The current expansion rate of the Universe is captured by the so-called Hubble constant, or its dimensionless equivalent, "little h", which is a key parameter in the, extremely successful, standard model of cosmology. The Hubble constant relates measurements of the expansion history of the Universe to its components, and “little h” appears in all astrophysical quantities which measurement or...
I will discuss recent results from the Pantheon+ team on constraining multiple cosmological parameters with Type Ia supernovae. The Pantheon+ and SH0ES teams released likely their final major update to the measurement of the Hubble constant, which parameterizes the current expansion rate of the universe. The result is in 5sigma tension with constraints from the Cosmic Microwave Background. I...
I will discuss recent and ongoing work focused on attempts to restore concordance amongst cosmological data sets, motivated by discrepancies between some measurements of the cosmic expansion rate (H_0) and the matter clustering amplitude (S_8). Particular attention will be paid to models invoking new physics in the high-redshift universe, including quasi-accelerating early dark energy models...
In the era of precision cosmology, exploring new and complementary approaches to measure how the Universe (and the structures therein) have evolved is of fundamental importance, to increase the accuracy in the measurements and keep under control systematic effects. In this talk, I will present a novel approach to obtain constraints on the expansion rate of the Universe based on the...
Time-delay cosmography with lensed quasars is the only single-step method to measure H0. It has its own advantages and drawbacks that I will review, before presenting the different avenues adopted by the TDCOSMO collaboration to improve results. Part of this effort resides in time delay measurements obtained at high temporal cadence for 50 lensed quasars, illustrating the need for medium-size...
I will present the Hubble diagram for a Universe where dark matter is universally charged under a dark non-linear electromagnetic force which features a screening mechanism of the K-mouflage type for repulsive forces. I will explicitly show that the cosmological evolution generates an inhomogeneous Hubble diagram that corresponds to a curvature dominated expansion at short distances and...
The Hubble tension is arguably the largest open question in modern cosmology. It could be a sign of new cosmological physics or unknown sources of systematics. To definitively answer this question, we need percent level measurements of the local distance scale. In this talk, I will present our recent work on calibrating the absolute luminosity of Type Ia supernovae from the wide-field Zwicky...
The current cosmological probes have provided an extraordinary confirmation of the standard LCDM cosmological model, that has been constrained with unprecedented accuracy. However, with the increase of the experimental sensitivity a few statistically significant tensions between different independent cosmological datasets emerged. While these tensions can be in portion the result of systematic...
Even though the current observational data show an extremely high level of agreement with predictions of the standard model of cosmology, LambdaCDM, the cosmic microwave background (CMB) temperature fluctuations measured by the WMAP and Planck satellites have shown a number of persistent anomalous features on large-angular scales that are unexpected or extremely unlikely in LambdaCDM...
Baryon acoustic oscillations (BAO) involve measuring the spatial distribution of galaxies to determine the growth rate of cosmic structures. In this talk we discuss the use of different BAO dataset to infer the parameters of different cosmological models. Explicitly, we use BAO + Chronometers data, the Pantheon type Ia supernova, and the Hubble diagram of gamma-ray bursts and quasars to put a...
Discrepant measurements of the Hubble parameter may signal physics beyond the standard cosmological model. I will present different mechanisms to solve the Hubble problem in viable theories beyond General Relativity, testing them against cosmological data and discussing their implications for precision tests of gravity. Among them, a simple model relying on an enhanced strength of gravity at...
"I will present the cosmological weak lensing results from the Dark Energy Survey (DES) using its first three years of data taken using the Dark Energy Camera on the 4m Blanco telescope. This analysis spans the full DES footprint, roughly 1/8th of the
night sky, with the final galaxy catalogue containing more than 100 million galaxies in riz photometric bands, constituting the most powerful...
The appearance of an initial (and sometimes also a final) cosmological singularity in practically all realistic models of the evolution of the universe is distinguishing feature of the modern cosmology. Tensions concerning this question are always present.There are attempts to construct cosmological models where the geometry is always regular. However, some approaches based on the description...
In this talk, we introduce CMB anomalies, especially the hemispherical asymmetry that has been consistently observed by WMAP and Planck data. These anomalies have been extensively discussed in the last decade as a signature of new physics and several scalar field models of inflation have been proposed in this regard. We will present a new understanding of inflationary quantum fluctuations...
I will make some short reminiscent about the geometrical idea of Barrow entropy for black holes and its cosmological horizon applications in the context of dark energy. I will relate it to some other nonextensive entropies such as Renyi and Tsallis – the former being formally related to that of Barrow. Finally, I will show that, amazingly, Barrow holographic dark energy gives a strong Bayesian...
