Results for "Dimitrios Makrakis"

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Algorithm for Mesoscopic Advection-DiffusionMay 31 2018Sep 11 2018In this paper, an algorithm is presented to calculate the transition rates between adjacent mesoscopic subvolumes in the presence of flow and diffusion. These rates can be integrated in stochastic simulations of reaction-diffusion systems that follow ... More
Channel Impulse Responses in Diffusive Molecular Communication with Spherical TransmittersApr 16 2016Sep 10 2016Molecular communication is an emerging paradigm for systems that rely on the release of molecules as information carriers. Communication via molecular diffusion is a popular strategy that is ubiquitous in nature and very fast over distances on the order ... More
Timing Control of Single Neuron Spikes with Optogenetic StimulationOct 31 2017Feb 13 2018This paper predicts the ability to externally control the firing times of a cortical neuron whose behavior follows the Izhikevich neuron model. The Izhikevich neuron model provides an efficient and biologically plausible method to track a cortical neuron's ... More
Active Versus Passive: Receiver Model Transforms for Diffusive Molecular CommunicationApr 15 2016Sep 10 2016This paper presents an analytical comparison of active and passive receiver models in diffusive molecular communication. In the active model, molecules are absorbed when they collide with the receiver surface. In the passive model, the receiver is a virtual ... More
Modeling Interference-Free Neuron Spikes with Optogenetic StimulationMay 14 2019This paper predicts the ability to externally control the firing times of a cortical neuron whose behavior follows the Izhikevich neuron model. The Izhikevich neuron model provides an efficient and biologically plausible method to track a cortical neuron's ... More
Simulating with AcCoRD: Actor-Based Communication via Reaction-DiffusionDec 01 2016This paper introduces AcCoRD (Actor-based Communication via Reaction-Diffusion). AcCoRD is a sandbox reaction-diffusion solver designed for the study of molecular communication systems. It uses a hybrid of microscopic and mesoscopic simulation models ... More
Simulating with AcCoRD: Actor-Based Communication via Reaction-DiffusionDec 01 2016Feb 02 2017This paper introduces AcCoRD (Actor-based Communication via Reaction-Diffusion) version 1.0. AcCoRD is a sandbox reaction-diffusion solver designed for the study of molecular communication systems. It uses a hybrid of microscopic and mesoscopic simulation ... More
Effect of Local Population Uncertainty on Cooperation in BacteriaAug 21 2017Bacteria populations rely on mechanisms such as quorum sensing to coordinate complex tasks that cannot be achieved by a single bacterium. Quorum sensing is used to measure the local bacteria population density, and it controls cooperation by ensuring ... More
Using Game Theory for Real-Time Behavioural Dynamics in Microscopic Populations with Noisy SignallingNov 13 2017Feb 04 2019This paper introduces the application of game theory to understand noisy real-time signalling and the resulting behavioural dynamics in microscopic populations such as bacteria and other cells. It presents a bridge between the fields of molecular communication ... More
Fourier integrals and a new representation of Maslov's canonical operator near causticsJul 08 2013We suggest a new representation of Maslov's canonical operator in a neighborhood of the caustics using a special class of coordinate systems ("eikonal coordinates") on Lagrangian manifolds.
