Physical Sciences and Mathematics Commons^™

Finite Symmetries Of S^4, Weimin Chen Chen, Slawomir Kwasik, Reinhard Shultz

Weimin Chen

This paper discusses topological and locally linear actions of finite groups on S4. Local linearity of the orientation preserving actions on S4 forces the group to be a subgroup of SO(5). On the other hand, orientation reversing topological actions of “exotic” groups G (i.e. G 6⊂ O(5)) on S4 are constructed, and local linearity and stable smoothability of the actions are studied.

Ropelength Criticality, Jason Cantarella, Joseph H.G. Fu, Robert B. Kusner, John M. Sullivan

Robert Kusner

The ropelength problem asks for the minimum-length configuration of a knotted diameter-one tube embedded in Euclidean three-space. The core curve of such a tube is called a tight knot, and its length is a knot invariant measuring complexity. In terms of the core curve, the thickness constraint has two parts: an upper bound on curvature and a self-contact condition.

We give a set of necessary and sufficient conditions for criticality with respect to this constraint, based on a version of the Kuhn–Tucker theorem that we established in previous work. The key technical difficulty is to compute the derivative of thickness …

Vimos Ultra-Deep Survey (Vuds): Witnessing The Assembly Of A Massive Cluster At Z~3.3, B.C. Lemaux, O. Cucciati, L.A.M. Tasca, O. Le Fevre, G. Zamorani, P. Cassata, B. Garilli, V. Le Brun, D. Maccagni, L. Pentericci, R. Thomas, E. Vanzella, E. Zucca, R. Amorin, S. Bardelli, P. Capak, L.P. Cassara, M. Castellano, A. Cimatti, J.G. Cuby, S. De La Torre, A. Durkalec, A. Fontana, Mauro Giavalisco, A. Grazian, N.P. Hathi, O. Ilbert, C. Moreau, S. Paltani, B. Ribeiro, M. Salvato, D. Schaerer, M Scodeggio, V. Sommariva, M. Talia, Y. Taniguchi, L. Tresse, D. Vergani, P.W. Wang, S. Charlot, T. Contini, S. Fotopoulou, R.R. Gal, D.D. Kocevski, C. Lopez-Sanjuan, L.M. Lubin, Y. Mellier, T. Sadibekova, N. Scoville

Mauro Giavalisco

Using new spectroscopic observations obtained as part of the VIMOS Ultra-Deep Survey (VUDS), we performed a systematic search for overdense environments in the early universe (z> 2) and report here on the discovery of Cl J0227-0421, a massive protocluster at z = 3.29. This protocluster is characterized by both the large overdensity of spectroscopically confirmed members, δgal = 10.5 ± 2.8, and a significant overdensity in photometric redshift members. The halo mass of this protocluster is estimated by a variety of methods to be ~3 × 1014ℳ⊙ at z ~ 3.3, which, evolved to z = 0 results in a …

A Mean-Field Analogue Of The Hong-Ou-Mandel Experiment With Bright Solitons, Zhi-Yuan Sun, Panos Kevrekidis, Peter Kruger

Panos Kevrekidis

In the present work, we theoretically propose and numerically illustrate a mean-field analog of the Hong-Ou-Mandel experiment with bright solitons. More specifically, we scatter two solitons off of each other (in our setup, the bright solitons play the role of a classical analog to the quantum photons of the original experiment), while the role of the beam splitter is played by a repulsive Gaussian barrier. In our classical scenario, distinguishability of the particles yields, as expected, a 0.5 split mass on either side. Nevertheless, for very slight deviations from the completely symmetric scenario, a near-perfect transmission can be constructed instead, …

A Comparative Analysis Of Numerical Approaches To The Mechanics Of Elastic Sheets, Michael Taylor, Benny Davidovitch, Zhanlong Qiu, Katia Bertoldi

Benny Davidovitch

No abstract provided.

A Sheet On Deformable Sphere: "Wrinklogami" Patterns Suppress Curvature-Induced Delamination, Evan Hohlfeld, Benny Davidovitch

Benny Davidovitch

No abstract provided.

