Results for "Lynn D. Matthews"

total 124454took 0.14s
Radio Stars and Their Lives in the GalaxyJan 29 2013Feb 26 2013This paper summarizes the three-day international workshop "Radio Stars and Their Lives in the Galaxy", held at the Massachusetts Institute of Technology Haystack Observatory on 2012 October 3-5. The workshop was organized to provide a forum for the presentation ... More
Radio Stars: from kHz to THzJul 25 2018Oct 12 2018Advances in technology and instrumentation have now opened up virtually the entire radio spectrum to the study of stars. An international workshop "Radio Stars: from kHz to THz" was held at the Massachusetts Institute of Technology Haystack Observatory ... More
First Resolved Images of the Mira AB Symbiotic Binary at Centimeter WavelengthsDec 07 2005We report the first spatially resolved radio continuum measurements of the Mira AB symbiotic binary system, based on observations obtained with the Very Large Array (VLA). This is the first time that a symbiotic binary has been resolved unambiguously ... More
VLA Observations of HI in the Circumstellar Envelopes of Asymptotic Giant Branch StarsJan 09 2007(Abridged) We have used the VLA to search for neutral atomic hydrogen in the circumstellar envelopes of five AGB stars. We have detected HI 21-cm emission coincident in both position and velocity with the semi-regular variable RS Cnc. The emission comprises ... More
Science with an ngVLA: Evolved StarsOct 15 2018This chapter reviews some of the expected contributions of the ngVLA to the understanding of the late evolutionary stages of low-to-intermediate mass stars, including asymptotic giant branch (AGB) stars, post-AGB stars, and pre-planetary nebulae. Such ... More
HI Imaging Observations of Superthin Galaxies. II. IC2233 and the Blue Compact Dwarf NGC2537Sep 26 2007We have used the VLA to image the HI 21-cm line emission in the edge-on Sd galaxy IC2233 and the blue compact dwarf NGC2537. We also present new optical B,R, and H alpha imaging of IC2233 obtained with the WIYN telescope. Despite evidence of localized ... More
Clues on the Structure and Composition of Galactic Disks from Studies of "Superthin" Spirals: the Case of UGC3697Dec 15 2004We summarize results from an HI+optical imaging study of the ``Integral Sign'' galaxy, UGC3697. UGC3697 is a low-mass, Sd spiral that exhibits a ``superthin'' disk morphology despite a prounced gasous and stellar warp. Our new observations show evidence ... More
VLA Observations of HI in the Circumstellar Envelopes of AGB StarsDec 18 2006We present the results of a VLA search for HI emission in the circumstellar envelopes of five nearby AGB stars: RS Cnc, IRC+10216, EP Aqr, R Cas, and R Aqr. We have detected emission coincident in both position and velocity with RS Cnc, implying that ... More
B and V CCD Photometry of Southern, Extreme Late-Type Spiral GalaxiesSep 15 1997We present B and V CCD aperture photometry for a morphologically-selected sample of forty-nine southern, extreme late-type spiral galaxies. All objects are moderate-to-low surface brightness Local Supercluster field galaxies that were detected previously ... More
Detections of CO in Late-Type, Low Surface Brightness Spiral GalaxiesJan 17 2005Feb 08 2005Using the IRAM 30-m telescope, we have obtained 12CO J=1-0 and 2-1 spectral line observations toward the nuclear regions of 15 edge-on, low surface brightness (LSB) spiral galaxies. Our sample comprises extreme late-type LSB spirals with disk-dominated ... More
Dark matter dominance at all radii in the superthin galaxy UGC 7321Jun 01 2009We model the shape and density profile of the dark matter halo of the low surface brightness, superthin galaxy UGC 7321, using the observed rotation curve and the HI scale height data as simultaneous constraints. We treat the galaxy as a gravitationally ... More
NEW INSIGHTS INTO NON-RADIATIVE HEATING IN LATE-A STAR CHROMOSPHERESJan 19 1995Using new and archival spectra from the Goddard High Resolution Spectrograph, we have searched for evidence of chromospheric and transition region emission in six stars of mid- to late-A spectral type. Two of the stars, alpha Aql (A7 IV-V) and alpha Cep ... More
Astro2020: Molecular Masers as Probes of the Dynamic Atmospheres of Dying StarsMar 13 2019More than half of the dust and heavy element enrichment in galaxies originates from the winds and outflows of evolved, low-to-intermediate mass stars on the asymptotic giant branch (AGB). However, numerous details of the physics of late-stage stellar ... More
