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Influence of disorder on the structural phase transition and magnetic interactions in Ba$_{3-x}$Sr$_x$Cr$_2$O$_8$Apr 29 2014Jul 16 2014The spin dimer system $\mathrm{Ba}_{3-x}\mathrm{Sr}_x\mathrm{Cr_2O_8}$ is a solid solution of the triplon Bose-Einstein condensation candidates $\mathrm{Ba_3Cr_2O_8}$ and $\mathrm{Sr_3Cr_2O_8}$. The magnetic intradimer interaction constant $J_0$ in this ... More

The modified complex Busemann-Petty problem on sections of convex bodiesJul 04 2008Since the answer to the complex Busemann-Petty problem is negative in most dimensions, it is natural to ask what conditions on the (n-1)-dimensional volumes of the central sections of complex convex bodies with complex hyperplanes allow to compare the ... More

Generalizing the differential algebra approach to input-output equations in structural identifiabilityFeb 22 2013Structural identifiability for parameter estimation addresses the question of whether it is possible to uniquely recover the model parameters assuming noise-free data, making it a necessary condition for successful parameter estimation for real, noisy ... More

Proceedings XV Jornadas sobre Programación y LenguajesDec 19 2015This volume contains a selection of the papers presented at the XV Jornadas sobre Programaci\'on y Lenguajes (PROLE 2015), held at Santander, Spain, during September 15th-17th, 2015. Previous editions of the workshop were held in C\'adiz (2014), Madrid ... More

A note on the Busemann-Petty problem for bodies of certain invarianceNov 10 2008Nov 20 2008The Busemann-Petty problem asks whether origin symmetric convex bodies in $\R^n$ with smaller hyperplane sections necessarily have smaller volume. The answer is affirmative if $n\leq 3$ and negative if $n\geq 4.$ We consider a class of convex bodies that ... More

Anti-Power $j$-fixes of the Thue-Morse WordAug 04 2018Recently, Fici, Restivo, Silva, and Zamboni introduced the notion of a $k$-anti-power, which is defined as a word of the form $w^{(1)} w^{(2)} \cdots w^{(k)}$, where $w^{(1)}, w^{(2)}, \ldots, w^{(k)}$ are distinct words of the same length. For an infinite ... More

Design of magnetic spirals in layered perovskites: extending the stability range far beyond room temperatureSep 27 2018In insulating materials with ordered magnetic spiral phases, ferroelectricity can emerge due to the breaking of inversion symmetry. This property is of both fundamental and practical interest, in particular with a view to exploiting it in low-power electronic ... More

The complex Busemann-Petty problem for arbitrary measuresJul 04 2008The complex Busemann-Petty problem asks whether origin symmetric convex bodies in C^n with smaller central hyperplane sections necessarily have smaller volume. The answer is affirmative if n\leq 3 and negative if n\geq 4. In this article we show that ... More

Tuning magnetic spirals beyond room temperature with chemical disorderAug 11 2016In the past years, magnetism-driven ferroelectricity and gigantic magnetoelectric effects have been reported for a number of frustrated magnets with spiral magnetic orders. Such materials are of high current interest due to their potential for spintronics ... More

The frequency dependence of scattering imprints on pulsar observationsJul 18 2016Aug 22 2016Observations of pulsars across the radio spectrum are revealing a dependence of the characteristic scattering time ($\tau$) on frequency, which is more complex than the simple power law with a theoretically predicted power law index. In this paper we ... More

The mass profile of galaxy clusters out to ~2 r200Jan 22 2003We analyze the internal dynamics of 43 non-interacting clusters which are selected from the 2dF Galaxy Redshift Survey 100k public release. We join together the 43 clusters into an ensemble cluster by appropriately scaling their galaxy velocities and ... More

Pure spinor superstring in AdS_4 x CP^3 with unconstrained ghostsSep 17 2012We construct the action for the pure spinor superstring in the coset description of AdS_4 x CP^3 superspace, using the variables which solve the pure spinor condition. As a test of the consistency of the approach, we use the background field method to ... More