A reanalysis of the SH0ES data for H_0: Effects of new degrees of freedom on the Hubble tension
Causal Fermion Systems is a new approach to unify General Relativity and the Standard Model of particle physics. The theory has been developed by Felix Finster over the past decade. I will give an introduction to the fundemental mathematical structures of the theory and explain how to obtain familiar descriptions as an effective description. Further i will give an overview of results obtained...
Asymptotic Safety (AS) Paradigm is an interesting set of ideas and methods towards a meaningful quantization of Gravity. A brief review of phenomenological consequences in the context of AS regarding cosmology with emphasis on dark energy is given. Furthermore, recent studies that suggest a natural explanation of the recent cosmic acceleration and its coincidence using large-scale structure...
Usually domaine walls are considered excluded from realisitic cosmology because the theoretical expectations for domaine wall tensions and thus also energy densities per area from high energy physics become so huge for cosmological purposes that they tend to spoil completely our cosmological models. However, we have under the attempts to fit the domaine wall tension in our model for dark...
Cosmological information contained within the non-linear regime of the Universe may prove crucial in solving the tension currently observed between weak lensing and CMB probes. However, this information lies beyond the reach of our conventional analyses which use two-point statistics. In this talk, I present the improvements in cosmological constraining power offered by an alternative weak...
"I will discuss our recent study were we have evaluated the consistency between lensing and clustering probes of large-scale
structure based on measurements of projected galaxy clustering from the Baryon Oscillation Spectroscopic Survey (BOSS) combined with overlapping galaxy–galaxy lensing from three surveys: the Dark Energy Survey Year 3 (DES Y3), the Hyper-Suprime Cam survey (HSC) Year 1,...
I will start by overviewing the main motivations to test gravity at cosmological scales. In particular, I shall focus on current cosmological constraints and the use of dark energy and alternative theories of gravity to alleviate cosmological tensions. Then, I will describe what are the main methods and tools -- including the Einstein-Boltzmann solver hi_class -- used to reach the precision...
We examine the possibility of "soft cosmology", namely small deviations from the usual cosmological framework due to the effective appearance of soft-matter properties in the Universe sectors. One effect of such a case would be that dark energy and/or dark matter exhibit a different equation-of-state parameter at large scales (which determine the universe expansion) and at intermediate scales...
An universe with a Cosmological Constant has been the reigning paradigm in the last decades. However, the Cosmological Principle opens a window to the possibility of having a dynamical Vacuum Energy density, $\rho_{\rm vac} (t)$. In this talk we will summarize our results on the renormalization of the vacuum energy in the context of quantum field theory (QFT). The quantum scaling with the...
Despite the many successes of concordance ÎCDM cosmology, increasingly accurate cosmological datasets are starting to reveal tensions. In such a landscape, ones attention naturally shifts towards new avenues to probe cosmology. The turnaround scale, defined as the scale separating gravitationally bound structures from the Hubble flow, has properties that make it a promising cosmological probe...
Even though the ΛCDM model is supported by overwhelming evidence, its predictive power has been recently called into question. In fact, the $H_0$ tension problem has prompted a reconsideration of novel approaches to formulating a consistent cosmological model. This issue might be resolved by considering theories beyond General Relativity. There exist many possible modifications of General...
Understanding the nature of the accelerated expansion of the Universe stands as one of the most important open questions in Cosmology. Currently the most well-accepted paradigm relies on the introduction of two unknown components to the standard model that govern the dynamics of the Universe at present times Dark Energy, proposed as the source for the acceleration, and Dark Matter, needed to...
The difference between the observational vacuum energy driving the expansion of the universe and the large vacuum energy density arising from zero point quantum field fluctuations has led to the cosmological constant problem. Well-tempering offers a formalism to dynamically cancel the cosmological constant and obtain a late-time, low energy vacuum state. The well-tempered recipe is applied...
The zero point calibration of the extragalactic distance scale is degenerate with any subsequent derivation of the Hubble constant (H0). Thus, it is imperative that calibration accuracy is continually improved for stellar standard candles. The optimal method for doing so is to closely match the observing conditions and underlying astrophysical environments between the calibration observations...
Since WMAP and Planck some anomalous features appeared in the Cosmic Microwave Background (CMB) large-angle anisotropy, the so-called anomalies. One of these is the hemispherical power asymmetry, i.e. a difference in the average power on the two hemispheres centered around (l, b) = (221, -20), which shows a relatively high level of significance. Such an anomaly could be the signature of a...