Chemical Potential In The First Law For Holographic Entanglement Entropy, David Kastor, Sourya Ray, Jennie Traschen

David Kastor

Entanglement entropy in conformal field theories is known to satisfy a first law. For spherical entangling surfaces, this has been shown to follow via the AdS/CFT correspondence and the holographic prescription for entanglement entropy from the bulk first law for Killing horizons. The bulk first law can be extended to include variations in the cosmological constant Λ, which we established in earlier work. Here we show that this implies an extension of the boundary first law to include varying the number of degrees of freedom of the boundary CFT. The thermodynamic potential conjugate to Λ in the bulk is called …

Innovative Representations Of Light, Behaving As Both Particles And Waves, Among The Paintings Of Monet And Renoir, Charles Smith

Charles Kay Smith

Monet and Renoir, friends collaborating in open air about 1865, discovered that sunlight filtering through a canopy of tree leaves does not produce the splotches and dapples that studio artists conventionally represented at the time but circles of light. Sometimes the circles of light punctuating the shade are clear, separate and crisp, as though light is being propagated as particles, but if the pin-hole gaps between leaves are very close together, they will project compound or superimposed circles that look like the waves that Thomas Young saw in his double slit experiment in 1803-4. Newton’s Opticks published in 1704 had …

Non-Vacuum Ads Cosmologies And The Approach To Equilibrium Of Entanglement Entropy, Sebastian Fischetti, David Kastor, Jennie Traschen

David Kastor

We extend standard results for vacuum asymptotically locally AdS (AlAdS) spacetimes, showing that such spacetimes can be constructed as foliations where the induced metric on each hypersurface satisfies Einstein's equation with stress-energy. By an appropriate choice of stress-energy on the hypersurfaces, the resulting AlAdS spacetime satisfies Einstein's equation with a negative cosmological constant and physical stress tensor. We use this construction to obtain AlAdS solutions whose boundaries are FRW cosmologies sourced by a massless scalar field or by a perfect fluid obeying the strong energy condition. We focus on FRW universes that approach Minkowski spacetime at late times, yielding AlAdS …

Crystal Graphs, Tokuyama's Theorem, And The Gindikin-Karpelevic Formula For G2, Holley Friedlander, Louis Gaudet, Paul E. Gunnells

Paul Gunnells

We conjecture a deformation of the Weyl character formula for type G2 in the spirit of Tokuyama’s formula for type A . Using our conjecture, we prove a combinatorial version of the Gindikin–Karpelevič formula for G2 , in the spirit of Bump–Nakasuji’s formula for type A .

Dissipative Superfluid Mass Flux Through Solid 4he, Ye. Vekhov, Robert Hallock

Robert Hallock

The thermomechanical effect in superfluid helium is used to create an initial chemical potential difference ∆u_0 across a solid 4_He sample. This ∆u_0 causes a flow of helium atoms from one reservoir filled with superfluid helium, through a sample cell filled with solid helium, to another superfluid-filled reservoir until potential equilibrium between the reservoirs is restored. The solid helium sample is separated from each of the reservoirs by Vycor rods that allow only the superfluid component to flow. With an improved technique, measurements of the flow F at several fixed solid helium temperatures T have been made as a function …

Mechanics Of Large Folds In Thin Interfacial Films, Vincent Demery, Benny Davidovitch, Christian D. Santangelo

Benny Davidovitch

A thin film at a liquid interface responds to uniaxial confinement by wrinkling and then by folding; its shape and energy have been computed exactly before self contact. Here, we address the mechanics of large folds, i.e. folds that absorb a length much larger than the wrinkle wavelength. With scaling arguments and numerical simulations, we show that the antisymmetric fold is energetically favorable and can absorb any excess length at zero pressure. Then, motivated by puzzles arising in the comparison of this simple model to experiments on lipid monolayers and capillary rafts, we discuss how to incorporate film weight, selfadhesion …

A Spitzer View Of The Giant Molecular Cloud Mon Ob1/Ngc 2264, Valerie A. Rapson, Judith L. Pipher, R. A. Gutermuth, Megeatj S. Thomas, Thomas S. Allen, Phillip C. Myers, Lori E. Allen

Robert A. Gutermuth

We present Spitzer 3.6, 4.5, 5.8, 8.0, and 24 μm images of the Mon OB1 East giant molecular cloud, which contains the young star forming region NGC 2264, as well as more extended star formation. With Spitzer data and Two Micron All Sky Survey photometry, we identify and classify young stellar objects (YSOs) with dusty circumstellar disks and/or envelopes in Mon OB1 East by their infrared-excess emission and study their distribution with respect to cloud material. We find a correlation between the local surface density of YSOs and column density of molecular gas as traced by dust extinction that is …

