Ruprecht Karls Universität Heidelberg

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joint [2020/02/20 16:29] – [Seminar calendar] manueljoint [2025/07/13 07:38] (current) – [Seminar calendar] hanqiong
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 ====== Selected topics in theory and observations of Dark Energy (ITP Cosmology Tunch) + Journal Club ====== ====== Selected topics in theory and observations of Dark Energy (ITP Cosmology Tunch) + Journal Club ======
  
-===Thursday, PW 12, Room 106=== +===Wednesday, PW 12, R 105 === 
-== 13:15 - 15:00 ==+In presence unless otherwise noted 
 +== 14:15 ==
  
 ---- ----
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-Go to the calendar of [[seminar|Cosmology seminars]] **(Usually on Tuesday, 3:15pm, Phil 19)**+Go to the calendar of [[seminar|Cosmology seminars]] **(Usually on Tuesdays, 2:15 pm)**
 ---- ----
  
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 ====Seminar calendar==== ====Seminar calendar====
 +
 +
 +__**Summer term 2025:**__
 +
 +Wednesday 14:15, Philosophenweg 12, Room 105 or online
 +
 +==30.07.  tbd ==
 +==23.07.  tbd ==
 +==16.07.  Discussion round (Luca absent) ==
 +==14.07.  Seminar talk by Prof. Roberto Capuzzo-Dolcetta  ==
 +Title: The classical Newtonian N-body problem
 +==09.07.  Presentation by Federico ==
 +==02.07.  Seminar talk by Laura Herold ==
 +==25.06.  Seminar talk ==
 +==18.06.  Andrea progress report ==
 +==11.06.  Seminar talk (cancelled) ==
 +==04.06.  Yannick Bachelor thesis summary (Luca absent) ==
 +==28.05.  Discussion round & Updates ==
 +==21.05.  Talk by Matteo Fontana ==
 +==14.05.  Seminar talk ==
 +==07.05.  Discussion round ==
 +==30.04.  Discussion round ==
 +==23.04.  Discussion round (Luca absent) ==
 +==16.04.  Discussion round ==
 +==09.04.  (cancelled) ==
 +==02.04.  No tunch ==
 +----
 +
 +
 +__**Winter term 2024/25:**__
 +
 +14:15, Philosophenweg 12, Room 105 or online
 +
 +==26.02  (in presence)Sijin Chen presentation from LMU ==
 +==19.02  Marie Sommerfeld progress report==
 +==11.02  (Tuesday 14:15 in presence) Prajwal Hassan Puttasiddappa==
 +Title: Probing Strong Gravity with Geodesics
 +
 +Abstract: We will discuss how one can use simple, classic methods—such as studying the paths of objects around massive bodies—to explore gravity in extreme environments, especially near black holes. Then, in the second half, I’ll introduce an exact solution from Brans-Dicke gravity and show how it differs from the black hole solutions of general relativity.
 +==05.02  No Tunch==
 +==29.01  Discussion round==
 +==22.01  No Tunch==
 +==15.01  Discussion round==
 +==08.01  Discussion round==
 +==01.01.2025  Christmas Break==
 +==25.12  Christmas Break==
 +==18.12  Federico Scali (In Presence)==
 +==11.12  Discussion round==
 +==04.12  No Tunch==
 +==27.11  No Tunch==
 +==20.11  Malte Schneider (In Presence - Blackboard Presentation) ==
 +Geodesic congruences, Raychaudhuri equation and Black Hole area theorem
 +==13.11  Tatiane de Paula Moraes report (In presence)==
 +==06.11  Discussion round==
 +==30.10  Malte Schneider progress report==
 +==23.10  Discussion round==
 +==16.10  Felipe Augusto - DALI Perturbation Theory==
 +==09.10  No Tunch==
 +==02.10  Discussion Round==
 +
 +
 +
 +
 +
 +
 +
 +
 +
 +
 +__**Summer term 2024:**__
 +
 +14:15, Philosophenweg 12, Room 105 or online
 +
 +==31.07  Vrund Patel progress report==
 +==24.07  Ángela Turnes progress report==
 +==17.07  Ziyang Zheng (In Presence - Blackboard Presentation) ==
 +Title:
 +Testing Relativistic Corrections on Large Scale Structure
 +
 +==10.07  Tjark Harder progress report==
 +==03.07  Felipe Augusto==
 +==26.06  Luca Amendola - Report on recently completed project about BOSS data==
 +==19.06  Discussion Round==
 +==12.06  Discussion Round==
 +
 +
 +
 +
 +
 +
 +
 +
 +
 +__**Winter term 2023/24:**__
 +
 +14:15, Philosophenweg 12, Room 105 or online
 +
 +==21.02 Discussion Round==
 +==14.02 Discussion Round==
 +==07.02 Discussion Round==
 +==31.01 Angela Mendes progress report==
 +==24.01 Leo Schey progress report==
 +==17.01 Discussion Round==
 +==10.01 Ziyang Zheng ==
 +Title:
 +Model-independent test on the cosmological Poisson equation
 +
 +Abstract:
 +In this talk I will present how one can test the cosmological Poisson equation by requiring only the validity of three main assumptions: the energy-momentum conservation equations of matter, the equivalence principle, and the cosmological principle. We first point out that one can only measure the combination ${\mathcal M}\equiv \Omega_m^{(0)}\mu$, where $\mu$ quantifies the deviation of the Poisson equation from the standard one and $\Omega_m^{(0)}$ is the fraction of  matter density at present. Then we employ a recent model-independent forecast for the growth rate $f(z)$ and the expansion rate $E(z)$ to obtain constraints on ${\mathcal M}$ for a survey that approximates a combination of the Dark
 +Energy Spectroscopic Instrument and Euclid.  We find that ${\mathcal M}$ can be measured only to within  20-30% up to $z=1.5$. We also project our constraints on some parametrizations of ${\mathcal M}$ proposed in literature, while still maintaining model-independence for the background expansion, the power spectrum shape, and the non-linear corrections. As expected, we find much weaker model-independent constraints than  found so far for such models. This means that the cosmological Poisson equation  remains quite open to various alternative gravity and dark energy models.
