Results for "Gabriele Travaglini"

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Effective actions, Wilson lines and the IR/UV mixing in noncommutative supersymmetric gauge theoriesAug 01 2003Mar 04 2004We study IR/UV mixing effects in noncommutative supersymmetric Yang-Mills theories with gauge group U(N) using background field perturbation theory. We compute three- and four-point functions of background fields, and show that the IR/UV mixed contributions ... More
A note on amplitudes in N=6 superconformal Chern-Simons theoryMay 30 2012Jul 30 2012We establish a connection between tree-level superamplitudes in ABJM theory and leading singularities associated to special three-particle cuts of one-loop superamplitudes where one of the tree amplitudes entering the cut is a four-point amplitude. Using ... More
A Wilson-Majorana Regularization for Lattice Chiral Gauge TheoriesOct 04 1996Jan 29 1998We discuss the regularization of chiral gauge theories on the lattice introducing only physical degrees of freedom. This is obtained by writing the Wilson term in a Majorana form, at the expense of the U(1) symmetry related to fermion number conservation. ... More
One-loop N=8 Supergravity Amplitudes from MHV DiagramsJun 07 2007We discuss the calculation of one-loop amplitudes in N=8 supergravity using MHV diagrams. In contrast to MHV amplitudes of gluons in Yang-Mills, tree-level MHV amplitudes of gravitons are not holomorphic in the spinor variables. In order to extend these ... More
Quantum MHV DiagramsSep 01 2006Over the past two years, the use of on-shell techniques has deepened our understanding of the S-matrix of gauge theories and led to the calculation of many new scattering amplitudes. In these notes we review a particular on-shell method developed recently, ... More
On higher-derivative effects on the gravitational potential and particle bendingMay 14 2019Using modern amplitude techniques we compute the leading classical and quantum corrections to the classical gravitational potential between two massive scalars induced by adding an $R^3$ term to Einstein gravity. We then study the scattering of massless ... More
On higher-derivative effects on the gravitational potential and particle bendingMay 14 2019Jun 17 2019Using modern amplitude techniques we compute the leading classical and quantum corrections to the classical gravitational potential between two massive scalars induced by adding an $R^3$ term to Einstein gravity. We then study the scattering of massless ... More
Fermion BMN operators, the dilatation operator of N=4 SYM, and pp-wave string interactionsMar 18 2004Mar 23 2004The goal of this paper is to study the BMN correspondence in the fermionic sector. On the field theory side, we compute matrix elements of the dilatation operator in N=4 Super Yang-Mills for BMN operators containing two fermion impurities. Our calculations ... More
Instanton Calculus and Nonperturbative Relations in N=2 Supersymmetric Gauge TheoriesMay 30 1996Using instanton calculus we check, in the weak coupling region, the nonperturbative relation $$ <\Tr\phi^2>=i\pi\left(\cf-{a\over 2} {\partial\cf\over\partial a}\right)$$ obtained for a N=2 globally supersymmetric gauge theory. Our computations are performed ... More
Wilsonian Effective Actions and the IR/UV Mixing in Noncommutative Gauge TheoriesNov 24 2000Dec 04 2000Using background field perturbation theory we study Wilsonian effective actions of noncommutative gauge theories with an arbitrary matter content. We determine the Wilsonian coupling constant and the gauge boson polarization tensor as functions of the ... More
MHV Amplitudes in N=4 Super Yang-Mills and Wilson LoopsJul 09 2007Jul 13 2007It is a remarkable fact that MHV amplitudes in maximally supersymmetric Yang-Mills theory at arbitrary loop order can be written as the product of the tree amplitude with the same helicity configuration and a universal, helicity-blind function of the ... More
Amplitudes in Pure Yang-Mills and MHV DiagramsDec 01 2006Jan 30 2007We show how to calculate the one-loop scattering amplitude with all gluons of negative helicity in non-supersymmetric Yang-Mills theory using MHV diagrams. We argue that the amplitude with all positive helicity gluons arises from a Jacobian which occurs ... More
