Miracle-dz/UniFAR-FTUs huggingface dataset:
Non-linear massive gravity

Massive gravity is a particular theoretical model that modifies gravity on cosmological scales and therefore could provide a dynamical explanation for the observed accelerated expansion of our Universe. In this thesis we investigate various theoretical problems of massive gravity, important for its consistency and phenomenological viability. It is known that the predictions from the linearized massive gravity contradict the predictions of General Relativity. It is, however, an artifact due to the breakdown of the perturbative expansion in the massless limit. In our work we investigate this problem in the diffeomorphism invariant formulation of massive gravity in which the graviton mass term is written in terms of four scalar fields. We determine the so-called Vainshtein scale below which the scalar modes of the massive graviton enter the non-perturbative regime for a wide class of non-linear mass terms. We find the asymptotic solutions of the spherically symmetric gravitational field below and above the Vainshtein radius, and show that massive gravity goes smoothly to the General Relativity below this scale. We also determine the corresponding corrections to the Newton potential. In general, any non-linear extension of the quadratic graviton mass term propagates the Boulware-Deser ghost. The only theory in which the ghost is not propagating in the high energy decoupling limit, is the de Rham-Gabadadze-Tolley theory. Here we show that the ghost arises in the fourth order of perturbations in this theory away from the decoupling limit. However, we further argue that the ghost can be avoided in the full non-linear theory if not all four scalar fields propagate independent degrees of freedom. In particular, we investigate the simple example of (1+1)-dimensional massive gravity and find that the theory exhibits a gauge symmetry, which reduces the number of degrees of freedom. We also generalize the diffeomorphism invariant formalism of massive gravity to arbitrary curved backgrounds. We find that, given a specific background metric, the resulting generally covariant massive gravity exhibits an internal symmetry in the configuration space of the scalar fields. The symmetry transformations of the scalar fields are given by the isometries of the reference metric. In particular, we investigate massive gravity on de Sitter space in this formalism. We confirm the known result that, in the case when the graviton mass is related to the cosmological constant as m^2=2\Lambda/3, the theory is partially massless and propagates only four degrees of freedom.
Asymptotic Behavior of a Poincaré Difference Equation

In this paper, we describe the asymptotic behavior of the solutions of the difference equation provided that the characteristic equation of the corresponding equation with constant coefficients has a dominant root and the sequences are in l 2 and of bounded variation. The main tools in the proof are perturbation theorems on asymptotic constancy and stability of the solutions, decomposition in the variation-of-constants formula and estimates on the complementary spaces.
Particle blocking and carrier fluid freezing effects on the magnetic properties of Fe3O4-based ferrofluids

We report the systematic dc and ac susceptibility studies on the particle blocking and carrier fluid freezing effects on the magnetization and relaxation processes in two different ferrofluids composed of Fe3O4 nanoparticles (mean size of ∼14 nm) suspended in hexane and dodecane, which respectively have freezing temperatures below (178 K) and above (264 K) the blocking temperature of magnetic nanoparticles (∼200 K). Experimental results reveal that these effects play a key role in the formation of glasslike peaks and magnetic anomalies in ferrofluids. Quantitative fits of the frequency dependent ac susceptibility to the Vogel–Fulcher model τ=τo exp[Ea/k(T−To)] clearly indicate that the blocking of magnetic nanoparticles in the frozen state significantly affects the interparticle dipole-dipole interaction, causing characteristic spin-glass-like dynamics.We report the systematic dc and ac susceptibility studies on the particle blocking and carrier fluid freezing effects on the magnetization and relaxation processes in two different ferrofluids composed of Fe3O4 nanoparticles (mean size of ∼14 nm) suspended in hexane and dodecane, which respectively have freezing temperatures below (178 K) and above (264 K) the blocking temperature of magnetic nanoparticles (∼200 K). Experimental results reveal that these effects play a key role in the formation of glasslike peaks and magnetic anomalies in ferrofluids. Quantitative fits of the frequency dependent ac susceptibility to the Vogel–Fulcher model τ=τo exp[Ea/k(T−To)] clearly indicate that the blocking of magnetic nanoparticles in the frozen state significantly affects the interparticle dipole-dipole interaction, causing characteristic spin-glass-like dynamics.
Generalized dualities in one-time physics as holographic predictions from two-time physics