 +
 +
 +==20.12 (2:15pm) Davi Rodriguez (online; Vitoria and Rio DJ)==
 +==20.12 (4pm) Yusuke Mikura (Nagoya and Trieste)==
 +Title: 
 +On UV completion of Higgs inflation in Palatini formalism
 +
 +Abstract: 
 +I will investigate UV completion of Higgs inflation in the Palatini formalism. It is known that the cutoff scales for the perturbative unitarity become much smaller than the Planck scale to be consistent with CMB observations. Expecting that the low cutoff scales originate in the curvature of a field-space spanned by the Higgs fields, I consider embedding the curved field-space into a higher dimensional flat space and apply this procedure to the Palatini-Higgs scenario. I will show that, while the new field introduced in this way successfully flattens the field-space, the new field can not uplift the cutoff up to the Planck scale. I will also compare the result with vanilla Higgs inflation.
 +
 +
 +==13.12 Tjark Harder progress report==
 +==06.12 No tunch==
 +==29.11 Discussion round==
 +==22.11 Vrund Patel progress report==
 +==15.11 No tunch==
 +==08.11 No tunch==
 +
 +
 +
 +
 +
 +
 +
 +
 +
 +
 +
 +
 +
 +
 +
 +__**Summer term 2023:**__
 +
 +14:15, Philosophenweg 12, Room 105
 +
 +== 27 September 2023 ONLINE Discussion Round ==
 +== 20 September 2023 L. Favaro, TBA ==
 +
 +Title: Detecting anomalies with Machine Learning
 +
 +In recent years, Machine Learning techniques have proven to be powerful
 +tools for data analysis both inside and outside of physics. The ability
 +to model high-dimensional spaces through expressive functions
 +parameterized by neural networks has enabled new solutions for complex
 +problems. These tools are general and highly portable to other fields.
 +In this talk, I will introduce the concept of anomaly searches and
 +detection. Anomaly detection was initially introduced in computer
 +science and has been constantly developed in particle physics, offering
 +enhanced sensitivity for model-agnostic searches.
 +I will present a density-based approach for the detection of
 +Out-Of-Distribution (OOD) events, leveraging Auto-Encoders and
 +Energy-Based Models for unsupervised training and improved likelihood
 +interpretation. I will demonstrate the strength and weaknesses of the
 +methodology with proof-of-concept results on LHC data, including top
 +tagging, semi-visible jet detection, and applications for online
 +triggering.
 +== 26 July 2023 Angela Turnes (online) ==
 +== 17 July 2023 11:30am, Marco Marinucci (Tel Aviv; ONLINE) ==
 +
 +Title: Unbiased cosmology from biased tracers
 +
 +Abstract: I will introduce the role played by symmetries in the perturbative expansion of the large-scale structure (LSS). In particular, I will describe how to establish which of the coefficients, usually referred as bias parameters, of the perturbation theory kernels are dictated by symmetries and which not. This
 + approach is especially relevant for non-standard models that respect the same symmetries as ΛCDM and where perturbation theory at higher orders has not been exhaustively explored, such as dark energy and modified gravity scenarios. I will describe how to use
 + this approach to perform general model-independent analysis based only on symmetry principles for realistic surveys. The bias parameters are usually treated as unknown nuisance parameters as they can depend on complex galaxy formation and evolution physics
 + and the assembly history (assembly bias). I will show how to use the semi-analytic code Galacticus to study the assembly bias for the primordial
 +non-Gaussian bias. I will show the dependence of this parameter on observable galaxy properties, such as the (g-r) color or the H\alpha emission line luminosity.
 + This is relevant since theoretical motivated priors on the non.ì-Gaussian parameter would possibly allow for a detection of primordial non-Gaussianities, giving us more insight on the very first moment of our Universe.
 +
 +
 +== 12 July 2023 Felipe Augusto (UFES Vitoria, Brazile; ONLINE) ==
 +
 +Title: Testing modified gravity with Galactic observables
 +
 +Abstract: We explore the potential of Milky Way observables, specifically the rotation curve and line of sight accelerations, as discriminators between modified and Newtonian gravity. Our investigation primarily centers around the Horndeski class of modified theories of gravity. 
