Initial Fluctuations Research Articles

A Fourier-cumulant analysis for multiharmonic flow fluctuation

The Fourier analysis of the final particle distribution followed by cumulant study of the Fourier coefficient event-by-event fluctuation is one of the main approaches for testing the collective evolution in the heavy-ion collision. Using a multidimensional generating function, we propose a method to extract any possible cumulant of multiharmonic flow fluctuations and classify them in terms of the order of cumulants and harmonics involved in them. In particular, we show that there are 33 distinct cumulants with order 2, 3, 4, 5 and harmonics 2, 3, 4, 5. We compute the normalized version of these cumulants from hydrodynamic simulation for Pb–Pb collisions based on T_mathtt{R}ENTo+VISH2+1+UrQMD. We compare the simulation with those normalized cumulants that the LHC has measured and predict the unmeasured ones. Comparing the initial and final state fluctuation normalized cumulants, we compute the linear and nonlinear hydrodynamic response couplings. We finally introduce the genuine three-particle correlation function containing information of all third-order cumulants.

Preliminary Experience of Imatinib after Nilotinib in the First Line Treatment of Chronic Myeloid Leukemia

Background Chronic myeloid leukaemia (CML) is a clonal myeloproliferative disorder, hallmarked by the BCR-ABL fusion gene which encodes for a constitutively activated BCR/ABL tyrosine-kinase, effectively treated with Tyrosine-Kinase Inhibitors (TKIs). The first line TKI Imatinib (IM) can obtain a high cumulative CCyR; compared to IM, deeper and faster molecular responses can be obtained in newly diagnosed CML patients with the second generation TKIs, Nilotinib (NIL) and Dasatinib. Despite the three TKIs have been evaluable as first line therapy for a long time, our experience largely concern the second generation TKIs after IM but not evidence are reported regarding IM after second generation TKIs.On behalf of the Rete Ematologica Lombarda (REL) we designed the PhilosoPhi34 study (EudraCT: 2012-005062-34). This study was divided into three consecutive phases. An initial recruitment phase, a “core” phase of treatment lasting for 12 months (mos) and an “observational” phase lasting for an additional period of 24 mos. NIL 300 mg BID standard dose was administered for one year (“core” phase). At the end of this “core” phase of the trial, during the “observational” period, treatment options were up to the Investigator's choice (i.e. any TKI approved as first line treatment could be used), based on individual patient evaluation.Furthermore, fluctuations of BCR/ABL ratio are known, in particular during the two first years of CML treatment, characterized by a higher risk of disease progression or relapse.Aims Despite this consideration, our purpose is to verify time courses of Molecular Response (MR) IS in the IM treated patients, during the “observational” phase of the PhilosoPhi34 study.Methods We evaluate the PhilosoPhi34 database. MR IS is reported at 3, 6 and 12 mos of NIL treatment (“core” phase) and every 6 mos in the “observational” phase. Until now, the “observational” phase is ongoing and the database is unlocked.Results Among the 74 reported pts who started the “observational” phase, with at minimum a CCyR, 62 pts maintained NIL, 10 pts switched to IM and 2 pts switched to other TKI. Other two pts switched to IM after 18 and 24 months of NIL treatment (i.e. +6 mos and +12 mos of the “observational” phase, respectively). Among the 62 pts that maintained NIL, 33 showed a MR ≥ 4.0 IS and 20 showed a MR 3.0 IS. In the NIL group 15/62 pts showed an increase of the BCR/ABL ratio after 6 mos of the “observational” phase, but only 5/33 (15%) pts lost MR4.0 IS and 1/20 (5%) pts transient lost MR3.0 IS. Overall, 1/62 pts failed at 26 mos of treatment (+14 mos of “observational” phase) harbouring a resistant mutation. All the other NIL treated pts, despite molecular fluctuations, maintained or improved MR over time. Among the 10 pts that switched to IM after 12 mos of NIL treatment, 6 were in MR ≥ 4.0 IS and 4 in MR3.0 IS. Of them, 7/10 pts showed an increase of the BCR/ABL ratio but only 1/6 (16,6%) pts lost MR4.0 IS and 1/4 (25%) pts lost MR3.0 (Table1). No pts failed treatment. Of note, the probability to lose MR≥ 4.0 IS or MR 3.0 IS between NIL treated pts vs IM treated pts proved not significant with the Fisher's test (p: 0.43 and p: 0.28, respectively).Conclusion As expected, our preliminary data show fluctuation of BCR/ABL ratio and of MR IS. IM treated pts present initial molecular fluctuations statistically similar to the fluctuation showed by NIL treated pts evaluated at the same time point. Despite fluctuations, MR IS is maintained or improved, over time. More data are necessary to confirm these exploratory results. Pointing out the possible adverse events occurring during long-term NIL treatment and the percentage of CML pts with vascular or metabolic disease at diagnosis, we consider a short-term treatment with NIL before IM a new possible strategy for CML cure. [Display omitted] DisclosuresOrlandi:Novartis: Speakers Bureau; Bristol-Myers Squibb: Speakers Bureau; Incyte: Speakers Bureau. Iurlo:Pfizer: Consultancy, Honoraria; Bristol Myers Squibb: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Rossi:Sanofi: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Teva: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees.

