RECERCAT - Articles publicats en revistes (Estructura i Constituents de la Matèria)
http://www.recercat.cat:80/handle/2072/48808
www.ub.eduSat, 26 Jul 2014 13:10:06 GMT2014-07-26T13:10:06ZThe Channel Imagehttp://www.recercat.cat:80/bitstream/id/26376/
http://www.recercat.cat:80/handle/2072/48808
A study of the Z production cross-section in pp collisions at s√=7 TeV using tau final states
http://www.recercat.cat:80/handle/2072/238225
A study of the Z production cross-section in pp collisions at s√=7 TeV using tau final states
Abellan Beteta, C.; Calvo Gómez, M.; Camboni, Alessandro; Comerma Montells, Albert; Domingo Bonal, F.; Garrido Beltrán, Lluís; Grabalosa Gándara, M.; Graciani Díaz, Ricardo; Graugés Pous, Eugeni; López Asamar, E.; Pérez-Calero Yzquierdo, Antonio; Picatoste Olloqui, Eduardo; Pie Valls, Blai; Potterat, Cédric; Rives Molina, V.; Ruiz, Hugo (Ruiz Pérez); Vázquez Gómez, R.; Vilasis-Cardona, X.; LHCb Collaboration
A measurement of the inclusive Z → ττ cross-section in pp collisions at s√=7TeV is presented based on a dataset of 1.0 fb−1 collected by the LHCb detector. Candidates for Z → τ τ decays are identified through reconstructed final states with two muons, a muon and an electron, a muon and a hadron, or an electron and a hadron. The production cross-section for Z bosons, with invariant mass between 60 and 120 GeV/c 2, which decay to τ leptons with transverse momenta greater than 20 GeV/c and pseudorapidities between 2.0 and 4.5, is measured to be σ pp→Z→ττ = 71.4 ± 3.5 ± 2.8 ± 2.5 pb; the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the integrated luminosity. The ratio of the cross-sections for Z → τ τ to Z → μμ is determined to be 0.93 ± 0.09, where the uncertainty is the combination of statistical, systematic, and luminosity uncertainties of the two measurements.
http://www.recercat.cat:80/handle/2072/238225V0 production in p+A collisions at √s = 41.6 GeV
http://www.recercat.cat:80/handle/2072/238224
V0 production in p+A collisions at √s = 41.6 GeV
Conde, P.; Garrido Beltrán, Lluís; Peralta, D.; HERA-B Collaboration
Inclusive doubly differential cross sections d 2 σ pA /dx F dp T 2 as a function of Feynman-x (x F ) and transverse momentum (p T ) for the production of K S 0 , Λ and Λ¯ in proton-nucleus interactions at 920 GeV are presented. The measurements were performed by HERA-B in the negative x F range (−0.12<x F <0.0) and for transverse momenta up to p T =1.6 GeV/c. Results for three target materials: carbon, titanium and tungsten are given. The ratios of production cross sections are presented and discussed. The Cronin effect is clearly observed for all three V 0 species. The atomic number dependence is parameterized as σ pA =σ pN ⋅A α where σ pN is the proton-nucleon cross section. The measured values of α are all near one. The results are compared with EPOS 1.67 and PYTHIA 6.3. EPOS reproduces the data to within ≈20% except at very low transverse momentum.
http://www.recercat.cat:80/handle/2072/238224Transfer entropy reconstruction and labeling of neuronal connections from simulated calcium imaging
http://www.recercat.cat:80/handle/2072/237838
Transfer entropy reconstruction and labeling of neuronal connections from simulated calcium imaging
Orlandi, Javier G.; Stetter, Olav; Soriano i Fradera, Jordi; Geisel, Theo; Battaglia, Demian
Neuronal dynamics are fundamentally constrained by the underlying structural network architecture, yet much of the details of this synaptic connectivity are still unknown even in neuronal cultures in vitro. Here we extend a previous approach based on information theory, the Generalized Transfer Entropy, to the reconstruction of connectivity of simulated neuronal networks of both excitatory and inhibitory neurons. We show that, due to the model-free nature of the developed measure, both kinds of connections can be reliably inferred if the average firing rate between synchronous burst events exceeds a small minimum frequency. Furthermore, we suggest, based on systematic simulations, that even lower spontaneous inter-burst rates could be raised to meet the requirements of our reconstruction algorithm by applying a weak spatially homogeneous stimulation to the entire network. By combining multiple recordings of the same in silico network before and after pharmacologically blocking inhibitory synaptic transmission, we show then how it becomes possible to infer with high confidence the excitatory or inhibitory nature of each individual neuron.
