Model-independent Results Research Articles

Epidemics on critical random graphs with heavy-tailed degree distribution

We study the susceptible–infected–recovered (SIR) epidemic on a random graph chosen uniformly over all graphs with certain critical, heavy-tailed degree distributions. We prove process level scaling limits for the number of individuals infected on day h on the largest connected components of the graph. The scaling limits contain non-negative jumps corresponding to some vertices of large degree. These weak convergence techniques allow us to describe the height profile of the α-stable continuum random graph (Goldschmidt et al., 2022; Conchon-Kerjan and Goldschmidt, 2023), extending results known in the Brownian case (Miermont and Sen, 2022). We also prove model-independent results that can be used on other critical random graph models.

Testing cosmic anisotropy with Padé approximations and the latest Pantheon+ sample

Cosmography can be used to constrain the kinematics of the Universe in a model-independent way. In this work, we attempt to combine the Pad$ e $ approximations with the latest Pantheon+ sample to test the cosmological principle. Based on the Pad$ e $ approximations, we first applied cosmographic constraints to different-order polynomials including third-order (Pad$ e $), fourth-order (Pad$ e $), and fifth-order (Pad$ e $) ones. The statistical analyses show that the Pad$ e $ polynomial has the best performance. Its best fits are $H_ $ = 72.53pm 0.28 km s$^ $ Mpc$^ $, $q_ $, and $j_ $. By further fixing $j_ $ = 1.00, it can be found that the Pad$ e $ polynomial can describe the Pantheon+ sample better than the regular Pad$ e $ polynomial and the usual cosmological models (including the Lambda CDM, $w$CDM, CPL, and $R_h$ = ct models). Based on the Pad$ e $ ($j_ $ = 1) polynomial and the hemisphere comparison method, we tested the cosmological principle and found the preferred directions of cosmic anisotropy, such as (l, b) = (304.6$^ circ circ $) and (311.1$^ circ circ $) for $q_ $ and $H_ $, respectively. These two directions are consistent with each other at a $1 confidence level, but the corresponding results of statistical isotropy analyses including isotropy and isotropy with real positions are quite different. The statistical significance of $ is stronger than that of $q_ $; that is, 4.75sigma and 4.39sigma for isotropy and isotropy with real positions, respectively. Reanalysis with fixed $q_ = -0.55$ (corresponds to $ m $ = 0.30) gives similar results. Overall, our model-independent results provide clear indications of a possible cosmic anisotropy, which must be taken seriously. Further testing is needed to better understand this signal.

Model-Independent Odderon Results Based on New TOTEM Data on Elastic Proton–Proton Collisions at 8 TeV

Evaluating the H(x,s|pp) scaling function of elastic proton–proton (pp) collisions from recent TOTEM data at s=8 TeV and comparing it with the same function of elastic proton–antiproton (pp¯) data of the D0 collaboration at s=1.96 TeV, we find, from this comparison alone, an at least 3.79 σ signal of odderon exchange. If we combine this model-independently obtained result with that of a similar analysis but using TOTEM elastic pp scattering data at s=7 TeV, which resulted in an at least 6.26 σ signal, the combined significance of odderon exchange increases to at least 7.08 σ. Further combinations of various datasets in the TeV energy range are detailed in the manuscript.

An overview of the optical characterization of free microparticles and their radiative properties

We discuss how the range of information available from microparticle analysis can be extended in a number of applications by measuring a specific set of optical properties of individual particles using light scattering. Central to these measurements are the real and imaginary components of the forward scattered field, the former being equal to the extinction cross-section except for a few particle-independent constants. Although still a niche technique, it has some inherent advantages and great potential for particle characterization, especially in the challenging near-wavelength size range. A selection of cases is covered from an experimental point of view, while some essential models are introduced to illustrate the underlying physical phenomena. We present a benchmark of experimental results from the literature and other examples that support optical diagnostics applied in science and industrial processes. As a key point of this work, we show that by accessing the fundamental properties of scatterers the inversion of light scattering data can be avoided. This provides model-independent results closer to application requirements without the drawbacks of case-specific assumptions.