Relativistic viscous effects on the primordial gravitational waves spectrum

We study the impact of the viscous effects of the primordial plasma on the evolution of the primordial gravitational waves (pGW) spectrum from Inflation until today, considering a self-consistent interaction that incorporates the back-reaction of the GW into the plasma. We use a relativistic causal hydrodynamic framework with a positive entropy production based on a Second-Order Theory (SOT) in which the viscous properties of the fluid are effectively described by a new set of independent variables. We study how the spin-2 modes typical of SOTs capture the simplest GW-fluid viscous interaction to first order. We consider that all non-ideal properties of the primordial plasma are due to an extra effectively massless self-interacting scalar field whose state becomes a many-particles one after Reheating and for which an effective fluid description is suitable. We numerically solve the evolution equations and explicitly compute the current GW spectrum obtaining two contributions. On the one hand we have the viscous evolution of the pGW: for the collision-dominated regime the GW source becomes negligible while in the collisionless limit there exists an absorption of the pGW energy due to the damping effect produced by the free-streaming spin-2 modes of the fluid and driven by the expansion of the Universe. The latter effect is characterized by a relative amplitude decrease of about 1 to 10 % with respect to the GW free evolution spectrum. On the other hand we get the GW production due to the decay of the initial spin-2 fluctuations of the fluid that is negligible compared with the above-mentioned contribution.This SOT framework captures the same qualitative effects on the evolution of GW coupled to matter reported in previous works in which a kinetic theory approach has been used.

Nearly scale-invariant curvature modes from entropy perturbations during the graceful exit phase

In this Letter, we describe how a spectrum of entropic perturbations generated during a period of slow contraction can source a nearly scale-invariant spectrum of curvature perturbations on length scales larger than the Hubble radius during the transition from slow contraction to a classical non-singular bounce (the `graceful exit' phase). The sourcing occurs naturally through higher-order scalar field kinetic terms common to classical (non-singular) bounce mechanisms. We present a concrete example in which, by the end of the graceful exit phase, the initial entropic fluctuations have become negligible and the curvature fluctuations have a nearly scale-invariant spectrum with an amplitude consistent with observations.