 +
 +== 5 July 2023 Ziyang Zheng (progress report) ==
 +Title：Model-independent forecasting of modified gravity
 +
 +== (rescheduled) 5 July 2023 Eunice Monyenye Omwoyo (UFES Vitoria, Brazil; ONLINE) ==
 +Title: PHOTON RINGS IN KERR DE SITTER SPACETIME
 +
 +Abstract: Recently, the Event Horizon Telescope (EHT) collaboration has provided interferometric observations of the black
 +holes M87 and Sagittarius A∗
 +(SgrA∗
 +) at the center of the galaxies Messier 87 and Milky Way, respectively, thus
 +providing valuable insights into the emission structure on horizon scales. Calculations within the framework of
 +General Relativity (GR), show that the black hole image is not a single continual entity. Rather, it is made up of
 +an infinite sequence of self-similar subrings converging to the critical curve. These subrings constitute the photon
 +ring, which in itself is observable. The critical curve represents the locus on the image plane resulting from photons
 +moving along bound orbits, and its shape follows from GR. While the shape of the critical curve is predicted by GR,
 +it cannot be directly observed. Despite that, the photon ring demonstrates a close approximation and resemblance
 +to the critical curve affirming its potential as a robust testing ground for GR. In this presentation, we will explore
 +photon rings in Kerr-de Sitter (KdS) spacetime. We will commence with an in depth analysis of the general structure
 +of photon orbits pertinent to the formation of the photon ring. We then explore analytic ray-tracing to investigate
 +direct images, lensing rings, and photon rings for equatorial disks around black holes. The photon ring exhibits a
 +sequence of successive images that are exponentially demagnified, rotated, and delayed in time. To comprehensively
 +conclude our discussion, we will analyze the critical parameters responsible for governing these essential characteristics
 +of demagnification, rotation, and delay in the consecutive subrings.
 +
 +== 28 June 2023 Andrea Macciò (NYU Abu Dhabi)==
 +Title: A dark future for dark matter
 +
 +Abstract: The origin nature of dark matter is one of the greatest puzzles in
 +modern physics.
 +Despite the large efforts from particle and astro physicists  in the
 +search for dark matter,
 +after almost four decades we are still quite in the dark and we have
 +been able only to
 +provide partial constraints on the nature of this elusive component in
 +our Universe.
 +I will present the current and future prospects for the search for dark
 +matter, and highlight
 +the challenges that lay in front of us for the next decade or more.
 +
 +== 21 June 2023 B. M. Schäfer (Heidelberg, ITA) ==
 +Title: Partition functions and Markov-chains for inference in cosmology
 +
 +Abstract: Monte Carlo Markov-chain methods are a standard tool in inference in cosmology for sampling posterior distributions. I’ll illustrate their relation to thermodynamics, in particular the sampling of the Metropolis-Hastings algorithm to a canonical partition sum. This analogy allows an efficient analytic description of non-Gaussian features, the computation of Shannon-entropies and lastly the definition of convergence criteria supplementing the Gelman-Rubin criterion. I conclude by giving an outlook on inference questions that could be addressed by the partition formalism
 +
 +== 14 June 2023 No tunch ==
 +== 7 June 2023 Ziad Sakr  ==
 +
 +Title : Testing the continuity equation at cosmological scales.
 +
 +Abstract : Extensions to LCDM or modified gravity theories are often
 +considered assuming conservation of the fluid equations. Here we report
 +progress on a project where we relax this assumption on the continuity
 +equation along with the common modified gravity parameters, i.e. the
 +ones modifying the Poisson and Weyl potential and try to put constraints
 +using cosmological observables that are sensitive to their
 +modifications.
 +
 +== 31 May 2023 N. Lorenz ==
 +
 +Title: Model independent forecasting DESI vs LSST
 +
 +Abstract: We will discuss briefly the necessity of another one among the many forecasts. Followed by a detailed selection of parameters, expected results and possible improvements in the future as well as difficulties concerning forecasts between DESI and LSST.
 +
 +== 24 May 2023 Leo Schey, report on f(Q) ==
 +== 17 May 2023 Simon Schreyer (ITP) == 
 +
 +
 +Title: "A broad introduction to accelerated expanding universes from string theory and their difficulties"
 +
 +Abstract: Obtaining accelerated expanding universes from string theory remains one of the core issues of string phenomenology. In principle, accelerated expanding universes can be realized through de Sitter vacua or string-theoretic quintessence models. Without assuming a background in string theory, I will introduce the main steps to obtain accelerated expanding universes. In particular, I will address the difficulties that arise in each approach. 
 +== 10 May 2023 Sumit Kumar (Max Planck Institute for gravitational physics, AEI, Hannover) ==
 +
 + Title: Cosmology with Gravitational Wave Merger Events: Current Status and Future Challenges
 +
 +Abstract: In recent years, with the LIGO-Virgo-KAGRA detector network, the catalog of Gravitational Waves (GW) merger events has grown to about 90 merger events. This brings us to the era of GW astronomy. In this talk, I will briefly discuss the techniques used to create the catalog of GW mergers (from searches to source properties estimation) and compare the results across various catalogs. I will then go on to discuss the current techniques to do cosmology with GW events and how it can help us resolve so-called Hubble tension in the future.  The third generation (3G) GW detectors such as Cosmic Explorer and Einstein Telescope are expected to be operational sometime during next decade and they will be an order of magnitude more sensitive compared to the current generation detectors. We will be able to probe to low frequencies such as 3-4 Hz and can detect binary black hole merger events up to very large redshift.  I will discuss the forecast of cosmological studies in the era of 3G detectors. Specifically, how the 3G detectors can help us probing large scale structure features, such as galaxy bias and baryon acoustic oscillations, solely from the GW observations, and hence provide an independent probe to cosmology.