Symplectic nilmanifolds with a symplectic non-free $Z_3$-actionJun 22 2005Dec 12 2006This paper expands some of the issues of the paper math.SG/0506449. We introduce a new technique to produce symplectic manifolds, by taking a symplectic non-free action of a finite group on a symplectic manifold and resolving symplectically the singularities ... More

Exact supersymmetry on the lattice: the Wess-Zumino modelSep 14 2004It is shown that the lattice Wess-Zumino model written in terms of Ginsparg-Wilson fermions is invariant under a generalized supersymmetry transformation which is determined by an iterative procedure in the coupling constant. This transformation is non-linear ... More

Tuning magnetic spirals beyond room temperature with chemical disorderAug 11 2016Jan 13 2017In the past years, magnetism-driven ferroelectricity and gigantic magnetoelectric effects have been reported for a number of frustrated magnets with spiral magnetic orders. Such materials are of high current interest due to their potential for spintronics ... More

Wess-Zumino model with exact supersymmetry on the latticeFeb 26 2004Sep 10 2004A lattice formulation of the four dimensional Wess-Zumino model that uses Ginsparg-Wilson fermions and keeps exact supersymmetry is presented. The supersymmetry transformation that leaves invariant the action at finite lattice spacing is determined by ... More

On s-sets in spaces of homogeneous typeDec 10 2013Let $(X,d,\mu)$ be a space of homogeneous type. In this note we study the relationship between two types of $s$-sets: relative to a distance and relative to a measure. We find a condition on a closed subset $F$ of $X$ under which we have that $F$ is $s$-set ... More

Microscopic studies of the normal and superconducting state of Ca3Ir4Sn13May 03 2013Oct 15 2013We report on muon spin rotation (muSR) studies of the superconducting and magnetic properties of the ternary intermetallic stannide Ca3Ir4Sn13. This material has recently been the focus of intense research activity due to a proposed interplay of ferromagnetic ... More

Laue three dimensional neutron diffractionFeb 08 2019This article presents a measurement technique and data analysis tool to perform 3D grain distribution mapping and indexing of oligocrystalline samples using neutrons: Laue three-dimensional neutron diffraction (Laue3DND). The approach builds on forward ... More

Planning Curricular Proposals on Sound and Music with Prospective Secondary-School TeachersAug 27 2008Sound is a preferred context to build foundations on wave phenomena, one of the most important disciplinary referents in physics. It is also one of the best-set frameworks to achieve transversality, overcoming scholastic level and activating emotional ... More

SpecSatisfiabilityTool: A tool for testing the satisfiability of specifications on XML documentsJan 09 2015We present a prototype that implements a set of logical rules to prove the satisfiability for a class of specifications on XML documents. Specifications are given by means of constrains built on Boolean XPath patterns. The main goal of this tool is to ... More

The character of the warm ionised mediumAug 22 2018Aug 23 2018$\textit{Herschel}$ observations of far infrared N$^+$ emission lines have demonstrated that dense plasma, with $n_e\sim30\,{\rm cm^{-3}}$, is ubiquitous in the inner Galactic plane. By combining the information from $\textit{Herschel}$ with other tracers ... More

Exact lattice Ward-Takahashi identity for the N=1 Wess-Zumino modelApr 13 2005We consider a lattice formulation of the four dimensional N=1 Wess-Zumino model that uses the Ginsparg-Wilson relation. This formulation has an exact supersymmetry on the lattice. We show that the corresponding Ward-Takahashi identity is satisfied, both ... More

Formality of Donaldson submanifoldsNov 01 2002May 21 2007We introduce the concept of s-formal minimal model as an extension of formality. We prove that any orientable compact manifold M, of dimension 2n or (2n-1), is formal if and only if M is (n-1)-formal. The formality and the hard Lefschetz property are ... More

The sharp maximal function approach to $L^{p}$ estimates for operators structured on Hörmander's vector fieldsNov 11 2015We consider a nonvariational degenerate elliptic operator structured on a system of left invariant, 1-homogeneous, H\"ormander's vector fields on a Carnot group in $R^{n}$, where the matrix of coefficients is symmetric, uniformly positive on a bounded ... More

A system for the simulation of simultaneous moves between two noncolocational playersAug 31 2007We describe a new system for the simulation of simultaneous moves between noncolocational players. This has applications in the burgeoning Rock-Paper-Scissors by mail movement.