The most promising theoretical models to resolve the H0 tension also predict temporal or spatial variations of the constants of nature such as the fine structure constant, alpha. We make use of novel astronomical instrumentation to remove previously dominant systematic effects, thus reaching precision of 1 part per million or better in measuring any departure of the fine structure constant...
Galaxy clusters are excellent natural laboratories at the edge between astrophyisics and cosmology, at those scales where possible departures from General Relativity (GR) can leave a detectable inprint. Moreover, clusters allow for jointly constraining both the relativistic and non-relativistic sectors of the gravitational interaction, through lensing and internal kinematics (of gas or member...
"Scalar-tensor theories offer the prospect of explaining the cosmological evolution of the Universe through an effective description of dark energy as a quantity with a non-trivial evolution. In this work, we investigate this feature of scalar-tensor
theories in the teleparallel gravity context. Teleparallel gravity is a novel description of geometric gravity as a torsional- rather than...
The Tip of the Red Giant Branch (TRGB) marks the luminosity at which the core helium flash in low-mass stars occurs, and provides a high-precision and accuracy standard candle. As such, the TRGB offers a critical, independent route to the measurement of Ho. Applied in the halo of galaxies, the TRGB method has a number of advantages: there is negligible extinction by dust, and it has little...
Following a new pathway to the definition of the Stochastic Quantization, which hinges on the functional similarities between the Ricci-Flow equation and the Stochastic Quantization Langevin equations, while making use of the Arnowitt-Deser-Misner variables and their conjugated Hamiltonian momenta, we have pushed forward a novel approach to investigate, in a geometrical way, the...
Gravity and general relativity are considered as an Effective Field Theory (EFT) at low energies and macroscopic distance scales. The conformal anomaly of light or massless quantum fields has significant effects on macroscopic scales, which allows the effective value of the vacuum energy to change in space and time. The EFT of vacuum energy thereby replaces the fixed constant Lambda of the...
Introducing modified measures re defines the scalar field potentials while providing spontaneous breaking of scale invariance. In this way one can obtain potentials with two flat regions , one suitable for inflation and the other suitable for the late universe. With two scalar fields the scalar potential can have three flat regions after spontaneous symmetry breaking, one for inflation and the...
The standard model of cosmology relies on the existence of dark matter particles which drive structure and galaxy formation. A rigorous prediction of this model is that each present-day galaxy must be embedded in a massive and extended halo of dark matter particles. The existence of such halos of dark matter can be tested for by applying Chandrasekhar dynamical friction. I will present the...
Cepheid variables are the best calibrated primary standard candles they are used to standardize the brightness of Type Ia supernovae (SNIa) in nearby galaxies and therefore are central in the determination of the local value of the Hubble constant (H0). The empirical measurement of the Hubble constant obtained by the SH0ES team from the Cepheid-SNIa method is now in 5-sigma tension with the...
Water megamasers residing in the accretion disks around supermassive black holes (SMBHs) in active galactic nuclei (AGN) provide unique tools for bypassing the distance ladder and making one-step, geometric distance measurements to their host galaxies. Â The Megamaser Cosmology Project (MCP) is an international, multi-facility campaign to find, monitor, and map such AGN accretion disk...
The recent tensions between cosmological data sets are difficult to accommodate within the standard Friedmann cosmological models. In this talk I will discuss how we might consider more general cosmologies, which could provide more flexibility. I will introduce the mathematical formalisms required to understand Friedmann within this generalized context, and the challenges and difficulties that...
The Hubble constant (H0) tension between Type Ia Supernovae (SNe Ia) and Planck measurements ranges from 4 to 6 Ï. To investigate this tension, we estimate H0 in the ÎCDM and w0waCDM models by dividing the Pantheon sample, a collection of 1048 SNe Ia, into 3, 4, 20, and 40 bins. For the first two divisions, a presence of SNe Ia in the hundreds for each bin is required to effectively account...
Neutrinos are a mysterious sector of the Standard Model with some unanswered fundamental questions. In the first part of our talk we will review the minimal framework with three neutrinos, and what cosmology can tell us about their masses and mixings. However, there also exist non-minimal frameworks which generically assume that the scale of new physics appears is just above 10 TeV (LHC). In...
Tensions in the concordance model are a further motivation to devise and implement tests of a key foundation of the model - the Cosmological Principle. I will survey current and future tests of the CP.
The failure to converge on a consensus value of the Hubble's constant triggered investigations into the reliability of geometric descriptions of the local spacetime that deviate from the standard cosmological metric. The question that arises is whether metrics with lower symmetries, while still simple, provide a reliable description of the data in the local patch of the universe where global...