http://www.recercat.cat:80/handle/2072/237838Integració del Racó de l'estudiant a l'entorn Android
http://www.recercat.cat:80/handle/2072/232366
Integració del Racó de l'estudiant a l'entorn Android
Sala Angordans, Roger
El projecte consisteix en integrar les principals funcionalitats del Racó de l'estudiant als dispositius mòbils Android. Concretament, la consulta d'avisos de les assignatures, el correu, l'ocupació de les aules, l'horari personal i l'agenda. Addicionalment, les notícies de la FIB i la localització.; Award-winning; Premi FIB Alumni al millor Projecte Final de Carrera (curs 2011-2012)
http://www.recercat.cat:80/handle/2072/232366Anomalies related to the TA2 phonon mode condensation in the Heusler Ni2MnGa alloy
http://www.recercat.cat:80/handle/2072/232365
Anomalies related to the TA2 phonon mode condensation in the Heusler Ni2MnGa alloy
Mañosa, Lluís; Gonzàlez Comas, Alfons; Obradó Llauradó, Eduard; Planes Vila, Antoni; Chernenko, V. A.; Kokorin, V. V.; Cesari, Eduard
http://www.recercat.cat:80/handle/2072/232365Symmetries of the free Schrödinger equation in the non-commutative plane
http://www.recercat.cat:80/handle/2072/230929
Symmetries of the free Schrödinger equation in the non-commutative plane
Batlle, C.; Gomis Torné, Joaquim; Kamimura, Kiyoshi
We study all the symmetries of the free Schr odinger equation in the non-commu- tative plane. These symmetry transformations form an infinite-dimensional Weyl algebra that appears naturally from a two-dimensional Heisenberg algebra generated by Galilean boosts and momenta. These infinite high symmetries could be useful for constructing non-relativistic interacting higher spin theories. A finite-dimensional subalgebra is given by the Schröodinger algebra which, besides the Galilei generators, contains also the dilatation and the expansion. We consider the quantization of the symmetry generators in both the reduced and extended phase spaces, and discuss the relation between both approaches.
http://www.recercat.cat:80/handle/2072/230929Symmetries of the free Schrödinger equation in the non-commutative plane
http://www.recercat.cat:80/handle/2072/230930
Symmetries of the free Schrödinger equation in the non-commutative plane
Batlle, C.; Gomis Torné, Joaquim; Kamimura, Kiyoshi
We study all the symmetries of the free Schrödinger equation in the non-commu- tative plane. These symmetry transformations form an infinite-dimensional Weyl algebra that appears naturally from a two-dimensional Heisenberg algebra generated by Galilean boosts and momenta. These infinite high symmetries could be useful for constructing non-relativistic interacting higher spin theories. A finite-dimensional subalgebra is given by the Schröodinger algebra which, besides the Galilei generators, contains also the dilatation and the expansion. We consider the quantization of the symmetry generators in both the reduced and extended phase spaces, and discuss the relation between both approaches.
http://www.recercat.cat:80/handle/2072/230930Dynamical sectors of a relativistic two particle model
http://www.recercat.cat:80/handle/2072/230928
Dynamical sectors of a relativistic two particle model
Dominici, D.; Gomis Torné, Joaquim; Kamimura, Kiyoshi; Longhi, G.
