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A coupled massive Thirring model of two interacting Dirac spinors in 1 + 1 dimensions with fields taking values in a Grassmann algebra is introduced, which is closely related to a SU(1) version of the Grassmannian Thirring model also introduced in this work. The Lax pair for the system is constructed, and its equations of motion are obtained from a zero curvature condition. It is shown that the system possesses several infinite hierarchies of conserved quantities, which strongly confirms its integrability. The model admits a canonical formulation and is invariant under space-time translations, Lorentz boosts and global U(1) gauge transformations, as well as discrete symmetries like parity and time reversal. The conserved quantities associated to the continuous symmetries are derived using Noether's theorem, and their relation to the lower-order integrals of motion is spelled out. New nonlocal integrable models are constructed through consistent nonlocal reductions between the field components of the general model. The Lagrangian, the Hamiltonian, the Lax pair and several infinite hierarchies of conserved quantities for each of these nonlocal models are obtained substituting its reduction in the expressions of the analogous quantities for the general model. It is shown that, although the Lorentz symmetry of the general model breaks down for its nonlocal reductions, these reductions remain invariant under parity, time reversal, global U(1) gauge transformations and space-time translations., Universidad Complutense de Madrid, Council of Scientific and Industrial Research (CSIR) (India), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

We provide a Maupertuis-type principle for the following system of ODE, of interest in special relativity: d/dt (mx˙/√1 −|˙x|2/c2) = ∇V(x), x ∈ ⊂ Rn, where m, c > 0 and V : → R is a function of class C1. As an application, we prove the existence of multiple periodic solutions with prescribed energy for a relativistic N-centre type problem in the plane., Depto. de Análisis Matemático y Matemática Aplicada, Instituto de Matemática Interdisciplinar (IMI), Fac. de Ciencias Matemáticas, TRUE, pub

CRUE-CSIC (Acuerdos Transformativos 2022), We show global existence of classical solutions for the nonlinear Nordström theory with a source term and a cosmological constant under the assumption that the source term is small in an appropriate norm, while in some cases no smallness assumption on the initial data is required. In this theory, the gravitational field is described by a single scalar function that satisfies a certain semi-linear wave equation. We consider spatial periodic deviation from the background metric, that is why we study the semi-linear wave equation on the three-dimensional torus T3 in the Sobolev spaces Hm(T3). We apply two methods to achieve the existence of global solutions, the first one is by Fourier series, and in the second one, we write the semi-linear wave equation in a non-conventional way as a symmetric hyperbolic system. We also provide results concerning the asymptotic behavior of these solutions and, finally, a blow-up result if the conditions of our global existence theorems are not met., CRUE-CSIC agreement with Springer Nature, Depto. de Análisis Matemático y Matemática Aplicada, Fac. de Ciencias Matemáticas, TRUE, pub

© The Author(s) 2023 We wish to thank the anonymous referees for many useful observations. This work has been partly supported by the research project PGC2018-094898-B-I00, MICINN, Spain, and by the Severo Ochoa Programme for Centres of Excellence in R & D (CEX2019-000904-S), Ministerio de Ciencia, Innovacion y Universidades y Agencia Estatal de Investigacion, Spain. D. R. N. acknowledges the financial support of EXINA S.L.P. T. and G. T. are members of the Gruppo Nazionale di Fisica Matematica (GNFM)., The theory of generalized Nijenhuis torsions, which extends the classical notions due to Nijenhuis and Haantjes, offers new tools for the study of normal forms of operator fields. We prove a general result ensuring that, given a family of commuting operator fields whose generalized Nijenhuis torsion of level m vanishes, there exists a local chart where all operators can be simultaneously block-diagonalized. We also introduce the notion of generalized Haantjes algebra, consisting of operators with a vanishing higher-level torsion, as a new algebraic structure naturally generalizing standard Haantjes algebras., Ministerio de Ciencia e Innovación (MICINN), Centros de Excelencia Severo Ochoa (MICINN), EXINA S.L.P. T., Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

©SISSA/ISAS 2004. The authors thank A.L. Maroto for his comments and careful reading of the manuscript, as well as partial support from the INFN-CICYT Florence-Madrid Collaboration. J.R.P thanks the hospitalit y of the INFN Sezione di Firenze as well as partial support from the Spanish CICYT projects PB98-0782 and BFM2000 1326., We identify the goldstino fields that give mass to the Kaluza Klein modes of five dimensional supergravity, when supersymmetry breaking is induced by brane effects. We then proof the four dimensional Equivalence Theorem that, in renormalizable gauges, allows for the replacement of Kaluza Klein modes of helicity ±1/2 gravitinos in terms of goldstinos. Finally we identify the five dimensional renormalizable gauge fixing that leads to the Equivalence Theorem., INFN-CICYT Florence-Madrid, Spanish CICYT, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© Springer-Verlag / Società Italiana di Fisica 2008. International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions (3. 2008. Isla de La Toja, España). We acknowledge financial support from Spanish research projects FPA2004-02602, FPA2005-02327, PR34/07-1856-BSCH, UCM-CAM 910309/08, FPA2007-29115-E and from the F.P.I. Programme (BES-2005-6726). D.C. wishes to thank support from the “Juan de la Cierva” Programme (Ministerio de Educación y Ciencia, Spain), We present a study of the pi pi scattering amplitude in the sigma and rho channels at finite temperature and nuclear density within a chiral unitary framework. Meson resonances are dynamically generated in our approach, which allows us to analyze the behavior of their associated scattering poles when the system is driven towards chiral-symmetry restoration. Medium effects are incorporated in three ways: (a) by thermal corrections of the unitarized scattering amplitudes, (b) by finite nuclear-density effects associated to a renormalization of the pion decay constant, and complementarily (c) by extending our calculation of the scalar-isoscalar channel to account for finite nuclear-density and temperature effects in a microscopic many-body implementation of pion dynamics. Our results are discussed in connection with several phenomenological aspects relevant for nuclear-matter and heavy-ion collision experiments, such as rho mass scaling versus broadening from dilepton spectra and chiral restoration signals in the sigma channel. We also elaborate on the molecular nature of pi pi resonances., Spanish research projects, Ministerio de Educacion y Ciencia (Spain), UCM-CAM, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

