TopSTO:a 115-line code for topology optimization of structures under stationary stochastic dynamic loading

The use of topology optimization in structural design under dynamic excitation is becoming more prevalent in the literature.While many such applications utilize frequency or time domain formulations,relatively few consider stochastic dynamic excitations.This paper presents an efficient and compact code called TopSTO for structural topology optimization considering stationary stochastic dynamic loading using a method derived from random vibration theory.The theory,described in conjunction with the implementation in the provided code,is illustrated for a seismically excited building.This work demonstrates the efficiency of the approach in terms of both the computational resources and minimal amount of code required.This code is intended to serve as a baseline for understanding the theory and implementation of this topology optimization approach and as a foundation for additional applications and developments.

Understanding the Formation of Galaxies with Warm Dark Matter

The formation of galaxies with warm dark matter is approximately adiabatic. The cold dark matter limit is singular and requires relaxation. In these lecture notes, we develop, step-by-step, the physics of galaxies with warm dark matter, and their formation. The theory is validated with observed spiral galaxy rotation curves. These observations constrain the properties of the dark matter particles.

A Comparison between Late Preterm and Term Infants with Respiratory Distress Syndrome, Early-Onset Sepsis, and Neonatal Jaundice in Ecuadorian Newborns

Background: To examine the differences in prevalence of respiratory distress syndrome, early-onset sepsis and jaundice, between late preterm infants versus term infants in Ecuadorian newborns. Methods: Study design: Epidemiological, observational, and cross-sectional, with two cohorts of patients. Settings: IESS Quito Sur Hospital at Quito, Ecuador, from February to April of 2020. Participants: This study included 204 newborns, 102 preterm infants, 102 term infants. Results: There are significant differences between late preterm infants and term infants, with a p-value of 0.000 in the prevalence of early sepsis, 70.59% vs. 35.29%. In respiratory distress syndrome between late and term premature infants, significant differences were observed with a p-value of 0.000, the proportion being 55.58% vs. 24.51% respectively. The prevalence of jaundice is higher in term infants with a p value of 0.002, 72.55%, versus 51.96% in late preterm infants, and the mean value of bilirubins in mg/dL was higher in term infants 14.32 versus 12.33 in late preterm infants;this difference is statistically significant with a p value of 0.004. Admission to the NICU is more frequent in late preterm infants with a p-value of 0.000, being 42.16% for late preterm infants vs. 7.84% in term infants;the mean of the hospital days with p-value 0.005, was higher in late preterm infants 4.97 days vs. 3.55 days for term newborns. Conclusion: Due to the conditions of their immaturity, late preterm infants are 2.86 times more likely to present early sepsis than full-term newborns. It is shown that late preterm infants are 2.69 times more likely to have respiratory distress syndrome compared to term infants, therefore, late preterm infants have a longer hospital stay of 4.97 days versus 3.55 days in term infants. Jaundice and mean bilirubin levels are higher in term infants due to blood group incompatibility and insufficient breastfeeding.

Measurements of the Dark Matter Mass, Temperature and Spin

We summarize several measurements of the dark matter temperature-to-mass ratio, or equivalently, of the comoving root-mean-square thermal velocity of warm dark matter particles vhrms(1). The most reliable determination of this parameter comes from well measured rotation curves of dwarf galaxies by the LITTLE THINGS collaboration: vhrms(1)=406±69 m/s. Complementary and consistent measurements are obtained from rotation curves of spiral galaxies measured by the SPARC collaboration, density runs of giant elliptical galaxies, galaxy ultra-violet luminosity distributions, galaxy stellar mass distributions, first galaxies, and reionization. Having measured vhrms(1), we then embark on a journey to the past that leads to a consistent set of measured dark matter properties, including mass, temperature and spin.

Are James Webb Space Telescope Observations Consistent with Warm Dark Matter?