We reconsider a model of two relativistic particles interacting via a multiplicative potential, as an example of a simple dynamical system with sectors, or branches, with different dynamics and degrees of freedom. The presence or absence of sectors depends on the values of rest masses. Some aspects of the canonical quantization are described. The model could be interpreted as a bigravity model in one dimension.
http://www.recercat.cat:80/handle/2072/230928Monitoring the decreasing trend of testicular cancer mortality in Spain during 2005-2019 through a Bayesian approach
http://www.recercat.cat:80/handle/2072/228923
Monitoring the decreasing trend of testicular cancer mortality in Spain during 2005-2019 through a Bayesian approach
Clèries Soler, Ramon; Martínez, José Miguel; Escribà, Josep Maria; Esteban, Laura; Pareja, Laura; Borràs Andrés, Josep Maria; Ribes Puig, Josepa
Purpose : To assess time trends of testicular cancer (TC) mortality in Spain for period 1985-2019 for age groups 15-74 years old through a Bayesian age-period-cohort (APC) analysis. Methods: A Bayesian age-drift model has been fitted to describe trends. Projections for 2005-2019 have been calculated by means of an autoregressive APC model. Prior precision for these parameters has been selected through evaluation of an adaptive precision parameter and 95% credible intervals (95% CRI) have been obtained for each model parameter. Results: A decrease of -2.41% (95% CRI: -3.65%; -1.13%) per year has been found for TC mortality rates in age groups 15-74 during 1985-2004, whereas mortality showed a lower annual decrease when data was restricted to age groups 15-54 (-1.18%; 95% CRI: -2.60%; -0.31%). During 2005-2019 is expected a decrease of TC mortality of 2.30% per year for men younger than 35, whereas a leveling off for TC mortality rates is expected for men older than 35. Conclusions: A Bayesian approach should be recommended to describe and project time trends for those diseases with low number of cases. Through this model it has been assessed that management of TC and advances in therapy led to decreasing trend of TC mortality during the period 1985-2004, whereas a leveling off for these trends can be considered during 2005-2019 among men older than 35.
http://www.recercat.cat:80/handle/2072/228923Nonmesonic weak decay of the hypertriton
http://www.recercat.cat:80/handle/2072/228922
Nonmesonic weak decay of the hypertriton
Bennhold, Cornelius; Ramos Gómez, Àngels; Aruliah, D. A.; Oelfke, U.
http://www.recercat.cat:80/handle/2072/228922Atomic Ordering and Martensitic Transitions in Cu-Zn-Al Shape Memory Alloys
http://www.recercat.cat:80/handle/2072/228220
Atomic Ordering and Martensitic Transitions in Cu-Zn-Al Shape Memory Alloys
Macqueron, J. L.; Morin, Michel; Guénin, G.; Planes Vila, Antoni; Elgueta, J.; Castán i Vidal, Maria Teresa
We present results from both, calorimetric and dilatometric studies of the isothermal ordering process taking place in a Cu-Zn-Al shape memory alloy after quenches from Tq temperatures ranging from 350 K to 1200 K. The dissipated energy and the length variations of the system are obtained during the process. The change of these quantities in the whole process have been compared with the difference [MATH] between Ms, measured after the relaxation and Ms measured just after the quench. We obtain that these three quantities present, as a function of Tq, the same qualitative behaviour. These changes are then associated with changes of the L21 ordering after the quench in the system. The relaxational process does not follow a single exponential decay. Instead, a continuous slowing down is observed. A relaxation time [MATH] has been defined to characterize the relaxation rate. We show that [MATH] depends on both the annealing and the quenching (Tq [MATH] 800 K) temperatures through an Arrhenius law.
http://www.recercat.cat:80/handle/2072/228220Identification of neuronal network properties from the spectral analysis of calcium imaging signals in neuronal cultures
http://www.recercat.cat:80/handle/2072/228080
Identification of neuronal network properties from the spectral analysis of calcium imaging signals in neuronal cultures
Tibau, Elisenda; Valencia, Miguel; Soriano i Fradera, Jordi
Neuronal networks in vitro are prominent systems to study the development of connections in living neuronal networks and the interplay between connectivity, activity and function. These cultured networks show a rich spontaneous activity that evolves concurrently with the connectivity of the underlying network. In this work we monitor the development of neuronal cultures, and record their activity using calcium fluorescence imaging. We use spectral analysis to characterize global dynamical and structural traits of the neuronal cultures. We first observe that the power spectrum can be used as a signature of the state of the network, for instance when inhibition is active or silent, as well as a measure of the network's connectivity strength. Second, the power spectrum identifies prominent developmental changes in the network such as GABAA switch. And third, the analysis of the spatial distribution of the spectral density, in experiments with a controlled disintegration of the network through CNQX, an AMPA-glutamate receptor antagonist in excitatory neurons, reveals the existence of communities of strongly connected, highly active neurons that display synchronous oscillations. Our work illustrates the interest of spectral analysis for the study of in vitro networks, and its potential use as a network-state indicator, for instance to compare healthy and diseased neuronal networks.
