Many-body states whose wave-function admits a representation in terms of a uniform binary-tree tensor decomposition are shown to obey to power-law two-body correlations functions. Any such state can be associated with the ground state of a translational invariant Hamiltonian which, depending on the dimension of the systems sites, involve at most couplings between third-neighboring sites. A detailed analysis of their spectra shows that they admit an exponentially large ground space.

1 aSilvi, Pietro1 aGiovannetti, Vittorio1 aMontangero, Simone1 aRizzi, Matteo1 aCirac, J. Ignacio1 aFazio, Rosario uhttp://hdl.handle.net/1963/390901188nas a2200157 4500008004300000245010800043210006900151260001900220520065100239100001800890700002300908700001800931700002600949700001900975856003600994 2010 en_Ud 00aHomogeneous multiscale entanglement renormalization ansatz tensor networks for quantum critical systems0 aHomogeneous multiscale entanglement renormalization ansatz tenso bIOP Publishing3 aIn this paper, we review the properties of homogeneous multiscale entanglement renormalization ansatz (MERA) to describe quantum critical systems.We discuss in more detail our results for one-dimensional (1D) systems (the Ising and Heisenberg models) and present new data for the 2D Ising model. Together with the results for the critical exponents, we provide a detailed description of the numerical algorithm and a discussion of new optimization\\nstrategies. The relation between the critical properties of the system and the tensor structure of the MERA is expressed using the formalism of quantum channels, which we review and extend.

1 aRizzi, Matteo1 aMontangero, Simone1 aSilvi, Pietro1 aGiovannetti, Vittorio1 aFazio, Rosario uhttp://hdl.handle.net/1963/406700629nas a2200121 4500008004300000245007900043210006900122260002200191520021000213100002100423700002700444856003600471 2010 en_Ud 00aHomogenization of fiber reinforced brittle material: the intermediate case0 aHomogenization of fiber reinforced brittle material the intermed bWalter de Gruyter3 aWe derive a cohesive fracture model by homogenizing a periodic composite material whose microstructure is characterized by the presence of brittle inclusions in a reticulated unbreakable elastic structure.1 aDal Maso, Gianni1 aZeppieri, Caterina Ida uhttp://hdl.handle.net/1963/360701528nas a2200121 4500008004100000020002200041245010900063210006900172260001000241520109900251100002001350856003601370 2009 en d a978-90-481-2810-500aHamiltonian perturbations of hyperbolic PDEs: from classification results to the properties of solutions0 aHamiltonian perturbations of hyperbolic PDEs from classification bSISSA3 aWe begin with presentation of classi cation results in the theory of Hamiltonian\\r\\nPDEs with one spatial dimension depending on a small parameter. Special\\r\\nattention is paid to the deformation theory of integrable hierarchies, including an\\r\\nimportant subclass of the so-called integrable hierarchies of the topological type\\r\\nassociated with semisimple Frobenius manifolds. Many well known equations of\\r\\nmathematical physics, such as KdV, NLS, Toda, Boussinesq etc., belong to this\\r\\nsubclass, but there are many new integrable PDEs, some of them being of interest\\r\\nfor applications. Connections with the theory of Gromov{Witten invariants\\r\\nand random matrices are outlined. We then address the problem of comparative\\r\\nstudy of singularities of solutions to the systems of first order quasilinear\\r\\nPDEs and their Hamiltonian perturbations containing higher derivatives. We\\r\\nformulate Universality Conjectures describing different types of critical behavior\\r\\nof perturbed solutions near the point of gradient catastrophe of the unperturbed\\r\\none.1 aDubrovin, Boris uhttp://hdl.handle.net/1963/647000381nas a2200097 4500008004300000245009500043210006900138100002000207700002000227856003600247 2009 en_Ud 00aHardy-Sobolev-Maz\\\'ja inequalities: symmetry and breaking symmetry of extremal functions0 aHardySobolevMazja inequalities symmetry and breaking symmetry of1 aGazzini, Marita1 aMusina, Roberta uhttp://hdl.handle.net/1963/256900927nas a2200133 4500008004300000245007300043210006900116520048700185100002100672700001900693700002000712700002500732856003600757 2009 en_Ud 00aA higher