 +- 
 +== 03 May 2023 ONLINE Discussion Round ==
 +== 26 April 2023 No tunch ==
 +== 19 April 2023 ONLINE Discussion Round: connection black holes and dark energy ==
 +
 +
 +
 +----
 +
 +__**Winter term 22/23:**__
 +
 +
 +== 15th March 2023 (replacement for 15th February): Selected topics in theory and observations of Dark Energy (Journal Club and Discussion Round) ==
 +
 +Follow-up on Bayesian statistical measures
 +
 +
 +== 22nd February 2023: Selected topics in theory and observations of Dark Energy (Journal Club and Discussion Round) ==
 +
 +Bayesian measures of complexity, robustness and surprise
 +
 +https://arxiv.org/abs/astro-ph/0602378
 +
 +https://arxiv.org/abs/1209.1897
 +
 +https://arxiv.org/abs/1402.3593
 +
 +https://arxiv.org/abs/1510.08483 
 +
 +
 +== 15th February 2023: ==
 +Cancelled
 +
 +
 +== 08th February 2023: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +== Note the unusual time: 12pm noon ==
 +
 +Pedro Riba Mello -- Surprise and Discordances
 +
 +In this talk I'll show how we can use the Surprise Statistics to explore discordances between datasets. The Surprise is a tool based on the Kullback-Leibler divergence and offers a way to quantify discordance between datasets in multiple dimensions in parameter space. The Surprise statistics has an analytical solution for gaussian distributions but for the general case of a non-gaussian distribution the Surprise and its distribution needs to be evaluated numerically. We’ll analyze multiple Supernova mocks created blindly and show an implementation to evaluate the non-gaussian case for the Surprise.
 +
 +== 01st February 2023: Physics Forum (General discussions about papers, research and work) ==
 +
 +
 +== 25th January 2023: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Luca Amendola - Golden hats of the Bronze Age: did they have an astronomical significance?
 +
 +Based on a paper published here:
 +
 +https://journal.equinoxpub.com/JSA
 +
 +See also this wikipedia article:
 +
 +https://en.wikipedia.org/wiki/Golden_hat
 +
 +== 18th January 2023: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Ziad Sakr - Forecasts on LCDM extensions from Euclid primary probes
 +
 +I will present some preparatory forecasts performed within the Euclid collaboration using the mission primary probes, i.e. galaxy clustering detected from spectroscopic measurements and the so called 3x2 probe or weak lensing + galaxy clustering and their cross correlations, detected from measurements of photometric redshifts, on extensions to LCDM standard cosmological model by means of the commonly used dark energy equation of state and growth index parameter but also on other more specific models of modified gravity such as f(R) or Brans-Dicke before finishing with additional forecasts on some model independent null tests.
 +
 +
 +== 11th January 2023: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Konstantin Meyer 
 +
 +Stellar streams and dark matter substructure
 +
 +
 +== 21st December 2022: Physics Forum (General discussions about papers, research and work) ==
 +
 +Christmas edition - favourite papers and Christmas quiz
 +
 +
 +== 14th December 2022: Selected topics in theory and observations of Dark Energy (Tunch) == 
 +
 +Luca Amendola - Testing gravity with GWs inspiral waveforms
 +
 +I will discuss a recent paper by Tsujkawa and collaborators (https://arxiv.org/abs/2209.13749) and a follow-up paper we are now working on.
 +
 +== 7th December 2022: Selected topics in theory and observations of Dark Energy (Journal Club) == 
 +
 +Prajwal Hassan Puttasiddappa 
 +
 +R. Jimenez et al.: Why is zero spatial curvature special?
 +
 +https://arxiv.org/abs/2210.10102
 +
 +
 +== 30th November 2022: ==
 +
 +cancelled  due to extra Cosmology Seminar
 +
 +
 +== 23rd November 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Tanmoy Modak - Probing cosmic inflation with CMB and 21cm intensity mapping
 +
 +In this talk I will discuss how well one can constrain the inflationary dynamics using future CMB and 21cm data. In particular, I will show that these data would provide stringent probe to the extended Starobinsky model. In addition, I will also provide projections for the Hubble slow-roll parameters.
 +
 +== 16th November 2022: Physics Forum (General discussions about papers, research and work) ==
 +
 +Discussion round on non-linear vs. linear scales in relation to the 21cm background
 +
 +
 +== 09th November 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Ziyang Zheng - Coupled and uncoupled early dark energy, and the cosmological tensions
 +
 +Some early dark energy (EDE) models with non-negligible dark energy fractions in the pre-recombination epochs are capable of  alleviating the Hubble tension quite efficiently. However, there has been an intensive discussion on whether these models enhance the power of matter fluctuations and worsen the tension with the large-scale structure (LSS) measurements. In this talk I will discuss the effect of several EDE models, considering also in some cases a coupling between the dark sector, and the effect of massive neutrinos. In the best case, namely ultra-light axion-like (ULA) potential, the Hubble tension is reduced to around 2$\sigma$, and the amount of clustering at linear scale is similar to the $\Lambda$CDM with the LSS estimator $\sigma_{12}$.
 +
 +== 26th October 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Caroline Heneka - A hands-on tutorial to run your own deep neural network
 +
 +== 19th October 2022: Physics Forum (General discussions about papers, research and work) ==
 +
 +Winter semester kick-off, presentation of 'Computer Vision Astrophysics' (and Cosmology)
 +
 +----
 +
 +
 +__**Summer term 22:**__
 +
 +== 28th July 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Adrian Schirra - Non-linear perturbation theory for the large-scale structure
 +
 +The increasing precision of large-scale structure surveys calls for accurate theoretical modeling. In this talk, I will present the non-linear perturbation theory, which is applicable in the weakly non-linear regime. I will calculate the one-loop corrections to the power spectrum, while taking into account redshift space distortions as well as galaxy bias. The predictions of this model can be compared to observational data with MCMC algorithms.
 +
 +== 27th July 2022, 11:00 am: Selected topics in theory and observations of Dark Energy (Tunch) (NOTE UNUSUAL DATE AND TIME) ==
 +
 +
 +Martin Kärcher (Aix-Marseille Université) - Tensor-Inverse Gravity - A new Hope to Replace the Cosmological Constant?