Probes of the large scale structures can give us insight into the nature of the dark Universe. In this talk I will show the latest results from the Kilo Degree Survey (KiDS) and its combination with spectroscopic galaxy surveys. KiDS is a purpose-built gravitational lensing survey with high quality images and a wide photometric coverage, resulting in very high-fidelity data. Combining weak...
I will discuss some recent works on reconstruction of gravity from a combination of currently available cosmological data , under conditions of theoretical stability, highlighting the imprints of cosmological tensions.
I will present the current observational status on the curvature of the Universe.
I will discuss the possibility that the Hubble tension is the signature of a fast triggered phase transition in the dark sector. Such a phase transition is called New Early Dark Energy (NEDE) and must have taken place just before recombination at the eV scale to resolve the tension fully. After discussing the cosmological NEDE phase transition, I will discuss the details of possible particle...
"In the current talk, I will present some dark energy models based on 3-forms that fully fit the available observational data. In addition, those models are harmless from a quantum point of view, in the sense
that the singularities or abrupt events they might induce are cured at the quantum level. Moreover, some of those models can support regular blackholes as well as wormholes that do not...
A compelling unified model of dark energy and early dark energy (EDE) is presented, using a scalar field with a simple exponential runaway potential, in the context of alpha-attractors. The field is originally trapped at an enhanced symmetry point, subsequently thaws to become successful EDE and eventually slow-rolls to become dark energy. EDE ameliorates the observed Hubble tension. Emphasis...
Fractional cosmology has emerged recently, based on the formalism of fractional calculus, which modifies the standard derivative to one fractional derivative of order $\alpha$. It generates changes in General Relativity, particularly in the Einstein field equations. In this mathematical framework, the Friedmann equations are modified with an additional term similar to an effective curvature....
Peculiar velocity surveys using supernovae or standard sirens can be combined with large-scale galaxy surveys to great benefit. I will present a new methodology to analyse in a comprehensive way standard candles and galaxy data at the linear level. I will show that this methodology also allows for competitive model-independent measurements of the expansion rate, i.e. without any assumptions on...
In the current era of precision cosmology, the emergence of crucial tensions in the determination of the universe expansion has led to a twofold need to determine a criterion for combining different probes in a physically meaningful way, and to extend the mapping of the expansion of the universe to include data at redshifts not currently covered. In this talk, I will present recent...
El Gordo (ACT-CL J0102-4915) is an extremely massive galaxy cluster (M200 = 2e15 Msun) at redshift z=0.87 composed of two subclusters with mass ratio 2 merging at speed Vinfall = 3000 km/s. Such a fast collision between individually rare massive clusters is unexpected in Lambda cold dark matter (LCDM) cosmology at such high z. Here, we determine the probability of finding a similar object in a...
Inspired by the discussion in the literature about possible hidden systematic errors in late universe cosmological probes and non-trivial physical models that are developed to describe the Hubble tension we test Pantheon SNe sample for possible deviation from the baseline LCDM analysis. Our work is based on the assumption that this deviation can be described by a Gaussian process and we make...
We study massive non-linear gauge theories with mass added by hand. First, we consider the massive Yang-Mills theory. The standard perturbative approach suggests that the massless limit of this theory is not smooth. Nevertheless, we show that the longitudinal modes - the source of this discontinuity - become strongly coupled at the Vainshtein scale. Beyond it, we show that the massless theory...
The standard Lambda Cold Dark Matter (ÎCDM) model of cosmology provides a good fit to a wide range of astrophysical and cosmological observations that have probed nearly all the epochs and scales of the Universe. However, in the recent years various tensions and anomalies are seriously questioning the validity of this baseline scenario, motivating both the need to test its underlying...
In this talk, we will show how the cosmology code PyCosmo, developed by the Cosmology Group at ETH Zurich, can be easily extended to beyond ΛCDM models. We will present how we added dark energy with a constant equation of state and massive neutrinos to the Boltzmann solver of PyCosmo. The possibility to easily extend the equation system is a core feature of PyCosmo, enabled by the SymPy...
The hypothesis that the late Universe is isotropic and homogeneous is a cornerstone of the standard cosmological model. The cosmic expansion rate H0 (i.e. Hubble constant) is assumed to be spatially constant, while coherent matter flow motions (bulk flows) are believed to be negligible at cosmic scales. Any deviation from this consensus can put the validity of the standard cosmological model...
One problem of the ÎCDM model is the tension between the S8 found in Cosmic Microwave Background (CMB) experiments and the smaller one obtained from large-scale observations in the late Universe. The Ï8 quantifies the relatively high level of clustering. Bayesian Analysis of the Redshift Space Distortion (RSD) selected data set yields S8 = 0.700+0.038 â0.037. The fit has 3Ï tension with...
