Auswahl der wissenschaftlichen Literatur zum Thema „Hubble tension“

This Essay explores consequences of a dark nonlinear electromagnetic sector in a universe with a net dark charge for matter. The cosmological dynamics can be described by a Lemaître model and can be understood, thanks to a screening mechanism driven by the electromagnetic nonlinearities that suppress the dark force on small scales. Only at low redshift, when the screening scale enters the Hubble horizon, do cosmological structures commence to feel the dark repulsion. This repulsive force enhances the local value of the Hubble constant, thus providing a promising scenario for solving the Hubble tension. Remarkably, the dark electromagnetic interaction can have a crucial impact on peculiar velocities, i.e. introducing a bias in their reconstruction methods, and having the potential to explain the presence of a dark flow.

Abstract Braneworld models with induced gravity exhibit phantom-like behavior of the effective equation of state of dark energy. They can, therefore, naturally accommodate higher values of H 0, preferred by recent local measurements while satisfying the cosmic microwave background constraints. We test the background evolution in such phantom braneworld scenarios with the current observational data sets. We find that the phantom braneworld prefers a higher value of H 0 even without the R19 prior, thereby providing a much better fit to the local measurements. Although this braneworld model cannot fully satisfy all combinations of cosmological observables, among existing dark energy candidates the phantom brane provides one of the most compelling explanations of cosmic evolution.

ABSTRACT Many late-time approaches for the solution of the Hubble tension use late time smooth deformations of the Hubble expansion rate H(z) of the Planck18/ΛCDM best fit to match the locally measured value of H0 while effectively keeping the comoving distance to the last scattering surface and Ω0mh2 fixed to maintain consistency with Planck CMB measurements. A well-known problem of these approaches is that they worsen the fit to low z distance probes. Here, we show that another problem of these approaches is that they worsen the level of the Ω0m − σ8 growth tension. We use the generic class of CPL parametrizations corresponding to evolving dark energy equation of state parameter $w(z)=w_0+w_1\frac{z}{1+z}$ with local measurements H0 prior and identify the pairs (w0, w1) that satisfy this condition. This is a generic class of smooth deformations of H(z) that are designed to address the Hubble tension. We show that for these models the growth tension between dynamical probe data and CMB constraints is worse than the corresponding tension of the standard Planck18/ΛCDM model. We justify this feature using a full numerical solution of the growth equation and fit to the data, as well as by using an approximate analytic approach. The problem does not affect recent proposed solutions of the Hubble crisis involving a SnIa intrinsic luminosity transition at zt ≃ 0.01.

ABSTRACT Dark energy is one of the greatest scientific mysteries of today. The idea that dark energy originates from quantum vacuum fluctuations has circulated since the late ’60s, but theoretical estimations of vacuum energy have disagreed with the measured value by many orders of magnitude, until recently. Lifshitz theory applied to cosmology has produced the correct order of magnitude for dark energy. Furthermore, the theory is based on well-established and experimentally well-tested grounds in atomic, molecular and optical physics. In this paper, we confront Lifshitz cosmology with astronomical data. We find that the dark–energy dynamics predicted by the theory is able to resolve the Hubble tension, the discrepancy between the observed and predicted Hubble constant within the standard cosmological model. The theory is consistent with supernovae data, Baryon Acoustic Oscillations and the Cosmic Microwave Background. Our findings indicate that Lifshitz cosmology is a serious candidate for explaining dark energy.

The recent measurements of the Hubble constant based on the standard [Formula: see text]CDM cosmology reveal an underlying disagreement between the early-Universe estimates and the late-time measurements. Moreover, as these measurements improve, the discrepancy not only persists but becomes even more significant and harder to ignore. The present situation places the standard cosmology in jeopardy and provides a tantalizing hint that the problem results from some new physics beyond the [Formula: see text]CDM model. It is shown that a nonconventional theory — the Milne model — which introduces a different evolution dynamics for the Universe, alleviates the Hubble tension significantly. Moreover, the model also averts some long-standing problems of the standard cosmology, for instance, the problems related with the cosmological constant, the horizon, the flatness, the Big Bang singularity, the age of the Universe and the nonconservation of energy.