This research was supported with financial resources from Agencia de Calidad, Acreditación y Prospectiva de las Universidades de Madrid (ACAP), Madrid, Spain., International academic rankings that compare world universities have proliferated recently. In accordance with latter conceptual and methodological advances in academic rankings approaches, five selection criteria are defined and four international university rankings are selected. A comparative analysis of the four rankings is presented taking into account both the indicators frequency and its weights. Results show that, although some indicators differ considerably across selected rankings and even many indicators are unique, indicators referred to research and scientific productivity from university academic staff have a prominent role across all approaches. The implications of obtained data for main rankings consumers are discussed., Agencia de Calidad, Acreditación y Prospectiva de las Universidades de Madrid (ACAP), Depto. de Estadística e Investigación Operativa, Fac. de Ciencias Matemáticas, TRUE, pub

©Springer. The financial support of the Universidad Complutense under project GR58/08-910556 and the Ministerio de Ciencia e Innovación under projects FIS2008-00200 and FIS2011-22566 are gratefully acknowledged., We study the superpotentials, quantum parameter space and phase transitions that arise in the study of large N dualities between N = 1 SUSY U(N) gauge theories and string models on local Calabi-Yau manifolds. The main tool of our analysis is a notion of spectral curve characterized by a set of complex partial ’t Hooft parameters and cuts given by projections on the spectral curve of minimal supersymmetric cycles of the underlying Calabi-Yau manifold. We introduce a prepotential functional via a variational problem which determines the complex density as an extremal constrained by the period conditions. This prepotential is shown to satisfy the special geometry relations of the spectral curve. We give a system of equations for the branch points of the spectral curves and determine the appropriate branch cuts as Stokes lines of a suitable set of polynomials. As an application, we use a combination of analytical and numerical methods to study the cubic model, determine the analytic condition satisfied by critical one-cut spectral curves, and characterize the transition curves between the one-cut and two-cut phases both in the space of spectral curves and in the quantum parameter space., Universidad Complutense de Madrid, Ministerio de Ciencia e Innovación (MICINN), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

©Springer. This work was partially supported by the DGES under grant PB98-0821. R. Zhdanov would like to acknowledge the financial support of the Spanish Ministry of Education and Culture during his stay at the Universidad Complutense de Madrid. The authors would also like to thank the referee for several helpful remarks., The B-N hyperbolic Sutherland spin model is expressed in terms of a suitable set of commuting Dunkl operators. This fact is exploited to derive a complete family of commuting integrals of motion of the model, thus establishing its integrability. The Dunkl operators are shown to possess a common flag of invariant finite-dimensional linear spaces of smooth scalar functions. This implies that the Hamiltonian of the model preserves a corresponding flag of smooth spin functions. The discrete spectrum of the restriction of the Hamiltonian to this spin flag is explicitly computed by triangularization. The integrability of the hyperbolic Sutherland spin chain of BN type associated with the dynamical model is proved using Polychronakos's "freezing trick"., DGES, Spanish Ministry of Education and Culture, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

©2004 Plenum Publishing Corporation. The authors thank Professor E. V. Ferapontov for the useful discussions. This work was supported by the Russian Foundation for Basic Research (Grant No. 04-01-00403, A. B. S.), the Presidential Program for Supporting Leading Scientific Schools (Grant No. NSh 1716.2003.1, A. B. S.), the Ministerio de Cultura y Deporte of Spain (grant to A. B. S.) and the DGCYT (Project No. BFM2002-01607, L. M. A.)., We investigate the diagonal hydrodynamic reductions of a hierarchy of integrable hydrodynamic chains and analyze their compatibility with previously introduced reductions of differential type., Russian Foundation for Basic Research, Presidential Program for Supporting Leading Scientific Schools, Ministerio de Cultura y Deporte of Spain, DGCYT, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© Springer. The research of DGU was supported in part by MICINN-FEDER grant MTM2009- 06973 and CUR-DIUE grant 2009SGR859. The research of NK was supported in part by NSERC grant RGPIN 105490-2011. The research of RM was supported in part by NSERC grant RGPIN-228057-2009., Exceptional orthogonal polynomial systems (X-OPSs) arise as eigenfunctions of Sturm-Liouville problems, but without the assumption that an eigenpolynomial of every degree is present. In this sense, they generalize the classical families of Hermite, Laguerre, and Jacobi, and include as a special case the family of CPRS orthogonal polynomials introduced by Cariena et al. (J. Phys. A 41:085301, 2008). We formulate the following conjecture: every exceptional orthogonal polynomial system is related to a classical system by a Darboux-Crum transformation. We give a proof of this conjecture for codimension 2 exceptional orthogonal polynomials (X-2-OPs). As a by-product of this analysis, we prove a Bochner-type theorem classifying all possible X-2-OPSs. The classification includes all cases known to date plus some new examples of X-2-Laguerre and X-2-Jacobi polynomials., MICINN-FEDER, CUR-DIUE, NSERC, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