Starbursts and the Evolution of Gas-Rich GalaxiesSep 22 2000Moderately luminous starbursts in the nearby universe often occur in disk galaxies that are at most subject to mild external perturbations. An investigation of this type of galaxy leads to a better understanding of starburst triggering mechanisms and ... More
Photometry of Polar-Ring GalaxiesJul 17 2007We have obtained photometry in B and R for seven confirmed or probable polar-ring galaxies from the Polar-Ring Catalog of Whitmore et al. (1990). The rings show a range of colors from B-R \approx 0.6 to B-R \approx 1.7. The bluest rings have bright HII ... More
The Stability of Low Surface Brightness Disks Based on Multi-Wavelength ModelingJul 29 2011To investigate the structure and composition of the dusty interstellar medium (ISM) of low surface brightness (LSB) disk galaxies, we have used multiwavelength photometry to construct spectral energy distributions for three low-mass, edge-on LSB galaxies. ... More
HI and CO in the circumstellar environment of the S-type star RS CncMar 08 2010This paper presents interferometric and single-dish CO observations along with HI data obtained for the oxygen-rich semi-regular variable RS Cnc, in order to probe its circumstellar environment at different scales. With the Plateau de Bure Interferometer ... More
Modeling the HI 21-cm line profile from circumstellar shells around red giantsMar 04 2015We present HI line profiles for various models of circumstellar shells around red giants. In the calculations we take into account the effect of the background at 21 cm, and show that in some circumstances it may have an important effect on the shape ... More
Astro2020: Unlocking the Secrets of Late-Stage Stellar Evolution and Mass Loss through Radio Wavelength ImagingMar 13 2019During the late phases of evolution, low-to-intermediate mass stars like our Sun undergo periods of extensive mass loss, returning up to 80% of their initial mass to the interstellar medium. This mass loss profoundly affects the stellar evolutionary history, ... More
On cycles of pairing-friendly elliptic curvesMar 06 2018Nov 02 2018A cycle of elliptic curves is a list of elliptic curves over finite fields such that the number of points on one curve is equal to the size of the field of definition of the next, in a cyclic way. We study cycles of elliptic curves in which every curve ... More
A conformally invariant gap theorem in Yang-Mills theoryAug 03 2017Nov 01 2017We show a sharp conformally invariant gap theorem for Yang-Mills connections in dimension 4 by exploiting an associated Yamabe-type problem.
Maximizing Influence in an Ising Network: A Mean-Field Optimal SolutionAug 24 2016The problem of influence maximization in social networks has typically been studied in the context of contagion models and irreversible processes. In this paper, we consider an alternate model that treats individual opinions as spins in an Ising network ... More
Optimally Influencing Complex Ising SystemsSep 29 2016In the study of social networks, a fundamental problem is that of influence maximization (IM): How can we maximize the collective opinion of individuals in a network given constrained marketing resources? Traditionally, the IM problem has been studied ... More
Maximizing Influence in an Ising Network: A Mean-Field Optimal SolutionAug 24 2016Feb 19 2017Influence maximization in social networks has typically been studied in the context of contagion models and irreversible processes. In this paper, we consider an alternate model that treats individual opinions as spins in an Ising system at dynamic equilibrium. ... More
Index-energy estimates for Yang-Mills connections and Einstein metricsJan 14 2019We prove a conformally invariant estimate for the index of Schr\"odinger operators acting on vector bundles over four-manifolds, related to the classical Cwikel-Lieb-Rozenblum estimate. Applied to Yang-Mills connections we obtain a bound for the index ... More
Hidden $U(1)_Y$ Ward-Takahashi identities in the spontaneously brokenAbelian Higgs model and the decoupling of certain heavy particles in its simple extensionsSep 22 2015Aug 14 2016This work is dedicated to the memory of R. Stora. The spontaneously broken (SSB) $U(1)_Y$ Abelian Higgs model (AHM) (the gauge theory of a scalar $\phi \propto (H+i\pi)= {\tilde H}e^{i{\tilde \pi}/<H>}$ and a transverse vector A) has a massless pseudo-scalar ... More