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Existe uma tensão ao redor de 3.4σ entre as determinações globais e locais da constante de Hubble H0 fornecidas por observações de supernovas de tipo Ia [1] e da radiação cósmica de fundo [2], respectivamente. Esta tensão não pode ser explicada pelo modelo de concordança ΛCDM e ela poderia ser produzida por erros sistemáticos desconhecidos na calibração da escadaria cósmica ou na análise da radiação cósmica de fundo. Contudo, na ausência destes erros, a tensão poderia ser uma sugestão da existência de física além do modelo ΛCDM. Por outro lado, é bem sabido que a teoria linear de perturbações prevê uma variância cósmica sobre o parâmetro de Hubble H0, produzida pelas velocidades peculiares e estruturas locais, que conduz a um erro sistemático na determinações locais de H0. No presente trabalho, nós consideramos a variância cósmica, prevista pela teoria de perturbações lineares, na presença de uma energia escura não padrão, com o fim de calcular o erro sistemático sobre a taxa de Hubble local. A energia escura não padrão é representada pelo modelo de quintessência e pelas parametrizações γCDM, γwCDM e γaCDM. Logo, nós incluímos o erro sistemático na análise estatística Bayesiana que usa dados da radiação cósmica de fundo, oscilações acústicas dos bárions, supernovas de tipo Ia, distorções no espaço de redshift e H0locl . Assim, nós mostramos o efeito da variância cósmica na determinação de parâmetros cosmológicos e o problema de tensão. Finalmente, nós realizamos a seleção de modelos usando os critérios de seleção AIC e BIC e também mostramos como o erro sistemático, fornecido pelos modelos de energia escura não padrão, poderia ajudar a aliviar a atual tensão nas determinações de H0.

In recent years, the increasingly precise constraints on the value of the Hubble constant, H0, have highlighted a discrepancy between the results arising from early-time and late-time measurements. A potential solution to this so-called Hubble tension is the hypothesis that we reside in a cosmic void, i.e. an underdense cosmic neighbourhood characterized by a faster local expansion rate. In this thesis, we model this scenario through the Lemaître-Tolman-Bondi formalism for an isotropic but inhomogeneous universe containing matter, curvature and a cosmological constant, which we denote by ΛLTB. We numerically implement this framework with two different formulations for the local matter density profile, respectively based upon a more realistic Gaussian ansatz and the idealized scenario of the so-called Oppenheimer-Snyder model. We then constrain the background cosmology and the void parameters involved in each case through a Markov Chain Monte Carlo analysis with a combination of recent data sets: the Pantheon Sample of type Ia supernovae, a collection of baryon acoustic oscillations data points from different galaxy surveys and the distance priors extracted from the latest Planck data release. For both models, the resulting bounds on the investigated parameter space suggest a preference for a -13% density drop with a size of approximately 300 Mpc, interestingly matching the prediction for the so-called KBC void already identified on the basis of independent analyses using galaxy distributions. We quantify the level of improvement on the Hubble tension by analyzing the ΛLTB constraints on the B-band absolute magnitude of the supernovae, which provides the calibration for the local measurements of H0. Since no significant difference is observed with respect to an analogous fit performed with the standard ΛCDM model, we conclude that the potential presence of a local void does not resolve the tension.