Model independent bounds for the number of e-folds during the evolution of the universe

We present a simple procedure to obtain universal bounds for quantities of cosmological interest, such as the number of e-folds during inflation, reheating, and radiation, as well as the reheating temperature. The main assumption is to represent each of the various epochs of evolution of the universe as being due to a single substance changing instantaneously into the next, describing a new era of evolution of the universe. This assumption, commonly used to obtain solutions of the Friedmann equations for simple cosmological models, is implemented here to find model-independent bounds on cosmological quantities of interest. In particular, we find that the bound Nk ≈ 56 for -1/3 < ω re < 1/3 is very robust as an upper bound on the number of e-folds during inflation and also as a lower bound when ω re > 1/3, where ω re is the effective equation of state parameter during reheating. These are model-independent results that any single-field model of inflation should satisfy. As an example we illustrate with the basic α attractor model the usual model dependent approach, and the one presented here, and show how they complement each other.

Cosmographic analysis of a model of the pulsating universe with diverse types of matter

In this paper, a model of a pulsating universe is investigated with periodic function of the scale factor together with a homogeneous, isotropic and spatially flat Friedman-Robertson-Walker metric. The parameters of the pulsating universe model coincide with observation parameters of the modern universe, taking into account the different contributions of various types of matter to its evolution. In the resulting solution, during periods of accelerated expansion of the universe, the scalar field with negative pressure makes a greater contribution to the expansion growth. The fermionic field and the vector field, which have positive pressure values during this period, prevent the growth of this expansion. During periods of compression, the fermionic field and the vector field have a greater influence on the dynamics of the evolution of the universe. In the resulting periodic solution, the universe goes through endless cycles of expansion and contraction. The observed modern accelerated expansion of the universe corresponds to one of these cycles. Cosmographic parameters are calculated - parameters of deceleration q, jerk j and snap s and energy conditions for the model under research. These parameters make it possible to link model-independent results obtained from cosmography with theoretically sound assumptions of gravity.

Model-independent Odderon Results Based on TOTEM data on Elastic Proton–Proton Scattering at 8 TeV

Model-independent Odderon Results Based on TOTEM data on Elastic Proton–Proton Scattering at 8 TeV

Midrapidity cluster formation in heavy-ion collisions

We study the production of clusters and hypernuclei at midrapidity employing the Parton-Hadron- Quantum-Molecular-Dynamics (PHQMD) approach, a microscopic n-body transport model based on the QMD propagation of the baryonic degrees of freedom with density dependent 2-body potential interactions. In PHQMD the cluster formation occurs dynamically, caused by the interactions. The clusters are recognized by the Minimum Spanning Tree (MST) algorithm. We present the PHQMD results for cluster and hypernuclei formation in comparison with the available experimental data at relativistic energies. PHQMD allows to study the time evolution of formed clusters and the origin of their production, which helps to understand how such weakly bound objects are formed and survive in the rather dense and hot environment created in heavy-ion collisions. It offers therefore an explanation of the ’ice in the fire’ puzzle. To investigate whether this explanation of the ’ice in the fire’ puzzle applies only to the MST results we study also the deuterons production by coalescence. We embed MST and coalescence in the PHQMD and UrQMD transport approaches in order to obtain model independent results. We find that both clustering procedures give very similar results for the deuteron observables in the UrQMD as well as in the PHQMD environment. This confirms that our solution for the ’ice in the fire’ puzzle is common to MST and coalescence and independent of the transport approach.

