Persona: Rodríguez Laguna, Javier
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0000-0003-2218-7980
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Rodríguez Laguna
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Javier
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Publicación Nonuniversality of front fluctuations for compact colonies of nonmotile bacteria(American Physical Society, 2018-07-10) Santalla, Silvia N.; Abad, José P.; Marín, Irma; Muñoz García, Javier; Vázquez, Luis; Cuerno, Rodolfo; Rodríguez Laguna, Javier; Espinosa Escudero, María del MarThe front of a compact bacterial colony growing on a Petri dish is a paradigmatic instance of non-equilibrium fluctuations in the celebrated Eden, or Kardar-Parisi-Zhang (KPZ), universality class. While in many experiments the scaling exponents crucially differ from the expected KPZ values, the source of this disagreement has remained poorly understood. We have performed growth experiments with B. subtilis 168 and E. coli ATCC 25922 under conditions leading to compact colonies in the classically alleged Eden regime, where individual motility is suppressed. Non-KPZ scaling is indeed observed for all accessible times, KPZ asymptotics being ruled out for our experiments due to the monotonic increase of front branching with time. Simulations of an effective model suggest the occurrence of transient nonuniversal scaling due to diffusive morphological instabilities, agreeing with expectations from detailed models of the relevant biological reaction-diffusion processes.Publicación Entanglement as geometry and flow(American Physical Society, 2020-05-20) Singha Roy, Sudipto; Santalla, Silvia N.; Sierra, Germán; Rodríguez Laguna, JavierWe explore the connection between the area law for entanglement and geometry by representing the entanglement entropies corresponding to all 2 N bipartitions of an N -party pure quantum system by means of a (generalized) adjacency matrix. In the cases where the representation is exact, the elements of that matrix coincide with the mutual information between pairs of sites. In others, it provides a very good approximation, and in all the cases it yields a natural entanglement contour which is similar to previous proposals. Moreover, for one-dimensional conformal invariant systems, the generalized adjacency matrix is given by the two-point correlator of an entanglement current operator. We conjecture how this entanglement current may give rise to a metric entirely built from entanglement.Publicación Ergotropy and entanglement in critical spin chains(American Physical Society, 2023-02-08) Mula, Begoña; Fernández, Julio J.; Santalla, Silvia N.; Alvarellos Bermejo, José Enrique; García Aldea, David; Rodríguez Laguna, Javier; Fernández Sánchez, EvamaríaA subsystem of an entangled ground state (GS) is in a mixed state. Thus, if we isolate this subsystem from its surroundings, we may be able to extract work applying unitary transformations, up to a maximal amount which is called ergotropy. Once this work has been extracted, the subsystem will still contain some bound energy above its local GS, which can provide valuable information about the entanglement structure. We show that the bound energy for half a free fermionic chain decays as the square of the entanglement entropy divided by the chain length, thus approaching zero for large system sizes, and we conjecture that this relation holds for all one-dimensional critical states.Publicación Casimir forces on deformed fermionic chains(American Physical Society, 2021-01-20) Mula, Begoña; Santalla, Silvia N.; Rodríguez Laguna, JavierWe characterize the Casimir forces for the Dirac vacuum on free-fermionic chains with smoothly varying hopping amplitudes, which correspond to ( 1 + 1 )-dimensional [( 1 + 1 )D] curved spacetimes with a static metric in the continuum limit. The first-order energy potential for an obstacle on that lattice corresponds to the Newtonian potential associated with the metric, while the finite-size corrections are described by a curved extension of the conformal field theory predictions, including a suitable boundary term. We show that for weak deformations of the Minkowski metric, Casimir forces measured by a local observer at the boundary are universal. We provide numerical evidence for our results on a variety of (1+1)D deformations: Minkowski, Rindler, anti–de Sitter (the so-called rainbow system), and sinusoidal metrics. Moreover, we show that interactions do not preclude our conclusions, exemplifying this with the deformed Heisenberg chain.Publicación Piercing the rainbow state: Entanglement on an inhomogeneous spin chain with a defect(American Physical Society, 2021-05-15) Sáenz de Buruaga, Nadir Samos; Santalla, Silvia N.; Sierra, Germán; Rodríguez Laguna, JavierThe rainbow state denotes a set of valence bond states organized concentrically around the center of a spin 1/2 chain. It is the ground state of an inhomogeneous XX Hamiltonian and presents a maximal violation of the area law of entanglement entropy. Here, we add a tunable exchange coupling constant at the center, γ , and show that it induces entanglement transitions of the ground state. At very strong inhomogeneity, the rainbow state survives for 0≤γ≤1 , while outside that region the ground state is a product of dimers. In the weak inhomogeneity regime, the entanglement entropy satisfies a volume law, derived from CFT in curved space-time, with an effective central charge that depends on the inhomogeneity parameter and γ . In all regimes we have found that the entanglement properties are invariant under the transformation γ ⟷ 1 − γ , whose fixed point γ = 1 / 2 corresponds to the usual rainbow model. Finally, we study the robustness of nontrivial topological phases in the presence of the defect.Publicación Nanowire reconstruction under external magnetic fields(AIP, 2020-12-23) Santalla, Silvia N.; Alvarellos Bermejo, José Enrique; Rodríguez Laguna, Javier; Fernández Sánchez, EvamaríaWe consider the different structures that a magnetic nanowire adsorbed on a surface may adopt under the influence of external magnetic or electric fields. First, we propose a theoretical framework based on an Ising-like extension of the 1D Frenkel–Kontorova model, which is analyzed in detail using the transfer matrix formalism, determining a rich phase diagram displaying structural reconstructions at finite fields and an antiferromagnetic–paramagnetic phase transition of second order. Our conclusions are validated using ab initio calculations with density functional theory, paving the way for the search of actual materials where this complex phenomenon can be observed in the laboratory.