http://www.recercat.cat:80/handle/2072/228080Topological phases in small quantum Hall samples
http://www.recercat.cat:80/handle/2072/227666
Topological phases in small quantum Hall samples
Grass, Tobias; Juliá-Díaz, Bruno; Lewenstein, M.
Topological order has proven a useful concept to describe quantum phase transitions which are not captured by the Ginzburg-Landau type of symmetry-breaking order. However, lacking a local order parameter, topological order is hard to detect. One way to detect it is via direct observation of anyonic properties of excitations which are usually discussed in the thermodynamic limit, but so far has not been realized in macroscopic quantum Hall samples. Here we consider a system of few interacting bosons subjected to the lowest Landau level by a gauge potential, and theoretically investigate vortex excitations in order to identify topological properties of different ground states. Our investigation demonstrates that even in surprisingly small systems anyonic properties are able to characterize the topological order. In addition, focusing on a system in the Laughlin state, we study the robustness of its anyonic behavior in the presence of tunable finite-range interactions acting as a perturbation. A clear signal of a transition to a different state is reflected by the system's anyonic properties.
http://www.recercat.cat:80/handle/2072/227666Asymmetric stochastic switching driven by intrinsic molecular noise
http://www.recercat.cat:80/handle/2072/227173
Asymmetric stochastic switching driven by intrinsic molecular noise
Frigola, David; Casanellas Vilageliu, Laura; Sancho, José M.; Ibañes Miguez, Marta
Low-copy-number molecules are involved in many functions in cells. The intrinsic fluctuations of these numbers can enable stochastic switching between multiple steady states, inducing phenotypic variability. Herein we present a theoretical and computational study based on Master Equations and Fokker-Planck and Langevin descriptions of stochastic switching for a genetic circuit of autoactivation. We show that in this circuit the intrinsic fluctuations arising from low-copy numbers, which are inherently state-dependent, drive asymmetric switching. These theoretical results are consistent with experimental data that have been reported for the bistable system of the gallactose signaling network in yeast. Our study unravels that intrinsic fluctuations, while not required to describe bistability, are fundamental to understand stochastic switching and the dynamical relative stability of multiple states.
http://www.recercat.cat:80/handle/2072/227173Asymmetric stochastic switching driven by intrinsic molecular noise
http://www.recercat.cat:80/handle/2072/227133
Asymmetric stochastic switching driven by intrinsic molecular noise
Frigola, David; Casanellas Vilageliu, Laura; Sancho, José M.; Ibañes Miguez, Marta
Low-copy-number molecules are involved in many functions in cells. The intrinsic fluctuations of these numbers can enable stochastic switching between multiple steady states, inducing phenotypic variability. Herein we present a theoretical and computational study based on Master Equations and Fokker-Planck and Langevin descriptions of stochastic switching for a genetic circuit of autoactivation. We show that in this circuit the intrinsic fluctuations arising from low-copy numbers, which are inherently state-dependent, drive asymmetric switching. These theoretical results are consistent with experimental data that have been reported for the bistable system of the gallactose signaling network in yeast. Our study unravels that intrinsic fluctuations, while not required to describe bistability, are fundamental to understand stochastic switching and the dynamical relative stability of multiple states.
http://www.recercat.cat:80/handle/2072/227133Langevin equations with multiplicative noise: Application to domain growth
http://www.recercat.cat:80/handle/2072/226985
Langevin equations with multiplicative noise: Application to domain growth
Sancho, José M.; Hernández Machado, Aurora; Ramírez de la Piscina, Laureano; Lacasta Palacio, Ana María
Langevin Equations of Ginzburg<br>Landau form, with multiplicative noise, are proposed to study the effects of fluctuations in domain growth. These equations are derived from a coarse-grained methodology. The Cahn<br>Hiliard<br>Cook linear stability analysis predicts some effects in the transitory regime. We also derive numerical algorithms for the computer simulation of these equations. The numerical results corroborate the analytical predictions of the linear analysis. We also present simulation results for spinodal decomposition at large times.
