Results for "Dario Tamascelli"

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Quantum annealing and the Schrödinger-Langevin-Kostin equationDec 03 2008We show, in the context of quantum combinatorial optimization, or quantum annealing, how the nonlinear Schr\"odinger-Langevin-Kostin equation can dynamically drive the system toward its ground state. We illustrate, moreover, how a frictional force of ... More
Quantum walks: a Markovian perspectiveJan 29 2008Jan 30 2008For a continuous-time quantum walk on a line the variance of the position observable grows quadratically in time, whereas, for its classical counterpart on the same graph, it exhibits a linear, diffusive, behaviour. A quantum walk, thus, propagates at ... More
Interacting quantum walksOct 15 2009In this work we present the quantum mechanical computer proposed by Feynman in 1985 and, since then, widely cited but seldom used. The main feature of the model is the presence of a built in clocking mechanism managing for the ordered application of the ... More
A quantum-walk-inspired adiabatic algorithm for graph isomorphismJan 07 2014We present a 2-local quantum algorithm for graph isomorphism GI based on an adiabatic protocol. By exploiting continuous-time quantum-walks, we are able to avoid a mere diffusion over all possible configurations and to significantly reduce the dimensionality ... More
Quantum Timing and Synchronization ProblemsApr 05 2005Feynman's model of a quantum computer provides an example of a continuous-time quantum walk. Its clocking mechanism is an excitation of a basically linear chain of spins with occasional controlled jumps which allow for motion on a planar graph. The spreading ... More
Dissipative dynamics of a spin system with three-body interactionJul 04 2011In this note we explicitly solve the Lindblad equation for a system of three spins with a three-body interaction, coupled to the environment by bath operators that inject or absorb spin carriers. We exemplify the properties of this solution in the context ... More
Time-dependent density functional theory for open spin chainsDec 24 2011The application of methods of time-dependent density functional theory (TDDFT) to systems of qubits provided the interesting possibility of simulating an assigned Hamiltonian evolution by means of an auxiliary Hamiltonian having different two-qubit interactions ... More
Dynamical kickback and non commuting impurities in a spin chainFeb 25 2008Feb 27 2008In an interacting continuous time quantum walk, while the walker (the cursor) is moving on a graph, computational primitives (unitary operators associated with the edges) are applied to ancillary qubits (the register). The model with one walker was originally ... More
Grover's algorithm on a Feynman computerOct 16 2006We present an implementation of Grover's algorithm in the framework of Feynman's cursor model of a quantum computer. The cursor degrees of freedom act as a quantum clocking mechanism, and allow Grover's algorithm to be performed using a single, time-independent ... More
Noise-assisted quantum transport and computationDec 11 2012The transmission of an excitation along a spin chain can be hindered by the presence of small fixed imperfections that create trapping regions where the excitation may get caught (Anderson localization). A certain degree of noise, ensuing from the interaction ... More
Speed and entropy of an interacting continuous time quantum walkApr 10 2006Apr 27 2006We present some dynamic and entropic considerations about the evolution of a continuous time quantum walk implementing the clock of an autonomous machine. On a simple model, we study in quite explicit terms the Lindblad evolution of the clocked subsystem, ... More
Entropy generation in a model of reversible computationOct 17 2006We present a model in which, due to the quantum nature of the signals controlling the implementation time of successive unitary computational steps, \emph{physical} irreversibility appears in the execution of a \emph{logically} reversible computation. ... More
An introduction to quantum annealingJul 05 2011Quantum Annealing, or Quantum Stochastic Optimization, is a classical randomized algorithm which provides good heuristics for the solution of hard optimization problems. The algorithm, suggested by the behaviour of quantum systems, is an example of proficuous ... More
Dephasing assisted transport on a biomimetic ring structureOct 13 2017We address two-level systems arranged in ring configurations affected by static disorder. In particular we investigate the role of dephasing in the transport of an excitation along the ring. We compare the efficiency of the transfer process on isotropic ... More