The author thanks the referees for their valuable remarks, Close insight into mathematical and conceptual structure of classical field theories shows serious inconsistencies in their common basis. In other words, we claim in this work to have come across two severe mathematical blunders in the very foundations of theoretical hydrodynamics. One of the defects concerns the traditional treatment of time derivatives in Eulerian hydrodynamic description. The other one resides in the conventional demonstration of the so-called Convection Theorem. Both approaches are thought to be necessary for cross-verification of the standard differential form of continuity equation. Any revision of these fundamental results might have important implications for all classical field theories. Rigorous reconsideration of time derivatives in Eulerian description shows that it evokes Minkowski metric for any flow field domain without any previous postulation. Mathematical approach is developed within the framework of congruences for general 4-dimensional differentiable manifold and the final result is formulated in form of a theorem. A modified version of the Convection Theorem provides a necessary cross- verification for a reconsidered differential form of continuity equation. Although the approach is developed for one-component (scalar) flow field, it can be easily generalized to any tensor field. Some possible implications for classical electrodynamics are also explored., Depto. de Análisis Matemático y Matemática Aplicada, Fac. de Ciencias Matemáticas, TRUE, pub

©Springer. L. S. Geng thanks the Ministerio de Educacion y Ciencia in the Program of estancias de doctores y tecnologos extranjeros for finantial support. This work is partly supported by DGICYT contracts FPA2007-29115-E, FIS2006-03438, FPA2005- 02327 and FPA2007- 62777, Santander/Complutense contract PR27/05-13955- BSCH, the Fundación Séneca contract 02975/PI/05, the Generalitat Valenciana and the EU Integrated Infrastructure Initiative Hadron Physics Project under contract RII3-CT-2004-506078., By describing within the chiral unitary approach the s-wave interaction of the vector meson nonet with the octet of pseudoscalar Goldstone Bosons, we find that the main component of the axial vector mesons b_1(1235), h_1(1170), h_1(1380), a_1(1260), f_1(1285) and the two states associated to the K_1(1270) does not follow the QCD dependence on the number of colors for ordinary qq̅ mesons., Ministerio de Educacion y Ciencia, DGICYT, Santander/Complutense, Fundacion Seneca, Generalitat Valenciana, Unión Europea, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

©Springer. This work was partially supported by the DGES under grant PB98-0821. R. Zhdanov would like to acknowledge the financial support by the Spanish Ministry of Education and Culture during his stay at the Universidad Complutense de Madrid., A new family of AN-type Dunkl operators preserving a polynomial subspace of finite dimension is constructed. Using a general quadratic combination of these operators and the usual Dunkl operators, several new families of exactly and quasi-exactly solvable quantum spin Calogero-Sutherland models are obtained. These include, in particular, three families of quasi-exactly solvable elliptic spin Hamiltonians., DGES, Spanish Ministry of Education and Culture, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© Società Italiana di Fisica. Conferencia: Hot Quarks Conference 2008 (2008. Aspen, Colorado). We are grateful to A. Dobado and F. Llanes-Estrada for their useful comments. We also acknowledge financial support from the Spanish research projects FPA2004-02602, PR27/05-13955-BSCH, FPA2005-02327 and FPI fellowship BES-2005-6726., We present recent results on the calculation of transport coefficients for a pion gas at zero chemical potential in Chiral Perturbation Theory (ChPT) using the Linear Response Theory (LRT). More precisely, we show the behavior of DC conductivity and shear viscosity at low temperatures. To compute transport coefficients, the standard power counting of ChPT has to be modified. The effects derived from imposing unitarity are also analyzed. As physical applications in relativistic heavy-ion collisions, we show the relation of the DC conductivity to soft-photon production and phenomenological effects related to a non-zero shear viscosity. In addition, our values for the shear viscosity to entropy ratio satisfy the KSS bound., Spanish research projects, BSCH, FPI programme, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

The authors is indebted to Profs. A.E. Chubykalo and V. Pope for helpful discussions and critical comments. The author also thanks the Editor and the referees for their valuable remarks., The historical background of the 19th century electromagnetic theory is revisited from the standpoint of the opposition between alternative approaches in respect to the problem of interactions. The 19th century electrodynamics became the battle-field of a paramount importance to test existing conceptions of interactions. Hertz’s experiments were designed to bring a solid experimental evidence in favor of one of them. The modern scientific method applied to analyze Hertz’s experimental approach as well as the analysis of his laboratory notes, dairy and private letters show that Hertz’s “crucial” experiments cannot be considered as conclusive at many points as it is generally implied. We found that alternative Helmholtz’s electrodynamics did not contradict any of Hertz’s experimental observations of transverse components as Maxwell’s theory predicted. Moreover, as we now know from recently published Hertz’s dairy and private notes, his first experimental results indicated clearly on infinite rate of propagation. Nevertheless, Hertz’s experiments provided no further explicit information on non-local longitudinal components which were such an essential feature of Helmholtz’s theory. Necessary and sufficient conditions for a decisive choice on the adequate account of electromagnetic interactions are discussed from the position of modern scientific method., Depto. de Análisis Matemático y Matemática Aplicada, Fac. de Ciencias Matemáticas, TRUE, pub

