Results for "Adam S. Charles"

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Interpreting Deep Learning: The Machine Learning Rorschach Test?Jun 01 2018Theoretical understanding of deep learning is one of the most important tasks facing the statistics and machine learning communities. While deep neural networks (DNNs) originated as engineering methods and models of biological networks in neuroscience ... More
Experimental tests of Bertrand's question and the Duhem-Quine problemJun 01 2018Dec 25 2018In this paper we report on an experimental test of Bertrand's question on the probability to find a random chord drawn inside a unit-radius circle with length greater than $\sqrt{3}$. In an experiment performed by tossing straws onto a circle, we confirm ... More
Learning spatially-correlated temporal dictionaries for calcium imagingFeb 08 2019Calcium imaging has become a fundamental neural imaging technique, aiming to recover the individual activity of hundreds of neurons in a cortical region. Current methods (mostly matrix factorization) are aimed at detecting neurons in the field-of-view ... More
Nonlinear quantum optics mediated by Rydberg interactionsFeb 19 2016Jul 07 2016By mapping the strong interaction between Rydberg excitations in ultra-cold atomic ensembles onto single photons via electromagnetically induced transparency, it is now possible to realize a nonlinear optical medium which exhibits a strong optical nonlinearity ... More
Nonparametric Methods in Astronomy: Think, Regress, Observe -- Pick Any ThreeJan 19 2018Telescopes are much more expensive than astronomers, so it is essential to minimize required sample sizes by using the most data-efficient statistical methods possible. However, the most commonly used model-independent techniques for finding the relationship ... More
Re-Weighted l_1 Dynamic Filtering for Time-Varying Sparse Signal EstimationAug 01 2012Jul 22 2015Signal estimation from incomplete observations improves as more signal structure can be exploited in the inference process. Classic algorithms (e.g., Kalman filtering) have exploited strong dynamic structure for time-varying signals while modern work ... More
Optical control of Faraday rotation in hot Rb vaporDec 09 2009We demonstrate controlled polarization rotation of an optical field conditional on the presence of a second field. Induced rotations of greater than pi/2 rad are seen with a transmission of 95%, corresponding to a ratio of phase shift to absorption of ... More
Sagnac Interferometry in a Slow-Light MediumDec 14 2005We use a Sagnac interferometer to measure the dispersive and absorptive properties of room temperature Rubidium vapor on the D_2 line at 780.2 nm. We apply a pump beam such that the resulting Lambda system exhibits Electromagnetically Induced Transparency. ... More
The Cosmic Microwave Background and the Stellar Initial Mass FunctionSep 10 2018Sep 24 2018We argue that an increased temperature in star-forming clouds alters the stellar initial mass function to be more bottom-light than in the Milky Way. At redshifts $z \gtrsim 6$, heating from the cosmic microwave background radiation produces this effect ... More
Enhanced optical cross section via collective coupling of atomic dipoles in a 2D arrayOct 27 2015Mar 10 2016Enhancing the optical cross section is an enticing goal in light-matter interactions, due to its fundamental role in quantum and non-linear optics. Here, we show how dipolar interactions can suppress off-axis scattering in a two-dimensional atomic array, ... More
Absolute absorption on the rubidium D lines: comparison between theory and experimentMay 08 2008We study the Doppler-broadened absorption of a weak monochromatic probe beam in a thermal rubidium vapour cell on the D lines. A detailed model of the susceptibility is developed which takes into account the absolute linestrengths of the allowed electric ... More
Polarization spectroscopy of an excited state transitionJul 13 2011Jul 26 2011We demonstrate polarization spectroscopy of an excited state transition in room temperature cesium vapor. An anisotropy induced by a circularly polarized pump beam on the D2 transition is observed using a weak probe on the 6P3/2 to 7S1/2 transition. When ... More