 +
 +In this talk I will present a specific kind of modified gravity model based on the idea of replacing the cosmological constant with a scalar constructed of the inverted Ricci tensor (see https://arxiv.org/pdf/2006.04209.pdf). I will introduce the model by summarizing the original article and then present our extension to other tensors. In particular we investigate if inverting the Einstein or Riemann tensor can lead to a solution to the impossible transition from matter-like to accelerated expansion as occurring in a simple case of Ricci-inverse gravity.
 +
 +
 +== 20th July 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Martin Kärcher - Cancelled
 +
 +== 13th July 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Cancelled.
 +
 +== 12th July 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Manuel Wittner - rehearsal
 +
 +== 06th July 2022: Physics Forum (General discussions about papers, research and work) ==
 +
 +== 29th June 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Cancelled.
 +
 +== 22nd June 2022: Physics Forum (General discussions about papers, research and work) ==
 +
 +== 15th June 2022: Physics Forum (General discussions about papers, research and work) ==
 +
 +== 08th June 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Cancelled.
 +
 +== 01st June 2022: Physics Forum (General discussions about papers, research and work) ==
 +
 +== 25th May 2022: Physics Forum (General discussions about papers, research and work) ==
 +
 +== 18th May 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Chiara Cecchini (University of Trento) - Primordial magnetic fields in scale-invariant inflation
 +
 +Magnetic fields permeate the Universe probed so far, from planetary scales to the Intergalactic Medium. An intriguing possibility is that they are remnants of primordial fields that originated during inflation. However, the amplification of vector perturbations in an exponentially expanding universe requires the breaking of EM conformal invariance. To this end, one can introduce a time-dependent coupling I(t) between the EM tensor and a scalar field with a non-trivial dynamics. In this work, we consider inflationary magnetogenesis in a scale-invariant model of quadratic gravity (arXiv:1512.07186). After constraining the model against spectral indices measurements, we investigate the optimal functional form of the coupling I(t) to generate a nearly scale-invariant spectrum of magnetic energy density and sufficiently strong fields at the end of inflation. We conclude by discussing the main problems with such a generation mechanism and a possible way out. A purely analytical analysis has been carried out.
 +
 +== 11th May 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Alejandro Hernández Arboleda (UFES - PPGCosmo, Brazil) - Screening tests with galaxy rotation curves
 +
 +Modified theories of gravity make use, in a general sense, of screening mechanisms such as Vainshtein screening, to hide the effects of their modifications  to Newtonian gravity and general relativity at local scales. Although the screening mechanism is responsible for suppressing "fifth forces" in the vicinity of massive sources, it can be broken inside them. In this tunch I will discuss updates of my research dealing with vainshtein screening breaking at the scale of galaxies using rotation curves and several dark matter profiles, focusing on the numerical methods used to study them.
 +
 +== 13th April 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Pedro da Silveira Ferreira - First constraints on the intrinsic CMB dipole and our velocity with Doppler and aberration
 +
 +We test the usual hypothesis that the Cosmic Microwave Background (CMB) dipole, its largest anisotropy, is due to our peculiar velocity with respect to the Hubble flow by measuring independently the Doppler and aberration effects on the CMB using Planck 2018 data. We remove the spurious contributions from the conversion of intensity into temperature and arrive at measurements which are independent from the CMB dipole itself for both temperature and polarization maps and both SMICA and NILC component-separation methods. Combining these new measurements with the dipole one we get the first constraints on the intrinsic CMB dipole. Assuming a standard dipolar lensing contribution we can put an upper limit on the intrinsic amplitude: 3.7 mK (95% CI). We estimate the peculiar velocity of the solar system without assuming a negligible intrinsic dipole contribution: v=(300+111−93) km/s with (l,b)=(276±33,51±19)∘ [SMICA], and v=(296+111−88) km/s with (l,b)=(280±33,50±20)∘ [NILC] with negligible systematic contributions. These values are consistent with the peculiar velocity hypothesis of the dipole.
 +
 +In this tunch, I will discuss our previous results (https://arxiv.org/abs/2011.08385 and https://arxiv.org/abs/2107.10846), and comment a bit about our next steps.
 +
 +
 +__**Winter term 21/22:**__
 +
 +== 30th March 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Cancelled.
 +
 +== 23rd March 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Raquel Fazolo - Skewness as a test of dark energy perturbations
 +We investigate the role played by dark energy perturbations in the skewness S_3 of large-scale matter distribution. We consider a two-fluid universe composed by matter and dark energy, with perturbations in both components, and we estimate numerically the skewness of the matter density field as a function of the dark energy parameters. We characterize today's S_3 value for quintessence and phantom dark energy cosmologies as well as its dependence on the matter density parameter Ω_m0 and the dark energy sound speed c_{s}^2 with accurate numerical fitting. These fits can be used to test cosmology against future high quality data on large scale structure. (arXiv:2202.08355)
 +
 +== 16th March 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Prajwal Hassan Puttasiddappa
 +
 +Higher-Derivative Screening and UV aspects
 +
 +In this Tunch I would like to present some aspects of higher
 +derivative screening mechanisms famously known as the Vainstein
 +mechanism. First, we shall see it in the context of extended-BDLCDM,
 +where we employ these mechanisms to screen the BD effects locally so
 +that we reconcile observationally constrained Newton's constant G_N but
 +still maintain BDLCDM cosmology in the cosmological scales. We will
 +realize that higher-order derivatives do not provide a suffiently large
 +gradient to screen BD effects locally [1]. The screening mechanism
 +itself is a result of the domination of dynamics of higher-order
 +operators. In the effective field theory context, we want to see to what
 +extent we can have a predictive theory [2]. So in the second part, our
 +concern will be on the UV aspects of these theories and their
 +implications to macroscopic physics [3].