Intersection Bodies with Certain SymmetriesJul 11 2013Jan 13 2015In this paper we study how certain symmetries of convex bodies affect their geometric properties. In particular, we consider the impact of symmetries generated by the block diagonal subgroup of orthogonal transformations, generalizing complex and quaternionic ... More

Nilmanifolds with a calibrated G_2-structureAug 04 2010Mar 31 2011We introduce obstructions to the existence of a calibrated G_2-structure on a Lie algebra g of dimension seven, not necessarily nilpotent. In particular, we prove that if there is a Lie algebra epimorphism from g to a six-dimensional Lie algebra h with ... More

Three-person impartial avoidance games for generating finite cyclic, dihedral, and nilpotent groupsJul 21 2016We study a three-player variation of the impartial avoidance game introduced by Anderson and Harary. Three players take turns selecting previously-unselected elements of a finite group. The losing player is the one who selects an element that causes the ... More

Plane curves in an immersed graph in $R^2$Oct 27 2012For any chord diagram on a circle there exists a complete graph on sufficiently many vertices such that any generic immersion of it to the plane contains a plane closed curve whose chord diagram contains the given chord diagram as a sub-chord diagram. ... More

Einstein almost cokähler manifoldsSep 15 2014Jan 08 2016We study an odd-dimensional analogue of the Goldberg conjecture for compact Einstein almost K\"ahler manifolds. We give an explicit non-compact example of an Einstein almost cok\"ahler manifold that is not cok\"ahler. We prove that compact Einstein almost ... More

Positive Definite Distributions and Normed SpacesJan 09 2010We answer a question of Alex Koldobsky on isometric embeddings of finite dimensional normed spaces.

Quotients of Spheres By Linear Actions of ToriMay 29 2012We consider quotients of spheres by linear actions of real tori. To each quotient we associate a matroid built out of a diagonalization of the torus action. We find the integral homology groups of the resulting quotient spaces in terms of the Tutte polynomial ... More

Determining Structurally Identifiable Parameter Combinations Using Subset ProfilingJul 08 2013Oct 04 2013Identifiability is a necessary condition for successful parameter estimation of dynamic system models. A major component of identifiability analysis is determining the identifiable parameter combinations, the functional forms for the dependencies between ... More

Weighted a priori estimates for the solution of the homogeneous Dirichlet problem for the powers of the Laplacian OperatorJun 07 2010Let $u$ be a weak solution of $ (-\Delta)^m u=f $ with Dirichlet boundary conditions in a smooth bounded domain $\Omega \subset \mathbb{R}^n$. Then, the main goal of this paper is to prove the following a priori estimate: $$ \|u\|_{W^{2m,p}_\omega(\Omega)} ... More

On non-formality of a simply-connected symplectic 8-manifoldJan 28 2008We show an alternative construction of the first example of a simply-connected compact symplectic non-formal 8-manifold given in arXiv:math/0506449. We also give an alternative proof of its non-formality using higher order Massey products.

Parameter identifiability and identifiable combinations in generalized Hodgkin-Huxley modelsNov 16 2015The use of Hodgkin-Huxley (HH) equations abounds in the literature, but the identifiability of the HH model parameters has not been broadly considered. Identifiability analysis addresses the question of whether it is possible to estimate the model parameters ... More

Modeling Epistemological Principles for Bias Mitigation in AI Systems: An Illustration in Hiring DecisionsNov 20 2017Artificial Intelligence (AI) has been used extensively in automatic decision making in a broad variety of scenarios, ranging from credit ratings for loans to recommendations of movies. Traditional design guidelines for AI models focus essentially on accuracy ... More