Cooperative Ordering in Lattices of Interacting Two-Level DipolesOct 17 2014Dec 09 2015We investigate the cooperative behavior of regular monolayers of driven two-level dipoles, using classical electrodynamics simulations. The dipolar response results from the interference of many cooperative eigenmodes, each frequency-shifted from the ... More
Off-resonance absorption and dispersion in a Doppler-broadened mediumMay 08 2009We study the absorptive and dispersive properties of Doppler-broadened atomic media as a function of detuning. Beginning from the exact lineshape calculated for a two-level atom, a series of approximations to the electric susceptibility are made. These ... More
Automatic Response Category Combination in Multinomial Logistic RegressionMay 10 2017We propose a penalized likelihood method that simultaneously fits the multinomial logistic regression model and combines subsets of the response categories. The penalty is non differentiable when pairs of columns in the optimization variable are equal. ... More
Ridge Fusion in Statistical LearningOct 15 2013May 05 2014We propose a penalized likelihood method to jointly estimate multiple precision matrices for use in quadratic discriminant analysis and model based clustering. A ridge penalty and a ridge fusion penalty are used to introduce shrinkage and promote similarity ... More
Short Term Memory Capacity in Networks via the Restricted Isometry PropertyJul 01 2013Mar 03 2015Cortical networks are hypothesized to rely on transient network activity to support short term memory (STM). In this paper we study the capacity of randomly connected recurrent linear networks for performing STM when the input signals are approximately ... More
Visualizing the PHATE of Neural NetworksAug 07 2019Understanding why and how certain neural networks outperform others is key to guiding future development of network architectures and optimization methods. To this end, we introduce a novel visualization algorithm that reveals the internal geometry of ... More
Optical preparation and measurement of atomic coherence at gigahertz bandwidthNov 18 2011We detail a method for the preparation of atomic coherence in a high density atomic medium, utilising a coherent preparation scheme of gigahertz bandwidth pulses. A numerical simulation of the preparation scheme is developed, and its efficiency in preparing ... More
Graph State Preparation and Cluster Computation with Global Addressing of Optical LatticesJan 28 2005We present a novel way to manipulate ultra-cold atoms where four atomic levels are trapped by appropriately tuned optical lattices. When employed to perform quantum computation via global control, this unique structure dramatically reduces the number ... More
Lensing Probabilities for Spectroscopically Selected Galaxy-Galaxy Strong LensesMar 17 2008Spectroscopic galaxy-galaxy lens searches are presently the most prolific method of identifying strong lens systems in large data sets. We study the probabilities associated with these lens searches, namely the probability of identifying a candidate with ... More
Practical designs for permutation symmetric problem Hamiltonians on hypercubesDec 19 2018We present a method to experimentally realize large-scale permutation-symmetric Hamiltonians for continuous-time quantum protocols such as quantum walk and adiabatic quantum computation. In particular, the method can be used to perform an encoded continuous-time ... More
Analog Sparse Approximation with Applications to Compressed SensingNov 17 2011Recent research has shown that performance in signal processing tasks can often be significantly improved by using signal models based on sparse representations, where a signal is approximated using a small number of elements from a fixed dictionary. ... More
Zeeman-tunable Modulation Transfer SpectroscopyJun 07 2019Active frequency stabilization of a laser to an atomic or molecular resonance underpins many modern-day AMO physics experiments. With a flat background and high signal-to-noise ratio, modulation transfer spectroscopy (MTS) offers an accurate and stable ... More
Zeeman-tunable Modulation Transfer SpectroscopyJun 07 2019Jul 31 2019Active frequency stabilization of a laser to an atomic or molecular resonance underpins many modern-day AMO physics experiments. With a flat background and high signal-to-noise ratio, modulation transfer spectroscopy (MTS) offers an accurate and stable ... More