 +
 +[1] JCAP 09 (2021) 040 (arXiv:2105.14819).
 +[2] JCAP 11( 2014) 016 (arXiv:1405.5213).
 +[3] JCAP 06 (2018) 039 (arXiv:1712.04019)
 +
 +== 10th March 2022: Journal Club (NOTE UNSUAL DATE) ==
 +
 +Nico Lorenz
 +
 +Clustering of Gravitational Wave and Supernovae events: a
 +multitracer analysis in Luminosity Distance Space \\
 +Sarah Libanore et al. \\
 +[[ https://arxiv.org/abs/2109.10857 | view arXiv ]]
 +
 +
 +== 02nd March: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Luca Amendola - Non-linear perturbation theory (part 2)
 +
 +== 23rd February 2022: Journal Club ==
 +
 +Prajwal Hassan Puttasiddappa - Cosmological Singularity in the Local analysis
 +
 +== 16th February 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Pedro da Silveira Ferreira - Rencontres de Moriond 2022 (Cosmology): Highlights and impressions
 +
 +In this tunch I will briefly present some of the highlights of the Moriond 2022 Cosmology conference (the 56th edition).
 +
 +== 09th February 2022: Journal Club ==
 +
 +Cancelled.
 +
 +== 02nd February 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Luca Amendola - Non-linear perturbation theory (part 1)
 +
 +== 26th January 2022: ==
 +
 +Cancelled.
 +
 +== 19th January 2022: ==
 +
 +Cancelled.
 +
 +== 12th January 2022: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Alejandro Hernández Arboleda (UFES - PPGCosmo, Brazil) - New test of dark matter theories with galaxy rotation curves
 +
 +Scalar field theories usually predict the existence of a "fifth force" which essentially codifies the modifications to Newtonian gravity and general relativity of such theories and controls the accelerated expansion of the universe at cosmological scales. In general, these theories make use of screening mechanisms, such as Vainshtein screening, to hide the effects of their modifications at local scales and satisfy solar system tests. Although the screening mechanism is responsible for suppressing the "fifth force" in the vicinity of massive sources, it can be broken inside them. In this tunch I will discuss the results of my investigation dealing with vainshtein screening breaking at the scale of galaxies using rotation curves and several dark matter profiles, focusing on the numerical methods used to study them.
 +
 +== 22nd December 2021: ==
 +
 +Cancelled.
 +
 +== 15th December 2021: Journal Club ==
 +
 +David Camarena
 +
 +Challenges for the statistical gravitational-wave method to measure the Hubble constant \\
 +Emery Trott, Dragan Huterer \\
 +[[ https://arxiv.org/abs/2112.00241 | view arXiv ]]
 +
 +== 08th December 2021: ==
 +
 +Cancelled.
 +
 +== 01st December 2021: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Rodrigo Von Marttens (Observatório Nacional, Rio de Janeiro) - Testing the consistency of the standard cosmological model
 +
 +First, we perform a general test of the ΛCDM and wCDM cosmological
 +models by comparing constraints on the geometry of the expansion
 +history to those on the growth of structure. Specifically, we split the
 +total matter energy density, Ω_M , and (for wCDM) dark energy equation
 +of state, w, into two meta-parameters each: one that captures the
 +geometry, and another that captures the growth. We constrain our split
 +models using current cosmological data, including type Ia supernovae,
 +baryon acoustic oscillations, redshift space distortions, gravitational
 +lensing, and cosmic microwave background (CMB) anisotropies. We focus
 +on two tasks: (i) constraining deviations from the standard model,
 +captured by the difference between the geometry and growth parameters,
 +and (ii) investigating whether the S 8 tension between the CMB and weak
 +lensing can be translated into a tension between geometry and growth,
 +i.e. ΔΩ_M ≠ 0, Δw ≠ 0. Lastly, we relax the conventional assumption of
 +a minimal coupling between the DM and DE, to reconstruct a possible
 +interaction in the dark sector in a model-independent way, using data
 +from type Ia supernovae, cosmic chronometers and baryonic acoustic
 +oscillations. According to our analysis, the ΛCDM model is consistent
 +with our model-independent approach at least at 3σ CL over the entire
 +range of redshift studied. On the other hand, our analysis shows that
 +the current background data do not allow us to rule out the existence
 +of an interaction in the dark sector.
 +
 +
 +== 24th November 2021: ==
 +
 +Cancelled.
 +
 +== 17th November 2021: ==
 +
 +Cancelled.
 +
 +== 10th November 2021: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Prajwal Hassan Puttasiddappa - Fifth force, Dark matter, and Gravitational Waves
 +
 +It was shown by L.Amendola, J.Rubio, C.Wetterich (2018) that a long-range, attractive fifth force, stronger than gravity could produce primordial black holes (PBH), and along with S.Savastano (2019) they also argued that primordial dark matter halos could be formed. The model contains a beyond standard model fermion field and a scalar field which mediates the fifth force between the former. Interestingly, unlike conventional PBH which forms before nucleosynthesis, these are formed in the radiation era! According to the estimates, it is plausible that these objects constitute the entire dark matter component in the universe. With their distinctive mass range and density, we show that they fall within the sensitivity range of future gravitational wave detectors. The presentation is mainly based on the original works (arXiv: 1711.09915, 1906.05300) along with a small portion of gravitational waves (arXiv: 1706.02111, 1207.5359).