On MDS convolutional Codes over $\mathbb Z_{p^r}$Jan 18 2016Maximum Distance Separable (MDS) convolutional codes are cha- racterized through the property that the free distance meets the generalized Singleton bound. The existence of free MDS convolutional codes over Z p r was recently discovered in [26] via the ... More

Correlators of chiral primaries and 1/8 BPS Wilson loops from perturbation theoryMay 12 2014We study at perturbative level the correlation functions of a general class of 1/8 BPS Wilson loops and chiral primaries in N = 4 Super Yang-Mills theory. The contours and the location of operator insertions share a sphere S^2 embedded into spacetime ... More

The Astrophysics of Resonant Orbits in the Kerr MetricJan 30 2015This paper gives a complete characterization of resonant orbits in a Kerr spacetime. A resonant orbit is defined as a geodesic for which the longitudinal and radial orbital frequencies are commensurate. Our analysis is based on expressing the resonance ... More

Coclosed $G-2$-structures inducing nilsolitonsNov 16 2016We show obstructions to the existence of a coclosed $G_2$-structure on a Lie algebra $\mathfrak g$ of dimension seven with non-trivial center. In particular, we prove that if there exist a Lie algebra epimorphism from $\mathfrak g$ to a six-dimensional ... More

Weakly Lefschetz symplectic manifoldsApr 27 2004Feb 08 2005The harmonic cohomology of a Donaldson symplectic submanifold and of an Auroux symplectic submanifold are compared with that of its ambient space. We also study symplectic manifolds satisfying a weakly Lefschetz property, that is, the $s$-Lefschetz propery. ... More

On $G_2$-structures, special metrics and related flowsOct 17 2018We review results about $G_2$-structures in relation to the existence of special metrics, such as Einstein metrics and Ricci solitons, and the evolution under the Laplacian flow on non-compact homogeneous spaces. We also discuss some examples in detail. ... More

Helly $\mathbf{EPT}$ graphs on bounded degree trees: forbidden induced subgraphs and efficient recognitionApr 29 2016The edge intersection graph of a family of paths in host tree is called an $EPT$ graph. When the host tree has maximum degree $h$, we say that $G$ belongs to the class $[h,2,2]$. If, in addition, the family of paths satisfies the Helly property, then ... More

The $dδ$--lemma for weakly Lefschetz symplectic manifoldsJan 17 2005For a symplectic manifold $(M,\omega)$, not necessarily hard Lefschetz, we prove a version of the Merkulov $d\delta$--lemma. We also study the $d\delta$--lemma and related cohomologies for compact symplectic solvmanifolds.

G_2-structures on Einstein solvmanifoldsJul 16 2012Dec 30 2013We study the $G_2$ analogue of the Goldberg conjecture on non-compact solvmanifolds. In contrast to the almost-K\"ahler case we prove that a 7-dimensional solvmanifold cannot admit any left-invariant calibrated $G_2$-structure $\varphi$ such that the ... More

$t$-Pebbling in $k$-connected diameter two graphsMar 01 2019Graph pebbling models the transportation of consumable resources. As two pebbles move across an edge, one reaches its destination while the other is consumed. The $t$-pebbling number is the smallest integer $m$ so that any initially distributed supply ... More

On SO(3)-bundles over the Wolf spacesSep 26 2017Nov 19 2017We study the formality of the total space of principal SU(2) and SO(3)-bundles over a Wolf space, that is a symmetric positive quaternionic K\"ahker manifold. We apply this to conclude that all the 3-Sasakian homogeneous spaces are formal. We also determine ... More

A $6$-dimensional simply connected complex and symplectic manifold with no Kähler metricOct 22 2014Nov 14 2014We construct a simply connected compact manifold which has complex and symplectic structures but does not admit K\"ahler metrics, in the lowest possible dimension where this can happen, that is, dimension 6. Such a manifold is automatically formal and ... More

On seven dimensional quaternionic contact solvable Lie groupsOct 27 2011Jan 24 2012We answer in the affirmative a question posed by Ivanov and Vassilev on the existence of a seven dimensional quaternionic contact manifold with closed fundamental 4-form and non-vanishing torsion endomorphism. Moreover, we show an approach to the classification ... More