http://www.recercat.cat:80/handle/2072/226985Percolation of spatially constrained Erdos-R enyi networks with degree correlations
http://www.recercat.cat:80/handle/2072/224825
Percolation of spatially constrained Erdos-R enyi networks with degree correlations
Schmeltzer, C.; Soriano i Fradera, Jordi; Sokolov, Igor M., 1958-; Rüdiger, S.
Motivated by experiments on activity in neuronal cultures [J. Soriano, M. Rodr ́ıguez Mart́ınez, T. Tlusty, and E. Moses, Proc. Natl. Acad. Sci. 105, 13758 (2008)], we investigate the percolation transition and critical exponents of spatially embedded Erd̋os-Ŕenyi networks with degree correlations. In our model networks, nodes are randomly distributed in a two-dimensional spatial domain, and the connection probability depends on Euclidian link length by a power law as well as on the degrees of linked nodes. Generally, spatial constraints lead to higher percolation thresholds in the sense that more links are needed to achieve global connectivity. However, degree correlations favor or do not favor percolation depending on the connectivity rules. We employ two construction methods to introduce degree correlations. In the first one, nodes stay homogeneously distributed and are connected via a distance- and degree-dependent probability. We observe that assortativity in the resulting network leads to a decrease of the percolation threshold. In the second construction methods, nodes are first spatially segregated depending on their degree and afterwards connected with a distance-dependent probability. In this segregated model, we find a threshold increase that accompanies the rising assortativity. Additionally, when the network is constructed in a disassortative way, we observe that this property has little effect on the percolation transition.
http://www.recercat.cat:80/handle/2072/224825Quantum Hall Phases of two-component bosons
http://www.recercat.cat:80/handle/2072/224824
Quantum Hall Phases of two-component bosons
Grass, Tobias; Raventós, D.; Lewenstein, M.; Juliá-Díaz, Bruno
The recent production of synthetic magnetic fields acting on electroneutral particles, such as atoms or photons, has boosted interest in the quantum Hall physics of bosons. Adding pseudospin 1/2 to the bosons greatly enriches the scenario, as it allows them to form an interacting integer quantum Hall (IQH) phase with no fermionic counterpart. Here we show that, for a small two-component Bose gas on a disk, the complete strongly correlated regime, extending from the integer phase at filling factor ν = 2 to the Halperin phase at filling factor ν = 2 / 3, is well described by composite fermionization of the bosons. Moreover we study the edge excitations of the IQH state, which, in agreement with expectations from topological field theory, are found to consist of forward-moving charge excitations and backward-moving spin excitations. Finally, we demonstrate how pair-correlation functions allow one to experimentally distinguish the IQH state from competing states, such as non-Abelian spin singlet (NASS) states.
http://www.recercat.cat:80/handle/2072/224824Matching stages of heavy-ion collision models
http://www.recercat.cat:80/handle/2072/224722
Matching stages of heavy-ion collision models
Cheng, Yun; Csernai, L. P.; Magas, V. K.; Schlei, B. R.; Strottman, D.
Heavy-ion reactions and other collective dynamical processes are frequently described by different theoretical approaches for the different stages of the process, like initial equilibration stage, intermediate locally equilibrated fluid dynamical stage, and final freeze-out stage. For the last stage, the best known is the Cooper-Frye description used to generate the phase space distribution of emitted, noninteracting particles from a fluid dynamical expansion or explosion, assuming a final ideal gas distribution, or (less frequently) an out-of-equilibrium distribution. In this work we do not want to replace the Cooper-Frye description, but rather clarify the ways of using it and how to choose the parameters of the distribution and, eventually, how to choose the form of the phase space distribution used in the Cooper-Frye formula. Moreover, the Cooper-Frye formula is used in connection with the freeze-out problem, while the discussion of transition between different stages of the collision is applicable to other transitions also. More recently, hadronization and molecular dynamics models have been matched to the end of a fluid dynamical stage to describe hadronization and freeze-out. The stages of the model description can be matched to each other on space-time hypersurfaces (just like through the frequently used freeze-out hypersurface). This work presents a generalized description of how to match the stages of the description of a reaction to each other, extending the methodology used at freeze-out, in simple covariant form which is easily applicable in its simplest version for most applications.