We compare observed with predicted distributions of galaxy stellar masses M* and galaxy rest-frame ultra-violet luminosities per unit bandwidth LUV, in the redshift range z=2 to 13. The comparison is presented as a function of the comoving warm dark matter free-streaming cut-off wavenumber kfs. For this comparison the theory is a minimal extension of the Press-Schechter formalism with only two parameters: the star formation efficiency, and a proportionality factor between the star formation rate per galaxy and LUV. These two parameters are fixed to their values obtained prior to the James Webb Space Telescope (JWST) data. The purpose of this comparison is to identify if, and where, detailed astrophysical evolution is needed to account for the new JWST observations.

A Comment on the Hubble Expansion Parameter Tension

We point out that the recent baryon acoustic oscillation measurement by the Dark Energy Survey collaboration relieves the Hubble expansion parameter tension.

Adding Dark Matter to the Standard Model

Detailed and redundant measurements of dark matter properties have recently become available. To describe the observations we consider scalar, vector and sterile neutrino dark matter models. A model with vector dark matter is consistent with all current observations.

Study of Baryon Acoustic Oscillations with SDSS DR13 Data and Measurements of Ω_kand Ω_DE(a)

We measure the baryon acoustic oscillation (BAO) observables , , and as a function of red shift z in the range 0.1 to 0.7 with Sloan Digital Sky Survey (SDSS) data release DR13. These observables are independent and satisfy a consistency relation that provides discrimination against miss-fits due to background fluctuations. From these measurements and the correlation angle of fluctuations of the Cosmic Microwave Background (CMB), we obtain , and for dark energy density allowed to vary as . We present measurements of at six values of the expansion parameter a. Fits with several scenarios and data sets are presented. The data is consistent with space curvature parameter? and constant.

Higher-Order Corrections for the Deflection of Light around a Massive Object. Diagonal PadéApproximants and Ray-Tracing Algorithms

From the Schwarzschild metric we obtain the higher-order terms for the deflection of light around a massive object using the Lindstedt-Poincaré method to solve the equation of motion of a photon around the stellar object. The asymptotic series obtained by this method was obtained up to order 20 in the expansion parameter, and was found to better approximate the numerical solution with higher order terms—a property that can’t be taken for granted for any asymptotic series. Additionally, we obtain diagonal Padé approximants from the perturbation expansion, and we show how these are a better fit for the numerical data than the original formal Taylor series. Furthermore, we use these approximants in ray-tracing algorithms to model the bending of light around massive objects.

Functional N-Representability in 2-Matrix,1-Matrix,and Density Functional Theories

The N-representability conditions on the reduced second-order reduced density matrix (2-RDM), impose restrictions not only in the context of reduced density matrix theory (RDMT), but also on functionals advanced in one-matrix theory such as natural orbital functional theory (NOFT), and on functionals depending on the one-electron density such as those of density functional theory (DFT). We review some aspects of the applications of these N-representability conditions in these theories and present some conclusions.

Exploring Inflation Options for Warm Dark Matter Coupled to the Higgs Boson

We extend the Standard Model with a scalar warm dark matter field S with an interaction with the Higgs boson ∅. This warm dark matter scenario is in agreement with cosmological observations if S and ∅ come into thermal and diffusive equilibrium before the temperature drops below the Higgs boson mass mH. We study inflation driven by the fields ∅ or S, and also study preheating and reheating, in order to constrain the parameters of this extension of the Standard Model. It is remarkable that, with the current data, these models pass a closure test with no free parameters.

A Study of Warm Dark Matter, the Missing Satellites Problem, and the UV Luminosity Cut-Off

In the warm dark matter scenario, the Press-Schechter formalism is valid only for galaxy masses greater than the “velocity dispersion cut-off”. In this work we extend the predictions to masses below the velocity dispersion cut-off, and thereby address the “Missing Satellites Problem” of the cold dark matter ΛCDM scenario, and the rest-frame ultra-violet luminosity cut-off required to not exceed the measured reionization optical depth. For warm dark matter we find agreement between predictions and observations of these two phenomena. As a by-product, we obtain the empirical Tully-Fisher relation from first principles.

The Adiabatic Invariant of Dark Matter in Spiral Galaxies

Collisionless dark matter can only expand adiabatically. To test this idea and constrain the properties of dark matter, we study spiral galaxies in the “Spitzer Photometry and Accurate Rotation Curves” (SPARC) sample. Fitting the rotation curves, we obtain the root-mean-square (rms) velocity and density of dark matter in the core of the galaxies. We then calculate the rms velocity vhrms (1) that dark matter particles would have if expanded adiabatically from the core of the galaxies to the present mean density of dark matter in the universe. We obtain this “adiabatic invariant” vhrms (1) for 40 spiral galaxies. The distribution of vhrms (1) has a mean 0.87 km/s and a standard deviation of 0.27 km/s. This low relative dispersion is noteworthy given the wide range of the properties of these galaxies. The adiabatic invariant vhrms (1) may, therefore, have a cosmological origin. In this case, the rms velocity of non-relativistic dark matter particles in the early universe when density perturbations are still linear is vhrms (a)=vhrms (1)/a, where a is the expansion parameter. The adiabatic invariant obtains the ratio of dark matter temperature Th (a) to mass mh in the early universe.

A Study of Dark Matter with Spiral Galaxy Rotation Curves

To constrain the properties of dark matter, we study spiral galaxy rotation curves measured by the THINGS collaboration. A model that describes a mixture of two self-gravitating non-relativistic ideal gases, “baryons” and “dark matter”, reproduces the measured rotation curves within observational uncertainties. The model has four parameters that are obtained by minimizing a x2 between the measured and calculated rotation curves. From these four parameters, we calculate derived galaxy parameters. We find that dark matter satisfies the Boltzmann distribution. The onset of Fermi-Dirac or Bose-Einstein degeneracy obtains disagreement with observations and we determine, with 99% confidence, that the mass of dark matter particles is mh> 16 eV if fermions, or mh> 45 eV if bosons. We measure the root-mean-square velocity of dark matter particles in the spiral galaxies. This observable is of cosmological origin and allows us to obtain the root-mean-square velocity of dark matter particles in the early universe when perturbations were still linear. Extrapolating to the past we obtain the expansion parameter at which dark matter particles become non-relativistic: ahNR=[4.17±0.34(STAT)±2.50(SYST)]×10−6. Knowing we then obtain the dark matter particle mass mh=69.0±4.2(stat)±31.0(syst)eV, and the ratio of dark matter-to-photon temperature Th/T=0.389±0.008(stat)±0.058(syst) after e+e−annihilation while dark matter remains ultra-relativistic. We repeat these measurements with ten galaxies with masses that span three orders of magnitude, and angular momenta that span five orders of magnitude, and obtain fairly consistent results. We conclude that dark matter was once in thermal equilibrium with the (pre?) Standard Model particles (hence the observed Boltzmann distribution) and then decoupled from the Standard Model and from self-annihilation at temperatures above mμ. These results disfavor models with freeze-out or freeze-in. We also measure the primordial amplitude of vector modes, and constrain the baryon-dark matter cross-section: . Finally, we consider sterile Majorana neutrinos as a dark matter candidate.

Fermion or Boson Dark Matter?

We measure properties of dark matter in four well motivated scenarios: fermions with ultra-relativistic thermal equilibrium (URTE), bosons with URTE, fermions with non-relativistic thermal equilibrium (NRTE), and bosons with NRTE. We attempt to discriminate between these four scenarios with studies of spiral galaxy rotation curves, and galaxy stellar mass distributions. The measurements show evidence for boson dark matter with a significance of 3.5σ, and obtain no significant discrimination between URTE and NRTE.

Ancient DNA of the pygmy marmoset type specimen Cebuella pygmaea(Spix,1823)resolves a taxonomic conundrum

The pygmy marmoset,the smallest of the anthropoid primates,has a broad distribution in Western Amazonia.Recent studies using molecular and morphological data have identified two distinct species separated by the Napo and Solimoes-Amazonas rivers.However,reconciling this new biological evidence with current taxonomy,i.e.,two subspecies,Cebuella pygmaea pygmaea(Spix,1823)and Cebuella pygmaea niveiventris(Lönnberg,1940),was problematic given the uncertainty as to whether Spix’s pygmy marmoset(Cebuella pygmaea pygmaea)was collected north or south of the Napo and Solimoes-Amazonas rivers,making it unclear to which of the two newly revealed species the name pygmaea would apply.Here,we present the first molecular data from Spix’s type specimen of Cebuella pygmaea,as well as novel mitochondrial genomes from modern pygmy marmosets sampled near the type locality(Tabatinga)on both sides of the river.With these data,we can confirm the correct names of the two species identified,i.e.,C.pygmaea for animals north of the Napo and Solimoes-Amazonas rivers and C.niveiventris for animals south of these two rivers.Phylogenetic analyses of the novel genetic data placed into the context of cytochrome b gene sequences from across the range of pygmy marmosets further led us to reevaluate the geographical distribution for the two Cebuella species.We dated the split of these two species to 2.54 million years ago.We discuss additional,more recent,subdivisions within each lineage,as well as potential contact zones between the two species in the headwaters of these rivers.

Cold or Warm Dark Matter?: A Study of Galaxy Stellar Mass Distributions

We compare the observed galaxy stellar mass distributions in the redshift range with expectations of the cold ΛCDM and warm ΛWDM dark matter models, and obtain the warm dark matter cut-off wavenumber: . This result is in agreement with the independent measurements with spiral galaxy rotation curves, confirms that kfs is due to warm dark matter free-streaming, and is consistent with the scenario of dark matter with no freeze-in and no freeze-out. Detailed properties of warm dark matter can be derived from kfs. The data disfavors the ΛCDM model.

Simulations and Measurements of Warm Dark Matter Free-Streaming and Mass

We compare simulated galaxy distributions in the cold ΛCDM and warm ΛWDM dark matter models. The ΛWDM model adds one parameter to the ΛCDM model, namely the cut-off wavenumber kfs of linear density perturbations. The challenge is to measure kfs. This study focuses on “smoothing lengths” π/kfs in the range from 12 Mpc to 1 Mpc. The simulations reveal two distinct galaxy populations at any given redshift z: hierarchical galaxies that form bottom up starting at the transition mas?Mfs, and stripped down galaxies that lose mass to neighboring galaxies during their formation, are near larger galaxies, often have filamentary distributions, and seldom fill voids. We compare simulations with observations, and present four independent measurements of kfs, and the mass mh of dark matter particles, based on the redshift of first galaxies, galaxy mass distributions, and rotation curves of spiral galaxies.

A Study of Dark Matter with Spiral Galaxy Rotation Curves. Part II

In Part II of this study of spiral galaxy rotation curves we apply corrections and estimate all identified systematic uncertainties. We arrive at a detailed, precise, and self-consistent picture of dark matter.

A Study of Three Galaxy Types, Galaxy Formation, and Warm Dark Matter

We try to bridge the gap between the theory of linear density-velocity-gravitational perturbations in the early universe, and the relaxed galaxies we observe today. We succeed quantitatively for dark matter if dark matter is warm. The density runs of baryons and of dark matter of relaxed galaxies are well described by hydro-static equations. The evolution from initial linear perturbations to final relaxed galaxies is well described by hydro-dynamical equations. These equations necessarily include dark matter velocity dispersion. If the initial perturbation is large enough, the halo becomes self-gravitating. The adiabatic compression of the dark matter core determines the final core density, and provides a negative stabilizing feedback. The relaxed galaxy halo may form adiabatically if dark matter is warm. The galaxy halo radius continues to increase indefinitely, so has an ill-defined mass.