Absolute absorption and dispersion of a rubidium vapour in the hyperfine Paschen-Back regimeAug 09 2012Here we report on measurements of the absolute absorption and dispersion properties of an isotopically pure 87Rb vapour for magnetic fields up to and including 0.6 T. We discuss the various regimes that arise when the hyperfine and Zeeman interactions ... More
Four-wave mixing in a non-degenerate four-level diamond configuration in the hyperfine Paschen-Back regimeMay 04 2017Oct 02 2017We present an experimental study of seeded four-wave mixing (4WM) using a diamond excitation scheme (with states from the 5S$_{1/2}$, 5P$_{1/2}$, 5P$_{3/2}$ and 5D$_{3/2}$ terms) in a thermal vapour of $^{87}$Rb atoms. We investigate the 4WM spectra under ... More
Electromagnetically induced absorption in a non-degenerate three-level ladder systemMay 14 2015We investigate, theoretically and experimentally, the transmission of light through a thermal vapour of three-level ladder-type atoms, in the presence of 2 counter-propagating control fields. A simple theoretical model predicts the presence of electromagnetically ... More
Direct measurement of excited-state dipole matrix elements using electromagnetically induced transparency in the hyperfine Paschen-Back regimeFeb 29 2016May 03 2016Applying large magnetic fields to gain access to the hyperfine Paschen-Back regime can isolate three-level systems in a hot alkali metal vapors, thereby simplifying usually complex atom-light interactions. We use this method to make the first direct measurement ... More
Measuring the Stokes parameters for light transmitted by a high-density rubidium vapour in large magnetic fieldsDec 16 2011Here we report on measurements of the absolute absorption and dispersion of light in a dense rubidium vapour on the D2 line in the weak-probe regime with an applied magnetic field. A model for the electric susceptibility of the vapour is presented which ... More
The hyperfine Paschen-Back Faraday effectJan 08 2014Mar 26 2014We investigate experimentally and theoretically the Faraday effect in an atomic medium in the hyperfine Paschen-Back regime, where the Zeeman interaction is larger than the hyperfine splitting. We use a small permanent magnet and a micro-fabricated vapour ... More
Optical transmission through a dipolar layerSep 16 2011Sep 20 2011The interaction between light and matter is fundamental to developments in quantum optics and information. Over recent years enormous progress has been made in controlling the interface between light and single emitters including ions, atoms, molecules, ... More
Selective reflection from Rb layer with thickness below $λ$/12 and applicationsFeb 25 2017We have studied the peculiarities of selective reflection from Rb vapor cell with thickness $L <$ 70 nm, which is over an order of magnitude smaller than the resonant wavelength for Rb atomic D$_1$ line $\lambda$ = 795 nm. A huge ($\approx$ 240 MHz) red ... More
Coherent Excitation Transfer in a Spin Chain of Three Rydberg AtomsAug 05 2014Mar 21 2015We study coherent excitation hopping in a spin chain realized using highly excited individually addressable Rydberg atoms. The dynamics are fully described in terms of an XY spin Hamiltonian with a long range resonant dipole-dipole coupling that scales ... More
Selective reflection from a Potassium atomic layer with a thickness as small as $λ/13$May 15 2019We demonstrate that a method using the derivative of the selective reflection signal from a nanocell is a convenient and robust tool for atomic laser spectroscopy, achieving a nearly Doppler-free spectral resolution. The recorded linewidth of the signal ... More
Absolute absorption on rubidium D1 line: including resonant dipole-dipole interactionsJul 15 2011Jul 18 2011Here we report on measurements of the absolute absorption spectra of dense rubidium vapour on the D1 line in the weak-probe regime for temperatures up to 170 C and number densities up to 3 \times 10^14 cm^-3. In such vapours, modifications to the homogeneous ... More
The cooperative Lamb shift in an atomic nanolayerJan 25 2012We present an experimental measurement of the cooperative Lamb shift and the Lorentz shift using an atomic nanolayer with tunable thickness and atomic density. The cooperative Lamb shift arises due to the exchange of virtual photons between identical ... More
Topological properties of a dense atomic lattice gasMar 09 2017We investigate the existence of topological phases in a dense two-dimensional atomic lattice gas. The coupling of the atoms to the radiation field gives rise to dissipation and a non-trivial coherent long-range exchange interaction whose form goes beyond ... More
