Localized Particle States and Dynamics Gravitational Effects

Scalar particles--i.e., scalar-field excitations--in de Sitter space exhibit behavior unlike either classical particles in expanding space or quantum particles in flat spacetime. Their energies oscillate forever, and their interactions are spread out in energy. Here it is shown that these features characterize not only normal-mode excitations spread out over all space, but localized particles or wave packets as well. Both one-particle and coherent states of a massive, minimally coupled scalar field in de Sitter space, associated with classical wave packets, are constructed explicitly. Their energy expectation values and corresponding Unruh-DeWitt detector response functions are calculated. Numerical evaluation of these quantities for a simple set of classical wave packets clearly displays these novel features. Hence, given the observed accelerating expansion of the Universe, it is possible that observation of an ultralow-mass scalar particle could yield direct confirmation of distinct predictions of quantum field theory in curved spacetime.Comment: 12 pages, 5 figure

Morphological & phylogenetic analysis of two species of heterokont alage [i.e. algae]

The freshwater heterokont algae Anthophysa vegetans and Botrydiopsis pyrenoidosa (strain SAG 31.83) were reexamined in the light microscope and their phylogenetic positions were investigated using DNA sequence analyses. Although differences in numbers of cells per colony and cell sizes were observed, these morphological data are consistent with previously published information for both species. In particular, the highly multinucleate nature of B. pyrenoidosa cells was confirmed by fluorescence microscopy using the DNA-binding fluorochrome DAPI. Parsimony and maximum likelihood analyses of nuclear small subunit ribosomal RNA (18S rRNA) gene sequences confirm placement of the colorless, colonial flagellate A. vegetans within the Chrysophyceae and imply that A. vegetans is most closely related to Poterioochromonas spp. and Ochromonas sphaerocystis. Evidence is presented for four independent losses of photosynthetic capacity within the Chrysophyceae. Botrydiopsis pyrenoidosa was first described by Trenkwalder, classified in the Xanthophyceae, and deposited in the Sammlung von Algenkulturen (strain SAG 31.83). Analyses of 18S rRNA gene sequence(s) derived from an authentic isolate indicate that B. pyrenoidosa is not closely related to Botrydiopsis intercedens and probably does not belong in the Xanthophyceae. The alga cannot be confidently placed in any known class of heterokont algae and a new genus, Polykaryon, is erected to include P. pyrenoidosum (Trenkwalder) Bailey et Misner. Polykaryon is treated as incertae sedis within the heterokont algal lineage. In a further investigation, coccoid vegetative cells of the heterokont alga Polykaryon pyrenoidosum (Trenkwalder) Bailey et Misner were examined by transmission electron microscopy. All cells are characterized by the presence of cell walls (80-740 nm) with an extracellular ‘fringe’ and most contain multiple nuclei that are spherical or elongate. One Golgi apparatus is present in each cell and this organelle is always associated with a nucleus. P. pyrenoidosum cells contain multiple chloroplasts lacking eyespots that that have bulging pyrenoids not traversed by thylakoids, photosynthetic membranes in groups of three, and girdle lamellae. Flagellar hairs (FHs) ca. 16 nm in cross sectional diameter are found within the endomembrane system of many vegetative cells and vacuoles containing FHs are observed in the cytosol and associated with chloroplasts and nuclei. Although the taxonomic affinities of the species remains obscure, the combination of ultrastructural features observed in this study serves to exclude the alga from many classes of heterokont algae. Although very unlikely, our results do not rule out the possibility that the species is an unusual member of the Chrysophyceae. Total evidence implies that P. pyrenoidosum is most similar to species placed in the Phaeothamniophyceae and Xanthophyceae

The Secreted Proteins of \u3cem\u3eAchlya hypogyna\u3c/em\u3e and \u3cem\u3eThraustotheca clavata\u3c/em\u3e Identify the Ancestral Oomycete Secretome and Reveal Gene Acquisitions by Horizontal Gene Transfer

Saprotrophic and parasitic microorganisms secrete proteins into the environment to breakdown macromolecules and obtain nutrients. The molecules secreted are collectively termed the “secretome” and the composition and function of this set of proteins varies depending on the ecology, life cycle, and environment of an organism. Beyond the function of nutrient acquisition, parasitic lineages must also secrete molecules to manipulate their host. Here,we use a combination of de novo genome and transcriptome sequencing and bioinformatic identification of signal peptides to identify the putative secreted proteome of two oomycetes, the facultative parasite Achlya hypogyna and free-living Thraustotheca clavata. By comparing the secretomes of these saprolegnialean oomycetes with that of eight other oomycetes, we were able to characterize the evolution of this protein set across the oomycete clade. These species span the last common ancestor of the two major oomycete families allowing us to identify the ancestral secretome. This putative ancestral secretome consists of at least 84 gene families. Only 11 of these gene families are conserved across all 10 secretomes analyzed and the two major branches in the oomycete radiation. Notably, we have identified expressed elicitin-like effector genes in the saprotrophic decomposer, T. clavata. Phylogenetic analyses show six novel horizontal gene transfers to the oomycete secretome from bacterial and fungal donor lineages, four of which are specific to the Saprolegnialeans. Comparisons between free-living and pathogenic taxa highlight the functional changes of oomycete secretomes associated with shifts in lifestyle