Efficient simulation of finite-temperature open quantum systemsNov 29 2018Chain-mapping techniques in combination with the time-dependent density matrix renormalization group are a powerful tool for the simulation of open-system quantum dynamics. For finite-temperature environments, however, this approach suffers from an unfavorable ... More
Graphics processing units accelerated semiclassical initial value representation molecular dynamicsDec 17 2013May 08 2014This paper presents a Graphics Processing Units (GPUs) implementation of the Semiclassical Initial Value Representation (SC-IVR) propagator for vibrational molecular spectroscopy calculations. The time-averaging formulation of the SC-IVR for power spectrum ... More
Non-perturbative treatment of non-Markovian dynamics of open quantum systemsSep 11 2017Jan 08 2018We identify the conditions that guarantee equivalence of the reduced dynamics of an open quantum system (OQS) for two different types of environments - one a continuous bosonic environment leading to a unitary system-environment evolution and the other ... More
Coherent Transport of Quantum States by Deep Reinforcement LearningJan 20 2019Some problems in physics can be handled only after a suitable \textit{ansatz }solution has been guessed. Such method is therefore resilient to generalization, resulting of limited scope. The coherent transport by adiabatic passage of a quantum state through ... More
Precursors of non-MarkovianityFeb 08 2019Using the paradigm of information backflow to characterize a non-Markovian evolution, we introduce so-called precursors of non-Markovianity, i.e. necessary properties that the system and environment state must exhibit at earlier times in order for an ... More
Restoring Heisenberg scaling in noisy quantum metrology by monitoring the environmentMar 15 2018Nov 29 2018We study quantum frequency estimation for $N$ qubits subjected to independent Markovian noise, via strategies based on time-continuous monitoring of the environment. Both physical intuition and an extended convexity property of the quantum Fisher information ... More
Probabilistic low-rank factorization accelerates tensor network simulations of critical quantum many-body ground statesOct 04 2017We provide evidence that randomized low-rank factorization is a powerful tool for the determination of the ground state properties of low-dimensional lattice Hamiltonians through tensor network techniques. In particular, we show that randomized matrix ... More
Quantum state transfer via Bloch oscillationsNov 30 2015The realization of reliable quantum channels, able to transfer a quantum state with high fidelity, is a fundamental step in the construction of scalable quantum devices. In this paper we describe a transmission scheme based on the genuinely quantum effect ... More
Simulating spin-boson models with trapped ionsApr 03 2017We propose a method to simulate the dynamics of spin-boson models with small crystals of trapped ions where the electronic degree of freedom of one ion is used to encode the spin while the collective vibrational degrees of freedom are employed to form ... More
Which-way interference within biomimetic unit-cells for efficient energy transferAug 29 2018We show that `which-way' interference within unit-cells enhances the propagation along linear arrays made upon these basic units. As a working example, we address the exciton transfer through linear aggregates of ring-like unit cells, the latter resembling ... More
Non-Markovianity by undersampling in quantum optical simulatorsMay 16 2017Dec 05 2017We unveil a novel source of non-Markovianity for the dynamics of quantum systems, which appears when the system does not explore the full set of dynamical trajectories in the interaction with its environment. We term this effect non-Markovianity by undersampling ... More
Optimized auxiliary oscillators for the simulation of general open quantum systemsApr 09 2019A method for the systematic construction of few-body damped harmonic oscillator networks accurately reproducing the effect of general bosonic environments in open quantum systems is presented. Under the sole assumptions of a Gaussian environment and regardless ... More
Characterization of qubit chains by Feynman probesJul 20 2016We address the characterization of qubit chains and assess the performances of local measurements compared to those provided by Feynman probes, i.e. nonlocal measurements realized by coupling a single qubit register to the chain. We show that local measurements ... More
All-optical quantum simulator of qubit noisy channelsDec 20 2016Feb 24 2017We suggest and demonstrate an all-optical quantum simulator for single-qubit noisy channels originating from the interaction with a fluctuating field. The simulator employs the polarization degree of freedom of a single photon, and exploits its spectral ... More