order model for image restoration: the one dimensional case0 ahigher order model for image restoration the one dimensional cas3 aThe higher order total variation-based model for image restoration proposed by Chan, Marquina, and Mulet in [6] is analyzed in one dimension. A suitable functional framework in which the minimization problem is well posed is being proposed and it is proved analytically that the\\nhigher order regularizing term prevents the occurrence of the staircase effect. The generalized version of the model considered here includes, as particular cases, some curvature dependent functionals.1 aDal Maso, Gianni1 aFonseca, Irene1 aLeoni, Giovanni1 aMorini, Massimiliano uhttp://hdl.handle.net/1963/317400361nas a2200097 4500008004300000245007700043210006900120100001600189700002200205856003600227 2009 en_Ud 00aHolomorphic equivariant cohomology of Atiyah algebroids and localization0 aHolomorphic equivariant cohomology of Atiyah algebroids and loca1 aBruzzo, Ugo1 aRubtsov, Vladimir uhttp://hdl.handle.net/1963/377401152nas a2200121 4500008004300000245007700043210006900120260000900189520075400198100002100952700002100973856003600994 2009 en_Ud 00aHomogenization of fiber reinforced brittle materials: the extremal cases0 aHomogenization of fiber reinforced brittle materials the extrema bSIAM3 aWe analyze the behavior of a fragile material reinforced by a reticulated elastic unbreakable structure in the case of antiplane shear. The microscopic geometry of this material is described by means of two small parameters: the period $\\\\varepsilon$ of the grid and the ratio $\\\\delta$ between the thickness of the fibers and the period $\\\\varepsilon$. We show that the asymptotic behavior as $\\\\varepsilon\\\\to0^+$ and $\\\\delta\\\\to0^+$ depends dramatically on the relative size of these parameters. Indeed, in the two cases considered, i.e., $\\\\varepsilon\\\\ll\\\\delta$ and $\\\\varepsilon\\\\gg\\\\delta$, we obtain two different limit models: a perfectly elastic model and an elastic model with macroscopic cracks, respectively.1 aBarchiesi, Marco1 aDal Maso, Gianni uhttp://hdl.handle.net/1963/270501495nas a2200109 4500008004100000245007100041210006900112260001000181520113800191100002001329856003601349 2008 en d00aHamiltonian partial differential equations and Frobenius manifolds0 aHamiltonian partial differential equations and Frobenius manifol bSISSA3 aIn the first part of this paper the theory of Frobenius manifolds\\r\\nis applied to the problem of classification of Hamiltonian systems of partial\\r\\ndifferential equations depending on a small parameter. Also developed is\\r\\na deformation theory of integrable hierarchies including the subclass of\\r\\nintegrable hierarchies of topological type. Many well-known examples\\r\\nof integrable hierarchies, such as the Korteweg–de Vries, non-linear\\r\\nSchr¨odinger, Toda, Boussinesq equations, and so on, belong to this\\r\\nsubclass that also contains new integrable hierarchies. Some of these new\\r\\nintegrable hierarchies may be important for applications. Properties of the\\r\\nsolutions to these equations are studied in the second part. Consideration\\r\\nis given to the comparative study of the local properties of perturbed and\\r\\nunperturbed solutions near a point of gradient catastrophe. A Universality\\r\\nConjecture is formulated describing the various types of critical behaviour\\r\\nof solutions to perturbed Hamiltonian systems near the point of gradient\\r\\ncatastrophe of the unperturbed solution.1 aDubrovin, Boris uhttp://hdl.handle.net/1963/647100434nas a2200121 4500008004100000022001400041245005200055210005100107300002300158100001900181700002500200856008700225 2008 eng d a1073-792800aHarish-Chandra integrals as nilpotent integrals0 aHarishChandra integrals as nilpotent integrals aArt. ID rnn062, 151 aBertola, Marco1 aFerrer, Aleix, Prats uhttps://www.math.sissa.it/publication/harish-chandra-integrals-nilpotent-integrals01180nas a2200109 4500008004300000245005200043210005000095520085100145100001700996700002101013856003601034 2007 en_Ud 00aHigh-order angles in almost-Riemannian geometry0 aHighorder angles in almostRiemannian geometry3 aLet X and Y be two smooth vector fields on a two-dimensional manifold M. If X and Y are everywhere linearly independent, then