Global $SU(3)_C\times SU(2)_L\times U(1)_Y$ linear sigma model: axial-vector Ward Takahashi identities, and decoupling of certain heavy BSM particles due to the Goldstone theoremSep 21 2015Jul 15 2017Dedicated to the memory of Raymond Stora (1930-2015). In the $SU(2)_L\times SU(2)_R$ Linear Sigma Model with PCAC, towers of Ward-Takahashi Identities (WTI) have long been known to give relations among 1-Scalar-Particle-Irreducible Green's functions, ... More
Global $U(1)_Y$xBRST symmetry and the LSS theorem: Ward-Takahashi identities governing Green's functions, on-shell T-Matrix elements, and the effective potential, in the spontaneously broken extended Abelian Higgs modelSep 21 2015Jan 08 2018The weak-scale U(1) Abelian Higgs Model (AHM) is the simplest spontaneous symmetry breaking (SSB) gauge theory. The extended AHM (E-AHM) adds certain heavy scalars $\Phi$ and fermions $\psi$. In Lorenz gauge, these theories have a global U(1) conserved ... More
The Goldstone theorem protects naturalness, and the absence of Brout-Englert-Higgs fine-tuning, in spontaneously broken SO(2)Jun 24 2013Nov 11 2014The Gell-Mann-Levy (GML), Schwinger and Standard Models were previously shown to lack a Brout-Englert-Higgs (BEH) fine-tuning problem due to quadratic divergences, with finite Euclidean cut-off \Lambda, because of the symmetries obeyed by all O(\Lambda^2) ... More
Maximizing Activity in Ising Networks via the TAP ApproximationFeb 28 2018Apr 17 2018A wide array of complex biological, social, and physical systems have recently been shown to be quantitatively described by Ising models, which lie at the intersection of statistical physics and machine learning. Here, we study the fundamental question ... More
Global $SU(3)_C x SU(2)_L x U(1)_Y$ linear sigma model with Standard Model quarks and leptons, and Dirac neutrinos: axial-vector Ward Takahashi identities and decoupling of certain heavy particles due to the Goldstone theoremSep 21 2015Aug 14 2016This work is dedicated to the memory of R. Stora. In the Linear Sigma Model (LSM), towers of Ward-Takahashi Identities (WTI) relate both 1-Scalar-Particle-Irreducible Green's functions and I-SP-Reducible T-Matrix elements for external scalars (a doublet ... More
Bounded gaps between primes in special sequencesJul 07 2014We use Maynard's methods to show that there are bounded gaps between primes in the sequence $\{\lfloor n\alpha\rfloor\}$, where $\alpha$ is an irrational number of finite type. In addition, given a superlinear function $f$ satisfying some properties described ... More
Nuclides as a liquid phase of $SU(2)_L \times SU(2)_R$ chiral perturbation theory I: emergence of pion-less SU(2) $χ$ PTNov 27 2018The Standard Model of particle physics, augmented with neutrino mixing, is at least very nearly the complete theory of interactions of known particles at energies accessible to Nature on Earth. Candidate effective theories of nuclear structure must therefore ... More
Calibration of ALMA as a phased array: ALMA observations during the 2017 VLBI campaignJan 28 2019We present a detailed description of the special procedures for calibration and quality assurance of Atacama Large Millimeter/submillimeter Array (ALMA) observations in Very Long Baseline Interferometry (VLBI) mode. These procedures are required to turn ... More
UV-Optical Pixel Maps of Face-On Spiral Galaxies -- Clues for Dynamics and Star Formation HistoriesNov 22 2002UV and optical images of the face-on spiral galaxies NGC 6753 and NGC 6782 reveal regions of strong on-going star formation that are associated with structures traced by the old stellar populations. We make NUV--(NUV-I) pixel color-magnitude diagrams ... More
Paramagnetic Spin Correlations in Colossal Magnetoresistive La0.7Ca0.3MnO3Feb 02 2012Apr 02 2012Neutron spectroscopy measurements reveal dynamic spin correlations throughout the Brillouin zone in the colossal magnetoresistive material La0.7Ca0.3MnO3 at 265 K (approximately 1.03 Tc). The long-wavelength behavior is consistent with spin diffusion, ... More
Spin-induced symmetry breaking in orbitally ordered NiCr_2O_4 and CuCr_2O_4Jun 25 2012At room temperature, the normal oxide spinels NiCr_2O_4 and CuCr_2O_4 are tetragonally distorted and crystallize in the I4_1/amd space group due to cooperative Jahn-Teller ordering driven by the orbital degeneracy of tetrahedral Ni$^{2+}$ ($t_2^4$) and ... More
QCD Scales in Finite NucleiDec 06 1995The role of QCD scales and chiral symmetry in finite nuclei is examined. The Dirac-Hartree mean-field coupling constants of Nikolaus, Hoch, and Madland (NHM) are scaled in accordance with the QCD-based prescription of Manohar and Georgi. Whereas the nine ... More
