arXiv subjects

Camille Noûs

Publications and source records attributed to Camille Noûs.

44 records · Page 3Linked to original sources

arXiv2020

Projection based adiabatic elimination of bipartite open quantum systems

Adiabatic elimination methods allow the reduction of the space dimension needed to describe systems dynamics which exhibits separation of time scale. For open quantum system, it consists in eliminating the fast part assuming it has almost instantaneously reached its steady-state and obtaining an approximation of the evolution of the slow part. These methods can be applied to eliminate a linear subspace within the system Hilbert space, or alternatively to eliminate a fast subsystems in a bipartite quantum system. In this work, we extend an adiabatic elimination method used for removing fast degrees of freedom within a open quantum system (Phys. Rev. A 2020, 101,042102) to eliminate a subsystem from an open bipartite quantum system. As an illustration, we apply our technique to a dispersively coupled two-qubit system and in the case of the open Rabi model.

quant-ph↗

arXiv2020

Sandpile toppling on Penrose tilings: identity and isotropic dynamics

We present experiments of sandpiles on grids (square, triangular, hexagonal) and Penrose tilings. The challenging part is to program such simulator; and our javacript code is available online, ready to play! We first present some identity elements of the sandpile group on these aperiodic structures, and then study the stabilization of the maximum stable configuration plus the identity, which lets a surprising circular shape appear. Roundness measurements reveal that the shapes are not approaching perfect circles, though they are close to be. We compare numerically this almost isotropic dynamical phenomenon on various tilings.

nlin.CG↗

arXiv2020

Complete NLO QCD study of single- and double-quarkonium hadroproduction in the colour-evaporation model at the Tevatron and the LHC

We study the Single-Parton-Scattering (SPS) production of double quarkonia (J/psi+J/psi, J/psi+Upsilon, and Upsilon+Upsilon) in pp and pp(bar) collisions at the LHC and the Tevatron as measured by the CMS, ATLAS, LHCb, and D0 experiments in the Colour-Evaporation Model (CEM), based on the quark-hadron-duality, including Next-to-Leading Order (NLO) QCD corrections up to alpha_s^5. To do so, we also perform the first true NLO --up to alpha_s^4-- study of the p_T-differential cross section for single-quarkonium production. This allows us to fix the non-perturbative CEM parameters at NLO accuracy in the region where quarkonium-pair data are measured. Our results show that the CEM at NLO in general significantly undershoots these experimental data and, in view of the other existing SPS studies, confirm the need for Double Parton Scattering (DPS) to account for the data. Our NLO study of single-quarkonium production at mid and large p_T also confirms the difficulty of the approach to account for the measured p_T spectra; this is reminiscent of the impossibility to fit single-quarkonium data with the sole 3S18 NRQCD contribution from gluon fragmentation. We stress that the discrepancy occurs in a kinematical region where the new features of the improved CEM are not relevant.

hep-ph↗

arXiv2020

Symmetry restoration and the gluon mass in the Landau gauge

We investigate the generation of a gluon screening mass in Yang-Mills theory in the Landau gauge. We propose a gauge-fixing procedure where the Gribov ambiguity is overcome by summing over all Gribov copies with some weight function. This can be formulated in terms of a local field theory involving constrained, nonlinear sigma model fields. We show that a phenomenon of radiative symmetry restoration occurs in this theory, similar to what happens in the standard nonlinear sigma model in two dimensions. This results in a nonzero gluon screening mass, as seen in lattice simulations.

hep-th↗

arXiv2020

Variable Length Memory Chains: characterization of stationary probability measures

Variable Length Memory Chains (VLMC), which are generalizations of finite order Markov chains, turn out to be an essential tool to modelize random sequences in many domains, as well as an interesting object in contemporary probability theory. The question of the existence of stationary probability measures leads us to introduce a key combinatorial structure for words produced by a VLMC: the Longest Internal Suffix. This notion allows us to state a necessary and sufficient condition for a general VLMC to admit a unique invariant probability measure. This condition turns out to get a much simpler form for a subclass of VLMC: the stable VLMC. This natural subclass, unlike the general case, enjoys a renewal property. Namely, a stable VLMC induces a semi-Markov chain on an at most countable state space. Unfortunately, this discrete time renewal process does not contain the whole information of the VLMC, preventing the study of a stable VLMC to be reduced to the study of its induced semi-Markov chain. For a subclass of stable VLMC, the convergence in distribution of a VLMC towards its stationary probability measure is established. Finally, finite state space semi-Markov chains turn out to be very special stable VLMC, shedding some new light on their limit distributions.

math.PR↗

arXiv2020

#P-completeness of counting update digraphs, cacti, and a series-parallel decomposition method

Automata networks are a very general model of interacting entities, with applications to biological phenomena such as gene regulation. In many contexts, the order in which entities update their state is unknown, and the dynamics may be very sensitive to changes in this schedule of updates. Since the works of Aracena et. al, it is known that update digraphs are pertinent objects to study non-equivalent block-sequential update schedules. We prove that counting the number of equivalence classes, that is a tight upper bound on the synchronism sensitivity of a given network, is #P-complete. The problem is nevertheless computable in quasi-quadratic time for oriented cacti, and for oriented series-parallel graphs thanks to a decomposition method.

cs.DM↗

arXiv2020

Asymptotic temperature of a lossy condensate

We monitor the time evolution of the temperature of phononic collective modes in a one-dimensional quasicondensate submitted to losses. At long times the ratio between the temperature and the energy scale $mc^2$, where $m$ is the atomic mass and $c$ the sound velocity takes, within a precision of 20\%, an asymptotic value. This asymptotic value is observed while $mc^2$ decreases in time by a factor as large as 2.5. Moreover this ratio is shown to be independent on the loss rate and on the strength of interactions. These results confirm theoretical predictions and the measured stationary ratio is in quantitative agreement with the theoretical calculations.

cond-mat.quant-gas↗

arXiv2020

Certifying the intrinsic character of a constitutive law for semi-crystalline polymers: a probation test

A study of methodological nature demonstrates the efficiency of a probation test allowing for the intrinsic character of a rheological constitutive law to be assessed. Such a law is considered here for Semi-Crystalline Polymers exhibiting necking and for large deformation. In the framework of a $(\dotσ, σ, \dot\varepsilon, \varepsilon)$ behavior's law, tensile experiments conducted at an imposed constant strain rate $\dot\varepsilon_0$ bring true stress responses from which constitutive (material) parameters can be identified from Model-Based Metrology concepts. The same experiment repeated at various strain rates gives then access to the dependence of the non-elastic parameters on the strain rate. Then the intrinsic law is tested severely by considering a new set of experiments carried out for constant displacement rates of the grips. In that case, the specimens show local strain rates which evolve strongly during the test (by a factor of 5-10 here). The parameter identification process requires then the introduction of the exact realized input strain and strain-rate command into the model. Accounting for strain rate dependency requires additionally the knowledge of the preliminary identified strain rate dependence of the non-elastic constitutive parameters for good predictions of the experimental response directly. This is what is proven here. The conclusion speaks in favor of a possible upgrade of international standards for the mechanical characterization of polymers based on constant strain-rate tensile tests and properly applied model-based metrology.

cond-mat.soft↗