 +
 +== 03rd November 2021: Journal Club ==
 +
 +Luca Amendola
 +
 +Measurements of the Hubble Constant: Tensions in Perspective \\
 +Wendy L. Freedman \\
 +[[ https://arxiv.org/abs/2106.15656 | view arXiv ]]
 +
 +== 20th October 2021: Journal Club ==
 +
 +Raquel Fazolo
 +
 +A model-independent reconstruction of dark energy to very high redshift \\
 +Adam Moss, Edmund Copeland, Steven Bamford, Thomas Clarke \\
 +[[ https://arxiv.org/abs/2109.14848 | view arXiv ]]
 +
 +__**Summer term 21:**__
 +
 +== 21st July 2021: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Lorenzo Pizzuti - Testing screening mechanisms with mass profiles of galaxy clusters
 +
 +Testing screening mechanisms with mass profiles of galaxy clusters
 +Abstract: Galaxy clusters constitute a powerful tool to investigate modification of gravity at cosmological scales; in particular, with the combination of cluster’s mass profiles derived with lensing and internal kinematic analyses, it is possible to constrain departures from General Relativity in a complementary way with respect to other cosmological and astrophysical probes. In this context, I will present MG-MAMPOSSt, a code to constrain modified gravity models by reconstructing the mass profile with the kinematic of cluster's member galaxies, along with recent results and forecasts on two classes of models characterized by different screening mechanisms, namely chameleon and Vainshtein screening. I will show the capability of the method when combined with lensing data as well as some criteria to control possible systematics in view of the application to the data of upcoming imaging and spectroscopic surveys.
 +
 +== 14th July 2021: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Martin Kärcher and Manuel Wittner - There is Something Wrong in the Action...
 +
 +Reasonable modified gravity theories, apart from resembling general
 +relativity on solar system scales, must satisfy some further conditions
 +in order to be consistent. One such condition is stability, i.e. the
 +absence of ghosts, gradient instabilities and tachyons. In this tunch,
 +we will elaborate on the exorcism of such ghosts; that is, using the
 +example of the novel inverse-Ricci gravity, we will explain how to find
 +conditions on the action level that render the theory stable. Special
 +attention will be paid to finding a proper gauge-choice with which the
 +analysis can be performed.
 +
 +== 07th July 2021: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Roberto Capuzzo-Dolcetta - Violent dynamics in the Galactic nucleus
 +
 +The central region of our Galaxy (as well as of most of others) is site of violent activity and constitutes an unique place to set constraints to various physical theories. In this talk I will give a short overview of the strong dynamics of stars around the Sgr A* massive object at the center of the Milky Way and present some results about an intriguing hypothesis concerning the growth of the central supermassive black hole observed in many galaxies including our Galaxy.
 +
 +== 30th June 2021: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Ziyang Zheng - Constraints on the fraction of early dark energy in the pre- andpost-recombination epochs
 +
 +Early dark energy (EDE) models present around the matter-radiation equality time $t_{eq}$ have been proposed as a promising solution to the famous $H_0$ tension (arXiv:1301.5279, arXiv:1811.04083), at the cost of increasing the large scale structure (LSS) formation processes with respect to the $\Lambda_{CDM}$ model. This issue could in principle be alleviated by  introducing a non-negligible EDE component in the post-recombination era. In this work we constrain the fraction of early dark energy during the whole cosmic history, with the EDE component represented by a fluid parametrization and also a more model-independent approach based on the binning of the EDE density. We also investigate the LSS tension when studied in terms of the recently proposed $\sigma_{12}$ and $S_{12}$ parameters.
 +
 +== 23rd June 2021: ==
 +
 +Replaced by extracurricular cosmology seminar.
 +
 +== 16th June 2021: ==
 +
 +Cancelled.
 +
 +== 09th June 2021: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Guilherme Brando - Fully relativistic predictions in Horndeski gravity from standard Newtonian N-body Simulations
 +
 +The N-body gauge allows the introduction of relativistic effects in Newtonian cosmological simulations. Here we extend this framework to general Horndeski gravity theories, and investigate the relativistic effects that the scalar field introduces in the matter power spectrum at intermediate and large scales. In particular, we show that the kineticity function at these scales enhances the amplitude of the signal of contributions coming from the extra degree of freedom. Using the Quasi-Static Approximation (QSA), we separate modified gravity effects into two parts: one that only affects small-scale physics, and one that is due to relativistic effects. This allows our formalism to be readily implemented in modified gravity N-body codes in a straightforward manner, e.g., relativistic effects can be included as an additional linear density field in simulations. We identify the emergence of gravity acoustic oscillations (GAOs) in the matter power spectrum at large scales, k∼10^−3−10^−2 Mpc−1. GAO features have a purely relativistic origin, coming from the dynamical nature of the scalar field. GAOs may be enhanced to detectable levels by the rapid evolution of the dark energy sound horizon in certain modified gravity models and can be seen as a new test of gravity at scales probed by future galaxy and intensity-mapping surveys.
 +
 +== 02nd June 2021: ==
 +
 +Cancelled.