Model-agnostic interpretation of 10 billion years of cosmic evolution traced by BOSS and eBOSS data

We present the first model-agnostic analysis of the complete set of Sloan Digital Sky Survey III (BOSS) and -IV (eBOSS) catalogues of luminous red galaxy and quasar clustering in the redshift range 0.2 ≤ z ≤ 2.2 (10 billion years of cosmic evolution), which consistently includes the baryon acoustic oscillations (BAO), redshift space distortions (RSD) and the shape of the transfer function signatures, from pre- and post-reconstructed catalogues in Fourier space. This approach complements the standard analyses techniques which only focus on the BAO and RSD signatures, and the full-modeling approaches which assume a specific underlying cosmology model to perform the analysis. These model-independent results can then easily be interpreted in the context of the cosmological model of choice. In particular, when combined with z > 2.1 Ly-α BAO measurements, the clustering BAO, RSD and Shape parameters can be interpreted within a flat-ΛCDM model yielding h = 0.6816 ± 0.0067, Ωm = 0.3001 ± 0.0057 and 109 × As = 2.43 ± 0.20 (or σ 8 = 0.858 ± 0.036) with a Big Bang Nucleosynthesis prior on the baryon density.Without any external dataset, the BOSS and eBOSS data alone imply Ωm = 0.2971 ± 0.0061 and 109 × As = 2.39+0.24 -0.43 (or σ 8 = 0.857 ± 0.040).For models beyond ΛCDM, eBOSS data alone (in combination with Planck) constrain the sum of neutrino mass to be Σmν < 0.40 eV with a BBN prior (Σmν < 0.082 eV) at 95% CL, the curvature energy density to Ωk = -0.022+0.032 -0.038 (Ωk = 0.0015 ± 0.0016) and the dark energy equation of state parameter to w = -0.998+0.085 -0.073 (w = -1.093+0.048 0.044) at 68% CL without a BBN prior.These results are the product of a substantial improvement of the state-of-the-art methodologies and represent the most precise model-agnostic cosmological constrains using spectroscopic large-scale data alone.

Cosmography in the multifield cosmological model

This paper analyzes a cosmological model containing the fermion field, scalar field and vector field with Yukawa interaction. Such a model allows one to research the contribution of various types of matter to the dynamics of the universe. In flat, homogeneous, and isotropic space-time, this coupling can provide the acceleration expansion of the universe. Cosmological reconstruction of dynamical equations is obtained using hybrid solution. This solution is researched by cosmography and energy condition. In the model under study, a zero energy condition, a strong energy condition, and a dominant energy condition are satisfied, and a weak energy condition, which is not mandatory, is not satisfied. It is shown how the cosmographic parameters – the parameters of deceleration q, jerk j, and snap s – can be related to the hybrid value of the scale factor. The resulting analysis makes it possible to relate the model-independent results obtained from cosmography to theoretically substantiated assumptions of gravity. The total density and pressure of the energy of the gravitational field are found in the form of the sum of contributions, which are associated with the bosonic, fermionic, vector fields, as well as the Yukawa type potential. In the model under study, in the early epoch, the bosonic field is responsible for the accelerated regime. Fermionic and vector fields have a positive pressure value, and therefore slow down the accelerated expansion of the universe. At a later time, a transition to a slow mode occurs, as the total pressure tends to zero.

The 6 × 2pt method: supernova velocities meet multiple tracers

ABSTRACT We present a new methodology to analyse in a comprehensive way large-scale and supernova (or any other distance indicator) surveys. Our approach combines galaxy and supernova position and redshift data with supernova peculiar velocities, obtained through their magnitude scatter, to construct a 6 × 2pt analysis that includes six power spectra. The 3 × 3 correlation matrix of these spectra expresses exhaustively the information content of the surveys at the linear level. We then proceed to forecast the performance of future surveys like Legacy Survey of Space and Time and 4MOST with a Fisher matrix analysis, adopting both a model-dependent and a model-independent approach. We compare the performance of the 6 × 2pt approach to that of the traditional one using only galaxy clustering and some recently proposed combinations of galaxy and supernova data and quantify the possible gains by optimally extracting the linear information. We show that the 6 × 2pt method shrinks the uncertainty area in the $\sigma _8, \, \gamma$ plane by more than half when compared to the traditional method. The combined clustering and velocity data on the growth of structures have uncertainties at similar levels to those of the cosmic microwave background but exhibit orthogonal degeneracies, and the combined constraints yield improvements of factors of 5 or more in each of the five cosmological parameters considered here. Concerning the model-independent results, we find that our method can improve the constraints on H(z)/H0 in all redshift bins by more than 70 per cent with respect to the galaxy clustering alone and by 30 per cent when supernova velocities (but not clustering) are considered, reaching a precision of 3–4 per cent at high redshifts.