Advancements in the field of cosmology over the past decades have dramatically increased our knowledge of the origin and evolution of the Universe, with increasing precision on measured cosmological parameters. The best model describing the evolution of our Universe is the Lambda Cold Dark Matter ($Lambda$CDM) model. While this model fits numerous observations, some tensions with respect to it have been highlighted. One of the most intriguing is the Hubble tension: a disagreement of $sim 5 sigma$ between the $H_0$ values measured at early- and late-time Universe. It is yet unclear whether this tension arises from subtle systematic uncertainties, or we are observing interesting new physics. Furthermore, the force behind the accelerated expansion of the Universe, called as Dark energy (DE), remains almost a mystery with little to no understanding about its nature and evolution. This thesis aims at using different types of astrophysical transients as cosmological probes. I work on advancing the standardization techniques of three types of transients currently detectable at different redshift scales -- supernovae Type Ia (SNe Ia, $z lesssim 1.2$), superluminous supernovae (SLSN, $z lesssim 4$), and kilonovae (KNe, $z lesssim 0.1$). I use these transients to estimate the Hubble constant and investigate the possibility to standardise their luminosities. The new methodologies developed here are particularly promising to address the Hubble tension problem and to constrain the DE evolution in the next decade with the advent of new instruments, such as the Vera Rubin Observatory, Roman Space Telescope, and the James Webb Space Telescope. For SNe Ia, I develop an innovative method to calibrate their distance scale based on the surface brightness fluctuations (SBF) distances of their host galaxies. I calibrate SN luminosity using a sample of 24 anchor SNe Ia hosted in galaxies with SBF distance measurements. With a Hubble flow sample of $sim 100$ SNe Ia, I estimate $H_0 = 70.50 pm 2.37 (stat) pm 3.38 (sys)$,si{km.s^{-1}.Mpc^{-1}}. This value sits midway in the range defined by the Hubble tension, and is consistent with early and the late Universe $H_0$ measurements within the errors. This work also examines the dependence of SNe Ia luminosity on its host galaxy properties in a comparative study involving different types of host galaxies. Our results point to possible intrinsic differences among the luminosity of SNe hosted in distinct types of environments. This dependence is particularly interesting for estimating the cosmological parameters, and to unveil the nature and environment of SN Ia explosion, which remains largely unknown. Additionally, I explore the use of SLSNe type I as a cosmological probe for the very high redshift Universe. These sources can be detected in their rest frame ultraviolet (UV) up to $z sim 7$ using optical and infrared telescopes. I evaluate their peak magnitude correlations with the light curve properties in the rest frame UV using a sample of 22 high redshift ($ 1 lesssim z lesssim 3.2$) SLSNe-I observed to date. I find a linear correlation between the UV peak absolute magnitudes and rise time, having an intrinsic scatter ($sigma_{int}$) of 0.29. Interestingly, this correlation is further tightened ($sigma_{int} approx 0.2$) eliminating those SLSNe which show a pre-peak bump. This result hints at the possibility that the ``Bumpy" SLSNe could belong to a different population. I also observe weak correlations between the peak luminosity and color indices of SLSNe light curves. No relationship is found between peak magnitudes in the UV band and the decline rate ($Delta M_{15}$) of the light curves in contrast to what is typically found in optical band. The correlations found here are promising and encourage further exploration into the use of SLSNe as high redshift cosmological probes. Finally, I contribute to the investigation of the use of Kilonovae as distance indicators in the local Universe. KNe enable to make an independent measurement of the $H_0$. I apply techniques similar to SNe Ia standardisation with two different sets of KNe properties; measured quantities (decline rate and color) and inferred ejecta quantities (mass, velocity and composition). Considering the only confirmed kilonova, AT2017gfo, associated with GW170817, I standardize it correlating its luminosity with the measured and the inferred quantities. We evaluate $H_0 = SI[parse-numbers = false, number-math-rm = ensuremath]{109^{+49}_{-35}}{km.s^{-1}.Mpc^{-1}}$ for the measured analysis, and $H_0 = SI[parse-numbers = false, number-math-rm = ensuremath]{85^{+22}_{-17}}{km.s^{-1}.Mpc^{-1}}$ and $H_0 = SI[parse-numbers = false, number-math-rm = ensuremath]{79^{+23}_{-15}}{km.s^{-1}.Mpc^{-1}}$ for the two inferred analyses. While waiting for larger samples, this work provides a proof-of-concept for a valuable method to obtain an independent constraint on $H_0$. In summary, my work gives new methodologies to constrain the cosmological parameters and understand astrophysical systematics using different types of transients. The analysis of multi-filter observations at different redshift scales enable us to evaluate the $H_0$ with a complementary set of astrophysical transients. For SN Ia, I demonstrate the potential of the use of SBF measurements to calibrate SN luminosity relations. My results point to an interesting astrophysical difference among SN Ia in different type of galaxies, which could reduce the $H_0$ tension and give information about the progenitor/environment of SN Ia. For SLSNe and KNe, my work inserts in the pioneering works exploring these sources as possible standard candles, with the former at high redshift to constrain dark energy evolution, and the latter as a new independent local probe for $H_0$. The transients explored here have the potential to probe local to $z gtrsim 10$ Universe, back to first generations of stars and well into the deceleration epoch. This work lays the framework for powerful cosmological tools in the upcoming years when larger data samples and larger distances will be accessible with the advent of new instruments.