A single-mode external cavity diode laser using an intra-cavity atomic Faraday filter with short-term linewidth $<400$ kHz and long-term stability of $<1$ MHzJul 07 2016We report on the development of a diode laser system - the `Faraday laser' - using an atomic Faraday filter as the frequency-selective element. In contrast to typical external-cavity diode laser systems which offer tunable output frequency but require ... More
Atomic Faraday filter with equivalent noise bandwidth less than 1 GHzFeb 25 2015We demonstrate an atomic bandpass optical filter with an equivalent noise bandwidth less than 1 GHz using the D$_1$ line in a cesium vapor. We use the ElecSus computer program to find optimal experimental parameters, and find that for important quantities ... More
Single-photon interference due to motion in an atomic collective excitationDec 16 2016May 23 2017We experimentally demonstrate the generation of heralded bi-chromatic single photons from an atomic collective spin excitation (CSE). The photon arrival times display collective quantum beats, a novel interference effect resulting from the relative motion ... More
Probing an excited-state atomic transition using hyperfine quantum beat spectroscopyAug 15 2014Oct 06 2014We describe a method to observe the dynamics of an excited-state transition in a room temperature atomic vapor using hyperfine quantum beats. Our experiment using cesium atoms consists of a pulsed excitation of the D2 transition, and continuous-wave driving ... More
Active narrowband filtering, line narrowing and gain using ladder electromagnetically induced transparency in an optically thick atomic vapourNov 28 2013Jan 24 2014Electromagnetically induced transparency (EIT) resonances using the $5\rm{S}_{1/2}\rightarrow5\rm{P}_{3/2}\rightarrow5\rm{D}_{5/2}$ ladder-system in optically thick Rb atomic vapour are studied. We observe a strong line narrowing effect and gain at the ... More
Three-photon electromagnetically induced transparency using Rydberg statesMay 11 2012Aug 01 2012We demonstrate electromagnetically induced transparency (EIT) in a four-level cascade system where the upper level is a Rydberg state. The observed spectral features are sub-Doppler and can be enhanced due to the compensation of Doppler shifts with AC ... More
Efficient Tracking of Sparse Signals via an Earth Mover's Distance Dynamics RegularizerJun 12 2018Feb 20 2019Sparse signal models have enjoyed great success, achieving state-of-the-art performance in many applications. Some algorithms further improve performance by taking advantage of temporal dynamics for streaming observations. However, the tracking regularizers ... More
Network Modeling of Short Over-Dispersed Spike-Counts: A Hierarchical Parametric Empirical Bayes FrameworkMay 10 2016May 28 2018Accurate statistical models of neural spike responses can characterize the information carried by neural populations. Yet, challenges in recording at the level of individual neurons commonly results in relatively limited samples of spike counts, which ... More
ElecSus: A program to calculate the electric susceptibility of an atomic ensembleSep 05 2014Feb 09 2015We present a computer program and underlying model to calculate the electric susceptibility of a gas, which is essential to predict its absorptive and dispersive properties. Our program focusses on alkali-metal vapours where we use a matrix representation ... More
Driven-dissipative many-body systems with mixed power-law interactions: Bistabilities and temperature-driven non-equilibrium phase transitionsDec 07 2015Feb 26 2016We investigate the non-equilibrium dynamics of a driven-dissipative spin ensemble with competing power-law interactions. We demonstrate that dynamical phase transitions as well as bistabilities can emerge for asymptotic van der Waals interactions, but ... More
Faraday filtering of Raman light in an isotopically pure alkali metal vaporApr 27 2009We present an application of the Faraday effect to produce a narrow band atomic filter in an alkali metal vapor. In our experiment two Raman beams separated in frequency by the ground state hyperfine splitting in 87Rb are produced using an EOM and then ... More
