primary field, new differential operators appear in the result. In the case of sl(2), these differential operators are the same as those of the confluent KZ equations.Comment: 15 pages. Corrected typos. Proposition 3.1 rewritten. Other minor changes, title change

Whorl-Specific Expression of the SUPERMAN Gene of Arabidopsis Is Mediated by cis Elements in the Transcribed Region

The SUPERMAN (SUP) gene of Arabidopsis is involved in controlling cell proliferation in stamen and carpel primordia and in ovules during flower development. The SUP gene encodes a transcription factor with a C2H2-type zinc finger motif, a serine/proline-rich domain, a basic domain, and a leucine-zipper-like domain and is expressed in a very limited region in stamen primordia and in the developing ovary during flower development. The SUP gene is susceptible to methylation, resulting in epigenetic gene silencing. To understand how the SUP gene is expressed spatially and temporally in its restricted domain, and why methylation of the transcribed region affects early-stage SUP expression, we have identified the SUP cis regulatory elements by characterizing SUP gene fusions. These studies show that the SUP gene has discrete upstream promoter elements required for expression in stamen primordia in early stages and in the ovary in later stages. The promoter activity for stamen primordia is modulated by several positive and negative elements located in the transcribed and translated regions. Several regulatory elements in the transcribed region correlate with the areas of the gene that are heavily methylated in epigenetic alleles; these data provide a possible explanation of how methylation of the transcribed region represses transcription