Entanglement-secured single-qubit quantum secret-sharingSep 09 2011In single-qubit quantum secret sharing, a secret is shared between N parties via manipulation and measurement of one qubit at a time. Each qubit is sent to all N parties in sequence; the secret is encoded in the first participant's preparation of the ... More
Macro Dark MatterOct 08 2014Jul 03 2015Dark matter is a vital component of the current best model of our universe, $\Lambda$CDM. There are leading candidates for what the dark matter could be (e.g. weakly-interacting massive particles, or axions), but no compelling observational or experimental ... More
Global $SU(2)_L \otimes$BRST symmetry and its LSS theorem: Ward-Takahashi identities governing Green's functions, on-shell T-Matrix elements, and $V_{eff}$, in the scalar-sector of certain spontaneously broken non-Abelian gauge theoriesNov 16 2017Apr 17 2018This work is dedicated to the memory of Raymond Stora (1930-2015). $SU(2)_L$ is the simplest spontaneous symmetry breaking (SSB) non-Abelian gauge theory: a complex scalar doublet $\phi=\frac{1}{\sqrt{2}}\begin{bmatrix}H+i\pi_3-\pi_2 +i\pi_1\end{bmatrix}\equiv\frac{1}{\sqrt{2}}\tilde{H}e^{2i\tilde{t}\cdot\tilde{\vec{\pi}}/<H>}\begin{bmatrix}10\end{bmatrix}$ ... More
Hidden $U(1)_Y$ Ward-Takahashi identities for off-shell Green's functions and on-shell T-Matrix elements in the scalar-sector of the extended Abelian Higgs modelSep 21 2015Jul 29 2016The weak-scale $U(1)_Y$-hypercharge Abelian Higgs Model (AHM) is the gauge theory of a complex scalar $\phi = \frac{1}{\sqrt 2}(H+i\pi)$ and a vector $A^\mu$. When the $U(1)_Y$ is spontaneously broken (SSB) the theory is in its Goldstone mode and $\phi\equiv ... More
$U(1)\otimes BRST$ symmetry, of on-shell T-matrix elements and (1-$φ$-I) Green's functions, determines the vacuum state of the Abelian Higgs Model from symmetry alone: minimization of the scalar-sector effective potential is unnecessaryJan 20 2017Apr 16 2018The weak-scale $U(1)_{Y}$ Abelian Higgs Model (AHM) is the spontaneous-symmetry-breaking gauge theory of a complex scalar $\phi = \frac{1}{\sqrt{2}}(H + i \pi)$ and a vector $A_{\mu}$. Global $U(1)_{Y}\otimes BRST$ symmetry emerges: when it is realized ... More
Transverse Spin and Classical Gluon Fields: Combining Two Perspectives on Hadronic StructureJul 15 2014In recent decades, the spin and transverse momentum of quarks and gluons were found to play integral roles in the structure of the nucleon. Simultaneously, the onset of gluon saturation in hadrons and nuclei at high energies was predicted to result in ... More
The Extraordinary `Superthin' Spiral Galaxy UGC7321. II. The Vertical Disk StructureJun 28 2000We explore the vertical light distribution as a function of galactocentric radius in the edge-on (i=88) Sd `superthin' galaxy UGC7321. UGC7321 is a low-luminosity spiral (M_B,i=-17.0) with a diffuse, low surface brightness stellar disk and no discernible ... More
Parameterized Post-Newtonian coefficients for Brans-Dicke gravity with d+1 dimensionsJan 28 2009We present calculations of Post-Newtonian parameters for Brans-Dicke tensor-scalar gravity in an arbitrary number of compact extra dimensions in both the Jordan and Einstein conformal frames. We find that the parameter gamma, which measures the amount ... More
Problems and Prospects from a Flood of Extragalactic TeV Neutrinos in IceCubeNov 04 2015The steep spectrum of neutrinos measured by IceCube extending from >1 PeV down to ~10 TeV has an energy flux now encroaching on the Fermi isotropic GeV background. We examine several implications starting from source energetics requirements for neutrino ... More
The Emergence of Localized GravityNov 20 2000Mar 09 2001We explore physics on the boundary of a Randall-Sundrum type model when the brane tension is slightly sub-critical. We calculate the masses of the Kaluza-Klein decomposition of the graviton and use a toy model to show how localized gravity emerges as ... More
On TeV Gamma Rays and the Search for Galactic NeutrinosNov 16 2015The IceCube neutrino discovery presents an opportunity to answer long-standing questions in high-energy astrophysics. For their own sake and relations to other processes, it is important to understand neutrinos arising from the Milky Way, which should ... More
Strichartz and Localized Energy Estimates for the Wave Equation in Strictly Concave DomainsNov 06 2014We prove localized energy estimates for the wave equation in domains with a strictly concave boundary when homogeneous Dirichlet or Neumann conditions are imposed. By restricting the solution to small, frequency dependent, space time collars of the boundary, ... More