Phase diagram of non-equilibrium phase transition in a strongly-interacting Rydberg atom vapourJun 28 2016Feb 14 2019Far-from equilibrium dynamics that lead to self-organization are highly relevant to complex dynamical systems not only in physics, but also in life-, earth-, and social sciences. It is challenging however to find systems with sufficiently controlled interactions ... More
Cooperative non-equilibrium phase transition in a dilute Rydberg ensembleFeb 26 2013Aug 27 2013We demonstrate a non-equilibrium phase transition in a dilute thermal atomic gas. The phase transition, between states of low and high Rydberg occupancy, is induced by resonant dipole-dipole interactions between Rydberg atoms. The gas can be considered ... More
Dressed-state electromagnetically induced transparency for light storage in uniform phase spin-wavesJul 27 2016We present, experimentally and theoretically, a scheme for dressed-state electromagnetically induced transparency (EIT) in a three-step cascade system where a four-level system is mapped into an effective three-level system. Theoretical analysis reveals ... More
Slow-light Faraday effect: an atomic probe with gigahertz bandwidthNov 14 2008The ability to control the speed and polarisation of light pulses will allow for faster data flow in optical networks of the future. Optical delay and switching have been achieved using slow-light techniques in various media, including atomic vapour. ... More
Finiteness of the Hopping Induced Energy Corrections in CupratesMar 09 2009The paper continues the rigorous investigations of the mean field Green function solution of the effective two-dimensional two-band Hubbard model [N. M. Plakida et al., Phys. Rev. B, Vol.51, 16599 (1995)] of the superconducting phase transitions in cuprates, ... More
Rigorous derivation of the mean field Green functions of the two-band Hubbard model of superconductivityApr 05 2007The Green function (GF) equation of motion technique for solving the effective two-band Hubbard model of high-T_c superconductivity in cuprates [N.M. Plakida et al., Phys. Rev. B, v. 51, 16599 (1995); JETP, v. 97, 331 (2003)] rests on the Hubbard operator ... More
The boundary layer problem in Bayesian adaptive quadratureSep 25 2006The boundary layer of a finite domain [a, b] covers mesoscopic lateral neighbourhoods, inside [a, b], of the endpoints a and b. The correct diagnostic of the integrand behaviour at a and b, based on its sampling inside the boundary layer, is the first ... More
Reliable operations on oscillatory functionsMay 14 1999Approximate $p$-point Leibniz derivation formulas as well as interpolatory Simpson quadrature sums adapted to oscillatory functions are discussed. Both theoretical considerations and numerical evidence concerning the dependence of the discretization errors ... More
Mean field solutions to singlet hopping and superconducting pairing within a two-band Hubbard modelSep 25 2006The mean field Green function solution of the two-band singlet-hole Hubbard model for high-$T\sb{c}$ superconductivity in cuprates (Plakida, N.M. et al., Phys. Rev. B51, 16599 (1995), JETP 97, 331 (2003)) involves expressions of higher order correlation ... More
Signature of Fermi surface jumps in positron spectroscopy dataAug 05 1999A subtractionless method for solving Fermi surface sheets ({\tt FSS}), from measured $n$-axis-projected momentum distribution histograms by two-dimensional angular correlation of the positron-electron annihilation radiation ({\tt 2D-ACAR}) technique, ... More
Effect of line broadening on the performance of Faraday filtersApr 14 2015We show that homogeneous line broadening drastically affects the performance of atomic Faraday filters. We use a computerized optimization algorithm to find the best magnetic field and temperature for Faraday filters with a range of cell lengths. The ... More
Real-Time Near-Field Terahertz Imaging with Atomic Optical FluorescenceMar 23 2016Oct 12 2016Terahertz (THz) near-field imaging is a flourishing discipline [1], with applications from fundamental studies of beam propagation [2,3] to the characterisation of metameterials [4,5] and waveguides [6,7]. Beating the diffraction limit typically involves ... More
Distributed Sequence Memory of Multidimensional Inputs in Recurrent NetworksMay 26 2016Recurrent neural networks (RNNs) have drawn interest from machine learning researchers because of their effectiveness at preserving past inputs for time-varying data processing tasks. To understand the success and limitations of RNNs, it is critical that ... More