In the conventional formalism of physics, with 1-time, systems with different Hamiltonians or Lagrangians have different physical interpretations and are considered to be independent systems unrelated to each other. However, in this paper we construct explicitly canonical maps in 1T phase space (including timelike components, specifically the Hamiltonian) to show that it is appropriate to regard various 1T-physics systems, with different Lagrangians or Hamiltonians, as being duals of each other. This concept is similar in spirit to dualities discovered in more complicated examples in field theory or string theory. Our approach makes it evident that such generalized dualities are widespread. This suggests that, as a general phenomenon, there are hidden relations and hidden symmetries that conventional 1T-physics does not capture, implying the existence of a more unified formulation of physics that naturally supplies the hidden information. In fact, we show that 2T-physics in (d+2)-dimensions is the generator of these dualities in 1T-physics in d-dimensions by providing a holographic perspective that unifies all the dual 1T systems into one. The unifying ingredient is a gauge symmetry in phase space. Via such dualities it is then possible to gain new insights toward new physical predictions not suspected before, and suggest new methods of computation that yield results not obtained before. As an illustration, we will provide concrete examples of 1T-systems in classical mechanics that are solved analytically for the first time via our dualities. These dualities in classical mechanics have counterparts in quantum mechanics and field theory, and in some simpler cases they have already been constructed in field theory. We comment on the impact of our approach on the meaning of spacetime and on the development of new computational methods based on dualities.
On the quantum mechanical three-body problem with zero-range interactions

In this note we discuss the quantum mechanical three-body problem with pairwise zero-range interactions in dimension three. We review the state of the art concerning the construction of the corresponding Hamiltonian as a self-adjoint operator in the bosonic and in the fermionic case. Exploiting a quadratic form method, we also prove self-adjointness and boundedness from below in the case of three identical bosons when the Hilbert space is suitably restricted, i.e., excluding the "s-wave" subspace.
The snowball effect of customer slowdown in critical many-server systems

Abstract Customer slowdown describes the phenomenon that a customer’s service requirement increases with experienced delay. In healthcare settings, there is substantial empirical evidence for slowdown, particularly when a patient’s delay exceeds a certain threshold. For such threshold slowdown situations, we design and analyze a many-server system that leads to a two-dimensional Markov process. Analysis of this system leads to insights into the potentially detrimental effects of slowdown, especially in heavy-traffic conditions. We quantify the consequences of underprovisioning due to neglecting slowdown, demonstrate the presence of a subtle bistable system behavior, and discuss in detail the snowball effect: A delayed customer has an increased service requirement, causing longer delays for other customers, who in turn due to slowdown might require longer service times.
Energy transfer in rotating turbulence

The influence of rotation on the spectral energy transfer of homogeneous turbulence is investigated in this paper. Given the fact that linear dynamics, e.g. the inertial waves regime found in an RDT (rapid distortion theory) analysis, cannot affect a homogeneous isotropic turbulent flow, the study of nonlinear dynamics is of prime importance in the case of rotating flows. Previous theoretical (including both weakly nonlinear and EDQNM theories), experimental and DNS (direct numerical simulation) results are collected here and compared in order to give a self-consistent picture of the nonlinear effects of rotation on turbulence. The inhibition of the energy cascade, which is linked to a reduction of the dissipation rate, is shown to be related to a damping of the energy transfer due to rotation. A model for this effect is quantified by a model equation for the derivative-skewness factor, which only involves a micro-Rossby number Roω=ω′/(2Ω) – ratio of r.m.s. vorticity and background vorticity – as the relevant rotation parameter, in accordance with DNS and EDQNM results. In addition, anisotropy is shown also to develop through nonlinear interactions modified by rotation, in an intermediate range of Rossby numbers (RoL<1 and Roω>1), which is characterized by a macro-Rossby number RoL based on an integral lengthscale L and the micro-Rossby number previously defined. This anisotropy is mainly an angular drain of spectral energy which tends to concentrate energy in the wave-plane normal to the rotation axis, which is exactly both the slow and the two-dimensional manifold. In addition, a polarization of the energy distribution in this slow two-dimensional manifold enhances horizontal (normal to the rotation axis) velocity components, and underlies the anisotropic structure of the integral length-scales. Finally a generalized EDQNM (eddy damped quasi-normal Markovian) model is used to predict the underlying spectral transfer structure and all the subsequent developments of classic anisotropy indicators in physical space. The results from the model are compared to recent LES results and are shown to agree well. While the EDQNM2 model was developed to simulate ‘strong’ turbulence, it is shown that it has a strong formal analogy with recent weakly nonlinear approaches to wave turbulence.
Multiple-Comparisons with a Control when Variances are Unknown and Unequal