A Mass Threshold In The Number Density Of Passive Galaxies At Z~2, V. Sommariva, A. Fontana, A. Lamastra, P. Santini, J.S. Dunlop, M. Castellano, H. Ferguson, R.J. Mclure, A. Galametz, Mauro Giavalisco, A Grazian, Y. Lu, N. Menci, A. Merson, D. Paris, L. Pentericci, R. Somerville, T. Targett

Mauro Giavalisco

The process that quenched star formation in galaxies at intermediate and high redshift is still the subject of considerable debate. One way to investigate this puzzling issue is to study the number density of quiescent galaxies at z ' 2, and its dependence on mass. Here we present the results of a new study based on very deep Ks-band imaging (with the HAWK-I instrument on the VLT) of two HST CANDELS fields (the UKIDSS Ultra-deep survey (UDS) field and GOODS-South). The new HAWK-I data (taken as part of the HUGS VLT Large Program) reach detection limits of Ks > 26 (AB …

Rapid Decline Of Lyman-Α Emission Toward The Reionization Era, V. Tilvi, C. Papovich, H.C. Ferguson, S.L. Finkelstein, J. Long, M. Song, M. Dickinson, A.M. Koekemoer, Mauro Giavalisco, B. Mobasher

Mauro Giavalisco

The observed deficit of strongly Lyman-α emitting galaxies at z > 6.5 is attributed to either increasing neutral hydrogen in the intergalactic medium (IGM) and/or to the evolving galaxy properties. To investigate this, we have performed very deep near-IR spectroscopy of z ≳7 galaxies using MOSFIRE on the Keck-I Telescope. We measure the Lyman-α fraction at z ∼ 8 using two methods. First, we derived NLy_/Ntot directly using extensive simulations to correct for incompleteness. Second, we used a Bayesian formalism (introduced by Treu et al. 2012) that compares the z > 7 galaxy spectra to models of the Lyman-α equivalent width (WLy_) …

Fabrication Conditions For Efficient Organic Photovoltaic Cells From Aqueous Dispersions Of Nanoparticles, Monojit Bag, Timothy S. Gehan, Lawrence A. Renna, Dana D. Algaier, Paulm M. Lahti, Dhandapani Venkataraman

Dhandapani Venkataraman

For environmentally friendly and cost-effective manufacturing of organic photovoltaic (OPV) cells, it is highly desirable to replace haloarenes with water as the active layer fabrication solvent. Replacing an organic solvent with water requires retooling the device fabrication steps. The optimization studies were conducted using poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) as active layer materials. These materials were dispersed in water as blend and separate nanoparticles using the miniemulsion method. Topologies of the active layers were investigated using atomic force microscopy and electron microscopy techniques. We have identified two essential steps to fabricate efficient OPVs from aqueous …

Kazhdan-Lusztig Cells In Planar Hyperbolic Coxeter Groups And Automata, Mikhail V. Belolipetsky, Paul E. Gunnells, Richard A. Scott

Paul Gunnells

Let C be a one- or two-sided Kazhdan–Lusztig cell in a Coxeter group (W, S), and let Red(C) be the set of reduced expressions of all w ∈ C, regarded as a language over the alphabet S. Casselman has conjectured that Red(C) is regular. In this paper, we give a conjectural description of the cells when W is the group corresponding to a hyperbolic polygon, and show that our conjectures imply Casselman's.

Roadmap To The Morphological Instabilities Of A Stretched Twisted Ribbon, Julien Chopin, Vincent Demery, Benny Davidovitch

Benny Davidovitch

We address the mechanics of an elastic ribbon subjected to twist and tensile load. Motivated by the classical work of green and a recent experiment that discovered a plethora of morphological instabilities, we introduce a comprehensive theoretical framework through which we construct a 4D phase diagram of this basic system, spanned by the exerted twist and tension as well as the thickness and length of the ribbon. Different types of instabilities appear in various "corners" of this 4D parameter space, and are addressed through distinct types of asymptotic methods. Our theory employs three instruments, whose concerted implementation is necessary to …

Entropy- And Flow- Induced Superfluid States, Johan Carlström, Egor Babaev

Egor Babaev

No abstract provided.