Detection of squeezing by on-chip glass-integrated homodyne analyzerOct 12 2017We design and demonstrate on-chip homodyne detection operating in the quantum regime, i.e. able to detect genuine nonclassical features. Our setup exploits a glass-integrated homodyne analyzer (IHA) entirely fabricated by femtosecond laser micromachining. ... More
A remark on the Generalized Hodge ConjectureSep 27 2010Oct 09 2012Let X be a smooth, projective variety over the field of complex numbers. On the space H of its rational cohomology of degree i we have the arithmetic filtration F^p. On the other hand, on the space of cohomology of degree i of X with complex coefficients ... More
Wilf's conjecture for numerical semigroups with large second generatorOct 25 2017We study Wilf's conjecture for numerical semigroups $S$ such that the second least generator $a_2$ of $S$ satisfies $a_2>\frac{c(S)+\mu(S)}{3}$, where $c(S)$ is the conductor and $\mu(S)$ the multiplicity of $S$. In particular, we show that for these ... More
The coupling of Poisson sigma models to topological backgroundsOct 17 2016We extend the coupling to the topological backgrounds, recently worked out for the 2-dimensional BF-model, to the most general Poisson sigma models. The coupling involves the choice of a Casimir function on the target manifold and modifies the BRST transformations. ... More
On the relation between local and geometric Lagrangians for higher spinsJan 21 2010Equations of motion for free higher-spin gauge fields of any symmetry can be formulated in terms of linearised curvatures. On the other hand, gauge invariance alone does not fix the form of the corresponding actions which, in addition, either contain ... More
Geometric massive higher spins and current exchangesApr 17 2008Generalised Fierz-Pauli mass terms allow to describe massive higher-spin fields on flat background by means of simple quadratic deformations of the corresponding geometric, massless Lagrangians. In this framework there is no need for auxiliary fields. ... More
Asymptotic safety goes on shellJul 15 2011Oct 12 2018It is well known in quantum field theory that the off-shell effective action depends on the gauge choice and field parametrization used in calculating it. Nevertheless, the typical scheme in which the scenario of asymptotically safe gravity is investigated ... More
Mixed integer predictive control and shortest path reformulationMar 15 2010Mixed integer predictive control deals with optimizing integer and real control variables over a receding horizon. The mixed integer nature of controls might be a cause of intractability for instances of larger dimensions. To tackle this little issue, ... More
Search for the θ_{13} Neutrino Mixing Angle Using Reactor Anti-NeutrinosFeb 01 2007The measurement of the last undetermined neutrino mixing angle \theta_{13} is the main goal of the future experimental research on neutrino oscillations. At present, \theta_{13} is only known to be much smaller than the two other mixing angles, \theta_{12} ... More
Nuclear Energy Density Functionals Constrained by Low-Energy QCDFeb 06 2008A microscopic framework of nuclear energy density functionals is reviewed, which establishes a direct relation between low-energy QCD and nuclear structure, synthesizing effective field theory methods and principles of density functional theory. Guided ... More
Graviton Production by a Thermal BathJul 24 2003Thermal fluctuations in the early universe plasma and in very hot astrophysical objects are an unavoidable source of gravitational waves (GW). Differently from previous studies on the subject, we approach this problem using methods based on field theory ... More
Fractal properties of quantum spacetimeNov 10 2008Mar 25 2009We show that in general a spacetime having a quantum group symmetry has also a scale dependent fractal dimension which deviates from its classical value at short scales, a phenomenon that resembles what observed in some approaches to quantum gravity. ... More
Low-spin models for higher-spin LagrangiansMar 03 2011Higher-spin theories are most commonly modelled on the example of spin 2. While this is appropriate for the description of free irreducible spin-s particles, alternative options could be equally interesting. In particular Maxwell's equations provide the ... More
Non-compact subsets of the Zariski space of an integral domainMay 03 2017Let $V$ be a minimal valuation overring of an integral domain $D$ and let $\mathrm{Zar}(D)$ be the Zariski space of the valuation overrings of $D$. Starting from a result in the theory of semistar operations, we prove a criterion under which the set $\mathrm{Zar}(D)\setminus\{V\}$ ... More
Star operations on numerical semigroups: antichains and explicit resultsApr 11 2016We introduce an order on the set of non-divisorial ideals of a numerical semigroup $S$, and link antichains of this order with the star operations on $S$; subsequently, we use this order to find estimates on the number of star operations on $S$. We then ... More