SYNOPTIC ABSTRACTSuppose given k independent populations π1,…,πk, where observations from πi are normally distributed N(μi,σ2i) (l≤i<k) with μ1,…,μk unknown, and suppose that joint (simultaneous) confidence intervals on the k-1 paired differences of means with a control μ1-μi. (2≤i≤k) (say) are desired. Previous work on this problem, with various assumptions about σ21,…,σ2k, is reviewed (Section 1). We develop a procedure which solves the general problem with σ21,…,σ2k unknown (Section 2). Tables needed to apply the procedure of Section 2 are given (Section 3). An example of application to a data set is given (Section 4). This paper is a sequel to a previous paper by the same authors which considered problems of ranking and selection with unknown and unequal variances.
Deviations from the Fowler–Nordheim theory and peculiarities of field electron emission from small-scale objects

Some reasons that require modifying the Fowler–Nordheim theory of field emission, especially for nanoscale emitters, are described. One such reason is that the microtip apex curvature radius can become comparable or even less than the width of the potential barrier on the metal–vacuum boundary. Therefore, the electric field near the surface is not homogeneous. Such deviation of the barrier shape from the traditional plane model and of the interaction between the electron and image charge must have an influence upon the emission characteristics. The possible approaches to this problem are reviewed. The results of the numerical solution of Schrodinger equation for electron tunneling, that allows us to calculate the emission current density and energy distribution of emitted electrons for arbitrary barrier shape, are presented. The problem of comparing the obtained results with the prediction of conventional Fowler–Nordheim theory is discussed.
Joint analysis of correlated repeated measures and recurrent events processes in the presence of death, with application to a study on acquired immune deficiency syndrome

Summary. In many longitudinal studies, we observe two correlated processes: a repeated measures process and a recurrent events process, both subject to a dependent terminal event. For example, in the ‘Terry Beirn community programs for clinical research on AIDS’ (CPCRA) study, higher CD4 cell counts are associated with lower risk of recurrent opportunistic diseases. They are also correlated with mortality, e.g. higher CD4 cell repeated measures and a lower rate of opportunistic disease imply better survival for patients infected with the human immunodeficiency virus. We propose a joint random‐effects model for the three correlated outcomes. The correlation is modelled by conditioning on shared random effects. Covariate effects can be taken into account in the model. Maximum likelihood estimation and inference are carried out through a Gaussian quadrature technique, assuming piecewise constant baseline hazards for recurrent events and death. The model can be fitted conveniently by Gaussian quadrature tools, e.g. SAS procedure NLMIXED. Simulation studies show that the estimation method yields satisfactory results. We apply this method to the CPCRA data.
LATITUDINAL AND ENERGY DEPENDENCE OF ENERGETIC NEUTRAL ATOM SPECTRAL INDICES MEASURED BY THE INTERSTELLAR BOUNDARY EXPLORER