©2005 Springer Science+Business Media, Inc. One of the authors (L. M. A.) thanks the members of the Physics Department of Lecce University for their warm hospitality. This work was supported in part by the DGCYT (Project No. BFM2002-01607), COFIN (Grant 2002 “Sintesi”), and the National Science Foundation (Grant No. DMS-0404931)., We present a general scheme for determining and studying integrable deformations of algebraic curves, based on the use of Lenard relations. We emphasize the use of several types of dynamical variables: branches, power sums, and potentials., DGCYT, COFIN, National Science Foundation, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© Springer, Quasi-exactly solvable Schrodinger operators have the remarkable property that a part of their spectrum can be computed by algebraic methods. Such operators lie in the enveloping algebra of a finite-dimensional Lie algebra of first order differential operators-the" hidden symmetry algebra. "In this paper we develop some general techniques for constructing quasi-exactly solvable operators. Our methods are applied to provide a wide variety of new explicit two-dimensional examples (on both flat and curved spaces) of quasi-exactly solvable Hamiltonians, corresponding to both semisimple and more general classes of Lie algebras., Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

©Springer., We consider the vectorial approach to the binary Darboux transformations for the Kadomtsev-Petviashvili hierarchy in its Zakharov-Shabat formulation. We obtain explicit formulae for the Darboux transformed potentials in terms of Grammian type determinants. We also study the n-th Gel'fand-Dickey hierarchy introducing spectral operators and obtaining similar results. We reduce the above-mentioned results to the Kadomtsev-Petviashvili I and II real forms, obtaining corresponding vectorial Darboux transformations. In particular for the Kadomtsev-Petviashvili I hierarchy, we get the line soliton, the lump solution, and the Johnson-Thompson lump, and the corresponding determinant formulae for the nonlinear superposition of several of them. For Kadomtsev-Petviashvili II apart from the line solitons, we get singular rational solutions with its singularity set describing the motion of strings in the plane. We also consider the I and II real forms for the Gel'fand-Dickey hierarchies obtaining the vectorial Darboux transformation in both cases., Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

Using a new characterization of the Lorentz quadrics, we establish a reformulation of the Special Relativity Theory., Depto. de Álgebra, Geometría y Topología, Fac. de Ciencias Matemáticas, TRUE, pub

© Springer-Verlag / Società Italiana di Fisica 2009. Hot Quarks Conference 2008 (2008. Aspen, CO). We would like to thank D. Kharzeev and R. Venugopalan for very useful conversations. We also acknowledge fi- nancial support from the Spanish research projects FPA2004-02602, FPA2005-02327, PR34/07-1856-BSCH, UCM-CAM 910309/08, FPA2007-29115-E and from the F.P.I. Programme (BES-2005-6726)., We present recent results on a systematic method to calculate transport coefficients for a meson gas (in particular, we analyze a pion gas) at low temperatures in the context of Chiral Perturbation Theory (ChPT). Our method is based on the study of Feynman diagrams taking into account collisions in the plasma by means of the non-zero particle width. This implies a modification of the standard ChPT power counting scheme. We discuss the importance of unitarity, which allows for an accurate high-energy description of scattering amplitudes, generating dynamically the rho(770) and f(0)(600) mesons. Our results are compatible with analyses of kinetic theory, both in the non-relativistic very low-T regime and near the transition. We show the behavior with temperature of the electrical and thermal conductivities as well as of the shear and bulk viscosities. We obtain the result that the bulk viscosity is negligible against the shear viscosity, except near the chiral phase transition where the conformal anomaly might induce larger bulk effects. Various asymptotic limits for transport coefficients, large-N(c) scaling and some applications to heavy-ion collisions are studied., Spanish research, UCM-CAM, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

©Springer. This work was supported by the Spanish Ministerio de Educación y Ciencia (Research Project No. FIS2008-00200/FIS)., We completely describe the singular sectors of the one-layer Benney system (classical long-wave equation) and dispersionless Toda system. The associated Euler-Poisson-Darboux equations E(1/2, 1/2) and E(-1/2,-1/2) are the main tool in the analysis. We give a complete list of solutions of the one-layer Benney system depending on two parameters and belonging to the singular sector. We discuss the relation between Euler-Poisson-Darboux equations E(ɛ, ɛ) with the opposite sign of ɛ., Ministerio de Educación y Ciencia, Spain, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

A general reduction theory for field theoretical Lagrangians on principal fiber bundles is presented. The reduced variational problem as well as the associated equations are formulated. The link between the solutions of the original problem and that of the reduced problem is discussed and an obstruction to the reconstruction of the solutions is isolated. The important case of semidirect products is discussed in detail and several concrete examples are presented., DGESIC, European Commission and the Swiss Federal Government, Research Training Network Mechanics and Symmetry in Europe (MASIE), Swiss National Science Foundation., Depto. de Álgebra, Geometría y Topología, Fac. de Ciencias Matemáticas, TRUE, pub