Two approaches to testing general relativity in the strong-field regimeJul 16 2009Observations of compact objects in the electromagnetic spectrum and the detection of gravitational waves from them can lead to quantitative tests of the theory of general relativity in the strong-field regime following two very different approaches. In ... More
Radiative Transfer in Obliquely Illuminated Accretion DisksJan 09 2001Mar 25 2002The illumination of an accretion disk around a black hole or neutron star by the central compact object or the disk itself often determines its spectrum, stability, and dynamics. The transport of radiation within the disk is in general a multi-dimensional, ... More
The peak energy of dissipative GRB photospheresNov 18 2011Mar 19 2012The radiation released at the transparency radius of an ultrarelativistic flow can account for the observed properties of gamma-ray bursts (GRBs) provided that sufficient energy is dissipated in the sub-photospheric region. Here, I investigate how the ... More
Observables in Strongly Coupled Anisotropic TheoriesJun 06 2013Dec 30 2013We review certain anisotropic gauge/gravity dualities, focusing more on a theory with space dependent axion term. Then we discuss and also present some new results for several observables: the static potential and force, the imaginary part of the static ... More
11D supergravity at ${\cal O}(l^3)$Jul 30 2004Aug 30 2004We compute certain spinorial cohomology groups controlling possible supersymmetric deformations of eleven-dimensional supergravity up to order $l^3$ in the Planck length. At ${\cal O}(l)$ and ${\cal O}(l^2)$ the spinorial cohomology groups are trivial ... More
Instanton interaction in de Sitter spacetimeFeb 09 2013Because of the presence of a cosmological horizon the dilute instanton gas approximation used for the derivation of the Coleman-De Luccia tunneling rate in de Sitter spacetime receives additional contributions due to the finite instanton separation. Here ... More
The path integral measure, constraints and ghosts for massive gravitons with a cosmological constantJul 24 2009Dec 06 2009For massive gravity in a de Sitter background one encounters problems of stability when the curvature is larger than the graviton mass. I analyze this situation from the path integral point of view and show that it is related to the conformal factor problem ... More
Effects of the cosmological expansion on the bubble nucleation rate for relativistic first-order phase transitionsApr 07 2008Sep 01 2008I calculate the first corrections to the dynamical pre-exponential factor of the bubble nucleation rate for a relativistic first-order phase transition in an expanding cosmological background by estimating the effects of the Hubble expansion rate on the ... More
A removability theorem for Sobolev functions and detour setsJun 23 2017We study the removability of compact sets for continuous Sobolev functions. In particular, we focus on sets with infinitely many complementary components, called "detour sets", which resemble the Sierpi\'nski gasket. The main theorem is that if $K\subset ... More
One dimensional diffusion in an asymmetric random environmentOct 02 2006According to a theorem of S. Schumacher, for a diffusion X in an environment determined by a stable process that belongs to an appropriate class and has index a, it holds that X_t/(log t)^a converges in distribution, as t goes to infinity, to a random ... More
Semi-hyperbolic rational maps and size of Fatou componentsFeb 15 2017Nov 06 2017Recently Merenkov and Sabitova introduced the notion of a homogeneous planar set. Using this notion they proved a result for Sierpi${\'n}$ski carpet Julia sets of hyperbolic rational maps that relates the diameters of the peripheral circles to the Hausdorff ... More
A secret sharing scheme using groupsAug 31 2010In this paper a secret sharing scheme based on the word problem in groups is introduced. The security of the scheme and possible variations are discussed in section 2. The article concludes with the suggestion of two categories of platform groups for ... More
Cross-Domain Collaborative Filtering via Translation-based LearningAug 11 2019With the proliferation of social media platforms and e-commerce sites, several cross-domain collaborative filtering strategies have been recently introduced to transfer the knowledge of user preferences across domains. The main challenge of cross-domain ... More
Dynamics-Adapted Cone KernelsMar 03 2014We present a family of kernels for analysis of data generated by dynamical systems. These so-called cone kernels feature an explicit dependence on the dynamical vector field operating in the phase-space manifold, estimated empirically through finite-differences ... More
Testing General Metric Theories of Gravity with Bursting Neutron StarsApr 18 2007Jan 10 2008I show that several observable properties of bursting neutron stars in metric theories of gravity can be calculated using only conservation laws, Killing symmetries, and the Einstein equivalence principle, without requiring the validity of the general ... More