One loop effective potential in heterotic M-theory

We have calculated the one loop effective potential of the vector multiplets arising from the compactification to five dimensions of heterotic M-theory on a Calabi-Yau manifold with h^{1,1}>1. We find that extensive cancellations between the fermionic and bosonic sectors of the theory cause the effective potential to vanish, with the exception of a higher order curvature term of the type which might arise from string corrections.Comment: Latex, 28 pages, 1 figur

Generic effective source for scalar self-force calculations

A leading approach to the modelling of extreme mass ratio inspirals involves the treatment of the smaller mass as a point particle and the computation of a regularized self-force acting on that particle. In turn, this computation requires knowledge of the regularized retarded field generated by the particle. A direct calculation of this regularized field may be achieved by replacing the point particle with an effective source and solving directly a wave equation for the regularized field. This has the advantage that all quantities are finite and require no further regularization. In this work, we present a method for computing an effective source which is finite and continuous everywhere, and which is valid for a scalar point particle in arbitrary geodesic motion in an arbitrary background spacetime. We explain in detail various technical and practical considerations that underlie its use in several numerical self-force calculations. We consider as examples the cases of a particle in a circular orbit about Schwarzschild and Kerr black holes, and also the case of a particle following a generic time-like geodesic about a highly spinning Kerr black hole. We provide numerical C code for computing an effective source for various orbital configurations about Schwarzschild and Kerr black holes.Comment: 24 pages, 7 figures, final published versio

Derivative expansions of the non-equilibrium effective action

New techniques for evaluating the closed time path action for non-equilibrium quantum fields are presented. A derivative expansion is performed using a proper time kernel. Applications relevant to the scalar field theory of warm inflation are discussed and dissipation terms resummed. The effective action of the electromagnetic field is also considered. In this case the leading term can be related to the conductivity of a plasma and has a simple interpretation in terms of the classical Drude theory of conductivity.Comment: 17 pages, 1 figure, ReVTe

Hamiltonian Approach to 2D Dilaton-Gravities and Invariant Adm Mass

The formula existing in the literature for the ADM mass of 2D dilaton gravity is incomplete. For example, in the case of an infalling matter shockwave this formula fails to give a time-independent mass, unless a very special coordinate system is chosen. We carefully carry out the canonical formulation of 2D dilaton gravity theories (classical, CGHS and RST). As in 4D general relativity one must add a boundary term to the bulk Hamiltonian to obtain a well-defined variational problem. This boundary term coincides with the numerical value of the Hamiltonian and gives the correct mass which obviously is time-independent.Comment: revised, 12 pages, PUPT-1379; we added a reference and corrected some minor typo

Quantum Dynamics of Lorentzian Spacetime Foam

A simple spacetime wormhole, which evolves classically from zero throat radius to a maximum value and recontracts, can be regarded as one possible mode of fluctuation in the microscopic ``spacetime foam'' first suggested by Wheeler. The dynamics of a particularly simple version of such a wormhole can be reduced to that of a single quantity, its throat radius; this wormhole thus provides a ``minisuperspace model'' for a structure in Lorentzian-signature foam. The classical equation of motion for the wormhole throat is obtained from the Einstein field equations and a suitable equation of state for the matter at the throat. Analysis of the quantum behavior of the hole then proceeds from an action corresponding to that equation of motion. The action obtained simply by calculating the scalar curvature of the hole spacetime yields a model with features like those of the relativistic free particle. In particular the Hamiltonian is nonlocal, and for the wormhole cannot even be given as a differential operator in closed form. Nonetheless the general solution of the Schr\"odinger equation for wormhole wave functions, i.e., the wave-function propagator, can be expressed as a path integral. Too complicated to perform exactly, this can yet be evaluated via a WKB approximation. The result indicates that the wormhole, classically stable, is quantum-mechanically unstable: A Feynman-Kac decomposition of the WKB propagator yields no spectrum of bound states. Though an initially localized wormhole wave function may oscillate for many classical expansion/recontraction periods, it must eventually leak to large radius values. The possibility of such a mode unstable against growth, combined withComment: 37 pages, 93-

Is Quantum Spacetime Foam Unstable?

A very simple wormhole geometry is considered as a model of a mode of topological fluctutation in Planck-scale spacetime foam. Quantum dynamics of the hole reduces to quantum mechanics of one variable, throat radius, and admits a WKB analysis. The hole is quantum-mechanically unstable: It has no bound states. Wormhole wave functions must eventually leak to large radii. This suggests that stability considerations along these lines may place strong constraints on the nature and even the existence of spacetime foam.Comment: 15 page

Inhibition of FGF receptor blocks adaptive resistance to RET inhibition in CCDC6-RET-rearranged thyroid cancer.

Genetic alterations in RET lead to activation of ERK and AKT signaling and are associated with hereditary and sporadic thyroid cancer and lung cancer. Highly selective RET inhibitors have recently entered clinical use after demonstrating efficacy in treating patients with diverse tumor types harboring RET gene rearrangements or activating mutations. In order to understand resistance mechanisms arising after treatment with RET inhibitors, we performed a comprehensive molecular and genomic analysis of a patient with RET-rearranged thyroid cancer. Using a combination of drug screening and proteomic and biochemical profiling, we identified an adaptive resistance to RET inhibitors that reactivates ERK signaling within hours of drug exposure. We found that activation of FGFR signaling is a mechanism of adaptive resistance to RET inhibitors that activates ERK signaling. Combined inhibition of FGFR and RET prevented the development of adaptive resistance to RET inhibitors, reduced cell viability, and decreased tumor growth in cellular and animal models of CCDC6-RET-rearranged thyroid cancer