© Springer. Financial support was provided by the Spanish MICINN through the projects FIS2008-06078- C03-01 and FIS2008-06078-C03-03 and by Junta de Andalucía through the projects FQM2288 and FQM219. The authors want to thank J.L. Jaramillo, S. Liberati, S. Sonego and M. Visser for some illuminating discussions., Observational indications combined with analyses of analogue and emergent gravity in condensed matter systems support the possibility that there might be two distinct energy scales related to quantum gravity: the scale that sets the onset of quantum gravitational effects E-B ( related to the Planck scale) and the much higher scale E-L signalling the breaking of Lorentz symmetry. We suggest a natural interpretation for these two scales: E-L is the energy scale below which a special relativistic spacetime emerges, E-B is the scale below which this spacetime geometry becomes curved. This implies that the first 'quantum' gravitational effect around E-B could simply be that gravity is progressively switched off, leaving an effective Minkowski quantum field theory up to much higher energies of the order of E-L. This scenario may have important consequences for gravitational collapse, inasmuch as it opens up new possibilities for the final state of stellar collapse other than an evaporating black hole., Spanish MICINN, Junta de Andalucia, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

For every Matrix Product State (MPS) one can always construct a so-called parent Hamiltonian. This is a local, frustration free, Hamiltonian which has the MPS as ground state and is gapped. Whenever that parent Hamiltonian has a degenerate ground state space (the so-called non-injective case), we construct another ’uncle’ Hamiltonian which is also local and frustration free, has the same ground state space, but is gapless, and its spectrum is R +. The construction is obtained by linearly perturbing the matrices building up the state in a random direction, and then taking the limit where the perturbation goes to zero. For MPS where the parent Hamiltonian has a unique ground state (the so-called injective case) we also build such uncle Hamiltonian with the same properties in the thermodynamic limit., Comunidad de Madrid, Ministerio de Ciencia e Innovación (MICINN), European CHIST-ERA, Unión Europea. FP7, NSF, ARO, Depto. de Análisis Matemático y Matemática Aplicada, Fac. de Ciencias Matemáticas, TRUE, pub

Projected entangled pair states (PEPS) are used in practice as an efficient parametrization of the set of ground states of quantum many body systems. The aim of this paper is to present, for a broad mathematical audience, some mathematical questions about PEPS., Unión Europea, Ministerio de Economía y Competitividad (MINECO), Comunidad de Madrid, Depto. de Análisis Matemático y Matemática Aplicada, Instituto de Ciencias Matemáticas (ICMAT), Fac. de Ciencias Matemáticas, FALSE, pub