Spherical Symmetric Solutions in Hořava-Lifshitz Gravity and their PropertiesOct 20 2010Nov 08 2010Non-projectable Ho\v{r}ava gravity for a spherically symmetric configuration with $\lambda=1$ exhibits an infinite set of solutions parametrized by a generic function $g^{2}(r)$ for the radial component of the shift vector. In the IR limit the infinite ... More
Oscillating shells: A model for a variable cosmic objectOct 23 1997A model for a possible variable cosmic object is presented. The model consists of a massive shell surrounding a compact object. The gravitational and self-gravitational forces tend to collapse the shell, but the internal tangential stresses oppose the ... More
Asymptotic safety goes on shellJul 15 2011Nov 11 2011It is well known in quantum field theory that the off-shell effective action depends on the gauge choice and field parametrization used in calculating it. Nevertheless, the typical scheme in which the scenario of asymptotically safe gravity is investigated ... More
Quantitative homogenization of the disordered $\nabla φ$ modelOct 15 2018We study the $\nabla \phi$ model with uniformly convex Hamiltonian $\mathcal{H} (\phi) := \sum V(\nabla \phi)$ and prove a quantitative rate of convergence for the properly rescaled partition function as well as a quantitative rate of convergence for ... More
Quantitative Homogenization of Differential FormsJun 20 2018We develop a quantitative theory of stochastic homogenization in the more general framework of differential forms. Inspired by recent progress in the uniformly elliptic setting, the analysis relies on the study of certain subadditive quantities. We establish ... More
The center of H(Y)Sep 22 2017Apr 13 2018Let $Y$ be a derived geometric stack defined over an algebraically closed field of characteristic zero and satisfying three technical conditions: eventual coconnectivity, perfection and local finite presentation. % For such $Y$, we consider the DG category ... More
Towards a classification of stable semistar operations on a Prüfer domainJul 24 2017We study stable semistar operations defined over a Pr\"ufer domain, showing that, if every ideal of a Pr\"ufer domain $R$ has only finitely many minimal primes, every such closure can be described through semistar operations defined on valuation overrings ... More
Essential nature of Newton's constant in unimodular gravityNov 20 2015We point out that in unimodular gravity Newton's constant is an essential coupling, i.e. it is independent of field redefinitions. We illustrate the consequences of this fact by a calculation in a standard simple approximation, showing that in this case ... More
On the extended Whittaker categoryNov 28 2014Mar 21 2019Let $G$ be a connected reductive group, with connected center, and $X$ a smooth complete curve, both defined over an algebraically closed field of characteristic zero. Let $\operatorname{Bun}_G$ denote the stack of $G$-bundles on $X$. In analogy with ... More
A game-theoretic approach to dynamic demand response managementOct 24 2014Within the realm of dynamic of \emph{smart buildings} and \emph{smart cities}, dynamic response management is playing an ever-increasing role thus attracting the attention of scientists from different disciplines. Dynamic demand response management involves ... More
Lagrangian flows driven by $BV$ fields in Wiener spacesOct 21 2013We establish the renormalization property for essentially bounded solutions of the continuity equation associated to $BV$ fields in Wiener spaces, with values in the associated Cameron-Martin space; thus obtaining, by standard arguments, new uniqueness ... More
Zero noise limits using local timesJan 28 2013We consider a well-known family of SDEs with irregular drifts and the correspondent zero noise limits. Using (mollified) local times, we show which trajectories are selected. The approach is completely probabilistic and relies on elementary stochastic ... More
Disformal invariance of second order scalar-tensor theoriesMay 12 2014The Horndeski action is the most general one involving a metric and a scalar field that leads to second-order field equations in four dimensions. Being the natural extension of the well-known scalar-tensor theories, its structure and properties are worth ... More
Jaffard families and localizations of star operationsOct 05 2016We generalize the concept of localization of a star operation to flat overrings; subsequently, we investigate the possibility of representing the set $\mathrm{Star}(R)$ of star operations on $R$ as the product of $\mathrm{Star}(T)$, as $T$ ranges in a ... More
Quantum Gravity from Simplices: Analytical Investigations of Causal Dynamical TriangulationsJul 20 2007A potentially powerful approach to quantum gravity has been developed over the last few years under the name of Causal Dynamical Triangulations. Numerical simulations have given very interesting results in the cases of two, three and four spacetime dimension. ... More