One-Loop Gauge Theory Amplitudes in N=4 Super Yang-Mills from MHV VerticesJul 26 2004Nov 27 2004We propose a new, twistor string theory inspired formalism to calculate loop amplitudes in N=4 super Yang-Mills theory. In this approach, maximal helicity violating (MHV) tree amplitudes of N=4 super Yang-Mills are used as vertices, using an off-shell ... More
One-loop N=8 supergravity coefficients from N=4 super Yang-MillsJun 02 2009We use supersymmetric generalised unitarity to calculate supercoefficients of box functions in the expansion of scattering amplitudes in N=8 supergravity at one loop. Recent advances have presented tree-level amplitudes in N=8 supergravity in terms of ... More
Tree-Level FormalismMar 17 2011Jul 29 2011We review two novel techniques used to calculate tree-level scattering amplitudes efficiently: MHV diagrams, and on-shell recursion relations. For the MHV diagrams, we consider applications to tree-level amplitudes and focus in particular on the N=4 supersymmetric ... More
New tests of the pp-wave correspondenceJun 24 2003Jul 15 2003The pp-wave/SYM correspondence is an equivalence relation, H_{string}= Delta -J, between the Hamiltonian H_{string} of string field theory in the pp-wave background and the dilatation operator Delta in N=4 Super Yang-Mills in the double scaling limit. ... More
Proof of the Dual Conformal Anomaly of One-Loop Amplitudes in N=4 SYMJun 18 2009We provide two derivations of the one-loop dual conformal anomaly of generic n-point superamplitudes in maximally supersymmetric Yang-Mills theory. Our proofs are based on simple applications of unitarity, and the known analytic properties of the amplitudes. ... More
A note on dual superconformal symmetry of the N=4 super Yang-Mills S-matrixJul 25 2008Sep 01 2008We present a supersymmetric recursion relation for tree-level scattering amplitudes in N=4 super Yang-Mills. Using this recursion relation, we prove that the tree-level S-matrix of the maximally supersymmetric theory is covariant under dual superconformal ... More
Analytic two-loop form factors in N=4 SYMJan 19 2012Mar 04 2012We derive a compact expression for the three-point MHV form factors of half-BPS operators in N=4 super Yang-Mills at two loops. The main tools of our calculation are generalised unitarity applied at the form factor level, and the compact expressions for ... More
All one-loop amplitudes in N=6 superconformal Chern-Simons theoryJul 30 2012We exploit a recently found connection between special triple-cut diagrams and tree-level recursive diagrams to derive a general formula capturing the multi-particle factorisation of arbitrary one-loop amplitudes in the ABJM theory. This formula contains ... More
From Trees to Loops and BackOct 31 2005Dec 15 2008We argue that generic one-loop scattering amplitudes in supersymmetric Yang-Mills theories can be computed equivalently with MHV diagrams or with Feynman diagrams. We first present a general proof of the covariance of one-loop non-MHV amplitudes obtained ... More
A Note on Loop Amplitudes in QEDAug 10 2009We consider the two-loop four-point amplitude in N=2 super QED, and show that there exists an approximate recursive structure similar to that captured by the ABDK/BDS ansatz for MHV amplitudes in N=4 super Yang-Mills. Furthermore, we present a simple ... More
One-Loop Amplitudes in N=4 Super Yang-Mills and Anomalous Dual Conformal SymmetryMay 27 2009We discuss what predictions can be made for one-loop superamplitudes in maximally supersymmetric Yang-Mills theory by using anomalous dual conformal symmetry. We show that the anomaly coefficient is a specific combination of two-mass hard and one-mass ... More
All rational one-loop Einstein-Yang-Mills amplitudes at four pointsMar 22 2018All four-point mixed gluon-graviton amplitudes in pure Einstein-Yang-Mills theory with at most one state of negative helicity are computed at one-loop order and maximal powers of the gauge coupling using D-dimensional generalized unitarity. The resulting ... More