We investigate the latitudinal and energy dependence of the globally distributed 0.5–6 keV energetic neutral atom (ENA) spectra measured by the Interstellar Boundary Explorer (IBEX) during the first 3 yrs of the mission. Our results are: (1) the ENA spectral indices at the two lowest energies (0.89 and 1.47 keV) exhibit no clear trend with ecliptic latitude θ, while those at ∼2.29 and ∼3.41 keV exhibit a clear latitudinal pattern; flatter spectra occur above 60° latitude and steeper spectra occur ±30° of the equator. (2) The latitudinal dependence of the spectral indices at different energies can be represented by the cosine function γ = a 0 + a 1 cos ( a 2 θ ) ? > with unique offsets, amplitudes, and phase angles; the higher energy ENA indices transition to successively larger amplitudes within ±45° of the equator. Our results confirm the previously reported latitudinal organization of the ENA spectra and their remarkable similarity to that of the solar wind (SW) speed observed by Ulysses in the inner heliosphere. While earlier studies showed that the ∼0.5–6 keV globally distributed ENA spectral indices could be represented as single power laws over much of the sky, our new results indicate that this is an over-simplification because the spectral indices have an energy and latitude dependence. This dependence is an important factor that must be taken into consideration by models and simulations that seek to map the IBEX ENA observations back to the latitudinal profile of the SW speed structure observed in the inner heliosphere.
Sub-attonewton force detection at millikelvin temperatures

A 290-nm-thick single-crystal silicon cantilever has been cooled in vacuum to a temperature of 110 mK in order reduce its thermal motion and thereby improve the achievable force resolution. Since the thermal conductivity of the silicon cantilever is extremely low at millikelvin temperatures, an improved optical fiber interferometer was developed to measure the subangstrom thermal motion with optical powers as low as 2 nW. At the lowest temperature, the cantilever exhibited a quality factor of 150 000 and achieved a noise temperature of 220 mK, with a corresponding force noise of 820 zN in a 1 Hz bandwidth.
Prescription du spectre de Steklov dans une classe conforme

Sur toute variete compacte de dimension $n\geq3$ a bord, on prescrit toute partie finie du spectre de Steklov dans une classe conforme donnee. En particulier, on prescrit la multiplicite des valeurs propres. Sur une surface compacte a bord donnee, on montre que la multiplicite de la $k$-ieme valeur propre est bornee independamment de la metrique. Sur le disque, on donne des resultats plus precis : la multiplicite de la 1\iere{} et la 2\ieme{} valeurs propres non nulles sont au plus~2 et~3 respectivement. Pour le probleme de Steklov-Neumann sur le disque, on montre que la multiplicite de la $k$-ieme valeur propre non nulle est au plus $k+1$.
Compulsory te reo Māori in Aotearoa New Zealand schools

While support for compulsory te reo Māori in schools in Aoteaora New Zealand is growing, there is a risk that any future policy could fail, or be only poorly implemented, unless we understand more deeply the factors which shape effective language policy implementation in schools. In this paper we employ a ‘future policy analysis' to explore what it would take to effectively implement a compulsory te reo Māori policy in schools in the future. We report on interviews with twelve purposively selected stakeholders (including Māori, Pākehā, Chinese and Samoan teachers, principals and one Member of Parliament) to elicit from their experiences and reflections the key elements required to implement te reo Māori well in schools. Participants identified that prioritising and valuing te reo Maori was foundational and essential for any potential policy shift at both national and school level. In addition, participants elaborated on how teacher expertise, resourcing, time and leadership support through senior management was integral to successful adoption and implementation. The paper concludes by recommending urgent attention to a range of future-focused strategies that beginning right now could bring about transformational change in our schools and give te reo Māori the mana it deserves.
Theoretical calculation of oxygen K electron-energy-loss near-edge structures of Si-doped MgO