Universal Temperature Dependence, Flux Extinction And The Role Of 3he Impurities In Superfluid Mass Transport Through Solid 4he, Ye. Vekhov, W. J. Mullin, Robert B. Hallock

Robert Hallock

The mass flux, F, carried by as-grown solid 4_He in the range 25.6-26.3 bar rises with falling temperature, and at a concentration-dependent temperature, T_d, the flux decreases sharply within a few mK. We study F as a function of 3_He impurity concentration, χ. We find that T_(d )is an increasing function of increasing χ. At temperatures above T_d the flux has a universal temperature dependence and the flux terminates in a narrow window near a characteristic temperature T_h ≈ 625 mK, which is independent of χ.

A Tale Of Two Distributions: From Few To Many Vortices In Quasi-Two-Dimensional Bose-Einstein Condensates, T. Kolokolnikov, Panos Kevrekidis, R. Carretero-Gonzalez

Panos Kevrekidis

Motivated by the recent successes of particle models in capturing the precession and interactions of vortex structures in quasi-two-dimensional Bose–Einstein condensates, we revisit the relevant systems of ordinary differential equations. We consider the number of vortices N as a parameter and explore the prototypical configurations (‘ground states’) that arise in the case of few or many vortices. In the case of few vortices, we modify the classical result illustrating that vortex polygons in the form of a ring are unstable for N≥7. Additionally, we reconcile this modification with the recent identification of symmetry-breaking bifurcations for the cases of N=2,…,5. We …

Dynamic And Energetic Stabilization Of Persistent Currents In Bose-Einstein Condensates, K.J. H. Law, T. W. Neely, Panos Kevrekidis, B. P. Anderson, A. S. Bradley, R. Carretero-Gonzalez

Panos Kevrekidis

We study conditions under which vortices in a highly oblate harmonically trapped Bose-Einstein condensate (BEC) can be stabilized due to pinning by a blue-detuned Gaussian laser beam, with particular emphasis on the potentially destabilizing effects of laser beam positioning within the BEC. Our approach involves theoretical and numerical exploration of dynamically and energetically stable pinning of vortices with winding number up to S=6, in correspondence with experimental observations. Stable pinning is quantified theoretically via Bogoliubov-de Gennes excitation spectrum computations and confirmed via direct numerical simulations for a range of conditions similar to those of experimental observations. The theoretical and numerical …

Exploring Vortex Dynamics In The Presence Of Dissipation: Analytical And Numerical Results, D. Yan, R. Carretero-Gonzalez, D. J. Frantzeskakis, Panos Kevrekidis, N. P. Proukakis, D. Spirn

Panos Kevrekidis

In this paper, we examine the dynamical properties of vortices in atomic Bose-Einstein condensates in the presence of phenomenological dissipation, used as a basic model for the effect of finite temperatures. In the context of this so-called dissipative Gross-Pitaevskii model, we derive analytical results for the motion of single vortices and, importantly, for vortex dipoles, which have become very relevant experimentally. Our analytical results are shown to compare favorably to the full numerical solution of the dissipative Gross-Pitaevskii equation where appropriate. We also present results on the stability of vortices and vortex dipoles, revealing good agreement between numerical and analytical …

Magnetic Fields In An Expanding Universe, David Kastor, Jennie Traschen

David Kastor

We find a solution to 4D Einstein-Maxwell theory coupled to a massless dilaton field describing a Melvin magnetic field in an expanding universe with 'stiff matter' equation of state parameter w=+1. As the universe expands, magnetic flux becomes more concentrated around the symmetry axis for dilaton coupling a<1/3√ and more dispersed for a>1/3√. An electric field circulates around the symmetry axis in the direction determined by Lenz's law. For a=0 the magnetic flux through a disk of fixed comoving radius is proportional to the proper area of the disk. This result disagrees with the usual expectation based on a test magnetic field that this …

Goal-Oriented Sensitivity Analysis For Lattice Kinetic Monte Carlo Simulations, Georgios Arampatzis, Markos Katsoulakis

Markos Katsoulakis

In this paper we propose a new class of coupling methods for the sensitivity analysis of high dimensional stochastic systems and in particular for lattice Kinetic Monte Carlo (KMC). Sensitivity analysis for stochastic systems is typically based on approximating continuous derivatives with respect to model parameters by the mean value of samples from a finite difference scheme. Instead of using independent samples the proposed algorithm reduces the variance of the estimator by developing a strongly correlated-"coupled"- stochastic process for both the perturbed and unperturbed stochastic processes, defined in a common state space. The novelty of our construction is that the …