Instanton Calculus, Topological Field Theories and N=2 Super Yang-Mills TheoriesMar 29 2000The results obtained by Seiberg and Witten for the low-energy Wilsonian effective actions of N=2 supersymmetric theories with gauge group SU(2) are in agreement with instanton computations carried out for winding numbers one and two. This suggests that ... More
One-loop Amplitudes in Six-Dimensional (1,1) Theories from Generalised UnitarityOct 07 2010Recently, the spinor helicity formalism and on-shell superspace were developed for six-dimensional gauge theories with (1,1) supersymmetry. We combine these two techniques with (generalised) unitarity, which is a powerful technique to calculate scattering ... More
Non-Supersymmetric Loop Amplitudes and MHV VerticesDec 10 2004Dec 15 2005We show how the MHV diagram description of Yang-Mills theories can be used to study non-supersymmetric loop amplitudes. In particular, we derive a compact expression for the cut-constructible part of the general one-loop MHV multi-gluon scattering amplitude ... More
Integrability and MHV diagrams in N=4 supersymmetric Yang-Mills theoryDec 02 2014Feb 02 2015We apply MHV diagrams to the derivation of the one-loop dilatation operator of N=4 super Yang-Mills in the SO(6) sector. We find that in this approach the calculation reduces to the evaluation of a single MHV diagram in dimensional regularisation. This ... More
Noncommutativity and Model BuildingDec 17 2001Apr 24 2002We propose a way to introduce matter fields transforming in arbitrary representations of the gauge group in noncommutative U(N) gauge theories. We then argue that in the presence of supersymmetry, an ordinary commutative SU(N) gauge theory with a general ... More
Dual conformal invariance for form factorsDec 21 2018Form factors of the stress-tensor multiplet operator in $\mathcal{N}=4$ supersymmetric Yang-Mills reveal surprisingly simple structures similar to those appearing in scattering amplitudes. In this paper we show that, as for the case of amplitudes, they ... More
On super form factors of half-BPS operators in N=4 super Yang-MillsFeb 06 2014Jun 05 2014We compute form factors of half-BPS operators in N=4 super Yang-Mills dual to massive Kaluza-Klein modes in supergravity. These are appropriate supersymmetrisations T_k of the scalar operators Tr(\phi^k) for any k, which for k=2 give the chiral part of ... More
Harmony of Super Form FactorsJul 25 2011Oct 30 2011In this paper we continue our systematic study of form factors of half-BPS operators in N=4 super Yang-Mills. In particular, we extend various techniques known for amplitudes to the case of form factors, including MHV rules, recursion relations, unitarity ... More
Four-point Amplitudes in N=8 Supergravity and Wilson LoopsMay 19 2008Sep 03 2008Prompted by recent progress in the study of N=4 super Yang-Mills amplitudes, and evidence that similar approaches might be relevant to N=8 supergravity, we investigate possible iterative structures and applications of Wilson loop techniques in maximal ... More
Non-holomorphic terms in N=2 SUSY Wilsonian actions and RG equationJun 12 1997In this paper we first investigate the Ansatz of one of the present authors for K(\Psi,\bar\Psi), the adimensional modular invariant non-holomorphic correction to the Wilsonian effective Lagrangian of an N=2 globally supersymmetric gauge theory. The renormalisation ... More
One-loop MHV Rules and Pure Yang-MillsApr 02 2007Jul 06 2007It has been known for some time that the standard MHV diagram formulation of perturbative Yang-Mills theory is incomplete, as it misses rational terms in one-loop scattering amplitudes of pure Yang-Mills. We propose that certain Lorentz violating counterterms, ... More
Integrability and unitarityFeb 23 2015Jun 15 2015We show how generalised unitarity can be used to determine the one-loop dilatation operator in N=4 super Yang-Mills. Our analysis focuses on two sectors, namely the bosonic SO(6) sector and the SU(2|3) sector. The calculation is performed on shell, with ... More
One-Loop Soft Theorems via Dual Superconformal SymmetryNov 20 2015We study soft theorems at one loop in planar N=4 super Yang-Mills theory through finite order in the infrared regulator and to subleading order in the soft parameter {\delta}. In particular, we derive a universal constraint from dual superconformal symmetry, ... More