Maximum solubility of Si in MgO has been reported to be 9.0 at. %. The local environment of the Si solute is of great interest. In order to foresee the difference of the O K-edge electron-energy-loss near-edge structure (ELNES) or x-ray absorption near-edge structure (XANES) due to the presence of the Si solute, first-principles molecular orbital calculations are performed using model clusters composed of 27 and 125 atoms that include a core hole. Extra peaks are found in the theoretical O K-edge photoabsorption cross section (PACS) of the Si-doped cluster. Their positions are found to depend strongly on the Si-O bond length. A realistic model cluster for the Si-doped MgO is constructed by total energy minimization using interatomic potentials. An Mg vacancy is included to keep the charge neutrality. The extra feature in the O K-edge PACS due to the presence of Si is then expected to be located mainly at the higher-energy shoulder of the main peak of the undoped MgO.
Women Are More Infected and Seek Care Faster but Are Less Severely Ill: Gender Gaps in COVID-19 Morbidity and Mortality during Two Years of a Pandemic in Israel

In the context of COVID-19 outcomes, global data have deduced a gender bias towards severe disease among males. The aim is to compare morbidity and mortality during two years of the COVID-19 pandemic in female and male patients with COVID-19, as well as to assess length of stay, time of health-seeking behavior after positive diagnosis, and vaccination differences. A retrospective-archive study was conducted in Israel from 1 March 2020 to 1 March 2022 (two consecutive years). Data were obtained from the Israeli Ministry of Health’s (MOH) open COVID-19 database. The findings indicate female infections are 1.12 times more likely, across almost all age groups, apart from the youngest (0–19) age groups. Despite this, the relative risk of severe illness, intubation and mortality is higher among men. In addition, our findings indicate that the mean number of days taken by unvaccinated men from positive diagnosis to hospital admission was greater than among unvaccinated women among the deceased population. The findings of this study reveal lessons learned from the COVID-19 global pandemic. Specifically, the study shows how human biological sex may have played a role in COVID-19 transmission, illness, and death in Israel. The conclusions of this study indicate that targeted approaches, which take into consideration sex and gender and the intersecting factors are necessary to engage in the fight against COVID-19 and ensure the most effective and equitable pandemic response.
Binary quadratic forms and ray class groups

Abstract Let K be an imaginary quadratic field different from $\open{Q}(\sqrt {-1})$ and $\open{Q}(\sqrt {-3})$. For a positive integer N, let KN be the ray class field of K modulo $N {\cal O}_K$. By using the congruence subgroup ± Γ1(N) of SL2(ℤ), we construct an extended form class group whose operation is basically the Dirichlet composition, and explicitly show that this group is isomorphic to the Galois group Gal(KN/K). We also present an algorithm to find all distinct form classes and show how to multiply two form classes. As an application, we describe Gal(KNab/K) in terms of these extended form class groups for which KNab is the maximal abelian extension of K unramified outside prime ideals dividing $N{\cal O}_K$.
Ballistic and pocket limitations of mobility in nanometer Si metal-oxide semiconductor field-effect transistors

Room-temperature magnetoresistance of nanometer bulk Si n-type metal-oxide semiconductor field-effect transistors was measured at magnetic fields up to 10 T. The electron magnetoresistance mobility was determined for transistors with the gate length in 30 to 740 nm range and was shown to decrease with decreasing the gate length. We show that the mobility reduction is caused both by the ballistic and the pocket effect and that for the strong inversion these two effects are of a comparable magnitude.
Formation of filaments in the Crab Nebula by a thermal synchrotron instability

Une etude de la formation de filaments dans la nebuleuse du crabe est realisee. Deux modeles d'expansion sont developpes. L'un, a 2 dimensions, ou les filaments sont formes par les instabilites synchrotron thermiques dans une enveloppe spherique en expansion, l'autre, a trois dimensions, ou les filaments sont formes dans un nuage en expansion isotrope. Les resultats numeriques sont presentes et analyses
Performance analysis of bearing-only target location algorithms

The performance of two well-known bearing-only location techniques, the maximum likelihood (ML) and the Stansfield estimators, is examined. Analytical expressions are obtained for the bias and the covariance matrix of the estimation error, which permit performance comparison for any case of interest. It is shown that the Stansfield algorithm provides biased estimates even for large numbers of measurements, in contrast with the ML method. The RMS error of the Stansfield technique is not necessarily larger than the RMS of the ML technique. However, it is shown that the ML technique is superior to the Stansfield method when the number of measurements is large enough. Simulation results verify the predicted theoretical performance. >