Steadily Increasing Star Formation Rates In Galaxies Observed At 3≲Zv5 In The Candels/Goods-S Field, Seong-Kook Lee, Henry C. Ferguson, Rachel S. Somerville, Mauro Giavalisco, Tommy Wiklind, Tomas Dahlen

Mauro Giavalisco

We investigate the star formation histories (SFHs) of high redshift (3 . z . 5) star-forming galaxies selected based on their rest-frame ultraviolet (UV) colors in the CANDELS/GOODS-S field. By comparing the results from the spectral-energy- distribution-fitting analysis with two different assumptions about the SFHs — i.e., exponentially declining SFHs as well as increasing ones, we conclude that the SFHs of high-redshift star-forming galaxies increase with time rather than exponentially decline. We also examine the correlations between the star formation rates (SFRs) and the stellar masses. When the galaxies are fit with rising SFRs, we find that the trend seen …

Properties Of Submillimeter Galaxies In The Candels Goods-South Field, Tommy Wiklind, Christopher J. Conselice, Thomas Dahlen, Mark E. Dickinson, Henry C. Ferguson, Norman A. Grogin, Yicheng Guo, Anton Koekemoer, Bahram Mobasher, Alice Mortlock, Adriano Fontana, Romeel Dave, Haojin Yan, Viviana Aequaviva, Matthew L.N. Ashby, Guillermo Barro, Karina L. Caputi, Marco Castellano, Avishai Dekel, Jennifer L. Donley, Giovanni G. Fazio, Mauro Giavalisco, Andrea Grazian, Nimish P. Hathi, Peter Kurezynski, Yu Lu, Elizabeth J. Mcgrath, Duilia F. De Mello, Michael Peth, Mohammed Sarafzedeh, Mauro Stefanon, Thomas Targett

Mauro Giavalisco

We derive physical properties of 10 submillimeter galaxies located in the CANDELS coverage of the GOODS-South Field. The galaxies were first identified as sub- millimeter sources with the LABOCA bolometer and subsequently targeted for 870µm continuum observation with ALMA. The high angular resolution of the ALMA imaging allows secure counterparts to be identified in the CANDELS multiband dataset. The CANDELS data provide deep photometric data from UV through near-infrared wavelengths. Using synthetic spectral energy distributions, we derive photometric redshifts, stellar masses, extinction, ages, and the star formation history. The redshift range is z=1.65-4.76, with two of the galaxies located at …

From Voids To Coma: The Prevalence Of Pre-Processing In The Local Universe, R. A. Gutermuth

Robert A. Gutermuth

We examine the effects of pre-processing across the Coma Supercluster, including 3505 galaxies over ∼500 deg2, by quantifying the degree to which star-forming (SF) activity is quenched as a function of environment. We characterize environment using the complementary techniques of Voronoi Tessellation, to measure the density field, and the Minimal Spanning Tree, to define continuous structures, and so we measure SF activity as a function of local density and the type of environment (cluster, group, filament, and void), and quantify the degree to which environment contributes to quenching of SF activity. Our sample covers over two orders of magnitude in …

G-Minimality And Invariant Negative Spheres In G-Hirzenbruch Surfaces, Weimin Chen Chen

Weimin Chen

In this paper we initiate a study on the notion of G-minimality of four-manifolds equipped with an action of a finite group G. Our work shows that even in the case of cyclic actions on CP2#CP2, the comparison of G-minimality in the various categories (i.e., locally linear, smooth, symplectic) is already a delicate and interesting problem. In particular, we show that if a symplectic Zn-action on CP2#CP2 has an invariant locally linear topological (−1)-sphere, then it must admit an invariant symplectic (−1)-sphere, provided that n = 2 or n is odd. For the case where n > 2 and even, the …

Mod 2 Homology For Gl(4) And Galois Representations, Avner Ash, Paul E. Gunnells, Mark Mcconnell

Paul Gunnells

We extend the computations in [AGM11] to find the mod 2 homology in degree 1 of a congruence subgroup Γ of SL(4,Z) with coefficients in the sharbly complex, along with the action of the Hecke algebra. This homology group is related to the cohomology of Γ with F2 coefficients in the top cuspidal degree. These computations require a modification of the algorithm to compute the action of the Hecke operators, whose previous versions required division by 2. We verify experimentally that every mod 2 Hecke eigenclass found appears to have an attached Galois representation, giving evidence for a conjecture in …