©2002 Plenum Publishing Corporation. International Conference on Nonlinear Evolution Equations and Dynamical Systems. (15. 2001. Cambridge, Inglaterrad). One of the authors (B. K.) is grateful to the organizers of the program “Integrable Systems” for the support and was also supported in part by the COFIN 2000 “Sintesi.” The stay of L. M. A. at Cambridge University as a BBV visiting professor was supported by the Fundaci´on Banco Bilbao Vizcaya Argentaria. E. M. was supported in part by the CICYT (Project No. PB98-0821)., A ∂¯formalism for studying dispersionless integrable hierarchies is applied to the dispersionless KP (dKP) hierarchy. We relate this formalism to the theory of quasiconformal mappings on the plane and present some classes of explicit solutions of the dKP hierarch., COFIN, Fundación Banco Bilbao Vizcaya Argentaria, CICYT, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© The Authors 2022 Authors are very thankful to V.Braun and A.Manashov for numerous discussions and helpful comments, and to M.Beneke and collaborators for the sharing of preliminary results of their computation. This study was supported by Deutsche Forschungsgemeinschaft (DFG) through the research Unit FOR 2926, "Next Generation pQCD for Hadron Structure: Preparing for the EIC", project number 30824754. I.S. is supported by the Spanish Ministry grant PID2019-106080GB-C21. This project has received funding from the European Union Horizon 2020 research and innovation program under grant agreement Num. 824093 (STRONG-2020)., We develop a method of transverse momentum dependent (TMD) operator expansion that yields the TMD factorization theorem on the operator level. The TMD operators are systematically ordered with respect to TMD-twist, which allows a certain separation of kinematic and genuine power corrections. The process dependence enters via the boundary conditions for the background fields. As a proof of principle, we derive the effective operator for hadronic tensor in TMD factorization up to the next-to-leading power (similar to q(T)/Q) at the next-to-leading order for any process with two detected states., Unión Europea. Horizonte 2020, Ministerio de Ciencia e Innovación (MICINN), German Research Foundation (DFG), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© The Author(s) 2022 Erratum to: Eur.Phys.J.C(2017)77:755, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© The Author(s) 2022 MG is funded by the predoctoral contract 2018-T1/TIC-10431 and acknowledges further support by the European Regional Development Fund under the Dora Plus scholarship grants. DRG is funded by the Atraccion de Talento Investigador programme of the Comunidad de Madrid (Spain) No. 2018-T1/TIC-10431, and acknowledges further support from the Ministerio de Ciencia, Innovacion y Universidades (Spain) project No. PID2019-108485GB-I00/AEI/10.13039/501100011033, and the FCT projects No. PTDC/FIS-PAR/31938/2017 and PTDC/FIS-OUT/29048/2017. AW is supported by the EU through the European Regional Development Fund CoE program TK133 "The Dark Side of the Universe". This work is also supported by the Spanish projects Nos. FIS2017-84440-C2-1-P and PID2020-117301GA-I00, the project PROMETEO/2020/079 (Generalitat Valenciana), and the Edital 006/2018 PRONEX (FAPESQPB/CNPQ, Brazil, Grant 0015/2019). MG thanks the Laboratory of Theoretical Physics at the University of Tartu, and AW the Department of Theoretical Physics at the Complutense University of Madrid, for their kind hospitality while doing this work., We study three aspects of the early-evolutionary phases in low-mass stars within Eddington-inspired Born-Infeld (EiBI) gravity, a viable extension of General Relativity. These aspects are concerned with the Hayashi tracks (i.e. the effective temperature-luminosity relation); the minimum mass required to belong to the main sequence; and the maximum mass allowed for a fully convective star within the main sequence. Using analytical models accounting for the most relevant physics of these processes, we find in all cases a dependence of these quantities not only on the theory's parameter, but also on the star's central density, a feature previously found in Palatini f(R) gravity. Using this, we investigate the evolution of these quantities with the (sign of the) EiBI parameter, finding a shift in the Hayashi tracks in opposite directions in the positive/negative branches of it, and an increase (decrease) for positive (negative) parameter in the two masses above. We use these results to elaborate on the chances to seek for traces of new physics in low-mass stars within this theory, and the limitations and difficulties faced by this approach., Ministerio de Ciencia e Innovación (MICINN), Ministerio de Economía y Competitividad (MINECO)/FEDER, Comunidad de Madrid, Generalitat Valenciana, Fundação para a Ciência e a Tecnologia (FCT), FAPESQPB/CNPQ, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© R.F.C., M.G.E. and I.S. are supported by the Spanish Ministry grant PID2019-106080GB-C21. This project has received funding from the European Union Horizon 2020 research and innovation program under grant agreement Num. 824093 (STRONG-2020). M.G.E. is supported by the Community of Madrid and UAH joint grant CM/BG/2021-002 (MultiNuS) within the agreement to fund Beatriz Galindo researchers. Y.M. is supported by the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 754496-FELLINI., We discuss the measurement of gluon transverse momentum distribution (TMD) in dijet and heavy hadron pair (HHP) production in semi-inclusive deep inelastic scattering. The factorization of these processes in position space shows the appearance of a specific new soft factor matrix element on top of angular and complex valued anomalous dimensions. We show in detail how these features can be treated consistently and we discuss a scale prescription for the evolution kernel of the dijet soft function. As a result we obtain phenomenological predictions for unpolarized and angular modulated cross-sections for the electron-ion collider (EIC) using current available information on unpolarized TMD., Unión Europea. Horizonte 2020, Ministerio de Ciencia e Innovación (MICINN), Comunidad de Madrid/Universidad de Alcalá de Henares (UAH), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© The Author(s) 2022 GGM would like to thank Alfredo Luis for very useful discussions. Financial support was provided by the Spanish Government through the projects PID2020-118159GB-C43, PID2020118159GB-C44, FIS2017-86497-C2-1-P, FIS2017-86497-C2-2-P (with FEDERcontribution), and by the Junta deAndalucia through the project FQM219. CB and GGM acknowledge financial support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award to the Instituto de Astrofisica de Andalucia (SEV-2017-0709). GGM is funded by the Spanish Government fellowship FPU20/01684., Taking the principles of quantum mechanics as they stand and applying them to gravity, leads to the conclusion that one might be able to generate superpositions of spacetimes, at least formally. We analyze such a possibility from an analogue gravity perspective. We present an analogue toy model consisting of a Bose-Einstein condensate in a double-well potential and identify the states that could potentially be interpreted as superposition of effective spacetimes. These states are unstable and the source of instability from a microscopic point of view can be related to the absence of a well-defined causal structure in the effective geometric description. We explore the consequences of these instabilities and argue that they resonate with Penrose's ideas about the decay that superpositions of states with sufficiently different gravitational fields associated should experience., Ministerio de Ciencia e Innovación (MICINN)/ FEDER, Ministerio de Ciencia e Innovación (MICINN)/AEI, Ministerio de Universidades, Junta de Andalucia, Centros de Excelencia Severo Ochoa (MICINN), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© The Authors 2022 E. M-M. is funded by the NSERC Discovery program as well as his Ontario Early Researcher Award. Financial support was provided by Grants PID2020-118159GB-C43 and PID2020118159GB-C44 funded by MCIN/AEI/10.13039/501100011033 and by "ESF Investing in your future". Financial support was also provided by the Junta de Andalucia through the project FQM219. C. B. acknowledges financial support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award to the Instituto de Astrofisica de Andalucia (SEV-2017-0709). V. B. is funded by the Spanish Government fellowship FPU17/04471., In this work we analyse the potential for a warp drive spacetime to develop instabilities due to the presence of quantum matter. Particularly, we look for points of infinite blueshift (which are analogous to points of a black hole inner horizon, known for its semiclassical instability), and categorise them through the behaviour of geodesics in their vicinity. We find that warp-drive bubbles in dimension 2+1 or higher are in fact likely to be stable, as they generally contain only isolated points where divergences are approached, leading to a finite limit for the overall accumulation of destabilising energy. Furthermore, any semiclassical instabilities in the warp drive due to energy-density buildups can be further diminished with particular, more "aerodynamic" shapes and trajectories for the drive., Ministerio de Ciencia e Innovación (MICINN)/AEI, Ministerio de Universidades, Junta de Andalucia, Centros de Excelencia Severo Ochoa (MICINN), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2022 The Authors. This study was supported by Deutsche Forschungsgemeinschaft (DFG) through the research Unit FOR 2926, "Next Generation pQCD for Hadron Structure: Preparing for the EIC", project number 430915485. I.S. is supported by the Spanish Ministry grant PID2019106080GB-C21. This project has received funding from the European Union Horizon 2020 research and innovation program under grant agreement Num. 824093 (STRONG-2020). S.L.G. is supported by the Austrian Science Fund FWF under the Doctoral Program W1252-N27 Particles and Interactions., Transverse momentum dependent (TMD) distributions match collinear parton density functions (PDF) in the limit of small transverse distances, which is accounted for by global extractions of TMD distributions. We study the influence of the collinear PDF value and uncertainties on the determination of unpolarized TMD distributions and the description of Drell-Yan (DY) and Z-boson production measurements at low transverse momenta. We take into account, for the first time in fits including TMD evolution, flavordependent non-perturbative TMD profiles. We carry out a Bayesian analysis to incorporate the propagation of PDF uncertainties into TMD extractions. We find that collinear PDF uncertainties and non-perturbative TMD flavor dependence are both essential to obtain reliable TMD determinations, and should be included in future global analyses., Unión Europea. Horizonte 2020, Ministerio de Ciencia e Innovación (MICINN), German Research Foundation (DFG), Austrian Science Fund (FWF), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