Loop group actions on categories and Whittaker invariantsOct 18 2013We develop some aspects of the theory of $D$-modules on ind-schemes of pro-finite type. These notions are used to define $D$-modules on (algebraic) loop groups and, consequently, actions of loop groups on DG categories. Let $N$ be the maximal unipotent ... More
String theory triplets and higher-spin curvaturesJan 27 2010May 05 2010Unconstrained local Lagrangians for higher-spin gauge theories are bound to involve auxiliary fields, whose integration in the partition function generates geometric, effective actions expressed in terms of curvatures. When applied to the triplets, emerging ... More
Critical behavior in spherical and hyperbolic spacesMar 26 2014Oct 02 2014We study the effects of curved background geometries on the critical behavior of scalar field theory. In particular we concentrate on two maximally symmetric spaces: $d$-dimensional spheres and hyperboloids. In the first part of the paper, by applying ... More
Loop group actions on categories and Whittaker invariantsOct 18 2013Dec 13 2017We develop some aspects of the theory of $D$-modules on ind-schemes of pro-finite type. These notions are used to define $D$-modules on (algebraic) loop groups and, consequently, actions of loop groups on DG categories. Let $N$ be the maximal unipotent ... More
Asymptotic stability of breathers in some Hamiltonian networks of weakly coupled oscillatorsSep 05 2012We consider a Hamiltonian chain of weakly coupled anharmonic oscillators. It is well known that if the coupling is weak enough then the system admits families of periodic solutions exponentially localized in space (breathers). In this paper we prove asymptotic ... More
Pink Work: Same-Sex Marriage, Employment and DiscriminationJul 17 2018This paper analyzes how the legalization of same-sex marriage in the U.S. affected gay and lesbian couples in the labor market. Results from a difference-in-difference model show that both partners in same-sex couples were more likely to be employed, ... More
Star operations on Kunz domainsMay 28 2018May 31 2018We study star operations on Kunz domains, a class of analytically irreducible, residually rational domains associated to pseudo-symmetric numerical semigroups, and we use them to refute a conjecture of Houston, Mimouni and Park. We also find an estimate ... More
Distributed control and game design: From strategic agents to programmable machinesJan 18 2019Large scale systems are forecasted to greatly impact our future lives thanks to their wide ranging applications including cooperative robotics, mobility on demand, resource allocation, supply chain management. While technological developments have paved ... More
Calculating the density of solutions of equations related to the Pólya-Ostrowski group through Markov chainsMar 12 2018Motivated by a problem in the theory of integer-valued polynomials, we investigate the natural density of the solutions of equations of the form $\theta_uu_q(n)+\theta_ww_q(n)+\theta_2\frac{n(n+1)}{2}+\theta_1n+\theta_0\equiv 0\bmod d$, where $d,q\geq ... More
BV-regularity for the Malliavin Derivative of the Maximum of the Wiener ProcessJan 07 2013We prove that, on the classical Wiener space, the random variable $\sup_{0\le t \le T} W_t$ admits a measure as second Malliavin derivative, whose total variation measure is finite and singular w.r.t.\ the Wiener measure.
Holographic Renormalization and Ward Identities with the Hamilton-Jacobi MethodMay 07 2002Feb 03 2003A systematic procedure for performing holographic renormalization, which makes use of the Hamilton-Jacobi method, is proposed and applied to a bulk theory of gravity interacting with a scalar field and a U(1) gauge field in the Stueckelberg formalism. ... More
Energetic model of tumor growthDec 22 2004A macroscopic model of the tumor Gompertzian growth is proposed. This approach is based on the energetic balance among the different cell activities, described by methods of statistical mechanics and related to the growth inhibitor factors. The model ... More
Spontaneous breaking of translational invariance in non-commutative lambda phi^4 theory in two dimensionsNov 16 2007The spontaneous breaking of of translational invariance in non-commutative self-interacting scalar field theory in two dimensions is investigated by effective action techniques. The analysis confirms the existence of the stripe phase, already observed ... More
On persistence of invariant tori and a theorem by NekhoroshevNov 15 2001Mar 09 2002We give a proof of a theorem by N.N. Nekhoroshev concerning Hamiltonian systems with $n$ degrees of freedom and $s$ integrals of motion in involution, where $1 \le s \le n$. Such a theorem ensures persistence of $s$-dimensional invariant tori under suitable ... More