Characterizing [h,2,1] graphs by minimal forbidden induced subgraphsJul 08 2013An undirected graph G is called a VPT graph if it is the vertex intersection graph of a family of paths in a tree. The class of graphs which admit a VPT representation in a host tree with maximum degree at most h is denoted by [h,2,1]. The classes [h,2,1] ... More

Recognizing [h,2,1] graphsDec 14 2011An (h,s,t)-representation of a graph G consists of a collection of subtrees of a tree T, where each subtree corresponds to a vertex of G such that (i) the maximum degree of T is at most h, (ii) every subtree has maximum degree at mots s, (iii) there is ... More

Laplacian flow of closed $G_2$-structures inducing nilsolitonsOct 07 2013Mar 27 2015We study the existence of left invariant closed $G_2$-structures defining a Ricci soliton metric on simply connected nonabelian nilpotent Lie groups. For each one of these $G_2$-structures, we show long time existence and uniqueness of solution for the ... More

Symplectic resolutions, Lefschetz property and formalityOct 03 2007We introduce a method to resolve a symplectic orbifold into a smooth symplectic manifold. Then we study how the formality and the Lefschetz property of the symplectic resolution are compared with that of the symplectic orbifold. We also study the formality ... More

Coclosed $G_2$-structures inducing nilsolitonsNov 16 2016Mar 27 2017We show obstructions to the existence of a coclosed $G_2$-structure on a Lie algebra $\mathfrak g$ of dimension seven with non-trivial center. In particular, we prove that if there exist a Lie algebra epimorphism from $\mathfrak g$ to a six-dimensional ... More

A characterization of claw-free CIS graphs and new results on the order of CIS graphsDec 13 2018A graph is CIS if every maximal clique interesects every maximal stable set. Currently, no good characterization or recognition algorithm for the CIS graphs is known. We characterize graphs in which every maximal matching saturates all vertices of degree ... More

Column distance of convolutional codes over ZprJul 31 2017Rosenthal et al. introduced and thoroughly studied the notion of Maximum Distance Profile (MDP) convolutional codes over (non-binary) finite fields refining the classical notion of optimum distance profile, see for instance [18, p.164]. These codes have ... More

Formality and the Lefschetz property in symplectic and cosymplectic geometryApr 09 2015We review topological properties of K\"ahler and symplectic manifolds, and of their odd-dimensional counterparts, coK\"ahler and cosymplectic manifolds. We focus on formality, Lefschetz property and parity of Betti numbers, also distinguishing the simply-connected ... More

Non-formal co-symplectic manifoldsMar 29 2012Jan 07 2014We study the formality of the mapping torus of an orientation-preserving diffeomorphism of a manifold. In particular, we give conditions under which a mapping torus has a non-zero Massey product. As an application we prove that there are non-formal compact ... More

Influence of the Fermi Surface Morphology on the Magnetic Field-Driven Vortex Lattice Structure Transitions in YBa$_{2}$Cu$_{3}$O$_{7-δ}:δ=$0, 0.15Mar 13 2015We report small-angle neutron scattering measurements of the vortex lattice (VL) structure in single crystals of the lightly underdoped cuprate superconductor YBa2Cu3O6.85. At 2 K, and for fields of up to 16 T applied parallel to the crystal c-axis, we ... More

The complex structure of Abell 2345: a galaxy cluster with non-symmetric radio relicsJul 06 2010We aim to obtain new insights into the internal dynamics of the cluster Abell 2345. This cluster exhibits two non-symmetric radio relics well studied through recent, deep radio data. Our analysis is based on redshift data for 125 galaxies acquired at ... More

Orbital resonances around Black holesApr 01 2013We compute the length and timescales associated with resonant orbits in the Kerr Metric for all orbital and spin parameters. Resonance induced effects are potentially observable when the Event Horizon telescope resolves the inner structure of Sgr A*, ... More