Distributed Sequence Memory of Multidimensional Inputs in Recurrent NetworksMay 26 2016Jan 27 2017Recurrent neural networks (RNNs) have drawn interest from machine learning researchers because of their effectiveness at preserving past inputs for time-varying data processing tasks. To understand the success and limitations of RNNs, it is critical that ... More
Ultra-high-speed Terahertz Imaging Using Atomic VapourMar 04 2019Terahertz (THz) technologies, generally defined as operating in the 0.1-10THz range, bridge the gap between electronic and photonic devices. Because THz radiation passes readily through materials such as plastics, paper and cloth it can be employed in ... More
Terahertz-driven phase transition applied as a room-temperature terahertz detectorSep 01 2017There are few demonstrated examples of phase transitions that may be driven directly by terahertz-frequency electric fields, and those that are known require field strengths exceeding 1 MVcm$^{-1}$. Here we report a room-temperature phase transition driven ... More
Collective Mode Interferences in Light--Matter InteractionsAug 25 2018Jul 05 2019We present a theoretical and experimental analysis of transient optical properties of a dense cold atomic gas. After the rapid extinction of a weak coherent driving field (mean photon number $\sim 1.5$), a transient `flash' is observed. Surprisingly the ... More
Observation of interference effects via four photon excitation of highly excited Rydberg states in thermal cesium vaporOct 06 2015Nov 22 2015We report on the observation of electromagnetically induced transparency (EIT) and absorption (EIA) of highly excited Rydberg states in thermal Cs vapor using a four-step excitation scheme. The advantage of this four-step scheme is that the final transition ... More
Spectral-gap immune characterization of electric fieldsDec 21 2016Nov 07 2017Synthesised light sources need reliable diagnostics for effective application to sub-femtosecond control and probing. However, commonly employed self-referencing techniques for pulsed-field characterisation fail in the presence of wide spectral gaps, ... More
Faster than superradiant light emission due to collective mode interferenceAug 25 2018Sep 07 2018The optical properties of an ensemble of light scatterers can be dramatically modified when the scatterers behave collectively rather than independently. Certain collective effects such as superradiance and subradiance are well known and have been observed ... More
Intrinsic Optical Bistability in a Strongly-Driven Rydberg EnsembleMar 04 2016We observe and characterize intrinsic optical bistability in a dilute Rydberg vapor. The bistability is characterized by sharp jumps between states of low and high Rydberg occupancy with jump up and down positions displaying hysteresis depending on the ... More
Manipulating ultracold atoms with a reconfigurable nanomagnetic system of domain wallsDec 02 2011Dec 05 2011The divide between the realms of atomic-scale quantum particles and lithographically-defined nanostructures is rapidly being bridged. Hybrid quantum systems comprising ultracold gas-phase atoms and substrate-bound devices already offer exciting prospects ... More
The set of maps F_{a,b}: x -> x+a+{b/{2 pi}} sin(2 pi x) with any given rotation interval is contractibleMay 14 1994Consider the two-parameter family of real analytic maps $F_{a,b}:x \mapsto x+ a+{b\over 2\pi} \sin(2\pi x)$ which are lifts of degree one endomorphisms of the circle. The purpose of this paper is to provide a proof that for any closed interval $I$, the ... More
Distributed Sequence Memory of Multidimensional Inputs in Recurrent NetworksMay 26 2016Nov 04 2016Recurrent neural networks (RNNs) have drawn interest from machine learning researchers because of their effectiveness at preserving past inputs for time-varying data processing tasks. To understand the success and limitations of RNNs, it is critical that ... More
Dynamic Filtering of Time-Varying Sparse Signals via l1 MinimizationJul 22 2015Feb 22 2016Despite the importance of sparsity signal models and the increasing prevalence of high-dimensional streaming data, there are relatively few algorithms for dynamic filtering of time-varying sparse signals. Of the existing algorithms, fewer still provide ... More
Ultra-high-speed Terahertz Imaging Using Atomic VapourMar 04 2019Mar 15 2019Terahertz (THz) technologies, generally defined as operating in the 0.1-10THz range, bridge the gap between electronic and photonic devices. Because THz radiation passes readily through materials such as plastics, paper and cloth it can be employed in ... More
Search for SUSY in (Leptons +) Jets + E_T^miss final statesNov 19 1998We study the observability of the squarks and gluinos in CMS at LHC. Classical E_T^miss + jets final state as well as a number of additional multilepton signatures (0 leptons, 1 lepton, 2 leptons of the same sign, 2 leptons of the opposite sign and 3 ... More
Study of leptoquark pair production at the LHC with the CMS detectorMay 19 1999May 27 1999We study the discovery potential of the CMS detector for the scalar leptoquark pair production at the LHC. Present and future exclusion limits are considered. We find that the maximal leptoquark mass reach is about 1.47 TeV for the branching ratio of ... More
Comparative Study of Simulated Nebulized and Spray Particle Deposition in Chronic Rhinosinusitis PatientsNov 01 2018Introduction: Topical intranasal drugs are widely prescribed for Chronic Rhinosinusitis (CRS), although delivery can vary with device type and droplet size. The study objective was to compare nebulized and sprayed droplet deposition in the paranasal sinuses ... More
Comparative Analysis of the Main Nasal Cavity and the Paranasal Sinuses in Chronic Rhinosinusitis: An Anatomic Study of Maximal Medical TherapyNov 01 2018Objective: Minimal literature exists investigating changes in inflammation with respect to the main nasal cavity (MNC) and paranasal sinuses (PS) before and after maximal medical therapy (MMT) for chronic rhinosinusitis (CRS). We hypothesized that MMT ... More
Habitable worlds with no signs of lifeSep 03 2013Sep 04 2013'Most habitable worlds in the cosmos will have no remotely detectable signs of life' is proposed as a biological hypothesis to be tested in studies of exoplanets. Habitable planets could be discovered elsewhere in the Universe, yet there are many hypothetical ... More
A High-z Correction to the Hubble LineApr 10 2005Apr 11 2005This paper was withdrawn as it may have appeared elsewhere, although in a different form.
Non-local charges, Zm gradings and coset space actionsMar 01 2005Aug 22 2005The construction of flat currents, and hence conserved non-local charges, for the superstring on AdS_5 x S^5 is generalised. It is shown that such currents exist for sigma-model type actions on all coset (super-)spaces G/H in which, at the level of the ... More
Identification of the Red Supergiant Progenitor of Supernova 2005cs: Do the Progenitors of Type II-P Supernovae Have Low Mass?Jul 18 2005The stars that end their lives as supernovae (SNe) have been directly observed in only a handful of cases, due mainly to the extreme difficulty in identifying them in images obtained prior to the SN explosions. Here we report the identification of the ... More
Knowing what you know in brain segmentation using Bayesian deep neural networksDec 03 2018Jun 16 2019In this paper, we describe a deep neural network for predicting FreeSurfer segmentations of structural MRI volumes, in seconds rather than hours. The network was trained and evaluated on an extremely large dataset (n = 11,148), obtained by combining data ... More
Knowing what you know in brain segmentation using deep neural networksDec 03 2018Dec 18 2018In this paper, we describe a deep neural network trained to predict FreeSurfer segmentations of structural MRI volumes, in seconds rather than hours. The network was trained and evaluated on an extremely large dataset (n = 11,148), obtained by combining ... More
The Impact of Speed and Bias on the Cognitive Processes of Experts and Novices in Medical Image Decision-makingSep 19 2017May 18 2018Training individuals to make accurate decisions from medical images is a critical component of education in diagnostic pathology. We describe a joint experimental and computational modeling approach to examine the similarities and differences in the cognitive ... More
Effect of buffer gas on electromagnetically induced transparency in a ladder system using thermal rubidium vaporMay 24 2010We report on the first observation of electromagnetically induced transparency (EIT) in a ladder system in the presence of a buffer gas. In particular we study the 5S1/2 - 5P3/2 - 5D5/2 transition in thermal rubidium vapor with a neon buffer gas at a ... More
The Effects of Latency Penalties in Evaluating Push Notification SystemsJun 09 2016We examine the effects of different latency penalties in the evaluation of push notification systems, as operationalized in the TREC 2015 Microblog track evaluation. The purpose of this study is to inform the design of metrics for the TREC 2016 Real-Time ... More
A Modest Proposal for Open Market Risk Assessment to Solve the Cyber-Security ProblemApr 29 2016We introduce a model for a market based economic system of cyber-risk valuation to correct fundamental problems of incentives within the information technology and information processing industries. We assess the makeup of the current day marketplace, ... More
Charged Schrodinger Black HolesJul 13 2009We construct charged and rotating asymptotically Schrodinger black hole solutions of IIB supergravity. We begin by obtaining a closed-form expression for the null Melvin twist of a broad class of type IIB backgrounds, including solutions of minimal five-dimensional ... More
Joint Quantum-State and Measurement Tomography with Incomplete MeasurementsMar 22 2018Oct 17 2018Estimation of quantum states and measurements is crucial for the implementation of quantum information protocols. The standard method for each is quantum tomography. However, quantum tomography suffers from systematic errors caused by imperfect knowledge ... More
$\mathrm{CAT}(0)$ Extensions of Right-angled Coxeter GroupsAug 21 2015We show that any split extension of a right-angled Coxeter group $W_{\Gamma}$ by a generating automorphism of finite order acts faithfully and geometrically on a $\mathrm{CAT}(0)$ metric space.
Recognizing Right-Angled Coxeter Groups Using InvolutionsOct 16 2014Dec 03 2015We consider the question of determining whether a given group (especially one generated by involutions) is a right-angled Coxeter group. We describe a group invariant, the involution graph, and we characterize the involution graphs of right-angled Coxeter ... More
Clustering with a Reject Option: Interactive Clustering as Bayesian Prior ElicitationJun 19 2016A good clustering can help a data analyst to explore and understand a data set, but what constitutes a good clustering may depend on domain-specific and application-specific criteria. These criteria can be difficult to formalize, even when it is easy ... More
Bounding the Radius of Convergence of Analytic FunctionsJul 21 2017Contour integration is a crucial technique in many numeric methods of interest in physics ranging from differentiation to evaluating functions of matrices. It is often important to determine whether a given contour contains any poles or branch cuts, either ... More
Torus and Z/p actions on manifoldsMay 01 2002Sep 30 2003Let G be either a finite cyclic group of prime order or S^1. We find new relations between cohomology of a manifold (or a Poincare duality space) M with a G-action on it and cohomology of the fixed point set, M^G. Our main tool is the notion of Poincare ... More
Cut numbers of 3-manifoldsDec 12 2001Sep 18 2003The cut number of a manifold M, c(M), is the largest number of disjoint two-sided hypersurfaces in M which do not separate M. Equivalently, it is the largest rank of a free group being an epimorphic image of pi_1(M). We investigate the relations between ... More
Skein modules at the 4th roots of unityNov 20 2000Aug 30 2001The Kauffman bracket skein modules, S(M,A), have been calculated for A=+1,-1, for all 3-manifolds M by relating them to the SL(2,C)-character varieties. We extend this description to the case when A is a 4-th root of 1 and M is either a surface x [0,1] ... More
A consistent approach to unstructured mesh generation for geophysical modelsMar 24 2017Geophysical model domains typically contain irregular, complex fractal-like boundaries and physical processes that act over a wide range of scales. Constructing geographically constrained boundary-conforming spatial discretizations of these domains with ... More
Automatic Contraction of Unstructured Tensor NetworksSep 10 2017Oct 08 2017The evaluation of partition functions is central to statistical physics. For lattice systems and other finite models the partition function may be expressed as the contraction of a tensor network. Unfortunately computing such contractions is difficult, ... More