BMN operators with vector impurities, Z_2 symmetry and pp-wavesMar 12 2003Jul 01 2003We calculate the coefficients of three-point functions of BMN operators with two vector impurities. We find that these coefficients can be obtained from those of the three-point functions of scalar BMN operators by interchanging the coefficient for the ... More
Simplifying instanton corrections to N=4 SYM correlatorsDec 13 2013Mar 24 2014We compute instanton corrections to non-minimal correlation functions of chiral primary operators in the N=4 super Yang-Mills super-current multiplet. Using a representation in terms of Mellin integrals, we find that these corrections can be written as ... More
The last of the simple remaindersJun 05 2014We compute the n-point two-loop form factors of the half-BPS operators Tr(phi_{AB}^n) in N=4 super Yang-Mills for arbitrary n >2 using generalised unitarity and symbols. These form factors are minimal in the sense that the n^{th} power of the scalar field ... More
Instanton Calculus and SUSY Gauge Theories on ALE ManifoldsDec 23 1997Apr 24 1998We study instanton effects along the Coulomb branch of an N=2 supersymmetric Yang-Mills theory with gauge group SU(2) on Asymptotically Locally Euclidean (ALE) spaces. We focus our attention on an Eguchi-Hanson gravitational background and on gauge field ... More
Recursion Relations for One-Loop Gravity AmplitudesJan 19 2007Jan 30 2007We study the application of recursion relations to the calculation of finite one-loop gravity amplitudes. It is shown explicitly that the known four, five, and six graviton one-loop amplitudes for which the external legs have identical outgoing helicities, ... More
Loop Amplitudes in Pure Yang-Mills from Generalised UnitarityJun 09 2005We show how generalised unitarity cuts in D = 4 - 2 epsilon dimensions can be used to calculate efficiently complete one-loop scattering amplitudes in non-supersymmetric Yang-Mills theory. This approach naturally generates the rational terms in the amplitudes, ... More
On Yangian symmetry of scattering amplitudes and the dilatation operator in N=4 super Yang-MillsJul 06 2015It is known that the Yangian of PSU(2,2|4) is a symmetry of the tree-level S-matrix of N=4 super Yang-Mills. On the other hand, the complete one-loop dilatation operator in the same theory commutes with the level-one Yangian generators only up to certain ... More
Notes on Noncommutative InstantonsAug 01 2001Oct 01 2001We study in detail the ADHM construction of U(N) instantons on noncommutative Euclidean space-time R_{NC}^4 and noncommutative space R_{NC}^2 x R^2. We point out that the completeness condition in the ADHM construction could be invalidated in certain ... More
PP-wave string interactions from n-point correlators of BMN operatorsJun 18 2002Sep 25 2002BMN operators are characterized by the fact that they have infinite R-charge and finite anomalous dimension in the BMN double scaling limit. Using this fact, we show that the BMN operators close under operator product expansion and form a sector in the ... More
Form factor recursion relations at loop levelDec 21 2018We introduce a prescription to define form factor integrands at loop level in planar $\mathcal{N}=4$ supersymmetric Yang-Mills theory. This relies on a periodic kinematic configuration that has been instrumental to describe form factors at strong coupling ... More
Exact Results in Noncommutative ${\cal N}=2$ Supersymmetric Gauge TheoriesFeb 08 2001Feb 12 2001We study the low-energy dynamics of noncommutative $\N=2$ supersymmetric U(N) Yang-Mills theories in the Coulomb phase. Exact results are derived for the leading terms in the derivative expansion of the Wilsonian effective action. We find that in the ... More
The SU(2|3) dynamic two-loop form factorsJun 28 2016Dec 22 2018We compute two-loop form factors of operators in the $SU(2|3)$ closed subsector of $N=4$ supersymmetric Yang-Mills. In particular, we focus on the non-protected, dimension-three operators $\mathrm{Tr} (X[Y,Z])$ and $\mathrm{Tr} ( \psi \psi)$ for which ... More
Three-point functions in N=4 Yang-Mills theory and pp-wavesJun 03 2002Jun 11 2002Recently it has been proposed that the coefficient of the three-point function of the BMN operators in N=4 supersymmetric Yang-Mills theory is related to the three-string interactions in the pp-wave background. We calculate three-point functions of these ... More
The connected prescription for form factors in twistor spaceAug 10 2016We propose a connected prescription formula in twistor space for all tree-level form factors of the stress tensor multiplet operator in $\mathcal{N}=4$ super Yang-Mills, which is a generalisation of the expression of Roiban, Spradlin and Volovich for ... More
Double-Soft Limits of Gluons and GravitonsApr 21 2015May 19 2015The double-soft limit of gluon and graviton amplitudes is studied in four dimensions at tree level. In general this limit is ambiguous and we introduce two natural ways of taking it: A consecutive double-soft limit where one particle is taken soft before ... More
Two-loop Sudakov Form Factor in ABJMMay 10 2013We compute the two-loop Sudakov form factor in three-dimensional N=6 superconformal Chern-Simons theory, using generalised unitarity. As an intermediate step, we derive the non-planar part of the one-loop four-point amplitude in terms of box integrals. ... More
A Twistor Approach to One-Loop Amplitudes in N=1 Supersymmetric Yang-Mills TheoryOct 28 2004We extend the twistor string theory inspired formalism introduced in hep-th/0407214 for calculating loop amplitudes in N=4 super Yang-Mills theory to the case of N=1 (and N=2) super Yang-Mills. Our approach yields a novel representation of the gauge theory ... More
A recursion relation for gravity amplitudesFeb 16 2005Jun 10 2005Britto, Cachazo and Feng have recently derived a recursion relation for tree-level scattering amplitudes in Yang-Mills. This relation has a bilinear structure inherited from factorisation on multi-particle poles of the scattering amplitudes - a rather ... More
Simplicity of Polygon Wilson Loops in N=4 SYMOct 26 2009Jun 28 2010Wilson loops with lightlike polygonal contours have been conjectured to be equivalent to MHV scattering amplitudes in N=4 super Yang-Mills. We compute such Wilson loops for special polygonal contours at two loops in perturbation theory. Specifically, ... More
On the Multi-Instanton Measure for Super Yang--Mills TheoriesAug 29 2000In this paper we revisit the arguments that have led to the proposal of a multi-instanton measure for supersymmetric Yang-Mills theories. We then recall how the moduli space of gauge connections on $\real^4$ can be built from a hyperk\"ahler quotient ... More
The SU(2|3) dynamic two-loop form factorsJun 28 2016We compute two-loop form factors of operators in the $SU(2|3)$ closed subsector of $N=4$ supersymmetric Yang-Mills. In particular, we focus on the non-protected, dimension-three operators $\mathrm{Tr} (X[Y,Z])$ and $\mathrm{Tr} ( \psi \psi)$ for which ... More
Dynamical Breaking of Supersymmetry in Noncommutative Gauge TheoriesMay 21 2001Aug 07 2001We propose a new mechanism of spontaneous supersymmetry breaking in noncommutative gauge theories. We find that in N=1 noncommutative gauge theories both supersymmetry and gauge invariance are dynamically broken. Supersymmetry is broken spontaneously ... More
Form Factors in N=4 Super Yang-Mills and Periodic Wilson LoopsNov 08 2010Dec 14 2010We calculate form factors of half-BPS operators in N=4 super Yang-Mills theory at tree level and one loop using novel applications of recursion relations and unitarity. In particular, we determine the expression of the one-loop form factors with two scalars ... More
A Note on Dual MHV Diagrams in N=4 SYMOct 07 2010Recently a reformulation of the MHV diagram method in N=4 supersymmetric Yang-Mills theory in momentum twistor space was presented and was shown to be equivalent to the perturbative expansion of the expectation value of a supersymmetric Wilson loop in ... More
A characterization theorem for the $L^{2}$-discrepancy of integer points in dilated polygonsApr 02 2015Let $C$ be a convex $d$-dimensional body. If $\rho$ is a large positive number, then the dilated body $\rho C$ contains $\rho^{d}\left\vert C\right\vert +\mathcal{O}\left( \rho^{d-1}\right) $ integer points, where $\left\vert C\right\vert $ denotes the ... More
General purpose readout board π LUP: overview and resultsJun 22 2018This work gives an overview of the PCI-Express board $\pi$LUP, focusing on the motivation that led to its development, the technological choices adopted and its performance. The $\pi$LUP card was designed by INFN and University of Bologna as a readout ... More
An L^1 estimate for half-space discrepancyMay 10 2010For every unit vector $\sigma\in\Sigma_{d-1}$ and every $r\ge0$, let % % \begin{displaymath} P_{\sigma,r}=[-1,1]^d\cap\{t\in\Rr^d:t\cdot\sigma\le r\} \end{displaymath} % % denote the intersection of the cube $[-1,1]^d$ with a half-space containing the ... More
Two-Loop Polygon Wilson Loops in N=4 SYMFeb 13 2009Jun 28 2010We compute for the first time the two-loop corrections to arbitrary n-gon lightlike Wilson loops in N=4 supersymmetric Yang-Mills theory, using efficient numerical methods. The calculation is motivated by the remarkable agreement between the finite part ... More
A Surprise in the Amplitude/Wilson Loop DualityApr 16 2010Apr 29 2010One of the many remarkable features of MHV scattering amplitudes is their conjectured equality to lightlike polygon Wilson loops, which apparently holds at all orders in perturbation theory as well as non-perturbatively. This duality is usually expressed ... More
From physical principles to classical Hamiltonian mechanicsJul 17 2014Oct 01 2014We derive the Hamiltonian formulation of classical mechanics directly, without reference to Lagrangian mechanics. We start from the definition of states in terms of labels used to identify them, and show how, under a deterministic and reversible process, ... More
Blazar jets: the spectraNov 20 2000The radiation observed by blazars is believed to originate from the transformation of bulk kinetic energy of relativistic jets into random energy. A simple way to achieve this is to have an intermittent central power source, producing shells of plasma ... More
Special Relativity at action in the UniverseMay 14 1999Nature succeeds in accelerating extended and massive objects to relativistic velocities. Jets in Active Galactic Nuclei and in galactic superluminal sources and gamma-ray bursts fireballs have bulk Lorentz factors from a few to several hundreds. A variety ... More
Extreme blazarsDec 10 1998The recent Cherenkov telescope observations and detections of the BL Lac objects Mkn 421, Mkn 501, 1ES 2344+514, PKS 2155--304 and possibly 1ES 1959+658 have shown that there exists a subclass of BL Lac objects emitting a substantial fraction of their ... More
Unification of all BlazarsJun 20 1997The overall spectra (SED) of blazars, from radio to gamma-ray energies, seem to obey well defined trends, with a continuity of properties between blazars of different classes. To quantify this statement we can either investigate their observed properties ... More
Synchrotron masers and fast radio burstsSep 15 2016Fast Radio Bursts (FRBs), with a typical duration of 1 ms and 1 Jy flux density at GHz frequencies, have brightness temperatures exceeding 1e33 K, requiring a coherent emission process. This can be achieved by bunching particles in volumes smaller than ... More
On the Large N Limit of 3D and 4D Hermitian Matrix ModelsApr 04 1995Apr 11 1995The large N limit of the hermitian matrix model in three and four Euclidean space-time dimensions is studied with the help of the approximate Renormalization Group recursion formula. The planar graphs contributing to wave function, mass and coupling constant ... More
The blazar sequence 2.0Sep 27 2016I discuss the spectral energy distribution (SED) of all blazars with redshift detected by the {\it Fermi} satellite and listed in the 3LAC catalog. I will update the so called "blazar sequence" from the phenomenological point of view, with no theory or ... More
Chemical evolution of neutron capture elements in our Galaxy and in the dwarf spheroidal galaxies of the Local GroupAug 30 2007By adopting a chemical evolution model for the Milky Way already reproducing the evolution of several chemical elements, we compare our theoretical results with accurate and new stellar data of neutron capture elements and we are able to impose strong ... More
On the cohomological dimension of the moduli space of Riemann surfacesMay 12 2014We prove that the Dolbeault cohomological dimension of the moduli space of Riemann surfaces of genus g>1 is at most 2g-2. We also prove an analogous bound for the moduli space of Riemann surfaces with marked points. The key step is to show that the Dolbeault ... More
Topology of representation spaces of surface groups in PSL(2,R) with assigned boundary monodromyJul 15 2016Aug 21 2016The aim of this paper is to determine the topology of the variety of representations of the fundamental group of a punctured surface in SL(2,R) with prescribed behavior at the punctures. In order to do that, we follow the strategy employed by Hitchin ... More
Self-organization of signal transductionOct 23 2012Jan 08 2013We propose a model of parameter learning for signal transduction, where the objective function is defined by signal transmission efficiency. We apply this to learn kinetic rates as a form of evolutionary learning, and look for parameters which satisfy ... More
Dynamic re-wiring of protein interaction: The case of transactivationSep 10 2006We are looking at local protein interaction networks from the perspective of directed, labeled graphs with quantitative values for monotonic changes in concentrations. These systems can be used to perform stability analysis for a stable attractor, given ... More
Learning intrinsic excitability in medium spiny neuronsFeb 21 2005Dec 13 2012We present an unsupervised, local activation-dependent learning rule for intrinsic plasticity (IP) which affects the composition of ion channel conductances for single neurons in a use-dependent way. We use a single-compartment conductance-based model ... More
Memorization in a neural network with adjustable transfer function and conditional gatingMar 07 2004The main problem about replacing LTP as a memory mechanism has been to find other highly abstract, easily understandable principles for induced plasticity. In this paper we attempt to lay out such a basic mechanism, namely intrinsic plasticity. Important ... More
Extracellular-to-intracellular signal transfer via G-proteinsMar 21 2005We look at the problem of signal transduction by extracellular agonist binding to a receptor protein at the membrane (sensor) via binding of G-proteins (effectors) to a highly integrative target molecule, such as the second messenger cAMP (target). We ... More
Regulation of Neuromodulator Receptor Efficacy - Implications for Whole-Neuron and Synaptic PlasticityJan 28 2004Membrane receptors for neuromodulators (NM) are highly regulated in their distribution and efficacy - a phenomenon which influences the individual cell's response to central signals of NM release. Even though NM receptor regulation is implicated in the ... More
Magnetic Katok Examples on the two-sphereJul 19 2015Jul 11 2016We show that there exist non-exact magnetic flows on the two-sphere having an energy level whose double cover is strictly contactomorphic to an irrational ellipsoid in $\mathbb C^2$. Our construction generalizes the examples of integrable Finsler metrics ... More
Onofri-type inequalities for singular Liouville equationsAug 28 2014We study the blow-up behaviour of minimizing sequences for the singular Moser-Trudinger functional on compact surfaces. Assuming non-existence of minimum points, we give an estimate for the infimum value of the functional. This result can be applied to ... More
On the radical idealizer chain of symmetric ordersOct 13 2003Sep 24 2004If $\Lambda $ is an indecomposable, non maximal, symmetric order, then the idealizer of the radical $\Gamma := \Id(J(\Lambda)) = J(\Lambda)^{#} $ is the dual of the radical. If $\Gamma $ is hereditary then $\Lambda $ has a Brauer tree (under modest additional ... More
Asymptotic geometry in higher products of rank one Hadamard spacesAug 26 2013Given a product X of locally compact rank one Hadamard spaces, we study asymptotic properties of certain discrete isometry groups. First we give a detailed description of the structure of the geometric limit set and relate it to the limit cone; moreover, ... More
Hopf-Tsuji-Sullivan dichotomy for quotients of Hadamard spaces with a rank one isometryJun 01 2017Jun 28 2018Let $X$ be a proper Hadamard space and $\Gamma< Isom(X)$ a non-elementary discrete group of isometries with a rank one isometry. We discuss and prove Hopf-Tsuji-Sullivan dichotomy for the geodesic flow on the set of parametrized geodesics of the quotient ... More
On automorphisms of extremal even unimodular lattices of dimension 48Dec 04 2012The automorphism groups of the three known extremal even unimodular lattices of dimension 48 and the one of dimension 72 are computed using the classification of finite simple groups. Restrictions on the possible automorphisms of 48-dimensional extremal ... More
An even unimodular 72-dimensional lattice of minimum 8Aug 17 2010Aug 26 2010An even unimodular 72-dimensional lattice $\Gamma $ having minimum 8 is constructed as a tensor product of the Barnes lattice and the Leech lattice over the ring of integers in the imaginary quadratic number field with discriminant $-7$. The automorphism ... More
Kneser-Hecke-operators in coding theorySep 21 2005Jul 18 2006The Kneser-Hecke-operator is a linear operator defined on the complex vector space spanned by the equivalence classes of a family of self-dual codes of fixed length. It maps a linear self-dual code $C$ over a finite field to the formal sum of the equivalence ... More
Equidistribution and counting of orbit points for discrete rank one isometry groups of Hadamard spacesAug 09 2018May 15 2019Let $X$ be a proper, geodesically complete Hadamard space, and $\ \Gamma<\mbox{Is}(X)$ a discrete subgroup of isometries of $X$ with the fixed point of a rank one isometry of $X$ in its infinite limit set. In this paper we prove that if $\Gamma$ has non-arithmetic ... More
Generalized Patterson-Sullivan measures for products of Hadamard spacesJul 19 2011Let $\Gamma$ be a discrete group acting by isometries on a product $X=X_1\times X_2$ of Hadamard spaces. We further require that $X_1$, $X_2$ are locally compact and $\Gamma$ contains two elements projecting to a pair of independent rank one isometries ... More
Enumeration of lattice polytopes by their volumeNov 08 2018A well known result by Lagarias and Ziegler states that there are finitely many equivalence classes of d-dimensional lattice polytopes having volume at most K, for fixed constants d and K. We describe an algorithm for the complete enumeration of such ... More
Singular Liouville Equations on $S^2$: Sharp Inequalities and Existence ResultsAug 09 2015We prove a sharp Onofri-type inequality and non-existence of extremals for a Moser-Tudinger functional on the sphere in the presence of potentials having positive order singularities. We also investigate the existence of critical points and give some ... More
Connectivity through bounds for the Castelnuovo-Mumford regularityDec 18 2014Dec 07 2016We present a simple method to obtain information regarding the connectivity of the 1-skeleta of a wide family of simplicial complexes through bounds for the Castelnuovo-Mumford regularity of their Stanley-Reisner rings. In this way we generalize and unify ... More
From physical principles to relativistic classical Hamiltonian and Lagrangian particle mechanicsMar 15 2015We show that classical particle mechanics (Hamiltonian and Lagrangian consistent with relativistic electromagnetism) can be derived from three fundamental assumptions: infinite reducibility, deterministic and reversible evolution, and kinematic equivalence. ... More
Observational Properties of Jets in Active Galactic NucleiJun 04 2004Parsec scale jet properties are shortly presented and discussed. Observational data are used to derive constraints on the jet velocity and orientation, the presence of velocity structures, and the connection between the pc and kpc scale. Two peculiar ... More
Collision-assisted Zeeman cooling of neutral atomsApr 14 2000We propose a new method to cool gaseous samples of neutral atoms. The gas is confined in a non dissipative optical trap in the presence of an homogeneous magnetic field. The method accumulates atoms in the $m_F=0$ Zeeman sub-level. Cooling occurs via ... More
The jet/disk connection in blazarsFeb 24 2010Feb 28 2010The new high energy data coming mainly from the Fermi and Swift satellites and from the ground based Cerenkov telescopes are making possible to study not only the energetics of blazar jets, but also their connection to the associated accretion disks. ... More