Quantum Fluctuations and Variable G Return Einstein’s Field Equation to Its Original Formulation

The standard ΛCDM model has successfully depicted most of the astronomical observations. However, the model faces several question marks such as, what was the cause of the Big Bang singularity, what is the physics behind dark matter? The origin of dark energy is still unclear. The present theory, CBU, standing for the Continuously Breeding Universe, has been developed along with known principles of physics. The theory incorporates important ideas from the past. The universe is a complex emerging system, which starts from the single fluctuation of a positron-electron pair. Expansion is driven by the emersion of new pairs. The gravitational parameter G is inversely proportional to the Einsteinian curvature radius r. The Planck length and Planck time tP are dependent of the curvature and accordingly by the size of the universe. It is shown that the solution to the Schrodinger equation of the initial positron-electron fluctuation includes an exponential function parameter equal to the Planck length of the initial event. The existence of a wave function provides a link between quantum mechanics and the theory of general relativity. The fast change of momentum increases the Heisenberg uncertainty window thereby enhancing the positron-electron pair production, especially strong in the early universe. When these findings are introduced in the energy-momentum tensor of Einstein’s Field Equation, the equation acquires a simple configuration without G and a cosmological constant. The universe is a macroscopic manifestation of the quantum world.

Effects of centrality fluctuation and deuteron formation on the proton number cumulant in Au+Au collisions at = 3 GeV from the JAM model * *Supported by the National Key Research and Development Program of China (2020YFE0202002, 2018YFE0205201), the National Natural Science Foundation of China (11828500, 11828501, 11575069, 11890711, 11861131009)

We studied the effects of centrality fluctuation and deuteron formation on the cumulant ( ) and correlation functions ( ) of protons up to the sixth order in the most central ( < 3 fm) Au+Au collisions at = 3 GeV in a microscopic transport model (JAM). The results are presented as a function of rapidity acceptance within the transverse momentum 0.4 < p T < 2 GeV/ c. We compared the results obtained by the centrality bin width correction (CBWC) using charged reference particle multiplicities with the CBWC using impact parameter bins. It was found that, at low energies, the centrality resolution for determining the collision centrality using charged particle multiplicities is not sufficient to reduce the initial volume fluctuation effect for higher-order cumulant analysis. New methods need to be developed to classify events with high centrality resolution for heavy-ion collisions at low energies. Finally, we observed that the formation of deuterons suppresses the higher-order cumulants and correlation functions of protons and found it to be similar to the efficiency effect. This work can serve as a noncritical baseline for the QCD critical point search in the high baryon density region.

Initial fluctuations and power spectrum of flow anisotropies in relativistic heavy-ion collisions

Flow has emerged as a crucial probe for the properties of the thermalized medium produced in relativistic heavy-ion collisions. The evolution of initial state fluctuations leaves imprints on the power spectrum of flow coefficients. Therefore, flow coefficients are a crucial probe of initial state fluctuations arising from the parton distributions of the colliding nuclei. This has a very strong correspondence with the physics of power spectrum of cosmic microwave background radiation (CMBR) anisotropies which directly probes initial inflationary fluctuations. Much work has been done to probe these interesting interconnections, in particular, in developing techniques for the measurements of higher flow coefficients. We present a short review of these developments. The effect of initial magnetic field on these features will also be reviewed. All this acquires special importance in view of upcoming electron-ion collider which will directly probe initial parton distribution of the colliding nucleus.

Gravitational wave constraints on the primordial black hole dominated early universe

We calculate the gravitational waves (GWs) induced by the density fluctuations due to the inhomogeneous distribution of primordial black holes (PBHs) in the case where PBHs eventually dominate and reheat the universe by Hawking evaporation. The initial PBH density fluctuations are isocurvature in nature. We find that most of the induced GWs are generated right after evaporation, when the universe transits from the PBH dominated era to the radiation dominated era and the curvature perturbation starts to oscillate wildly. The strongest constraint on the amount of the produced GWs comes from the big bang nucleosynthesis (BBN). We improve previous constraints on the PBH fraction and find that it cannot exceed 10-4. Furthermore, this maximum fraction decreases as the mass increases and reaches 10-12 for MPBH∼ 5×108 g, which is the largest mass allowed by the BBN constraint on the reheating temperature. Considering that PBH may cluster above a given clustering scale, we also derive a lower bound on the scale of clustering. Interestingly, the GW spectrum for MPBH∼ 104 -108 g enters the observational window of LIGO and DECIGO and could be tested in the future. Although we focus on the PBH dominated early universe in this paper, our methodology is applicable to any model with early isocurvature perturbation.