Comparison of Lithium Gadolinium Borate Crystal Shards in Scintillating and Nonscintillating Plastic MatricesSep 16 2011We present a method for detecting neutrons using scintillating lithium gadolinium borate crystal shards in a plastic matrix while maintaining high gamma rejection. We have procured two cylindrical detectors, 5"\times5", containing 1% crystal by mass. ... More

Pebbling in Semi-2-TreesApr 14 2016Graph pebbling is a network model for transporting discrete resources that are consumed in transit. Deciding whether a given configuration on a particular graph can reach a specified target is ${\sf NP}$-complete, even for diameter two graphs, and deciding ... More

Modeling Spatial Invasion of Ebola in West AfricaJul 30 2015May 25 2016The 2014-2015 Ebola Virus Disease (EVD) epidemic in West Africa was the largest ever recorded, representing a fundamental shift in Ebola epidemiology with unprecedented spatiotemporal complexity. We developed spatial transmission models using a gravity-model ... More

Effects of adaptive protective behavior on the dynamics of sexually transmitted infectionsJun 29 2015Sexually transmitted infections (STIs) continue to present a complex and costly challenge to public health programs. The preferences and social dynamics of a population can have a large impact on the course of an outbreak as well as the effectiveness ... More

Identifiability results for several classes of linear compartment modelsOct 30 2014Identifiability concerns finding which unknown parameters of a model can be estimated from given input-output data. If some subset of the parameters of a model cannot be determined given input-output data, then we say the model is unidentifiable. In past ... More

Solvable Lie algebras are not that hypoFeb 10 2010Oct 30 2010We study a type of left-invariant structure on Lie groups, or equivalently on Lie algebras. We introduce obstructions to the existence of a hypo structure, namely the 5-dimensional geometry of hypersurfaces in manifolds with holonomy SU(3). The choice ... More

Pebbling in Split GraphsNov 16 2012Graph pebbling is a network optimization model for transporting discrete resources that are consumed in transit: the movement of two pebbles across an edge consumes one of the pebbles. The pebbling number of a graph is the fewest number of pebbles t so ... More

Pebbling in Semi-2-TreesApr 14 2016Jan 14 2017Graph pebbling is a network model for transporting discrete resources that are consumed in transit. Deciding whether a given configuration on a particular graph can reach a specified target is ${\sf NP}$-complete, even for diameter two graphs, and deciding ... More

On the existence of bounded solutions for a nonlinear elliptic systemNov 01 2010This work deals with the system $(-\Delta)^m u= a(x) v^p$, $(-\Delta)^m v=b(x) u^q$ with Dirichlet boundary condition in a domain $\Omega\subset\RR^n$, where $\Omega$ is a ball if $n\ge 3$ or a smooth perturbation of a ball when $n=2$. We prove that, ... More

Laplacian coflow on the 7-dimensional Heisenberg groupApr 02 2017Nov 21 2017We study the Laplacian coflow and the modified Laplacian coflow of $G_2$-structures on the $7$-dimensional Heinseberg group. For the Laplacian coflow we show that the solution is always ancient, that is it is defined in some interval $(-\infty,T)$, with ... More

Formality of 7-dimensional 3-Sasakian manifoldsNov 28 2015We prove that any simply connected compact 3-Sasakian manifold, of dimension seven, is formal if and only if its second Betti number is $b_2<2$. In the opposite, we show an example of a 7-dimensional Sasaki-Einstein manifold, with second Betti number ... More

The Observational Distribution of Internal Velocity Dispersions in Nearby Galaxy ClustersJun 17 1996We analyze the internal velocity dispersions of a sample of 172 nearby galaxy clusters (z < 0.15), each of which has at least 30 available galaxy redshifts, and spans a large richness range. Cluster membership selection is based on nonparametric methods. ... More

Symplectic half-flat solvmanifoldsNov 17 2011Jul 24 2012We classify solvable Lie groups admitting left invariant symplectic half-flat structure. When the Lie group has a compact quotient by a lattice, we show that these structures provide solutions of supersymmetric equations of type IIA.