Dark matter investigation with DAMA set-ups

Experimental observations and theoretical arguments at Galaxy and larger scales suggested that a large fraction of the universe is composed by Dark Matter particles. This motivated the DAMA experimental efforts to investigate the presence of such particles in the galactic halo by exploiting a model-independent signature and very highly radiopure set-ups deep underground. Here, a review of the model-independent positive results, obtained by the DAMA set-ups at the Gran Sasso National Laboratory of the INFN, and some of the implications will be given.

From lattice QCD to in-medium heavy-quark interactions via deep learning

Bottomonium states are key probes for experimental studies of the quark-gluon plasma (QGP) created in high-energy nuclear collisions. Theoretical models of bottomonium productions in high-energy nuclear collisions rely on the in-medium interactions between the bottom and antibottom quarks, which can be characterized by real (VR(T, r)) and imaginary (VI(T, r)) potentials, as functions of temperature and spatial separation. Recently, the masses and thermal widths of up to 3S and 2P bottomonium states in QGP were calculated using lattice quantum chromodynamics (LQCD). Starting from these LQCD results and through a novel application of deep neural network (DNN), here, we obtain model-independent results for VR(T, r) and VI(T, r). The temperature dependence of VR(T, r) was found to be very mild between T ≈ 0 − 330 MeV. Meanwhile, VI(T, r) shows rapid increase with T and r, which is much larger than the perturbation theory based expectations.

Vector-like quarks decaying into singly and doubly charged bosons at LHC

We investigate the production of vector-like quarks with charge 5/3 at the LHC and their subsequent decays into new singly or doubly charged bosons plus a heavy quark (top or bottom). In particular, we explore final states with same-sign di-leptons (electron or muon pairs), with the leptons coming from the decay of the new bosons and, in the case of production of singly charged bosons, from top quarks as well. These processes are predicted by classes of models based on extensions of the gauge group of the Standard Model, such as the 331 Model, where the electroweak symmetry is described by SU(3)L × U(1)X, X being a new abelian charge. For this purpose, a CMS search for vector-like partners with charge 5/3 decaying into Wt is recast to obtain model-independent bounds and projected reaches at future luminosity stages of the LHC. The results are then interpreted as mass bounds for the new particles predicted in the 331 Model and as a constraint on the scale of its spontaneous symmetry breaking. The complete set of model-independent results are provided as recast efficiencies, to allow for reinterpretation in different scenarios.

The role of non-universal Z couplings in explaining the Vus anomaly

The tension among measurements of Vus from different channels, the so-called Cabibbo Angle Anomaly, can be interpreted as a signal of lepton flavor universality (LFU) violation in the W boson couplings. We investigate this issue in the framework of effective field theory, keeping the gauge structure of the Standard Model (SM) unchanged. We introduce gauge-invariant dimension-6 effective operators that couple the Higgs doublet to leptons, thereby giving non-universal tree-level contributions to the couplings of electroweak gauge bosons. Due to the SU(2)L gauge symmetry, a tension arises between the Vus measurements that are affected by new W couplings, and the electroweak precision measurements, which are also affected by the new Z couplings. We show that this tension can be alleviated by allowing additional sources of gauge-invariant couplings of Z boson to left- or right-handed leptons, and find the optimal regions indicated by the current data in the Wilson-coefficient space. We illustrate our model-independent results with the examples of minimal extensions of the SM involving the vector-like lepton (VLL) models. We point out that dimension-6 operators coupling the Higgs doublet to leptons can affect the rate of h→ττ decay significantly in general, however this effect is restricted to less than a per cent level for the minimal VLL models.

Consistent Treatment of Axions in the Weak Chiral Lagrangian.