A geometric approach to Sundman infnitesimal time-reparametrisation is given and some of its applications are used to illustrate the general theory. Special emphasis is put on geodesic motions and systems described by mechanical type Lagrangians. The Jacobi metric appears as a particular case of a Sundman transformation., Financial support from the Spanish Ministerio de Ciencia, Innovación y Universidades, projects PGC2018-098265-B-C31 and PGC2018-098265-B-C33 (MINECO, Madrid) and DGA project E48_20R Anánalysis física Matemática., Peer Reviewed, Postprint (published version)

© The Author(s) 2021 We thank Pier Monni, Alexey Vladimirov, Chen Wang (for D(empty set) collaboration), Aram Apyan (CMS collaboration) for valuable communications and suggestions. D.G.R. and I.S. are supported by the Spanish Ministry grant PID2019-106080GB-C21. D.G.R. acknowledges the support of the Universidad Complutense de Madrid through the predoctoral grant CT17/17-CT18/17. This project has received funding from the European Union Horizon 2020 research and innovation program under grant agreement Num. 824093 (STRONG-2020). S.L.G. is supported by the Austrian Science Fund FWF under the Doctoral Program W1252-N27 Particles and Interactions., At hadron colliders, the differential cross section for W production can be factorized and it is sensitive transverse momentum dependent distributions (TMD) for low boson transverse momentum. While, often, the corresponding non-perturbative QCD contributions are extrapolated from Z boson production, here we use an existing extraction (based on the code Artemide) of TMD which includes data coming from Drell-Yan and semi-inclusive deep inelastic scattering, to provide checks and predictions for the W case. Including fiducial cuts with different configurations and kinematical power corrections, we consider transverse momentum dependent cross sections within several intervals of the vector boson transverse mass. We perform the same study for the p(T)(W-)/p(T)(W+) and p(T)(Z)/p(T)(W) distributions. We compare our predictions with recent extractions of these quantities at ATLAS and CMS and results from TeVatron. The results encourage a broader experimental and phenomenological work, and a deeper study of TMD for the W case., Unión Europea. H2020, Ministerio de Ciencia e Innovación (MICINN), Universidad Complutense de Madrid, Austrian Science Fund (FWF), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2021 Springer The authors wish to thank the anonymous referees for useful suggestions, which improved the readability of the article. J.C. would like to thank Aleksander M. Kubicki for several enlightening discussions. G.M. would like to thank the support provided by the Santander/UC3M Excellence Chair Programme 2019/2020. The research of P.T. has been supported by the research project PGC2018-094898-B-I00, Ministerio de Ciencia, Innovacion y Universidades and Agencia Estatal de Investigacion, Spain, and by the Severo Ochoa Programme for Centres of Excellence in R&D (CEX2019-000904-S), Ministerio de Ciencia, Innovacion y Universidades y Agencia Estatal de Investigacion, Spain. G. M and P. T. are members of the Gruppo Nazionale di Fisica Matematica (INDAM), Italy., We present a mathematical construction of new quantum information measures that generalize the notion of logarithmic negativity. Our approach is based on formal group theory. We shall prove that this family of generalized negativity functions, due their algebraic properties, is suitable for studying entanglement in many-body systems. Under mild hypotheses, the new measures are computable entanglement monotones. Also, they are composable: their evaluation over tensor products can be entirely computed in terms of the evaluations over each factor, by means of a specific group law. In principle, they might be useful to study separability and (in a future perspective) criticality of mixed states, complementing the role of Renyi's entanglement entropy in the discrimination of conformal sectors for pure states., Ministerio de Ciencia, Innovacion y Universidades (MICINN), Centros de Excelencia Severo Ochoa (MICINN), Banco Santander/Universidad Carlos III de Madrid, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