$L^q$ bounds on restrictions of spectral clusters to submanifolds for low regularity metricsFeb 28 2012Aug 06 2012We prove $L^q$ bounds on the restriction of spectral clusters to submanifolds in Riemannian manifolds equipped with metrics of $C^{1,\alpha}$ regularity for $0 \leq \alpha \leq 1$. Our results allow for Lipschitz regularity when $\alpha =0$, meaning they ... More
On refined local smoothing estimates for the Schrödinger equation in exterior domainsJun 04 2011Mar 12 2013We consider refinements of the local smoothing estimates for the Schr\"odinger equation in domains which are exterior to a strictly convex obstacle in $\RR^n$. By restricting the solution to small, frequency dependent collars of the boundary, it is expected ... More
Gamma Rays, Electrons, Hard X-Rays, and the Central Parsec of the Milky WayNov 02 2015The complex interplay of processes at the Galactic Center is at the heart of numerous past, present, and (likely) future mysteries. We aim at a more complete understanding of how spectra extending to >10 TeV result. We first construct a simplified model ... More
Constructing Gravitational DimensionsMar 13 2003It would be extremely useful to know whether a particular low energy effective theory might have come from a compactification of a higher dimensional space. Here, this problem is approached from the ground up by considering theories with multiple interacting ... More
Resummation and NLO Matching of Event Shapes with Effective Field TheorySep 18 2007Dec 31 2007The resummed differential thrust rate in e+e- annihilation is calculated using Soft-Collinear Effective Theory (SCET). The resulting distribution in the two-jet region T~1 is found to agree with the corresponding expression derived by the standard approach. ... More
Ordered Kinematic Endpoints for 5-body Cascade DecaysOct 27 2016We present expressions for the kinematic endpoints of 5-body cascade decay chains proceeding through all possible combinations of 2-body and 3-body decays, with one stable invisible particle in the final decay stage. When an invariant mass can be formed ... More
A Computational Approach to Extinction Events in Chemical Reaction Networks with Discrete State SpacesJan 08 2017Jan 10 2017Recent work of M.D. Johnston et al. has produced sufficient conditions on the structure of a chemical reaction network which guarantee that the corresponding discrete state space system exhibits an extinction event. The conditions consist of a series ... More
Translated Chemical Reaction NetworksMay 24 2013Jun 11 2013Many biochemical and industrial applications involve complicated networks of simultaneously occurring chemical reactions. Under the assumption of mass action kinetics, the dynamics of these chemical reaction networks are governed by systems of polynomial ... More
Approximate Maximum A Posteriori Inference with Entropic PriorsSep 29 2010In certain applications it is useful to fit multinomial distributions to observed data with a penalty term that encourages sparsity. For example, in probabilistic latent audio source decomposition one may wish to encode the assumption that only a few ... More
Precision direct photon spectra at high energy and comparison to the 8 TeV ATLAS dataJun 07 2016The direct photon spectrum is computed to the highest currently available precision and compared to ATLAS data from 8 TeV collisions at the LHC. The prediction includes threshold resummation at next-to-next-to-next-to-leading logarithmic order through ... More
A Resonant-Mode Model of Pulsar Radio EmissionOct 15 2003It is argued that the polar gap and flux tube in the pulsar magnetosphere act as a resonant cavity/waveguide system which is excited by oscillations in the primary beam current and accelerating potential. The modes will be converted, probably scattered, ... More
Spin wave damping arising from phase coexistence below $T_c$ in colossal magnetoresistive La$_{0.7}$Ca$_{0.3}$MnO$_3$Aug 29 2017Sep 12 2017While the spin dynamics of La$_{0.7}$Ca$_{0.3}$MnO$_3$ in the ferromagnetic phase are known to be unconventional, previous measurements have yielded contradictory results regarding the damping of spin wave excitations. Neutron spectroscopy measurements ... More
The Molecular ISM of Low Surface Brightness Spiral GalaxiesSep 15 2005I summarize some results from the recent CO survey of late-type, low surface brightness (LSB) spiral galaxies by Matthews et al. (2005). We have now detected CO emission from six late-type, LSB spirals, demonstrating that despite their typical low metallicities ... More
A Tale of Two Pulsars and the Origin of TeV Gamma Rays from the Galactic CenterNov 03 2015The Galactic Center (GC) has been long known to host gamma-ray emission detected to >10 TeV. HESS data now points to two plausible origins: the supermassive black hole (perhaps with >PeV cosmic rays and neutrinos) or high-energy electrons from the putative ... More
A Linear Programming Approach to Dynamical Equivalence, Linear Conjugacy, and the Deficiency One TheoremJan 22 2016Mar 01 2016The well-known Deficiency One Theorem gives structural conditions on a chemical reaction network under which, for any set of parameter values, the steady states of the corresponding mass action system may be easily characterized. It is also known, however, ... More
A Computational Approach to Steady State Correspondence of Regular and Generalized Mass Action SystemsJul 17 2014Jul 21 2014It has been recently observed that the dynamical properties of mass action systems arising from many models of biochemical reaction networks can be derived by considering the corresponding properties of a related generalized mass action system. The correspondence ... More
On logarithmic improvements of critical geodesic restriction bounds in the presence of nonpositive curvatureJul 11 2016Jul 19 2016We consider upper bounds on the growth of $L^p$ norms of restrictions of eigenfunctions and quasimodes to geodesic segments in a nonpositively curved manifold in the high frequency limit. This sharpens results of Chen and Sogge as well as Xi and Zhang, ... More
A note on "MAPK networks and their capacity for multistationarity due to toric steady states"Jul 21 2014We provide a short supplement to the paper "MAPK networks and their capacity for multistationarity due to toric steady states" by P\'erez Mill\'an and Turjanski. We show that the capacity for toric steady states in the three networks analyzed in that ... More
Constrained Willmore and CMC tori in the 3-sphereDec 10 2012Constrained Willmore surfaces are critical points of the Willmore functional under conformal variations. As shown in [5] one can associate to any conformally immersed constrained Willmore torus f a compact Riemann surface \Sigma, such that f can be reconstructed ... More
Constrained Willmore Tori and Elastic Curves in 2-Dimensional Space FormsMar 06 2013May 15 2014In this paper we consider two special classes of constrained Willmore tori in the 3-sphere. The first class is given by the rotation of closed elastic curves in the upper half plane - viewed as the hyperbolic plane - around the x-axis. The second is given ... More
Dirac ToriJan 29 2014We consider conformal immersions $f: T^2\rightarrow \mathbb{R}^3$ with the property that $H^2 f^*g_{\mathbb{R}^3}$ is a flat metric. These so called Dirac tori have the property that its Willmore energy is uniformly distributed over the surface and can ... More
Ramsey Transfer to ReductsJun 17 2017Apr 12 2018We introduce a notion weaker than an infinitary interpretation which we call a semi-retraction. We say a countable structure has the Ramsey property if its age does. For a countable structure $B$ with the Ramsey property we show a countable semi-retraction ... More
WFPC2 Observations of Compact Star Cluster Nuclei in Low Luminosity Spiral GalaxiesApr 15 1999We have used the Wide Field Planetary Camera 2 aboard the Hubble Space Telescope to image the compact star cluster nuclei of the nearby, late-type, low-luminosity spiral galaxies NGC 4395, NGC 4242, and ESO 359-029. We also analyze archival WFPC2 observations ... More
Characterization of NIP theories by ordered graph-indiscerniblesJun 25 2011Jun 28 2011We generalize the Unstable Formula Theorem characterization of stable theories from \citep{sh78}: that a theory $T$ is stable just in case any infinite indiscernible sequence in a model of $T$ is an indiscernible set. We use a generalized form of indiscernibles ... More
Equivariant constrained Willmore tori in the 3-sphereNov 17 2012May 15 2014In this paper we study equivariant constrained Willmore tori in the 3-sphere. These tori admit a 1-parameter group of M\"obius symmetries and are critical points of the Willmore energy under conformal variations. We show that the associated spectral curve ... More
Sums-of-Squares Formulas over Algebraically Closed FieldsOct 19 2015Oct 31 2016In this paper, we consider whether existence of a sums-of-squares formula depends on the base field. We reformulate the question of existence as a question in algebraic geometry. We show that, for large enough p, existence of sums-of-squares formulas ... More