PopStar: A new grid of Evolutionary Synthesis Models in the Virtual ObservatoryNov 21 2007We present a new set of theoretical evolutionary synthesis models, PopStar. This grid of Single Stellar Populations covers a wide range in both, age and metallicity. The models use the most recent evolutionary tracks together with the use of new NLTE ... More

Non-Kaehler Heterotic String Compactifications with non-zero fluxes and constant dilatonApr 10 2008Jun 17 2008We construct new explicit compact supersymmetric valid solutions with non-zero field strength, non-flat instanton and constant dilaton to the heterotic equations of motion in dimension six. We present balanced Hermitian structures on compact nilmanifolds ... More

A compact $G_2$-calibrated manifold with first Betti number $b_1=1$Aug 21 2018Dec 29 2018We construct a compact formal 7-manifold with a closed $G_2$-structure and with first Betti number $b_1=1$, which does not admit any torsion-free $G_2$-structure, that is, it does not admit any $G_2$-structure such that the holonomy group of the associated ... More

Quantifying CDS Sortability of Permutations by Strategic Pile SizeNov 29 2018The special purpose sorting operation, context directed swap (CDS), is an example of the block interchange sorting operation studied in prior work on permutation sorting. CDS has been postulated to model certain molecular sorting events that occur in ... More

Revisiting the Magnetic Structure and Charge Ordering in La$_{1/3}$Sr$_{2/3}$FeO$_3$ by Neutron Powder Diffraction and Mössbauer SpectroscopyFeb 23 2018May 17 2018The magnetic ordering of La$_{1/3}$Sr$_{2/3}$FeO$_3$ perovskite has been studied by neutron powder diffraction and $^{57}$Fe M\"ossbauer spectroscopy down to 2 K. From symmetry analysis, a chiral helical model and a collinear model are proposed to describe ... More

Homotopic properties of Kähler orbifoldsMay 10 2016We prove the formality and the evenness of odd-degree Betti numbers for compact K\"ahler orbifolds, by adapting the classical proofs for K\"ahler manifolds. As a consequence, we obtain examples of symplectic orbifolds not admitting any K\"ahler orbifold ... More

Contact 5-manifolds with SU(2)-structureJun 04 2007Jun 20 2008We consider 5-manifolds with a contact form arising from a hypo structure, which we call \emph{hypo-contact}. We provide conditions which imply that there exists such a structure on an oriented hypersurface of a 6-manifold with a half-flat SU(3)-structure. ... More

Compact supersymmetric solutions of the heterotic equations of motion in dimensions 7 and 8Jun 26 2008Nov 16 2008We construct explicit compact solutions with non-zero field strength, non-flat instanton and constant dilaton to the heterotic string equations in dimensions seven and eight. We present a quadratic condition on the curvature which is necessary and sufficient ... More

On formality of Sasakian manifoldsFeb 27 2014Nov 11 2015We investigate some topological properties, in particular formality, of compact Sasakian manifolds. Answering some questions raised by Boyer and Galicki, we prove that all higher (than three) Massey products on any compact Sasakian manifold vanish. Hence, ... More

Dynamically induced heat rectification in quantum systemsJun 27 2018Oct 02 2018Heat rectifiers are systems that conduct heat asymmetrically for forward and reversed temperature gradients. Here, we present an analytical study of heat rectification in linear quantum systems. We demonstrate that asymmetric heat currents can be induced ... More

Dynamic sea level changes following changes in the thermohaline circulationAug 13 2004Using the coupled climate model CLIMBER-3a, we investigate changes in sea surface elevation due to a weakening of the thermohaline circulation (THC). In addition to a global sea level rise due to a warming of the deep sea, this leads to a regional dynamic ... More

Surface-sensitive macrobolometers for the identification of external charged particlesSep 04 2009We report the performance of two prototype TeO2 macrobolometers, operated at ~25 mK, able to identify events due to energy deposited at the detector surface. This capability is obtained by thermally coupling thin Ge active layers to the main energy absorber ... More

Bremsstrahlung function, leading Luscher correction at weak coupling and localizationNov 16 2015Nov 27 2015We discuss the near BPS expansion of the generalized cusp anomalous dimension with L units of R-charge. Integrability provides an exact solution, obtained by solving a general TBA equation in the appropriate limit: we propose here an alternative method ... More