Numerical Study of Hydrogen Auto-Ignition Process in an Isotropic and Anisotropic Turbulent Field

The physical mechanisms underlying the dynamics of the flame kernel in stationary isotropic and anisotropic turbulent field are studied using large eddy simulations (LES) combined with a pdf approach method for the combustion model closure. Special attention is given to the ignition scenario, ignition delay, size and shape of the flame kernel among different turbulent regimes. Different stages of ignition are analysed for various levels of the initial velocity fluctuations and turbulence length scales. Impact of these parameters is found small for the ignition delay time but turns out to be significant during the flame kernel propagation phase and persists up to the stabilisation stage. In general, it is found that in the isotropic conditions, the flame growth and the rise of the maximum temperature in the domain are more dependent on the initial fluctuations level and the length scales. In the anisotropic regimes, these parameters have a substantial influence on the flame only during the initial phase of its development.

Modeling the Dynamics of Heavy-Ion Collisions with a Hydrodynamic Model Using a Graphics Processor

Dense bulk matter is formed during heavy-ion collision and expands towards a vacuum. It behaves as a perfect fluid, described by relativistic hydrodynamics. In order to study initial condition fluctuation and properties of jet propagation in dense hot matter, we assume a Cartesian laboratory frame with several million cells in a stencil with high-accuracy data volume grids. Employing numerical algorithms to solve hydrodynamic equations in such an assumption requires a lot of computing power. Hydrodynamic simulations of nucleus + nucleus interactions in the range of energies of the Large Hadron Collider (LHC) are carried out using our program, which uses Graphics Processing Units (GPUs) and Compute Unified Device Architecture (CUDA). In this work, we focused on transforming hydrodynamic quantities into kinetic descriptions. We implemented the hypersurface freeze-out conditions using marching cubes techniques. We developed freeze-out procedures to obtain the momentum distributions of particles on the hypersurface. The final particle distributions, elliptic flow, and higher harmonics are comparable to the experimental LHC data.

Ternary Phase-Field Simulations of the Skin-Sublayer Structures in Poly(vinylidene fluoride) Microporous Membranes Prepared by a Nonsolvent-Induced Phase Separation.

In this paper, the existing phase-field model based on the nonsolvent-induced phase separation (NIPS) method was optimized. Two-dimensional simulations using the relevant parameters of a poly(vinylidene fluoride) (PVDF) membrane system were carried out, simulating and analyzing the effects of changes in initial concentrations, concentration fluctuations, and diffusion rates of the solvent on the skin layer and sublayer structures of the membranes. These simulations modeled the process of preparing PVDF microporous membranes by the NIPS method to better understand the structural development of PVDF microporous membranes under different conditions. It was found that dense skin layers were formed at the mass-transfer exchange interface of the PVDF microporous membranes, whose number increased with the decrease of the concentration fluctuation, which has little effect on the structure of the sublayer. The initial concentration of PVDF and the diffusion rate of the solvent had a little impact on the number of skin layers yet played a relatively large role in the formation time of the skin layers and the structure of the sublayers. Also, the validity of the model was verified by corresponding experiments. Hence, the model can be applied to other PVDF ternary membrane systems by modifying specific thermodynamic and kinetic parameters.

Quantum Higgs inflation

The Higgs field is an attractive candidate for the inflaton because it is an observationally confirmed fundamental scalar field. Importantly, it can be modeled by the most general renormalizable scalar potential. However, if the classical Higgs potential is used in models of inflation, it is ruled out by detailed observations of the cosmic microwave background. Here, a new application of non-adiabatic quantum dynamics to cosmological models is shown to lead to a multi-field Higgs-like potential, consistent with observations of a slightly red-tilted power spectrum and a small tensor-to-scalar ratio, without requiring non-standard ingredients. These methods naturally lead to novel effects in the beginning of inflation, circumventing common fine-tuning issues by an application of uncertainty relations to estimate the initial quantum fluctuations in the early universe. Moreover, inflation ends smoothly as a consequence of the derived multi-field interactions.