Hydrogen Dissociation and Diffusion on Transition Metal(=Ti,Zr,V,Fe,Ru,Co,Rh,Ni,Pd,Cu,Ag)-doped Mg(0001) SurfacesNov 14 2008The kinetics of hydrogen absorption by magnesium bulk is affected by two main activated processes: the dissociation of the H$_2$ molecule and the diffusion of atomic H into the bulk. In order to have fast absorption kinetics both activated processed need ... More
Deformation of a flexible polymer in a random flow with long correlation timeDec 09 2010The effects induced by long temporal correlations of the velocity gradients on the dynamics of a flexible polymer are investigated by means of theoretical and numerical analysis of the Hookean and FENE dumbbell models in a random renewing flow. For Hookean ... More
Mutations as Levy flightsMay 31 2016Jul 01 2016Data on single-nucleotide polymorphisms and large chromosomal rearrangements, coming from a long time evolution experiment with Escherichia Coli, are analyzed in order to argue that mutations along a cell lineage can be modeled as Levy flights in the ... More
On the Dirac monopole's conceptJul 05 1999Jul 06 1999The Dirac monopole is discussed in view of the gauge invariance in Quantum Electrodynamics. It is shown the monopole existence implies the violation of the gauge invariance principle. The monopole field is essentially a longitudinal field and so a mass ... More
The monopoles in the structure of the electronJun 15 1999The classical electron is presented as made up of an electric charge and two Dirac monopoles of opposite charge performing a magnetic dipole. It is discussed that a valid variational principle for this system can be defined. The Dirac quantization condition ... More
Partial sum of matrix entries of representations of the symmetric group and its asymptoticsJun 29 2016Many aspects of the asymptotics of Plancherel distributed partitions have been studied in the past fifty years, in particular the limit shape, the distribution of the longest rows, characters of the associated representation matrices of the symmetric ... More
Imposing causality on a matrix modelDec 22 2008Jun 28 2009We introduce a new matrix model that describes Causal Dynamical Triangulations (CDT) in two dimensions. In order to do so, we introduce a new, simpler definition of 2D CDT and show it to be equivalent to the old one. The model makes use of ideas from ... More
Dissipatively driven strongly interacting bosons in a gauge fieldMay 22 2017The interplay between dissipation, interactions and gauge fields opens the possibility to rich emerging physics. Here we focus on a set-up in which the system is coupled at its extremities to two different baths which impose a current. We then study the ... More
Stability of spectral eigenspaces in nonlinear Schrodinger equationsAug 03 2006We consider the time-dependent non linear Schrodinger equations with a double well potential in dimensions d =1 and d=2. We prove, in the semiclassical limit, that the finite dimensional eigenspace associated to the lowest two eigenvalues of the linear ... More
Complexity of control-affine motion planningSep 10 2013Dec 20 2013In this paper we study the complexity of the motion planning problem for control-affine systems. Such complexities are already defined and rather well-understood in the particular case of nonholonomic (or sub-Riemannian) systems. Our aim is to generalize ... More
A particle system approach to cell-cell adhesion modelsJan 20 2016We investigate micro-to-macroscopic derivations in two models of living cells, in presence to cell-cell adhesive interactions. We rigorously address two PDE-based models, one featuring non-local terms and another purely local, as a a result of a law of ... More
Generalized modularity matricesFeb 04 2015Various modularity matrices appeared in the recent literature on network analysis and algebraic graph theory. Their purpose is to allow writing as quadratic forms certain combinatorial functions appearing in the framework of graph clustering problems. ... More
Solutions for dissipative quadratic open systems: part I - bosonsSep 23 2016Sep 26 2016This is a work in two parts in which we show how to solve a large class of Lindblad master equations for non-interacting particles on $L$ sites. In part I we concentrate on bosonic particles. We show how to reduce the problem to diagonalizing an $L \times ... More
Boundary conditions for the Baumgarte-Shapiro-Shibata-Nakamura formulation of Einstein's field equationsOct 30 2009Feb 11 2010We discuss the initial-boundary value problem for the Baumgarte-Shapiro-Shibata-Nakamura evolution system of Einstein's field equations which has been used extensively in numerical simulations of binary black holes and neutron stars. We specify nine boundary ... More