Surprises from the resummation of ladders in the ABJ(M) cusp anomalous dimensionMar 02 2016May 31 2016We study the cusp anomalous dimension in N=6 ABJ(M) theory, identifying a scaling limit in which the ladder diagrams dominate. The resummation is encoded into a Bethe-Salpeter equation that is mapped to a Schroedinger problem, exactly solvable due to ... More

Balanced Hermitian metrics from SU(2)-structuresAug 08 2008We study the intrinsic geometrical structure of hypersurfaces in 6-manifolds carrying a balanced Hermitian SU(3)-structure, which we call {\em balanced} SU(2)-{\em structures}. We provide conditions which imply that such a 5-manifold can be isometrically ... More

Compact supersymmetric solutions of the heterotic equations of motion in dimension 5Nov 13 2008Jun 09 2009We construct explicit compact supersymmetric solutions with non-zero field strength, non-flat instanton and constant dilaton to the heterotic string equations in dimension five. We present a quadratic condition on the curvature which is necessary and ... More

The redshift-space two-point correlation functions of galaxies and groups in the Nearby Optical Galaxy sampleFeb 27 2001We use the two-point correlation function in redshift space, $\xi(s)$, to study the clustering of the galaxies and groups of the Nearby Optical Galaxy (NOG) sample, which is a nearly all-sky, complete, magnitude-limited sample of $\sim$7000 bright and ... More

Dying radio galaxies in the LOFAR Lockman HoleMar 06 2016After the jets have switched off, radio galaxies undergo a fading phase which is often named the dying phase. The luminosity evolution of the remnant plasma during this period is still poorly constrained because of the paucity of objects detected. Using ... More

Non-Kaehler Heterotic String Solutions with non-zero fluxes and non-constant dilatonFeb 25 2014Conformally compact and complete smooth solutions to the Strominger system with non vanishing flux, non-trivial instanton and non-constant dilaton using the first Pontrjagin form of the (-)-connection} on 6-dimensional non-Kaehler nilmanifold are presented. ... More

Strong Kaehler with torsion structures from almost contact manifoldsSep 22 2009Nov 18 2010For an almost contact metric manifold $N$, we find conditions for which either the total space of an $S^1$-bundle over $N$ or the Riemannian cone over $N$ admits a strong K\"ahler with torsion (SKT) structure. In this way we construct new 6-dimensional ... More

Powers of distances to lower dimensional sets as Muckenhoupt weightsJun 03 2013Let $(X,d,\mu)$ be an Ahlfors metric measure space. We give sufficient conditions on a closed set $F\subseteq X$ and on a real number $\beta$ in such a way that $d(x,F)^\beta$ becomes a Muckenhoupt weight. We give also some illustrations to regularity ... More

Probing the pairing symmetry in the over-doped Fe-based superconductor Ba_0.35Rb_0.65Fe_2As_2 as a function of hydrostatic pressureFeb 19 2016We report muon spin rotation experiments on the magnetic penetration depth lambda and the temperature dependence of lambda^{-2} in the over-doped Fe-based high-temperature superconductor (Fe-HTS) Ba_{1-x}Rb_ xFe_2As_2 (x = 0.65) studied at ambient and ... More

A new magnetic phase in the nickelate perovskite TlNiO$_3$Feb 01 2017The RNiO$_3$ perovskites are known to order antiferromagnetically below a material-dependent N\'eel temperature $T_\text{N}$. We report experimental evidence indicating the existence of a second magnetically-ordered phase in TlNiO$_3$ above $T_\text{N} ... More

Dipolar spin ice states with fast monopole hopping rate in CdEr$_2$X$_4$ (X = Se, S)May 30 2017Mar 20 2018Excitations in a spin ice behave as magnetic monopoles, and their population and mobility control the dynamics of a spin ice at low temperature. CdEr$_2$Se$_4$ is reported to have the Pauling entropy characteristic of a spin ice, but its dynamics are ... More