Intrinsic Nanoscale Inhomogeneities in Transition Metal OxidesDec 29 2006Neutron elastic, inelastic and high energy x-ray scattering techniques are used to explore the nature of the polaron order and dynamics in La0.7Ca0.3MnO3. Static polaron correlations develop within a narrow temperature regime as the Curie temperature ... More
A Constraint Propagation Algorithm for Sums-of-Squares Formulas over the IntegersOct 11 2018Sums-of-squares formulas over the integers have been studied extensively using their equivalence to consistently signed intercalate matrices. This representation, combined with combinatorial arguments, has been used to produce sums-of-squares formulas ... More
Inhomogeneous Magnetism in La-doped CaMnO3. (II) Mesoscopic Phase Separation due to Lattice-coupled FM InteractionsMar 17 2003A detailed investigation of mesoscopic magnetic and crystallographic phase separation in Ca(1-x)La(x)MnO3, 0.00<=x<=0.20, is reported. Neutron powder diffraction and DC-magnetization techniques have been used to isolate the different roles played by electrons ... More
Unusual Coupling Between Field-induced Spin Fluctuations and Spin Density Wave in Intermetallic CeAg2Ge2Aug 31 2010Mar 17 2011We report on the experimental evidences for an unusual coupling between the magnetic field- induced fluctuations of correlated Ce-ions coinciding with the discontinuous movement of the underlying spin density wave in the intermetallic rare earth compound ... More
Indiscernibles, EM-types, and Ramsey Classes of TreesAug 14 2012Jan 05 2014It was shown in \cite{sc12} that for a certain class of structures $\I$, $\I$-indexed indiscernible sets have the modeling property just in case the age of $\I$ is a Ramsey class. We expand this known class of structures from ordered structures in a finite ... More
Cutting and shuffling a hemisphere: non-orthogonal axesOct 11 2018We examine the dynamics of cutting-and-shuffling a hemispherical shell driven by alternate rotation about two horizontal axes using the framework of piecewise isometry (PWI) theory. Previous restrictions on how the domain is cut-and-shuffled are relaxed ... More
Surges of collective human activity emerge from simple pairwise correlationsFeb 28 2018Jan 04 2019Human populations exhibit complex behaviors---characterized by long-range correlations and surges in activity---across a range of social, political, and technological contexts. Yet it remains unclear where these collective behaviors come from, or if there ... More
Learning about non-Newtonian fluids in a student-driven classroomMar 13 2012We describe a simple, low-cost experiment and corresponding pedagogical strategies for studying fluids whose viscosities depend on shear rate, referred to as non-Newtonian fluids. We developed these materials teaching for the Compass Project, an organization ... More
CMB Spectral Distortions from Cooling Macroscopic Dark MatterApr 23 2018May 30 2018We propose a new mechanism by which dark matter (DM) can affect the early universe. The hot interior of a macroscopic DM, or macro, can behave as a heat reservoir so that energetic photons are emitted from its surface. This results in spectral distortions ... More
Auxiliary field diffusion Monte Carlo calculations of light and medium-mass nuclei with local chiral interactionsFeb 25 2018Quantum Monte Carlo methods have recently been employed to study properties of nuclei and infinite matter using local chiral effective field theory interactions. In this work, we present a detailed description of the auxiliary field diffusion Monte Carlo ... More
Acceleration of Relativistic Electrons by MHD Turbulence: Implications for Non-thermal Emission from Black Hole Accretion DisksMar 12 2014Jul 27 2014We use analytic estimates and numerical simulations of test particles interacting with magnetohydrodynamic (MHD) turbulence to show that subsonic MHD turbulence produces efficient second-order Fermi acceleration of relativistic particles. This acceleration ... More
Resonance Broadening and Heating of Charged Particles in Magnetohydrodynamic TurbulenceApr 01 2012Sep 06 2012The heating, acceleration, and pitch-angle scattering of charged particles by MHD turbulence are important in a wide range of astrophysical environments, including the solar wind, accreting black holes, and galaxy clusters. We simulate the interaction ... More
Magnetic Structure of Heavy Fermion Ce2RhIn8Feb 13 2001Mar 02 2001Magnetic structure of the heavy fermion antiferromagnet Ce2RhIn8 is determined using neutron diffraction.