Constraints on Braneworld Gravity Models from a Kinematic Limit on the Age of the Black Hole XTE J1118+480Dec 20 2006In braneworld gravity models with a finite AdS curvature in the extra dimension, the AdS/CFT correspondence leads to a prediction for the lifetime of astrophysical black holes that is significantly smaller than the Hubble time, for asymptotic curvatures ... More
Hydrodynamic Effects on the QPO Frequencies of Accreting Compact ObjectsOct 16 2000The variability properties of accreting compact objects predicted by dynamical models are characterized by a number of distinct frequencies that are specific to each model. Because the accretion disks around neutron stars and black holes are hydrodynamic ... More
UHECRs from magnetic reconnection in relativistic jetsJul 09 2010Aug 16 2010Ultra-high energy cosmic rays (UHECRs) may be produced in active galactic nuclei (AGN) or gamma-ray burst (GRB) jets. I argue that magnetic reconnection in jets can accelerate UHECRs rather independently of physical processes in the magnetic dissipation ... More
Powerful GeV emission from a gamma-ray-burst shock wave scattering stellar photonsMay 02 2008Sep 04 2008The gamma-ray bursts (GRBs) of long duration are very likely to be connected to the death of massive stars. The gamma-ray emission is believed to come from energy released internally in a flow that moves at ultrarelativistic speed. The fast flow drives ... More
Reconnection-driven plasmoids in blazars: fast flares on a slow envelopeNov 01 2012Mar 13 2013Minute-timescale TeV flares have been observed in several blazars. The fast flaring requires compact regions in the jet that boost their emission towards the observer at an extreme Doppler factor of delta>50. For TeV photons to avoid annihilation in the ... More
Superflares from magnetars revealing the GRB central engineJan 07 2010Aug 16 2010Long-duration gamma-ray bursts (GRBs) may be powered by the rotational energy of a millisecond magnetar. I argue that the GRB-driving magnetars lie at the high end of the distribution of magnetic field strengths of magnetars. The field of GRB magnetars ... More
Spectra of black-hole binaries in the low/hard state: from radio to X-raysApr 07 2005We propose a jet model for the low/hard state of Galactic black-hole X-ray sources that can explain the energy spectra from radio to X-rays. The model assumes that i) there is a magnetic field along the axis of the jet; ii) the electron density in the ... More
k-Strings as Fundamental StringsMar 31 2015It has been noticed that the k-string observables can be expressed in terms of the fundamental string ones. We identify a sufficient condition for a generic gravity dual background which when satisfied the mapping can be done. The condition is naturally ... More
Semi-classical Strings in Sasaki-Einstein ManifoldsApr 20 2009We find point-like and classical string solutions on the AdS_5 x X^5, where X^5 are the 5-dimensional Sasaki-Einstein manifolds Ypq and Lpqr. The number of acceptable solutions is limited drastically in order to satisfy the constraints on the parameters ... More
Massive IIA supergravitiesAug 29 2005We perform a systematic search for all possible massive deformations of IIA supergravity in ten dimensions. We show that there exist exactly two possibilities: Romans supergravity and Howe-Lambert-West supergravity. Along the way we give the full details ... More
Nahm Equations and Boundary ConditionsApr 10 1998Jun 01 1998We derive certain boundary conditions in Nahm's equations by considering a system of N parallel D1-branes perpendicular to a D3-brane in type IIB string theory.
Quantum mechanics and data assimilationMar 02 2019A framework for data assimilation combining aspects of operator-theoretic ergodic theory and quantum mechanics is developed. This framework adapts the Dirac-von Neumann formalism of quantum dynamics and measurement to perform data assimilation (filtering) ... More
Non-removability of Sierpinski carpetsSep 14 2018We prove that all Sierpi\'nski carpets in the plane are non-removable for (quasi)conformal maps. More precisely, we show that for any two Sierpi\'nski carpets $S,S'\subset \widehat{\mathbb{C}}$ there exists a homeomorphism $f\colon \widehat{\mathbb{C}}\to ... More
Quantum mechanics and data assimilationMar 02 2019May 31 2019A framework for data assimilation combining aspects of operator-theoretic ergodic theory and quantum mechanics is developed. This framework adapts the Dirac--von Neumann formalism of quantum dynamics and measurement to perform sequential data assimilation ... More
A removability theorem for Sobolev functions and detour setsJun 23 2017Jun 26 2019We study the removability of compact sets for continuous Sobolev functions. In particular, we focus on sets with infinitely many complementary components, called "detour sets", which resemble the Sierpi\'nski gasket. The main theorem is that if $K\subset ... More
Non-removability of the Sierpinski GasketApr 26 2018Dec 13 2018We prove that the Sierpi\'nski gasket is non-removable for quasiconformal maps, thus answering a question of Bishop. The proof involves a new technique of constructing an exceptional homeomorphism from $\mathbb R^2$ into some non-planar surface $S$, and ... More