they define a Riemannian metric on M (the metric for which they are orthonormal) and they give to M the structure of metric space. If X and Y become linearly dependent somewhere on M, then the corresponding Riemannian metric has singularities, but under generic conditions the metric structure is still well defined. Metric structures that can be defined locally in this way are called almost-Riemannian structures. The main result of the paper is a generalization to almost-Riemannian structures of the Gauss-Bonnet formula for domains with piecewise-C2 boundary. The main feature of such formula is the presence of terms that play the role of high-order angles at the intersection points with the set of singularities.1 aBoscain, Ugo1 aSigalotti, Mario uhttp://hdl.handle.net/1963/199500967nas a2200109 4500008004300000245005100043210004700094520063600141100002000777700002400797856003600821 2007 en_Ud 00aThe holomorphic anomaly for open string moduli0 aholomorphic anomaly for open string moduli3 aWe complete the holomorphic anomaly equations for topological strings with their dependence on open moduli. We obtain the complete system by standard path integral arguments generalizing the analysis of BCOV (Commun. Math. Phys. 165 (1994) 311) to strings with boundaries. We study both the anti-holomorphic dependence on open moduli and on closed moduli in presence of Wilson lines. By providing the compactification a\\\' la Deligne-Mumford of the moduli space of Riemann surfaces with boundaries, we show that the open holomorphic anomaly equations are structured on the (real codimension one) boundary components of this space.1 aBonelli, Giulio1 aTanzini, Alessandro uhttp://hdl.handle.net/1963/211300819nas a2200097 4500008004300000245011600043210006900159520043700228100002000665856003600685 2006 en_Ud 00aOn Hamiltonian perturbations of hyperbolic systems of conservation laws, II: universality of critical behaviour0 aHamiltonian perturbations of hyperbolic systems of conservation 3 aHamiltonian perturbations of the simplest hyperbolic equation $u_t + a(u) u_x=0$ are studied. We argue that the behaviour of solutions to the perturbed equation near the point of gradient catastrophe of the unperturbed one should be essentially independent on the choice of generic perturbation neither on the choice of generic solution. Moreover, this behaviour is described by a special solution to an integrable fourth order ODE.1 aDubrovin, Boris uhttp://hdl.handle.net/1963/178601265nas a2200121 4500008004300000245012600043210006900169520081600238100002001054700001501074700001801089856003601107 2006 en_Ud 00aOn Hamiltonian perturbations of hyperbolic systems of conservation laws I: quasitriviality of bihamiltonian perturbations0 aHamiltonian perturbations of hyperbolic systems of conservation 3 aWe study the general structure of formal perturbative solutions to the Hamiltonian perturbations of spatially one-dimensional systems of hyperbolic PDEs. Under certain genericity assumptions it is proved that any bihamiltonian perturbation can be eliminated in all orders of the perturbative expansion by a change of coordinates on the infinite jet space depending rationally on the derivatives. The main tools is in constructing of the so-called quasi-Miura transformation of jet coordinates eliminating an arbitrary deformation of a semisimple bihamiltonian structure of hydrodynamic type (the quasitriviality theorem). We also describe, following \\\\cite{LZ1}, the invariants of such bihamiltonian structures with respect to the group of Miura-type transformations depending polynomially on the derivatives.1 aDubrovin, Boris1 aSi-Qi, Liu1 aYoujin, Zhang uhttp://hdl.handle.net/1963/253500866nas a2200097 4500008004300000245013100043210006900174520046700243100002200710856003600732 2006 en_Ud 00aHomogeneous polynomial forms for simultaneous stabilizability of families of linear control systems: a tensor product approach0 aHomogeneous polynomial forms for simultaneous stabilizability of3 aThe paper uses the formalism of tensor products in order to deal with the problem of simultaneous\\nstabilizability of a family of linear control systems by means of Lyapunov functions which are homogeneous polynomial forms. While the feedback synthesis seems to be nonconvex, the simultaneous stability