In questa Tesi proponiamo uno studio analitico volto alla quantificazione di sinergie e complementarità tra sonde cosmologiche indipendenti in un contesto di inferenza dei parametri cosmologici. Tramite lo sviluppo di un codice computazionale versatile e robusto, sfruttiamo la statistica bayesiana per ricavare da una selezione di sonde cosmologiche a z<8 precisi vincoli su di un'ampia rosa di modelli cosmologici. In particolare, affianchiamo a due delle principali sonde, SuperNovae di Tipo Ia e Oscillazioni Barioniche Acustiche, alcune delle sonde più promettenti emerse di recente: Cronometri Cosmici, Quasar e Gamma-Ray Burst. Analizzandole sistematicamente al variare delle ipotesi cosmologiche esploriamo, oltre al modello standard ΛCDM, alcune delle sue più valide estensioni includendo una variazione nella geometria assunta e nella forma dell'equazione di stato dell'energia oscura. Abbiamo così la possibilità di identificare punti di forza e debolezza di ciascun metodo, e di valutare il contributo di ognuno al vincolo dei parametri cosmologici. Introduciamo perciò un primo metodo analitico per la quantificazione di sinergie e complementarità tra sonde cosmologiche indipendenti tramite la definizione di un parametro di ortogonalità che misuri l’angolo reciproco tra i vincoli delle varie sonde. Sfruttiamo quindi questo parametro per individuare la combinazione più efficace in funzione dei vincoli cosmologici che si desidera imporre. L'analisi congiunta di tutte le sonde produce interessanti risultati nell'ambito del paradigma cosmologico moderno. Indagando la forma dell'equazione di stato dell'energia oscura otteniamo w=-1.00±0.07 (1σ), mentre dallo studio della geometria ricaviamo Ωk=-0.07±0.11 (1σ). Per una cosmologia standard, troviamo un valore della costante di Hubble pari a 69.4±3.2 km/s/Mpc (1σ) non ancora competitivo nel contesto della Tensione di Hubble ma che, con l'inclusione di ulteriori sonde innovative, promette di raggiungere una maggiore precisione.

We are now entering the era of precision cosmology. Astrophysical and cosmological tests can be done at high precision to constrain physics beyond standard model. We make inferences on the running of the primordial perturbations spectral index and the effective number of neutrinos in the early universe and show an important statistical degeneracy in their posterior distributions. We calculate the cosmic birefringence spectrum due to a PNGB which may cause early dark energy, showing that the typical acoustic oscillations appear in this spectrum as well.

This chapter deals with the early exploration of observational and experimental consequences of general relativity. It explores Erwin Freundlich's failed attempts to verify gravitational light bending and the redshift. The long collaboration between Einstein and Freundlich suffered a setback caused by personal tensions and disagreements around the end of 1921. Nevertheless, they continued to collaborate until both of them had to leave Germany when the Nazis came to power. The chapter also focuses on the triumphal confirmation of light bending during a solar eclipse by Arthur Eddington's expedition. Finally, this chapter considers the Hubble's discovery of the redshift of distant galaxies, which established the notion of an expanding universe.

It is possible to explain the discrepancy (tension) between the local measurement of the cosmological parameter H 0 (theHubble constant) and its value derived from the Planck-mission measurements of the Cosmic Microwave Background (CMB)by considering contamination of the CMB by emission from some medium surrounding distant extragalactic sources, such asextremely cold coarse-grain (grey) dust. Though being distant, such a medium would still be in the foreground with respectto the CMB, and, as any other foreground, it would alter the CMB power spectrum. This could contribute to the dispersionof CMB temperature fluctuations. By generating random samples of CMB with different dispersions, we have checked thatthe increased dispersion leads to a smaller estimated value of H 0 , the rest of the cosmological model parameters remainingfixed. This might explain the reduced value of the Planck-derived parameter H 0 with respect to the local measurements.

It is shown that ∼ 10 % of the total dark matter mass can be transformed into gravitational radiation by primordial blackhole (PBH) mergers inside the compact clusters. If the mass transformation occurred after recombination, but at redshiftsz ≥ 10, the generated gravitational radiation do not contribute to the current density of the Universe. This effect increasesthe rate of cosmological expansion in the era of recombination compared to models without the mass transfer. Accordingly,the Hubble constant, obtained from measurements in the early Universe, changes, which can provide a solution to the“Hubble tension” problem.