Seeing in Color: Jet SuperstructureJan 28 2010Jul 07 2010A new class of observables is introduced which aims to characterize the superstructure of an event, that is, features, such as color flow, which are not determined by the jet four-momenta alone. Traditionally, an event is described as having jets which ... More
Annihilation decays of bound states at the LHCDec 03 2009Apr 13 2010At the Large Hadron Collider, heavy particles may be produced in pairs close to their kinematic threshold. If these particles have strong enough attractive interactions they may form bound states. Consequently, the bound states may decay through annihilation ... More
Unification and the Hierarchy from AdS5Aug 16 2001In AdS5, the coupling for bulk gauge bosons runs logarithmically, not as a power law. For this reason, one can preserve perturbative unification of couplings. Depending on the cutoff, this can occur at a high scale. We discuss subtleties in the calculation ... More
The No-U-Turn Sampler: Adaptively Setting Path Lengths in Hamiltonian Monte CarloNov 18 2011Hamiltonian Monte Carlo (HMC) is a Markov chain Monte Carlo (MCMC) algorithm that avoids the random walk behavior and sensitivity to correlated parameters that plague many MCMC methods by taking a series of steps informed by first-order gradient information. ... More
Visualizing and Understanding Convolutional NetworksNov 12 2013Nov 28 2013Large Convolutional Network models have recently demonstrated impressive classification performance on the ImageNet benchmark. However there is no clear understanding of why they perform so well, or how they might be improved. In this paper we address ... More
1-loop matching and NNLL resummation for all partonic 2 to 2 processes in QCDAug 16 2010Apr 17 2012The Wilson Coefficients for all 4-parton operators which arise in matching QCD to Soft-Collinear Effective Theory (SCET) are computed at 1-loop. Any dijet observable calculated in SCET beyond leading order will require these results. The Wilson coefficients ... More
Quark branching in QCD matter to any order in opacity beyond the soft gluon emission limitJul 10 2018Nov 09 2018Cold nuclear matter effects in reactions with nuclei at a future electron-ion collider (EIC) lead to a modification of semi-inclusive hadron production, jet cross sections, and jet substructure when compared to the vacuum. At leading order in the strong ... More
A Stratum Approach to Global Stability of Complex Balanced SystemsAug 10 2010Oct 19 2010It has long been known that complex balanced mass-action systems exhibit a restrictive form of behaviour known as locally stable dynamics. This means that within each compatibility class $\mathcal{C}_{\mathbf{x}_0}$---the forward invariant space where ... More
Spin relaxation near a ferromagnetic transitionSep 26 2015We study spin relaxation in dilute magnetic semiconductors near a ferromagnetic transition, where spin fluctuations become strong. An enhancement in the scattering rate of itinerant carriers from the spin fluctuations of localized impurities leads to ... More
Hard-Soft-Collinear Factorization to All OrdersMar 25 2014Mar 06 2015We provide a precise statement of hard-soft-collinear factorization of scattering amplitudes and prove it to all orders in perturbation theory. Factorization is formulated as the equality at leading power of scattering amplitudes in QCD with other amplitudes ... More
Quark and Gluon Jet SubstructureNov 29 2012Apr 12 2013Distinguishing quark-initiated jets from gluon-initiated jets has the potential to significantly improve the reach of many beyond-the-standard model searches at the Large Hadron Collider and to provide additional tests of QCD. To explore whether quark ... More