Most of the attempts to reconcile the s8 and H0 tensions are focusing on extensions to LCDM that can be considered as either late or early times modifications of general relativity with limited success as to be able to evade constraints from local and deep probes at once. In this work we focus on models that rather act in the intermediate redshifts to try to escape constraints from the current...
Galaxy angular momenta (GAM) are determined by the initial conditions (ICs) in the vicinity of the corresponding protohaloes and have a potential to improve our knowledge of cosmological ICs on Mpc scales. In this talk I will describe our observational efforts studying this correlation. Using ICs determined from SDSS galaxy positions and GAM inferred from the sense of rotation of the spiral...
We investigate the cosmological applications of new gravitational scalar-tensor theories and analyze them in the context of H0 tension. In these theories the Lagrangian contains the Ricci scalar and its first and second derivatives, in a specific combination that makes them free of ghosts. In the Einstein frame they are proved to be a subclass of bi-scalar extensions of general relativity....
The current constraints on the growth of perturbations are subject of debate. Cosmic shear observations show a lower value than that predicted by Planck. For instance, KiDS finds results 3\sigma away from Planck's value and data from DESY1 also points in the same direction. In this talk I will show a data driven reconstruction of the structure growth history from a combination of 6 different...
"As it was recently argued, the Hawking evaporation of ultra-light primordial black holes (PBH) domi- nating the early universe can increase the effective number of extra neutrino species ∆Neff, which is proportional to the initial PBH abundance and the total number of extra degrees of freedom produced from Hawking evaporation on the top of the Standard Model (SM) ones. Hence, by increasing...
A dark energy-like component in the early universe, known as early dark energy (EDE), is a proposed solution to the Hubble tension. Currently, there is no consensus in the literature as to whether EDE can simultaneously solve the Hubble tension and provide an adequate fit to the data from the cosmic microwave background (CMB) and large-scale structure of the universe. In this talk, I will give...
The prospect of nonparametric reconstructions of cosmological parameters from observational data sets has been a popular topic in the literature for a number of years. This has mainly taken the form of a technique based on Gaussian processes but this approach is exposed to several foundational issues ranging from overfitting to kernel consistency problems. In this talk, I will discuss the...
In this talk I will introduce and discuss the concepts of bulk flows and peculiar velocities, the importance of which has progressively been shown to be more significant in modern cosmology. Alongside this, I will also discuss recent theoretical developments of a new way of expanding luminosity distances in terms of null geodesics, allowing us to obtain null analogues of the well-known...
Minkowski Functionals are high-order statistics that can be extracted from spherical maps such as the CMB, providing additional information to that in the angular power spectrum. The expected value of these functionals can be very accurately predicted for Gaussian isotropic maps, which turn them into an excellent tool to look for Non-Gaussianities and violations of the Cosmological Principle...
Intrinsic alignment (IA) modelling and photometric redshift estimation are two of the main sources of systematic uncertainty in weak lensing surveys. We investigate the impact of redshift errors and their interplay with different IA models. Generally, errors on the mean $\delta_z$ and on the width $\sigma_z$ of the redshift bins can both lead to biases in cosmological constraints. We find that...
Gravitational waves (GWs) can be used to measure the Hubble parameter. The optimal technique, a "Standard Siren", requires the identification of the electromagnetic (E/M) counterpart of the GW source. However, a significant fraction of GWs will not have E/M counterparts. Such "Dark Sirens" can still help constrain the Hubble parameter by statistical techniques. In this work, we investigate the...
Early dark energy (EDE) is a dark energy-like component active in the early stages of the universe and is one of many proposed ways of resolving the Hubble tension. Up to now, it is not agreed upon if EDE can solve the Hubble tension whilst fitting the cosmic microwave background and large scale structure simultaneously or not. In this talk, I will review the status of EDE in the current...
The era of gravitational-wave cosmology has finally begun. The multi-messenger observations of GW170817 allowed it to be used as a standard siren, providing a direct measurement of the Hubble constant calibrated by the theory of general relativity. In addition to this "bright siren" approach, a "dark siren" approach has been implemented utilizing statistical correlations with host galaxies to...
Galaxies are known to be good although biased tracers of the underlying dark matter field. This bias, mostly driven by history of hierarchical clustering and galaxy/halo assembly history, results in the dependence of galaxy clustering on their physical properties which is not easy to model. On the other hand, making use of galaxies as tracers of cosmic structure for cosmological purposes...