We present a consistent implementation of weak decays involving an axion or axionlike particle in the context of an effective chiral Lagrangian. We argue that previous treatments of such processes have used an incorrect representation of the flavor-changing quark currents in the chiral theory. As an application, we derive model-independent results for the decays K^{-}→π^{-}a and π^{-}→e^{-}ν[over ¯]_{e}a at leading order in the chiral expansion and for arbitrary axion couplings and mass. In particular, we find that the K^{-}→π^{-}a branching ratio is almost 40 times larger than previously estimated.

Effect of Energy Degeneracy on the Transition Time for a Series of Metastable States

We consider the problem of metastability for stochastic dynamics with exponentially small transition probabilities in the low temperature limit. We generalize previous model-independent results in several directions. First, we give an estimate of the mixing time of the dynamics in terms of the maximal stability level. Second, assuming the dynamics is reversible, we give an estimate of the associated spectral gap. Third, we give precise asymptotics for the expected transition time from any metastable state to the stable state using potential-theoretic techniques. We do this in a general reversible setting where two or more metastable states are allowed and some of them may even be degenerate. This generalizes previous results that hold for a series of only two metastable states. We then focus on a specific Probabilistic Cellular Automata (PCA) with configuration space {mathcal {X}}={-1,+1}^varLambda where varLambda subset {mathbb {Z}}^2 is a finite box with periodic boundary conditions. We apply our model-independent results to find sharp estimates for the expected transition time from any metastable state in {underline{-1}, {underline{c}}^o,{underline{c}}^e} to the stable state underline{+1}. Here {underline{c}}^o,{underline{c}}^e denote the odd and the even chessboard respectively. To do this, we identify rigorously the metastable states by giving explicit upper bounds on the stability level of every other configuration. We rely on these estimates to prove a recurrence property of the dynamics, which is a cornerstone of the pathwise approach to metastability.

DAMA/LIBRA–phase2 results and implications on several dark matter scenarios

The first DAMA/LIBRA–phase2 model-independent results (exposure: [Formula: see text], and software energy threshold at 1 keV). They further confirm — with high confidence level — the evidence already observed by DAMA/NaI and DAMA/LIBRA–phase1 on the basis of the exploited model-independent dark matter (DM) annual modulation signature. The total exposure of the three experiments above the 2 keV software energy threshold is [Formula: see text]. Here, several DM candidate particles and related scenarios are analyzed including the latest results. Thanks to the increased exposure and to the lower software energy threshold, corollary model-dependent analyses permit to significantly restrict the allowed regions for the parameters spaces of various dark matter candidates and astrophysical, particle and nuclear physics scenarios.

Model independent results for the inflationary epoch and the breaking of the degeneracy of models of inflation

We address the problem of determining inflationary characteristics in a model independent way. We start from a recently proposed equation which allows to accurately calculate the value of the inflaton at horizon crossing ϕk. We then use an equivalent form of this equation to write a formula that relates the number of e-folds from horizon crossing to the pivot scale Nke+Nep with the tensor-to-scalar index r, hence a general bound for Nke+Nep follows. Nke is the number of e-folds from the scale factor ak during inflation to the end of inflation at ae and Nep is the number of e-folds from ae to the pivot scale factor ap. In particular, at present r < 0.063 implies Nke+Nep< 112.5 e-folds at k=kp and 128.1 e-folds at the present scale with wavenumber mode k0. We also give a lower bound to the size of the universe during the inflationary epoch that gave rise to the current observable universe. We also discussed the problem of degeneracy of inflationary models and argue that this degeneration can only be resolved by studying model predictions from the reheating epoch.

It only takes a few moments to hedge options

We propose a novel non-structural method for hedging European options, relying on two model-independent results: First, under suitable regularity conditions, an option price can be disentangled into a linear combination of risk-neutral moments. Second, there exists an explicit approximate functional form linking the risk-neutral moments to the futures price of the underlying asset and the related variance swap contracts. We show that S&P 500 call prices are mainly explained by two factors that are related to level and volatility of the underlying index. We empirically compare the performance of two strategies where the vega exposure is adjusted either by a direct position in a variance swap contract or, indirectly, through an at-the-money call. While both strategies ensure effective immunization in periods of market turmoil, taking direct exposure on variance swaps is not optimal during extended periods of subdued volatility.