Onset of Rayleigh–Taylor Convection in a Porous Medium

The Rayleigh–Taylor instability and the initial stage of density-driven convection in a porous medium is simulated numerically in reference to geologic problems. A two-layer fluid system in which the lower layer is formed by pure water and the upper layer by an aqueous solution of salts is considered. The upper layer is more dense and viscous. The determination of the characteristic time of the onset of convection in the numerical solution is discussed. The parameters which depend on and do not depend of the initial density fluctuations are revealed. The effect of the viscosity contrast on the onset and development of convection flow and mass transfer is analyzed. The quantitative discrepancies related to neglecting the viscosity contrast in geologic fluids are estimated.

Stabilization of the Q-switching pulse energy of a composite YAG/Yb:YAG/Cr:YAG laser used as a laser ignitor

We propose a stabilization method for a Q-switched composite YAG/Yb:YAG/Cr:YAG laser configured for use as a laser igniter. The method is based on reducing the fluctuations in the magnitude of the initial seed signal caused by interference of the initial resonator modes. We have shown that a stable laser output could be achieved using a Fabry-Perot etalon, which can reduce the number of modes, to reduce the initial noise fluctuation in a resonator.

Can axion clumps be formed in a pre-inflationary scenario?

The QCD axion and an axion-like particle (ALP) are compelling candidates of dark matter. For the QCD axion, it is known that when the Peccei-Quinn (PQ) symmetry is spontaneously broken after inflation, the large initial fluctuation can lead to axion clump formation. On the other hand, when the symmetry is already broken during inflation, it has been believed that the axion clump formation does not occur due to the small amplitude of the initial axion fluctuation. We revisit this prevailing understanding, considering both the QCD axion and an ALP. In our analysis, the clump formation was not observed for the QCD axion even if we consider an extremely fine-tuned initial condition. Meanwhile, for an ALP which allows a more general potential form, we show that the clump formation can take place through the tachyonic instability or/and the resonance instability, considering a multiple cosine potential.

Heart rate fluctuation predicts mortality in critically ill patients in the intensive care unit: a retrospective cohort study.

BackgroundTo evaluate the association between heart rate (HR) fluctuation and mortality in critically ill patients in the intensive care unit (ICU).MethodsA total of 27,814 patients were enrolled from the Medical Information Mart for Intensive Care database and were divided into 3 groups: low HR fluctuation [<25 beats per minute (bpm)], control (25–34 bpm), and high HR fluctuation (≥35 bpm), based on the initial 24-hour HR fluctuation (calculated as the maximum HR minus minimum HR). Multivariate Cox regression and restricted cubic spline models were used.ResultsCompared to the control group, higher risk of 28-day and 1-year mortality remained significant in an adjusted model, with hazard ratios of 1.210 [95% confidence interval (CI), 1.103–1.327] and 1.150 (95% CI, 1.078–1.227), respectively, in the high HR fluctuation group, as well as hazard ratios of 1.130 (95% CI, 1.035–1.232) and 1.087 (95% CI, 1.022–1.157), respectively, in the low HR fluctuation group. Restricted cubic splines showed a U-type curve, with the lowest risk of mortality at an HR fluctuation of 30 bpm.ConclusionsThis retrospective cohort study revealed that both high and low HR fluctuation correlated with increased mortality in critically ill ICU patients, providing new insights for optimizing HR control strategies.