A Gauss--Newton iteration for Total Least Squares problemsAug 04 2016The Total Least Squares solution of an overdetermined, approximate linear equation $Ax \approx b$ minimizes a nonlinear function which characterizes the backward error. We show that a globally convergent variant of the Gauss--Newton iteration can be tailored ... More
Pseudo-spin-dependent scattering in carbon nanotubesSep 24 2010Oct 11 2011The breaking of symmetry is the ground on which many physical phenomena are explained. This is important in particular for bipartite lattice structure as graphene and carbon nanotubes, where particle-hole and pseudo-spin are relevant symmetries. Here ... More
Two loop results from the derivative expansion of the blocked actionDec 04 1997A derivative expansion of the Wegner-Houghton equation is derived for a scalar theory. The corresponding full non-perturbative renormalization group equations for the potential and the wave-function renormalization function are presented. We also show ... More
Spectral geometry as a probe of quantum spacetimeNov 02 2009Mar 19 2010Employing standard results from spectral geometry, we provide strong evidence that in the classical limit the ground state of three-dimensional causal dynamical triangulations is de Sitter spacetime. This result is obtained by measuring the expectation ... More
Inhomogeneous phase of a Gluon Plasma at finite temperature and densityMar 20 2007By considering the non-perturbative effects associated with the fundamental modular region, a new phase of a Gluon Plasma at finite density is proposed. It corresponds to the transition from glueballs to non-perturbative gluons which condense at a non ... More
Noncommutative electrodynamics and ultra high energy gamma raysOct 09 2003Plane waves in noncommutative classical electrodynamics (NCED) have a peculiar dispersion relation. We investigate the kinematical conditions on this deformed "mass shell" which come from ultra high energy gamma rays and discuss noncommutative dynamical ... More
Tumor Gompertzian growth by cellular energetic balanceJul 12 2004Dec 21 2004A macroscopic model of the tumor Gompertzian growth is proposed. The new approach is based on the energetic balance among the different cell activities, described by methods of statistical mechanics and related to the growth inhibitor factors. The model ... More
CFT/CFT interpolating RG flows and the holographic c-functionDec 18 2001Mar 06 2002We consider holographic RG flows which interpolate between non-trivial ultra-violet (UV) and infra-red (IR) conformal fixed points. We study the ``superpotentials'' which characterize different flows and discuss their expansions near the fixed points. ... More
Estimating orthant probabilities of high dimensional Gaussian vectors with an application to set estimationMar 16 2016The computation of Gaussian orthant probabilities has been extensively studied for low dimensional vectors. Here we focus on the high dimensional case and we present a two step procedure relying on both deterministic and stochastic techniques. The proposed ... More
Direct data-driven control of constrained linear parameter-varying systems: A hierarchical approachSep 14 2016In many nonlinear control problems, the plant can be accurately described by a linear model whose operating point depends on some measurable variables, called scheduling signals. When such a linear parameter-varying (LPV) model of the open-loop plant ... More
AdS_4/CFT_3 duals from M2-branes at hypersurface singularities and their deformationsSep 11 2009We construct three-dimensional N=2 Chern-Simons-quiver theories which are holographically dual to the M-theory Freund-Rubin solutions AdS_4 x V_{5,2}/Z_k (with or without torsion G-flux), where V_{5,2} is a homogeneous Sasaki-Einstein seven-manifold. ... More
Possible causes of a rise with energy of the cosmic ray positron fractionOct 27 2008Jan 20 2009Based on general considerations rather than model-dependent fits to specific scenarios, we argue that an increase with energy of the positron fraction in cosmic rays, suggested by several experiments at E>~7 GeV, most likely requires a primary source ... More
Notes on toric Sasaki-Einstein seven-manifolds and AdS_4/CFT_3Aug 06 2008Sep 16 2008We study the geometry and topology of two infinite families Y^{p,k} of Sasaki-Einstein seven-manifolds, that are expected to be AdS_4/CFT_3 dual to families of N=2 superconformal field theories in three dimensions. These manifolds, labelled by two positive ... More
Optical properties of bialkali photocathodesAug 17 2004The optical properties of the `bialkali' KCsSb and RbCsSb photomultiplier cathodes have been experimentally investigated in the visible range. The measurements carried out include the absolute reflectance at near-normal incidence, the polarization-dependent ... More