by means of homogeneous polynomial forms of the uncontrollable modes yields (convex) necessary but not sufficient conditions for simultaneous stabilizability.1 aAltafini, Claudio uhttp://hdl.handle.net/1963/222601156nas a2200121 4500008004300000245007100043210006800114520075900182100002000941700001900961700001800980856003600998 2006 en_Ud 00aA Hopf bundle over a quantum four-sphere from the symplectic group0 aHopf bundle over a quantum foursphere from the symplectic group3 aWe construct a quantum version of the SU(2) Hopf bundle $S^7 \\\\to S^4$. The quantum sphere $S^7_q$ arises from the symplectic group $Sp_q(2)$ and a quantum 4-sphere $S^4_q$ is obtained via a suitable self-adjoint idempotent $p$ whose entries generate the algebra $A(S^4_q)$ of polynomial functions over it. This projection determines a deformation of an (anti-)instanton bundle over the classical sphere $S^4$. We compute the fundamental $K$-homology class of $S^4_q$ and pair it with the class of $p$ in the $K$-theory getting the value -1 for the topological charge. There is a right coaction of $SU_q(2)$ on $S^7_q$ such that the algebra $A(S^7_q)$ is a non trivial quantum principal bundle over $A(S^4_q)$ with structure quantum group $A(SU_q(2))$.1 aLandi, Giovanni1 aPagani, Chiara1 aReina, Cesare uhttp://hdl.handle.net/1963/217900679nas a2200121 4500008004100000245003100041210003100072260000900103520036500112100002100477700002300498856003600521 2005 en d00aHybrid necessary principle0 aHybrid necessary principle bSIAM3 aWe consider a hybrid control system and general optimal control problems for this system. We suppose that the switching strategy imposes restrictions on control sets and we provide necessary conditions for an optimal hybrid trajectory, stating a hybrid necessary principle (HNP). Our result generalizes various necessary principles available in the literature.1 aGaravello, Mauro1 aPiccoli, Benedetto uhttp://hdl.handle.net/1963/164101254nas a2200121 4500008004100000245008600041210006900127260001800196520084100214100002101055700002001076856003601096 2004 en d00aH-bubbles in a perturbative setting: the finite-dimensional reduction\\\'s method0 aHbubbles in a perturbative setting the finitedimensional reducti bSISSA Library3 aGiven a regular function $H\\\\colon\\\\mathbb{R}^{3}\\\\to\\\\mathbb{R}$, we look for $H$-bubbles, that is, regular surfaces in $\\\\mathbb{R}^{3}$ parametrized on the sphere $\\\\mathbb{S}+^{2}$ with mean curvature $H$ at every point. Here we study the case of $H(u)=H_{0}+\\\\varepsilon H_{1}(u)=:H_{\\\\varepsilon}(u)$, where $H_{0}$ is a nonzero constant, $\\\\varepsilon$ is the smallness parameter, and $H_{1}$ is any $C^{2}$-function. We prove that if $\\\\bar p\\\\in\\\\mathbb{R}^{3}$ is a ``good\\\'\\\' stationary point for the Melnikov-type function $\\\\Gamma(p)=-\\\\int_{|q-p|<|H_{0}|^{-1}}H_{1}(q)\\\\,dq$, then for $|\\\\varepsilon|$ small there exists an $H_{\\\\varepsilon}$-bubble $\\\\omega^{\\\\varepsilon}$ that converges to a sphere of radius $|H_{0}|^{-1}$ centered at $\\\\bar p$, as $\\\\varepsilon\\\\to 0$.1 aCaldiroli, Paolo1 aMusina, Roberta uhttp://hdl.handle.net/1963/160701010nas a2200145 4500008004300000245005800043210005800101260001300159520057100172100002100743700001900764700002000783700002500803856003600828 2004 en_Ud 00aHigher order quasiconvexity reduces to quasiconvexity0 aHigher order quasiconvexity reduces to quasiconvexity bSpringer3 aIn this paper it is shown that higher order quasiconvex functions suitable in the variational treatment of problems involving second derivatives may be extended to the space of all matrices as classical quasiconvex functions. Precisely, it is proved that a smooth strictly 2-quasiconvex function with p-growth at infinity, p>1, is the restriction to symmetric matrices of a 1-quasiconvex function with the same growth. As a consequence, lower semicontinuity results for second-order variational problems are deduced as corollaries of well-known first order theorems.1 aDal Maso, Gianni1 aFonseca, Irene1 aLeoni, Giovanni1 aMorini, Massimiliano uhttp://hdl.handle.net/1963/291100868nas a2200145 4500008004300000245005900043210005800102260002300160520042200183100001800605700002100623700001900644700002300663856003600686 2003 en_Ud 00aHybrid optimal control: case study of a car