Time Series Analysis of Production Decline in Carbonate Reservoirs with Machine Learning

Classical decline methods, such as Arps yield decline curve analysis, have advantages of simple principles and convenient applications, and they are widely used for yield decline analysis. However, for carbonate reservoirs with high initial production, rapid decline, and large production fluctuations, with most wells having no stable production period, the adaptability of traditional decline methods is inadequate. Hence, there is an urgent need to develop a new decline analysis method. Although machine learning methods based on multiple regression and deep learning have been applied to unconventional oil reservoirs in recent years, their application effects have been unsatisfactory. For example, prediction errors based on multiple regression machine learning methods are relatively large, and deep learning sample requirements and the actual conditions of reservoir management do not match. In this study, a new equal probability gene expression programming (EP-GEP) method was developed to overcome the shortcomings of the conventional Arps decline model in the production decline analysis of carbonate reservoirs. Through model validation and comparative analysis of prediction effects, it was proven that the EP-GEP model exhibited good prediction accuracy, and the average relative error was significantly smaller than those of the traditional Arps model and existing machine learning methods. The successful application of the proposed method in the production decline analysis of carbonate reservoirs is expected to provide a new decline analysis tool for field reservoir engineers.

Initial state fluctuations and the sub-leading flow modes from the experimental data and HYDJET++ model

A few microseconds after the birth of the Universe, the Universe was filled with the matter consisting of quarks and gluons, called quark gluon plasma (QGP). That primordial QGP lasts for about a few $$\upmu s$$ until the Universe cooled down and expanded enough that colored quarks had to confine within the colorless new formed hadrons. In high-energy nuclear collisions, where a high baryon density, or a high temperature could be achieved, small pieces of the QGP can be recreated and studied experimentally. Such created QGP undergoes an explosion, called the Little Bang. In spite of its small size (about 1000 $$fm^{3}$$ ) and short duration (a few fm/c, where c is the speed of light), the QGP is well described by relativistic hydrodynamics, including even the small perturbations on top of the explosion. In high-energy nucleus–nucleus (AA) collisions which have been performed at the Relativistic Heavy Ion Collider and at the Large Hadron Collider, the QGP was created with extremely high temperature and the baryon density close to zero. One of observables used to study QGP is azimuthal anisotropy. It was found that the initial state fluctuations have a significant influence on azimuthal anisotropies. We present results on azimuthal anisotropies measured in ultra-central PbPb collisions at $$\sqrt{s}_{NN}$$ = 2.76 TeV by the CMS and ALICE collaborations, as well as the leading and sub-leading flow modes for the elliptic and triangular anisotropies. The measured flow modes are also compared with the predictions from the HYDJET++ model.

Rapidity decorrelation caused by hydrodynamic fluctuations and initial longitudinal fluctuations

Factorisation breaking of the anisotropic flow coefficients is actively studied to understand the longitudinal dynamics of the quark-gluon plasma produced in high-energy nuclear collisions. Yet no hydrodynamic models have successfully described the centrality dependence of the factorisation breaking in various collisions systems. In this study, we reproduce the centrality dependence of the factorisation ratio in Pb+Pb collisions at LHC by constructing an integrated dynamical model with hydrodynamic fluctuations and initial longitudinal fluctuations. Hydrodynamic fluctuations are thermal fluctuations arising during the hydrodynamic stage of the high-energy nuclear collisions. We include the hydrodynamic fluctuations obeying the fluctuation-dissipation theorem. For the initial longitudinal fluctuations, we run PYTHIA for each binary p+p collision, scale the distribution of the produced particles by the number of participants and assume the distribution to be the entropy density distribution. We switch on and off the hydrodynamic fluctuations to investigate the effects on the longitudinal rapidity decorrelation.

Effects of initial state fluctuations on the mean transverse momentum

We show that in ideal hydrodynamic simulations of heavy-ion collisions, initial state fluctuations result in an increase of the mean transverse momentum of outgoing hadrons, 〈pt〉. Specifically, 〈pt〉 is larger by a few percent if realistic fluctuations are implemented than with smooth initial conditions, the multiplicity and impact parameter being kept fixed. We show that result can be traced back to the fact that for a given total entropy, the initial energy contained in the fluid is larger if the density profile is bumpy. We discuss the implication of these results for the extraction of the equation of state of QCD from experimental data.