http://www.recercat.cat:80/handle/2072/224722Local description of quantum inseparability
http://www.recercat.cat:80/handle/2072/224721
Local description of quantum inseparability
Sanpera Trigueros, Anna; Tarrach, R., 1948-; Vidal Bonafont, Guifré
We show how to decompose any density matrix of the simplest binary composite systems, whether separable or not, in terms of only product vectors. We determine for all cases the minimal number of product vectors needed for such a decomposition. Separable states correspond to mixing from one to four pure product states. Inseparable states can be described as pseudomixtures of four or five pure product states, and can be made separable by mixing them with one or two pure product states.
http://www.recercat.cat:80/handle/2072/224721On the interplay between Q^2 and t dependence in exclusive diffractive production of real photons and vector mesons in ep collisions
http://www.recercat.cat:80/handle/2072/224463
On the interplay between Q^2 and t dependence in exclusive diffractive production of real photons and vector mesons in ep collisions
Fiore, Roberto; Jenkovszky, Lázsló L.; Lavorini, A.; Magas, V. K.
We show how the familiar phenomenological way of combining the Q2 (photon virtuality) and t (squared momentum transfer) dependences of the scattering amplitude in Deeply Virtual Compton Scattering (DVCS) [1, 2] and Vector Meson Production (VMP) [2] processes can be understood in an off-mass-shell generalization of dual amplitudes with Mandelstam analyticity [3]. By comparing different approaches, we managed also to constrain the numerical values of the free parameters.
http://www.recercat.cat:80/handle/2072/224463Low-mass diffraction dissociation at the LHC ; role of the background
http://www.recercat.cat:80/handle/2072/224462
Low-mass diffraction dissociation at the LHC ; role of the background
Jenkovszky, Lázsló L.; Kuprash, O. E.; Magas, V. K.
A dual model with a nonlinear proton Regge trajectory in the missing mass (M_X^2) channel is constructed. A background based on a direct-channel exotic trajectory, developed and applied earlier for the inclusive electron-proton cross section description in the nucleon resonance region, is used. The parameters of the model are determined from the extrapolations to earlier experiments. Predictions for the low-mass (2 < M_X^2 < 8GeV^2) diffraction dissociation cross sections at the LHC energies are given.
http://www.recercat.cat:80/handle/2072/224462Momentum dependence of the phi-meson nuclear transparency
http://www.recercat.cat:80/handle/2072/224409
Momentum dependence of the phi-meson nuclear transparency
Hartmann, M.; Kiselev, Yu. T.; Polyanskiy, A.; Paryev, E. Ya.; Büscher, M.; Chiladze, D.; Dymov, S.; Dzyuba, A.; Gebel, R.; Hejny, V.; Kämpfer, B.; Keshelashvili, I.; Koptev, V.; Lorentz, B.; Maeda, Y.; Magas, V. K.; Merzliakov, S.; Mikirtytchiants, S.; Nekipelov, M.; Ohm, H.
The production of φ mesons in proton collisions with C, Cu, Ag, and Au targets has been studied via the φ → K + K − decay at an incident beam energy of 2.83 GeV using the ANKE detector system at COSY. For the first time, the momentum dependence of the nuclear transparency ratio, the in-medium φ width, and the differential cross section for φ -meson production at forward angles have been determined for these targets over the momentum range of 0.6-1.6 GeV /c. There are indications of a significant momentum dependence in the value of the extracted φ width, which corresponds to an effective φN absorption cross section in the range of 14-21 mb.
http://www.recercat.cat:80/handle/2072/224409Fluid dynamical prediction of changed v1-flow at energies available at the CERN Large Hadron Collider
http://www.recercat.cat:80/handle/2072/224408
Fluid dynamical prediction of changed v1-flow at energies available at the CERN Large Hadron Collider
Csernai, L. P.; Magas, V. K.; Stöcker, Horst; Strottman, D.
Substantial collective flow is observed in collisions between lead nuclei at Large Hadron Collider (LHC) as evidenced by the azimuthal correlations in the transverse momentum distributions of the produced particles. Our calculations indicate that the global v1-flow, which at RHIC peaked at negative rapidities (named third flow component or antiflow), now at LHC is going to turn toward forward rapidities (to the same side and direction as the projectile residue). Potentially this can provide a sensitive barometer to estimate the pressure and transport properties of the quark-gluon plasma. Our calculations also take into account the initial state center-of-mass rapidity fluctuations, and demonstrate that these are crucial for v1 simulations. In order to better study the transverse momentum flow dependence we suggest a new"symmetrized" vS1(pt) function, and we also propose a new method to disentangle global v1 flow from the contribution generated by the random fluctuations in the initial state. This will enhance the possibilities of studying the collective Global v1 flow both at the STAR Beam Energy Scan program and at LHC.
http://www.recercat.cat:80/handle/2072/224408Quantum chaos in SU(3) models with trapped ions
http://www.recercat.cat:80/handle/2072/222876
Quantum chaos in SU(3) models with trapped ions
Grass, Tobias; Juliá-Díaz, Bruno; Kus, Marek; Lewenstein, M.
A scheme to generate long-range spin-spin interactions between three-level ions in a chain is presented, providing a feasible experimental route to the rich physics of well-known SU(3) models. In particular, we demonstrate different signatures of quantum chaos which can be controlled and observed in experiments with trapped ions.
http://www.recercat.cat:80/handle/2072/222876Giant monopole energies from a constrained relativistic mean-field approach
http://www.recercat.cat:80/handle/2072/220110
Giant monopole energies from a constrained relativistic mean-field approach
Chen, Wei-Chia; Piekarewicz, J.; Centelles Aixalà, Mario
Background:Average energies of nuclear collective modes may be efficiently and accurately computed using a nonrelativistic constrained approach without reliance on a random phase approximation (RPA). Purpose: To extend the constrained approach to the relativistic domain and to establish its impact on the calibration of energy density functionals. Methods: Relativistic RPA calculations of the giant monopole resonance (GMR) are compared against the predictions of the corresponding constrained approach using two accurately calibrated energy density functionals. Results: We find excellent agreement at the 2% level or better between the predictions of the relativistic RPA and the corresponding constrained approach for magic (or semimagic) nuclei ranging from 16 O to 208 Pb. Conclusions: An efficient and accurate method is proposed for incorporating nuclear collective excitations into the calibration of future energy density functionals.
http://www.recercat.cat:80/handle/2072/220110Electric dipole polarizability in 208Pb: insights from the droplet model
http://www.recercat.cat:80/handle/2072/220109
Electric dipole polarizability in 208Pb: insights from the droplet model
Roca-Maza, X.; Brenna, M.; Colò, G.; Centelles Aixalà, Mario; Viñas Gausí, Xavier; Agrawal, B. K.; Paar, N.; Vretenar, D.; Piekarewicz, J.
We study the electric dipole polarizability α D in 208 Pb based on the predictions of a large and representative set of relativistic and nonrelativistic nuclear mean-field models. We adopt the droplet model as a guide to better understand the correlations between α D and other isovector observables. Insights from the droplet model suggest that the product of α D and the nuclear symmetry energy at saturation density J is much better correlated with the neutron skin thickness r np of 208 Pb than the polarizability alone. Correlations of α D J with r np and with the symmetry energy slope parameter L suggest that α D J is a strong isovector indicator. Hence, we explore the possibility of constraining the isovector sector of the nuclear energy density functional by comparing our theoretical predictions against measurements of both α D and the parity-violating asymmetry in 208 Pb. We find that the recent experimental determination of α D in 208 Pb in combination with the range for the symmetry energy at saturation density J = [31 ± (2) est] MeV suggests r np (208 Pb) = 0 . 165 ± (0 . 009) expt ± (0 . 013) theor ± (0.021) est fm and L = 43 ± (6) expt ± (8) theor ± (12) est MeV
http://www.recercat.cat:80/handle/2072/220109Model-Free Reconstruction of Excitatory Neuronal Connectivity from Calcium Imaging Signals
http://www.recercat.cat:80/handle/2072/218394
Model-Free Reconstruction of Excitatory Neuronal Connectivity from Calcium Imaging Signals
Stetter, Olav; Battaglia, Demian; Soriano i Fradera, Jordi; Geisel, Theo
A systematic assessment of global neural network connectivity through direct electrophysiological assays has remained technically infeasible, even in simpler systems like dissociated neuronal cultures. We introduce an improved algorithmic approach based on Transfer Entropy to reconstruct structural connectivity from network activity monitored through calcium imaging. We focus in this study on the inference of excitatory synaptic links. Based on information theory, our method requires no prior assumptions on the statistics of neuronal firing and neuronal connections. The performance of our algorithm is benchmarked on surrogate time series of calcium fluorescence generated by the simulated dynamics of a network with known ground-truth topology. We find that the functional network topology revealed by Transfer Entropy depends qualitatively on the time-dependent dynamic state of the network (bursting or non-bursting). Thus by conditioning with respect to the global mean activity, we improve the performance of our method. This allows us to focus the analysis to specific dynamical regimes of the network in which the inferred functional connectivity is shaped by monosynaptic excitatory connections, rather than by collective synchrony. Our method can discriminate between actual causal influences between neurons and spurious non-causal correlations due to light scattering artifacts, which inherently affect the quality of fluorescence imaging. Compared to other reconstruction strategies such as cross-correlation or Granger Causality methods, our method based on improved Transfer Entropy is remarkably more accurate. In particular, it provides a good estimation of the excitatory network clustering coefficient, allowing for discrimination between weakly and strongly clustered topologies. Finally, we demonstrate the applicability of our method to analyses of real recordings of in vitro disinhibited cortical cultures where we suggest that excitatory connections are characterized by an elevated level of clustering compared to a random graph (although not extreme) and can be markedly non-local.
http://www.recercat.cat:80/handle/2072/218394Critical Behavior and Axis Defining Symmetry Breaking in Hydra Embryonic Development
http://www.recercat.cat:80/handle/2072/218393
Critical Behavior and Axis Defining Symmetry Breaking in Hydra Embryonic Development
Gamba, Andrea; Nicodemi, Mario; Soriano i Fradera, Jordi; Ott, Albrecht
The formation of a hollow cellular sphere is often one of the first steps of multicellular embryonic development. In the case of Hydra, the sphere breaks its initial symmetry to form a foot-head axis. During this process a gene, ks1, is increasingly expressed in localized cell domains whose size distribution becomes scale-free at the axis-locking moment. We show that a physical model based solely on the production and exchange of ks1-promoting factors among neighboring cells robustly reproduces the scaling behavior as well as the experimentally observed spontaneous and temperature-directed symmetry breaking.
http://www.recercat.cat:80/handle/2072/218393Neutron skin of 208Pb, nuclear symmetry energy, and the parity radius experiment
http://www.recercat.cat:80/handle/2072/217610
Neutron skin of 208Pb, nuclear symmetry energy, and the parity radius experiment
Roca-Maza, X.; Centelles Aixalà, Mario; Viñas Gausí, Xavier; Warda, M.
A precise determination of the neutron skin thickness of a heavy nucleus sets a basic constraint on the nuclear symmetry energy (the neutron skin thickness is the difference of the neutron and proton rms radii of the nucleus). The parity radius experiment (PREX) may achieve it by electroweak parity-violating electron scattering (PVES) on 208Pb. We investigate PVES in nuclear mean field approach to allow the accurate extraction of the neutron skin thickness of 208Pb from the parity-violating asymmetry probed in the experiment. We demonstrate a high linear correlation between the parity-violating asymmetry and the neutron skin thickness in successful mean field forces as the best means to constrain the neutron skin of 208Pb from PREX, without assumptions on the neutron density shape. Continuation of the experiment with higher precision in the parity-violating asymmetry is motivated since the present method can support it to constrain the density slope of the nuclear symmetry energy to new accuracy.
http://www.recercat.cat:80/handle/2072/217610