with gears0 aHybrid optimal control case study of a car with gears bTaylor and Francis3 aThe purpose of this paper is to show the use of some analytical tools for hybrid optimal control. We illustrate both the hybrid maximum principle and the hybrid necessary principle at work on a simple example of a car with gears. The model is sufficiently rich to generate non-trivial optimization problems and the obtained results match with intuition. Finally, computer simulations confirm the theoretical analysis.1 aD'Apice, Ciro1 aGaravello, Mauro1 aManzo, Rosanna1 aPiccoli, Benedetto uhttp://hdl.handle.net/1963/302200338nas a2200097 4500008004100000245006300041210006100104260001800165100002100183856003600204 2000 en d00aHigh-order Averaging and Stability of Time-Varying Systems0 aHighorder Averaging and Stability of TimeVarying Systems bSISSA Library1 aSarychev, Andrey uhttp://hdl.handle.net/1963/146500796nas a2200097 4500008004100000245004400041210004400085520051200129100002100641856003600662 1999 en d00aHyperbolic Systems of Conservation Laws0 aHyperbolic Systems of Conservation Laws3 aThis is a survey paper, written in the occasion of an invited talk given by the author at the Universidad Complutense in Madrid, October 1998. Its purpose is to provide an account of some recent advances in the mathematical theory of hyperbolic systems of conservation laws in one space dimension. After a brief review of basic concepts, we describe in detail the method of wave-front tracking approximation and present some of the latest results on uniqueness and stability of entropy weak solutions.1 aBressan, Alberto uhttp://hdl.handle.net/1963/185500369nas a2200097 4500008004100000245008900041210006900130260001800199100001800217856003600235 1997 en d00aHomogeneous tangent vectors and high order necessary conditions for optimal controls0 aHomogeneous tangent vectors and high order necessary conditions bSISSA Library1 aAncona, Fabio uhttp://hdl.handle.net/1963/101500757nas a2200121 4500008004100000245007900041210006900120260001800189520035600207100001600563700002100579856003500600 1994 en d00aHilbert schemes of points on some K3 surfaces and Gieseker stable boundles0 aHilbert schemes of points on some K3 surfaces and Gieseker stabl bSISSA Library3 aBy using a Fourier-Mukai transform for sheaves on K3 surfaces we show that for a wide class of K3 surfaces $X$ the punctual Hilbert schemes $\\\\Hilb^n(X)$ can be identified, for all $n\\\\geq 1$, with moduli spaces of Gieseker stable vector bundles on $X$ of rank $1+2n$. We also introduce a new Fourier-Mukai type transform for such surfaces.

1 aBruzzo, Ugo1 aMaciocia, Antony uhttp://hdl.handle.net/1963/93700882nas a2200109 4500008004100000245009500041210006900136260001000205520050100215100002000716856003600736 1992 en d00aHamiltonian formalism of Whitham-type hierarchies and topological Landau - Ginsburg models0 aHamiltonian formalism of Whithamtype hierarchies and topological bSISSA3 aWe show that the bi-hamiltonian structure of the averaged Gelfand-Dikii\\r\\nhierarchy is involved in the Landau-Ginsburg topological models (for An-Series):\\r\\nthe Casimirs for the first P.B. give the correct coupling parameters for the perturbed\\r\\ntopological minimal model; the correspondence {coupling parameters} ~ {primary\\r\\nfields} is determined by the second P.B. The partition function (at the tree level) and\\r\\nthe chiral algebra for LG models are calculated for any genus g.1 aDubrovin, Boris uhttp://hdl.handle.net/1963/647600362nas a2200097 4500008004100000245007700041210006900118260001800187100002400205856003500229 1989 en d00aHyperbolic equations as ordinary differential equations in Banach spaces0 aHyperbolic equations as ordinary differential equations in Banac bSISSA Library1 aVidossich, Giovanni uhttp://hdl.handle.net/1963/77300294nas a2200109 4500008004100000245002400041210002400065260001800089100002000107700002200127856003500149 1988 en d00aHoles and obstacles0 aHoles and obstacles bSISSA Library1 aMusina, Roberta1 aMancini, Giovanni uhttp://hdl.handle.net/1963/50100291nas a2200097 4500008004100000245004200041210003700083260001800120100002000138856003500158 1988 en d00aH-surfaces with obstacles. (Italian)0 aHsurfaces with obstacles Italian bSISSA Library1 aMusina, Roberta uhttp://hdl.handle.net/1963/491