CRUE-CSIC (Acuerdos Transformativos 2021) © The Author(s) 2021 the CRUE-CSIC agreement with Springer Nature. The authors gratefully thank Prof. Y. Kosmann-Schwarzbach for useful discussions. Also, P. T. wishes to thank heartily Prof. N. Kamran for a careful reading of the manuscript, discussions and encouragement. We also wish to thank the Referees for many helpful suggestions.The research of P. T. has been supported by the research project PGC2018-094898-B-I00, Ministerio de Ciencia, Innovación y Universidades and Agencia Estatal de Investigación, Spain, and by the Severo Ochoa Programme for Centres of Excellence in R&D (CEX2019-000904-S), Ministerio de Ciencia, Innovación y Universidades y Agencia Estatal de Investigación, Spain. The research of G. T. has been supported by the research project FRA2020-2021, Universitá degli Studi di Trieste, Italy. P. T. is member of the Gruppo Nazionale di Fisica Matematica (GNFM)., We propose a new, infinite class of brackets generalizing the Frolicher-Nijenhuis bracket. This class can be reduced to a family of generalized Nijenhuis torsions recently introduced. In particular, the Haantjes bracket, the first example of our construction, is relevant in the characterization of Haantjes moduli of operators. We also prove that the vanishing of a higher-level Nijenhuis torsion of an operator field is a sufficient condition for the integrability of its eigen-distributions. This result (which does not require any knowledge of the spectral properties of the operator) generalizes the celebrated Haantjes theorem. The same vanishing condition also guarantees that the operator can be written, in a local chart, in a block-diagonal form., Ministerio de Ciencia e Innovacion (MICINN), Centros de Excelencia Severo Ochoa (MICINN), Universitá degli Studi di Trieste, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© The Author(s) 2021 We are very grateful to Z. H. Guo for useful comments and to F. Karsch and A. Lahiri for providing detailed lattice results. Work partially supported by research contract PID2019106080GB-C21 (spanish "Ministerio de Ciencia e Innovacion"), the European Union Horizon 2020 research and innovation program under grant agreement No 824093 and the Swiss National Science Foundation, project No. PZ00P2_174228. A. V-R acknowledges support from a fellowship of the UCM predoctoral program., © The Author(s) 2021 We use recently derived Ward identities and lattice data for the light- and strange-quark condensates to reconstruct the scalar and pseudoscalar susceptibilities (chi S kappa, chi PK) in the isospin 1/2 channel. We show that chi S kappa develops a maximum above the QCD chiral transition, after which it degenerates with chi PK. We also obtain chi S kappa within Unitarized Chiral Perturbation Theory (UChPT) at finite temperature, when it is saturated with the K0(700) (or kappa) meson, the dominant lowest-energy state in the isospin 1/2 scalar channel of pi K scattering. Such UChPT result reproduces the expected peak structure, revealing the importance of thermal interactions, and makes it possible to examine the chi S kappa dependence on the light- and strange-quark masses. A consistent picture emerges controlled by the ml/ms ratio that allows one studying K-kappa degeneration in the chiral, two-flavor and SU(3) limits. These results provide an alternative sign for O(4)xU(1)A restoration that can be explored in lattice simulations and highlight the role of strangeness, which regulated by the strange-quark condensate helps to reconcile the current tension among lattice results regarding U(1)A restoration., Unión Europea. H2020, Ministerio de Ciencia e Innovación (MICINN), Swiss National Science Foundation (SNSF), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© The Authors. M.G.E., R.F.C. and I.S. are supported by the Spanish Ministry grant PID2019-106080GB-C21. This project has received funding from the European Union Horizon 2020 research and innovation program under grant agreement Num. 824093 (STRONG-2020). Y.M. is supported by the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 754496-FELLINI., We study a transverse momentum dependent (TMD) factorization framework for the processes of dijet and heavy-meson pair production in deep-inelastic-scattering in an electron-proton collider, considering the measurement of the transverse momentum imbalance of the two hard probes in the Breit frame. For the factorization theorem we employ soft-collinear and boosted-heavy-quark effective field theories. The factorized cross-section for both processes is sensitive to gluon unpolarized and linearly polarized TMD distributions and requires the introduction of a new soft function. We calculate the new soft function here at one-loop, regulating rapidity divergences with the delta -regulator. In addition, using a factorization consistency relation and a universality argument regarding the heavy-quark jet function, we obtain the anomalous dimension of the new soft function at two and three loops., Unión Europea. Horizonte 2020, Ministerio de Ciencia e Innovación (MICINN), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

In this article, subleading (in 1/N) corrections to the action of the one loop dilatation operator in the su(3) sector of N = 4 super Yang-Mills theory are studied. We focus on the system of operators dual to two giant graviton systems, which have a bare dimension ∼ O(N) and are a linear combination of restricted Schur polynomials with p = 2 long columns. At the leading order the dilatation operator gives rise to the free part of an emergent Yang-Mills theory, arising from the open string excitations of the giant gravitons. We verify that the terms we study describe interactions between these open string excitations. The interactions have the U(1)×U(1) gauge invariance expected for a pair of separated branes., Ministerio de Ciencia e Innovación (MICINN)/FEDER, Centro de Excelencia Severo Ochoa, Junta de Andalucía, IPARCOS, Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub