RECERCAT - Articles publicats en revistes (Estructura i Constituents de la Matèria)
http://www.recercat.cat:80/handle/2072/48808
www.ub.eduSat, 02 Aug 2014 01:21:25 GMT2014-08-02T01:21:25ZThe Channel Imagehttp://www.recercat.cat:80/bitstream/id/26376/
http://www.recercat.cat:80/handle/2072/48808
Differential branching fraction and angular analysis of the B+→K+μ+μ− decay
http://www.recercat.cat:80/handle/2072/238385
Differential branching fraction and angular analysis of the B+→K+μ+μ− decay
LHCb Collaboration; Abellan Beteta, C.; Calvo Gómez, M.; Camboni, Alessandro; Comerma Montells, Albert; Domingo Bonal, F.; Garrido Beltrán, Lluís; Grabalosa Gándara, Marc; Graciani Díaz, Ricardo; Graugés, Eugeni; Lopez 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.
The angular distribution and differential branching fraction of the decay B +→ K + μ + μ − are studied with a dataset corresponding to 1.0fb−1 of integrated luminosity, collected by the LHCb experiment. The angular distribution is measured in bins of dimuon invariant mass squared and found to be consistent with Standard Model expectations. Integrating the differential branching fraction over the full dimuon invariant mass range yields a total branching fraction of B (B + → K + μ + μ −) = (4.36 ± 0.15 ± 0.18) × 10−7. These measurements are the most precise to date of the B + → K + μ + μ − decay.
http://www.recercat.cat:80/handle/2072/238385Differential branching fraction and angular analysis of the decay B_s^0 → ϕμ + μ -
http://www.recercat.cat:80/handle/2072/238386
Differential branching fraction and angular analysis of the decay B_s^0 → ϕμ + μ -
LHCb Collaboration; Abellan Beteta, C.; Calvo Gómez, M.; Camboni, Alessandro; Comerma Montells, Albert; Garrido Beltrán, Lluís; Graciani Díaz, Ricardo; Graugés, Eugeni; Lopez Asamar, E.; Oyanguren, A.; Pérez-Calero Yzquierdo, Antonio; Picatoste Olloqui, Eduardo; Potterat, Cédric; Rives Molina, V.; Ruiz, Hugo (Ruiz Pérez); Ruiz Valls, P.; Vázquez Gómez, R.; Vilasis-Cardona, X.
The determination of the differential branching fraction and the first angular analysis of the decay B0s → ϕμ + μ − are presented using data, corresponding to an integrated luminosity of 1.0 fb−1, collected by the LHCb experiment at s√=7 TeV. The differential branching fraction is determined in bins of q 2, the invariant dimuon mass squared. Integration over the full q 2 range yields a total branching fraction of B(B0s→ϕμ+μ−)=(7.07+0.64−0.59±0.71±0.71) × 10−7, where the first uncertainty is statistical, the second systematic, and the third originates from the branching fraction of the normalisation channel. An angular analysis is performed to determine the angular observables F L, S 3, A 6, and A 9. The observables are consistent with Standard Model expectations.
http://www.recercat.cat:80/handle/2072/238386Differential Branching Fraction and Angular Analysis of the Decay B-0 -> K*(0)mu(+)mu(-)
http://www.recercat.cat:80/handle/2072/238384
Differential Branching Fraction and Angular Analysis of the Decay B-0 -> K*(0)mu(+)mu(-)
Abellan Beteta, C.; Calvo Gómez, M.; Camboni, Alessandro; Comerma Montells, Albert; Domingo Bonal, F.; Garrido Beltrán, Lluís; Gascón Fora, David; Grabalosa Gándara, Marc; Graciani Díaz, Ricardo; Graugés, Eugeni; Lopez Asamar, E.; Musy, Marco; Pérez-Calero Yzquierdo, Antonio; Picatoste Olloqui, Eduardo; Pie Valls, Blai; Potterat, Cédric; Puig Navarro, Albert; Roselló, M.; Ruiz, Hugo (Ruiz Pérez); Vázquez Gómez, R.; Vilasis-Cardona, X.; LHCb Collaboration
The angular distributions and the partial branching fraction of the decay B0→K*0μ+μ− are studied by using an integrated luminosity of 0.37 fb−1 of data collected with the LHCb detector. The forward-backward asymmetry of the muons, AFB, the fraction of longitudinal polarization, FL, and the partial branching fraction dB/dq2 are determined as a function of the dimuon invariant mass. The measurements are in good agreement with the standard model predictions and are the most precise to date. In the dimuon invariant mass squared range 1.00<br>6.00 GeV2/c4, the results are AFB=−0.06+0.13−0.14±0.04, FL=0.55±0.10±0.03, and dB/dq2=(0.42±0.06±0.03)×10−7 c4/GeV2. In each case, the first error is statistical and the second systematic.
http://www.recercat.cat:80/handle/2072/238384First observation of the decay B+→π+μ+μ−
http://www.recercat.cat:80/handle/2072/238387
First observation of the decay B+→π+μ+μ−
LHCb Collaboration; Abellan Beteta, C.; Calvo Gómez, M.; Camboni, Alessandro; Comerma Montells, Albert; Domingo Bonal, F.; Garrido Beltrán, Lluís; Gascón Fora, David; Grabalosa Gándara, Marc; Graciani Díaz, Ricardo; Graugés Pous, Eugeni; Lopez Asamar, E.; Pérez-Calero Yzquierdo, Antonio; Picatoste Olloqui, Eduardo; Pie Valls, Blai; Potterat, Cédric; Puig Navarro, Albert; Roselló, M.; Ruiz, Hugo (Ruiz Pérez); Vázquez Gómez, R.; Vilasis-Cardona, X.
A discovery of the rare decay B + → π + μ + μ − is presented. This decay is observed for the first time, with 5.2 σ significance. The observation is made using pp collision data, corresponding to an integrated luminosity of 1.0 fb−1, collected with the LHCb detector. The measured branching fraction is (2.3 ± 0.6 (stat.) ± 0.1 (syst.))×10−8, and the ratio of the B + → π + μ + μ − and B + → K + μ + μ − branching fractions is measured to be 0.053 ± 0.014 (stat.) ± 0.001 (syst.).
http://www.recercat.cat:80/handle/2072/238387Differential branching fraction and angular analysis of the decay B 0 → K ∗0 μ + μ -
http://www.recercat.cat:80/handle/2072/238383
Differential branching fraction and angular analysis of the decay B 0 → K ∗0 μ + μ -
LHCb Collaboration; Abellan Beteta, C.; Calvo Gómez, M.; Camboni, Alessandro; Comerma Montells, Albert; Garrido, Lluís (Garrido Beltrán); Graciani Díaz, Ricardo; Graugés, Eugeni; Lopez Asamar, E.; Oyanguren, A.; Pérez-Calero Yzquierdo, Antonio; Picatoste Olloqui, Eduardo; Potterat, Cédric; Rives Molina, V.; Ruiz, H. (Hugo); Ruiz Valls, P.; Vázquez Gómez, R.; Vilasis-Cardona, X.
The angular distribution and differential branching fraction of the decay B 0→ K ∗0 μ + μ − are studied using a data sample, collected by the LHCb experiment in pp collisions at s√=7 TeV, corresponding to an integrated luminosity of 1.0 fb−1. Several angular observables are measured in bins of the dimuon invariant mass squared, q 2. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q20=4.9±0.9GeV2/c4 , where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions.
http://www.recercat.cat:80/handle/2072/238383First evidence for the two-body charmless baryonic decay
http://www.recercat.cat:80/handle/2072/238351
First evidence for the two-body charmless baryonic decay
LHCb Collaboration; Calvo Gómez, M.; Camboni, Alessandro; Comerma Montells, Albert; Garrido Beltrán, Lluís; Graciani Díaz, Ricardo; Graugés Pous, Eugeni; Oyanguren, A.; Pérez-Calero Yzquierdo, Antonio; Picatoste Olloqui, Eduardo; Potterat, Cédric; Rives Molina, V.; Ruiz, Hugo (Ruiz Pérez); Ruiz Valls, P.; Vilasis-Cardona, X.
The results of a search for the rare two-body charmless baryonic decays TeX and TeX are reported. The analysis uses a data sample, corresponding to an integrated luminosity of 0.9 fb−1, of pp collision data collected by the LHCb experiment at a centre-of-mass energy of 7 TeV. An excess of TeX candidates with respect to background expectations is seen with a statistical significance of 3.3 standard deviations. This is the first evidence for a two-body charmless baryonic B 0 decay. No significant TeX signal is observed, leading to an improvement of three orders of magnitude over previous bounds. If the excess events are interpreted as signal, the 68.3% confidence level intervals on the branching fractions are $ TeX $ where the first uncertainty is statistical and the second is systematic.
http://www.recercat.cat:80/handle/2072/238351First evidence for the annihilation decay mode B+→D+sϕ
http://www.recercat.cat:80/handle/2072/238352
First evidence for the annihilation decay mode B+→D+sϕ
Abellan Beteta, C.; Calvo Gómez, M.; Camboni, Alessandro; Comerma Montells, Albert; Domingo Bonal, F.; Garrido Beltrán, Lluís; Grabalosa Gándara, Marc; Graciani Díaz, Ricardo; Graugés Pous, Eugeni; Lopez 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
Evidence for the hadronic annihilation decay mode B+→D+sϕ is found with greater than 3σ significance. The branching fraction and CP asymmetry are measured to be $ B(B+→D+sϕ)=(1.87+1.25−0.73(stat)±0.19(syst)±0.32(norm))×10−6,ACP(B+→D+sϕ)=−0.01±0.41(stat)±0.03(syst). $ The last uncertainty on B(B+→D+sϕ) is from the branching fractions of the B+→D+sD¯¯¯0 normalization mode and intermediate resonance decays. Upper limits are also set for the branching fractions of the related decay modes B+(c)→D+(s)K∗0,B+(c)→D+(s)K¯¯¯∗0 and B+c→D+sϕ , including the result B(B+→D+K∗0)<1.8×10−6 at the 90% credibility level.
http://www.recercat.cat:80/handle/2072/238352First measurement of time-dependent CP violation in B0s→K+K− decays
http://www.recercat.cat:80/handle/2072/238350
First measurement of time-dependent CP violation in B0s→K+K− decays
Calvo Gómez, M.; Camboni, Alessandro; Comerma Montells, Albert; Garrido Beltrán, Lluís; Graciani Díaz, Ricardo; Graugés Pous, Eugeni; Oyanguren, A.; Pérez-Calero Yzquierdo, Antonio; Picatoste Olloqui, Eduardo; Potterat, Cédric; Rives Molina, V.; Ruiz, Hugo (Ruiz Pérez); Ruiz Valls, P.; Vilasis-Cardona, X.; LHCb Collaboration
Direct and mixing-induced CP-violating asymmetries in B0s→K+K− decays are measured for the first time using a data sample of pp collisions, corresponding to an integrated luminosity of 1.0 fb−1, collected with the LHCb detector at a centre-of-mass energy of 7 TeV. The results are C KK = 0.14 ± 0.11 ± 0.03 and S KK = 0.30 ± 0.12 ± 0.04, where the first uncertainties are statistical and the second systematic. The corresponding quantities are also determined for B 0 → π + π − decays to be C ππ = −0.38 ± 0.15 ± 0.02 and S ππ = −0.71 ± 0.13 ± 0.02, in good agreement with existing measurements.
http://www.recercat.cat:80/handle/2072/238350Angular distributions of leptons from J/ ψ's produced in 920 GeV fixed-target proton-nucleus collisions
http://www.recercat.cat:80/handle/2072/238336
Angular distributions of leptons from J/ ψ's produced in 920 GeV fixed-target proton-nucleus collisions
Conde, P.; Garrido Beltrán, Lluís; Peralta, D.; HERA-B Collaboration
A study of the angular distributions of leptons from decays of J/ψ"s produced in p-C and p-W collisions at s√=41.6~GeV has been performed in the J/ψ Feynman-x region −0.34<x F <0.14 and for J/ψ transverse momenta up to 5.4 GeV/c. The data were collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The results, based on a clean selection of 2.3×105 J/ψ"s reconstructed in both the e + e − and μ + μ − decay channels, indicate that J/ψ"s are produced polarized. The magnitude of the effect is maximal at low p T . For p T >1 GeV/c a significant dependence on the reference frame is found: the polar anisotropy is more pronounced in the Collins-Soper frame and almost vanishes in the helicity frame, where, instead, a significant azimuthal anisotropy arises.
http://www.recercat.cat:80/handle/2072/238336N=1 SQCD-like theories with N_f massive flavors from AdS/CFT and beta functions
http://www.recercat.cat:80/handle/2072/238335
N=1 SQCD-like theories with N_f massive flavors from AdS/CFT and beta functions
Barranco, Alejandro; Pallante, Elisabetta; Russo, J. G. (Jorge Guillermo)
We study new supergravity solutions related to large-N c N=1 supersymmetric gauge field theories with a large number N f of massive flavors. We use a recently proposed framework based on configurations with N c color D5 branes and a distribution of N f flavor D5 branes, governed by a function N f S(r). Although the system admits many solutions, under plausible physical assumptions the relevant solution is uniquely determined for each value of x ≡ N f /N c . In the IR region, the solution smoothly approaches the deformed Maldacena-Núñez solution. In the UV region it approaches a linear dilaton solution. For x < 2 the gauge coupling β g function computed holographically is negative definite, in the UV approaching the NSVZ β function with anomalous dimension γ 0 = −1/2 (approaching − 3/(32π 2)(2N c − N f )g 3)), and with β g → −∞ in the IR. For x = 2, β g has a UV fixed point at strong coupling, suggesting the existence of an IR fixed point at a lower value of the coupling. We argue that the solutions with x > 2 describe a"Seiberg dual" picture where N f − 2N c flips sign.
http://www.recercat.cat:80/handle/2072/238335A 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, Marc; 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/2072/230930
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/2072/230930Symmetries 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/2072/230929Dynamical 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/2072/224721