Constraining Brans-Dicke Gravity with Millisecond Pulsars in Ultracompact BinariesJan 12 2005The five accreting, millisecond X-ray pulsars in ultracompact binaries that were recently discovered with the Rossi X-ray Timing Explorer provide excellent candidates for constraining the deviations from general relativity described by the Brans-Dicke ... More
Compton Scattering in Static and Moving Media. II. System-Frame Solutions for Spherically Symmetric FlowsNov 29 2000Mar 23 2001I study the formation of Comptonization spectra in spherically symmetric, fast moving media in a flat spacetime. I analyze the mathematical character of the moments of the transfer equation in the system-frame and describe a numerical method that provides ... More
Probing strongly coupled anisotropic plasmaFeb 20 2012Jul 09 2012We calculate the static potential, the drag force and the jet quenching parameter in strongly coupled anisotropic N=4 super Yang-Mills plasma. We find that the jet quenching is in general enhanced in presence of anisotropy compared to the isotropic case ... More
Spherically symmetric, static spacetimes in a tensor-vector-scalar theoryFeb 28 2005Apr 27 2005Recently, a relativistic gravitation theory has been proposed [J. D. Bekenstein, Phys. Rev. D {\bf 70}, 083509 (2004)] that gives the Modified Newtonian Dynamics (or MOND) in the weak acceleration regime. The theory is based on three dynamic gravitational ... More
Flares in GRB afterglows from delayed magnetic dissipationJun 19 2006One of the most intriguing discoveries made by the Swift satellite is the flaring activity in about half of the afterglow lightcurves. Flares have been observed on both long and short duration GRBs and on time scales that range from minutes to ~1 day ... More
Supersymmetric AdS vacua and separation of scalesJun 26 2012Sep 03 2012The moduli space of the supersymmetric massive IIA AdS4xS2(B4) vacua, where S2(B4) is a two-sphere bundle over a four-dimensional Kaehler-Einstein base B4, includes three independent parameters which can be thought of as corresponding to the sizes of ... More
Gravitational effects on critical Q-ballsNov 30 2004Mar 09 2007In a cosmological phase transition in theories that admit Q-balls there is a value of the soliton charge above which the soliton becomes unstable and expands, converting space to the true vacuum, much like a critical bubble in the case of ordinary tunneling. ... More
A note on recurrent random walksOct 02 2006For any recurrent random walk (S_n)_{n>0} on R, there are increasing sequences (g_n)_{n>0} converging to infinity for which (g_n S_n)_{n>0} has at least one finite accumulation point. For one class of random walks, we give a criterion on (g_n)_{n>0} and ... More
Restricted Linear Constrained Minimization of quadratic functionalsSep 17 2010In this work a linearly constrained minimization of a positive semidefinite quadratic functional is examined. Our results are concerning infinite dimensional real Hilbert spaces, with a singular positive operator related to the functional, and considering ... More
Accreting Neutron Stars and Black Holes: A Decade of DiscoveriesOct 22 2004This is a review of recent observational and theoretical developments related to accreting neutron stars and black holes in binary systems.
Data-driven spectral decomposition and forecasting of ergodic dynamical systemsJul 08 2015Sep 28 2016We develop a framework for dimension reduction, mode decomposition, and nonparametric forecasting of data generated by ergodic dynamical systems. This framework is based on a representation of the Koopman and Perron-Frobenius groups of unitary operators ... More
Prompt GRB emission from gradual energy dissipationNov 16 2007Sep 04 2008I calculate the emission expected from a Poynting-flux-dominated gamma-ray burst (GRB) flow in which energy is dissipated gradually by magnetic reconnection. In this picture, the energy of the radiating particles is determined by heating and cooling balance ... More
Prompt emission spectra from the photosphere of a GRBFeb 17 2006Sep 08 2006I explore the observational appearance of the photosphere of an ultrarelativistic flow with internal dissipation of energy (``dissipative'' GRB models). As a case study, I use the magnetic reconnection model (AC model) that makes robust predictions on ... More
Mean value results and $Ω$-results for the hyperbolic lattice point problem in conjugacy classesOct 05 2016Oct 12 2016For $\Gamma$ a Fuchsian group of finite covolume, we study the lattice point problem in conjugacy classes on the Riemann surface $\Gamma \backslash \mathbb{H}$. Let $\mathcal{H}$ be a hyperbolic conjugacy class in $\Gamma$ and $\ell$ the $\mathcal{H}$-invariant ... More
Properties of Confinement in HolographyMay 26 2015We review certain properties of confinement with added focus on the ones we study with holography. Then we discuss observables whose unique behavior can indicate the presence of confinement. Using mainly the Wilson loop in the gauge/gravity formalism, ... More
Low-mass pre--main-sequence stars in the Magellanic CloudsFeb 29 2012[Abridged] The stellar Initial Mass Function (IMF) suggests that sub-solar stars form in very large numbers. Most attractive places for catching low-mass star formation in the act are young stellar clusters and associations, still (half-)embedded in star-forming ... More
Scalar and fermion contributions to the vacuum energyMar 03 2013I consider a theory of a real scalar and a fermion field, with a Yukawa interaction and a potential term that admits two degenerate minima at the tree level. I calculate the quantum vacuum energy difference between these two vacua and I find a finite, ... More
Quantum-classical interactions through the path integralJul 26 2006Mar 09 2007I consider the case of two interacting scalar fields, \phi and \psi, and use the path integral formalism in order to treat the first classically and the second quantum-mechanically. I derive the Feynman rules and the resulting equation of motion for the ... More
Diffusion in random environment and the renewal theoremOct 20 2003Oct 23 2004According to a theorem of S. Schumacher and T. Brox, for a diffusion $X$ in a Brownian environment it holds that $(X_t-b_{\log t})/\log^2t\to 0 $ in probability, as $t\to\infty$, where $b_{\cdot}$ is a stochastic process having an explicit description ... More
Leveraging Trust and Distrust in Recommender Systems via Deep LearningMay 31 2019The data scarcity of user preferences and the cold-start problem often appear in real-world applications and limit the recommendation accuracy of collaborative filtering strategies. Leveraging the selections of social friends and foes can efficiently ... More
Potential theory on Sierpinski carpets with applications to uniformizationMay 31 2018This research is motivated by the study of the geometry of fractal sets and is focused on uniformization problems: transformation of sets to canonical sets, using maps that preserve the geometry in some sense. More specifically, the main question addressed ... More
Feynman rules for Gauss's lawApr 18 2016Jun 26 2016I work on a set of Feynman rules that were derived in order to incorporate the constraint of Gauss's law in the perturbation expansion of gauge field theories and calculate the interaction energy of two static sources. The constraint is implemented via ... More
Graviton mass and cosmological constant: a toy modelOct 01 2010Oct 25 2010I consider a simple model where the graviton mass and the cosmological constant depend on a scalar field with appropriate couplings and I calculate the graviton propagator and the resulting effective action for the scalar field.
Fivebrane instantons and Calabi-Yau fourfolds with fluxJan 31 2007Feb 15 2007Using recent results on eleven-dimensional superspace, we compute the contribution of fivebrane instantons with four fermionic zeromodes in M-theory compactifications on Calabi-Yau fourfolds with flux. We find that no superpotential is generated in this ... More
M-theory on eight-manifolds revisited: N=1 supersymmetry and generalized Spin(7) structuresNov 04 2005Apr 10 2006The requirement of ${\cal N}=1$ supersymmetry for M-theory backgrounds of the form of a warped product ${\cal M}\times_{w}X$, where $X$ is an eight-manifold and ${\cal M}$ is three-dimensional Minkowski or AdS space, implies the existence of a nowhere-vanishing ... More
Generalized geometry lectures on type II backgroundsJun 28 2016The first part of these notes is a self-contained introduction to generalized complex geometry. It is intended as a `user manual' for tools used in the study of supersymmetric backgrounds of supergravity. In the second part we review some past and recent ... More
Curved 11D SupergeometryJul 28 2004Dec 01 2004We examine the theta-expansion of the eleven-dimensional supervielbein. We outline a systematic procedure which can be iterated to any order. We give explicit expressions for the vielbein and three-form potential components up to order ${\cal O}(\th^5)$. ... More
Probes and Tests of Strong-Field Gravity with Observations in the Electromagnetic SpectrumJun 09 2008Neutron stars and black holes are the astrophysical systems with the strongest gravitational fields in the universe. In this article, I review the prospect of probing with observations of such compact objects some of the most intriguing General Relativistic ... More
The Influence of Gas Dynamics on Measuring the Properties of the Black Hole in the Center of the Milky Way with Stellar Orbits and PulsarsNov 30 2011Observations of stars and pulsars orbiting the black hole in the center of the Milky Way offer the potential of measuring not only the mass of the black hole but also its spin and quadrupole moment, thereby providing observational verification of the ... More
Measurements of Black Hole Spins and Tests of Strong-Field General RelativityFeb 10 2004Fast variability studies of accreting black holes in the Galaxy offer us a unique opportunity to measure the spins of black holes and test the strong-field behavior of general relativity. In this review, I summarize the arguments often used in attempts ... More
Models of Quasi-Periodic Variability in Neutron Stars and Black HolesDec 12 2000Black holes and weakly-magnetic accreting neutron stars show strong quasi-periodic variability over timescales that span a very wide range. This property offer us a unique opportunity to improve our understanding of basic physical processes in strong ... More
Neutrino-cooled accretion and GRB variabilityApr 12 2007For accretion rates Mdot~0.1 Msun/s to a few solar mass black hole the inner part of the disk is expected to make a transition from advection dominance to neutrino cooling. This transition is characterized by sharp changes of the disk properties. I argue ... More
On the non-BPS string solutions in Sasaki-Einstein gauge/gravity dualityDec 18 2009We present an extensive analysis on several string solutions in AdS_5 x Ypq and find some interesting properties of their energy-spin relations. Their energy depends always on the parameter a(p,q) which characterizes these manifolds. The range of this ... More
Semiclassical strings in marginally deformed toric AdS/CFTOct 07 2010We study string solutions in the beta-deformed Sasaki-Einstein gauge/gravity dualities. We find that the BPS point-like strings move in the submanifolds where the two U(1) circles shrink to zero size. In the corresponding T^3 fibration description, the ... More
The Generic Expansion in Analytic Modified GravityMay 30 2019In this Thesis, we treat the problem of the existence of generic perturbations of the regular and singular state in higher-order gravity in cases of vacuum and radiation models that derives from the lagrangian $R+\epsilon R^2$. We show that there is a ... More
Localization of favorite points for diffusion in random environmentDec 18 2006For a diffusion X_t in a one-dimensional Wiener medium W, it is known that there is a certain process b_x(W) that depends only on the environment W, so that X_t-b_{logt}(W) converges in distribution as t goes to infinity. We prove that, modulo a relatively ... More
Minimization of Constrained Quadratic forms in Hilbert SpacesMar 29 2010A common optimization problem is the minimization of a symmetric positive definite quadratic form $< x,Tx >$ under linear constrains. The solution to this problem may be given using the Moore-Penrose inverse matrix. In this work we extend this result ... More
A Metric for Rapidly Spinning Black Holes Suitable for Strong-Field Tests of the No-Hair TheoremMay 16 2011May 20 2011According to the no-hair theorem, astrophysical black holes are uniquely characterized by their masses and spins and are described by the Kerr metric. Several parametric deviations from the Kerr metric have been suggested to study observational signatures ... More
Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum: II. Black-Hole ImagesMay 11 2010Jun 01 2010According to the no-hair theorem, all astrophysical black holes are fully described by their masses and spins. This theorem can be tested observationally by measuring (at least) three different multipole moments of the spacetimes of black holes. In this ... More
Bounds on Neutron-Star Moments of Inertia and the Evidence for General Relativistic Frame DraggingMar 26 1999May 11 1999Recent X-ray variability observations of accreting neutron stars may provide the first evidence for frame dragging effects around spinning relativistic objects. Motivated by this possibility and its implications for neutron-star structural properties, ... More
Testing Strong-field Gravity with Quasi-Periodic OscillationsMay 04 2004The frequencies of quasi-periodic oscillations around neutron stars are believed to be related to characteristic frequencies in the gravitational fields of the compact objects. In different variability models, these include the Keplerian, epicyclic, and ... More
A Digital Signature Scheme for Long-Term SecurityMar 19 2012Aug 24 2015In this paper we propose a signature scheme based on two intractable problems, namely the integer factorization problem and the discrete logarithm problem for elliptic curves. It is suitable for applications requiring long-term security and provides a ... More
Entanglement Entropy of the Klebanov-Strassler with dynamical flavorsMay 06 2015We present a detailed study of the Entanglement Entropy for the confining Klebanov-Strassler background coupled to a large number of dynamical flavors in the Veneziano limit. As we vary the number of the massless flavors the behavior of the entropy strongly ... More
3d N=1 effective supergravity and F-theory from M-theory on fourfoldsJun 24 2015Sep 23 2015We consider 3d N=1 M-theory compactifications on Calabi-Yau fourfolds, and the effective 3d theory of light modes obtained by reduction from eleven dimensions. We study in detail the mass spectrum at the vacuum and, by decoupling the massive multiplets, ... More
IIA supergravity and M-theory on manifolds with SU(4) structureDec 05 2013Mar 20 2014We give the general form of supersymmetric backgrounds with two real supercharges of M-theory and type IIA supergravity (with non-zero Romans mass in general) of the form $\mathbb{R}^{1,d} \times \M_8$, d=1,2, on eight-dimensional manifolds with SU(4) ... More
A Late-Time Flattening of Light Curves in Gamma-Ray Burst AfterglowsJul 11 2013The afterglow emission from Gamma-Ray Bursts (GRBs) is usually interpreted as synchrotron radiation from relativistic electrons accelerated at the GRB external shock, that decelerates from ultra-relativistic to non-relativistic speeds as it sweeps up ... More
The S2 star as a probe of the accretion disk of Sgr A*Mar 08 2013How accretion proceeds around the massive black hole in the Galactic center and other highly sub-Eddington accretors remains poorly understood. The orbit of the S2 star in the Galactic center passes through the accretion disk of the massive black hole ... More
Convergence of density expansions of correlation functions and the Ornstein-Zernike equationNov 06 2016We prove convergence of the multi-body correlation function as a power series in the density. We work in the context of the cluster expansion in the canonical ensemble and we obtain bounds uniform in the volume and the number of particles. In the thermodynamic ... More
Reconstructing the Neutron-Star Equation of State from Astrophysical MeasurementsMay 12 2009Feb 16 2010The properties of matter at ultra-high densities, low temperatures, and with a significant asymmetry between protons and neutrons can be studied exclusively through astrophysical observations of neutron stars. We show that measurements of the masses and ... More
Capital Structure in U.S., a Quantile Regression Approach with Macroeconomic ImpactsJan 20 2018The major perspective of this paper is to provide more evidence into the empirical determinants of capital structure adjustment in different macroeconomics states by focusing and discussing the relative importance of firm-specific and macroeconomic characteristics ... More
3D Object Reconstruction from Hand-Object InteractionsApr 03 2017Recent advances have enabled 3d object reconstruction approaches using a single off-the-shelf RGB-D camera. Although these approaches are successful for a wide range of object classes, they rely on stable and distinctive geometric or texture features. ... More
The sub-solar Initial Mass Function in the Large Magellanic CloudOct 12 2008The Magellanic Clouds offer a unique variety of star forming regions seen as bright nebulae of ionized gas, related to bright young stellar associations. Nowadays, observations with the high resolving efficiency of the Hubble Space Telescope allow the ... More
GRB afterglow light curves from realistic density profilesJun 09 2011The afterglow emission that follows gamma-ray bursts (GRBs) contains valuable information about the circumburst medium and, therefore, about the GRB progenitor. Theoretical studies of GRB blast waves, however, are often limited to simple density profiles ... More
Koopman spectra in reproducing kernel Hilbert spacesJan 23 2018Jun 01 2018Every invertible, measure-preserving dynamical system induces a Koopman operator, which is a linear, unitary evolution operator acting on the $L^2$ space of observables associated with the invariant measure. Koopman eigenfunctions represent the quasiperiodic, ... More
Area Law Behaviour of Mutual Information at Finite TemperatureJul 10 2019Entanglement entropy in free scalar field theory at its ground state is dominated by an area law term. However, when mixed states are considered this property ceases to exist. We show that in such cases the mutual information obeys an "area law". The ... More
Holographic three-point correlators in the Schrodinger/dipole CFT correspondenceJun 21 2018We calculate, for the first time, three-point correlation functions involving "heavy" operators in the Schrodinger/null-dipole CFT correspondence at strong coupling. In particular, we focus on the three-point functions of the dilaton modes and two "heavy" ... More
Koopman spectra in reproducing kernel Hilbert spacesJan 23 2018May 19 2019Every invertible, measure-preserving dynamical system induces a Koopman operator, which is a linear, unitary evolution operator acting on the $L^2$ space of observables associated with the invariant measure. Koopman eigenfunctions represent the quasiperiodic, ... More
Capital Structure and Speed of Adjustment in U.S. Firms. A Comparative Study in Microeconomic and Macroeconomic Conditions - A Quantille Regression ApproachNov 11 2018The major perspective of this paper is to provide more evidence regarding how "quickly", in different macroeconomic states, companies adjust their capital structure to their leverage targets. This study extends the empirical research on the topic of capital ... More
The hyperbolic lattice point problem in conjugacy classesApr 06 2015Mar 31 2016For $\Gamma$ a cocompact or cofinite Fuchsian group, we study the hyperbolic lattice point problem in conjugacy classes, which is a modification of the classical hyperbolic lattice point problem. We use large sieve inequalities for the Riemann surfaces ... More