 +
 +== 26th April 2021: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Walter Riquelme - Primordial non-Gaussianity from the angular clustering: prospects for DES
 +
 +Primordial non-Gaussianity (PNG) is claimed to be a smoking gun to differentiate between the vast collection of inflationary models. The current constraints on PNG, parametrized by fNL, are obtained from the CMB, which has reached the cosmic variance limit. A promising way to look for PNG is using the Large Scale Structures (LSS) of the universe, with the potential of breaking the sigma(fNL)~1 barrier. In this talk, I will present an analysis of the methods for looking at Primordial non-Gaussianity in the Large Scale Structure of the Universe, with the main focus on the Dark Energy Survey (DES). We use the Angular Correlation Function (ACF) and show how it is modified by Primordial Non-Gaussianity via a scale-dependent bias (Dalal et al. 2008). One of the main focus of the work is on the integral constraint (IC) condition, which is found to be key to obtain unbiased PNG constraints. The IC corrects for the fact that the mean density of the Universe is measured from the observed galaxies. The methods are analyzed and optimized for two kinds of simulations: COLA mocks that follow the DES angular and redshift distribution and N-Body simulations with non-Gaussian initial conditions. With the aforementioned simulations, we focus on optimizing the methods to constraint fNL to obtain precise and unbiased results, preparing the ground for the DES Y3 data. We highlight the potential that DES and future photometric surveys could have in constraining PNG.
 +
 +== 19th May 2021: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Jenny Wagner - Matter Matryoshkas -- The emergence of self-similar cosmic structures
 +
 +From galaxy clusters to star clusters structures resemble each other like Matryoshka dolls. While self-similarity establishes a unified, scale-independent description of cosmic structures, we have not fully grasped its emergence yet. Instead, heuristic functions like the Navarro-Frenk-White profile are fitted to mass densities of observed structures in the Newtonian framework. This talk shows that the fitting functions are set by the interactions generating the structure and that they represent the smoothed distribution of its constituents. Forgoing resolution and boundary effects, structure morphologies caused by gravitation in general relativity can already be found in works on self-similar inhomogeneous spacetimes from the 1970s and 80s. Thus, any structure morphology dominated by scale-free gravitational interactions is of self-similar type and can be understood in terms of fundamental principles.
 +
 +Literature: 
 +
 +https://www.worldscientific.com/doi/epdf/10.1142/S0218271820430178
 +
 +https://www.sciencedirect.com/science/article/abs/pii/0003491683900246
 +
 +https://link.springer.com/article/10.1007/BF00645031
 +
 +
 +== 12th May 2021: Journal Club ==
 +
 +C. Wetterich
 +
 +Cosmology from pregeometry \\
 +C. Wetterich \\
 +[[ https://arxiv.org/abs/2104.14013 | view arXiv ]]
 +
 +== 05th May 2021: Journal Club ==
 +
 +Raquel Fazolo
 +
 +Evolution of hierarchical clustering in the CFHTLS-Wide since z ∼ 1 \\
 +M. Wolk, H. J. McCracken, S. Colombi, J. N. Fry, M. Kilbinger, P. Hudelot, Y. Mellier and O. Ilbert \\
 +[[ https://arxiv.org/abs/1301.3301 | view arXiv ]]
 +
 +== 28th April 2021: ==
 +
 +Cancelled.
 +
 +== 21st April 2021: Journal Club ==
 +
 +Prajwal Hassan Puttasiddappa - "Probing Quantum Nature of Gravity" \\
 +
 +Quantizing gravity in conventional way fails theoretically at 2 loop level for pure gravity and at 1 loop with matter. It was also argued that, possibility of detecting a single quanta of gravitation is very less due to our sensitivity limitations. On the other hand, quantum mechanics has fundamental formalism problems. Many people tried to answer these two questions together by Gravitizing Quantum Mechanics. But, could we actually see if gravity participates in quantum mechanical experiments? What are the directions in this aspect? Can we finally see the quantum nature of gravity? That too on a low energy table-top experiment? We will briefly explore the recent experimental directions.
 +
 +Based on:
 +
 +Tabletop experiments for quantum gravity: a user's manual \\
 +Daniel Carney, Philip C. E. Stamp and Jacob M. Taylor \\
 +[[ https://arxiv.org/abs/1807.11494 | view arXiv ]]
 +
 +Underground test of gravity-related wave function collapse \\
 +Sandro Donadi et al.
 +Nature Phys. 17 (2021) 1, 74-78
 +
 +== 14th April 2021: Journal Club ==
 +
 +David Camarena
 +
 +On the use of the local prior on the absolute magnitude of Type Ia supernovae in cosmological inference \\
 +David Camarena and Valerio Marra \\
 +[[ https://arxiv.org/abs/2101.08641 | view arXiv ]]
 +
 +__**Winter term 20/21:**__
 +
 +== 24th February 2021: Selected topics in theory and observations of Dark Energy (Tunch - Cultural edition) ==
 +
 +Ziyang Zheng - China
 +
 +Ice & Snow festival, natural landscapes, lantern festival,
 +hot springs, cherry blossoms, Ice houses..... Welcome to my cultural
 +tunch! I would like to introduce my hometown-the northeast of China, as
 +well as my previous institute in southern China-USTC, have a look at the
 +differences between northern & southern china!
 +
 +Prajwal Hassan Puttasiddappa - India: Perspectives and Science Undercurrent
 +
 +I will introduce you to some of India's contributions to the field of
 +Physics and Mathematics with a jot of personal journey and inspirations.
 +I will convey some facts about my previous university education and
 +their research interests. The idea is to share the "Indian" perspective
 +on nature and its phenomena.
 +
 +== 17th February 2021: Selected topics in theory and observations of Dark Energy (Tunch - Cultural edition) ==
 +
 +Raquel Fazolo - Brazil
 +
 +== 03rd February 2021: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Abdolali Banihashemi - A hint from Hubble: Does H_0 tension reveal the secrets of dark energy?
 +
 +In this talk we will have a brief review on H_0 tension and
 +then we investigate, theoretically and observationally, a model in which
 +dark energy emerges as a critical phenomenon.
 +
 +== 20th January 2021: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Manuel Wittner - Implications of string theory on the QCD axion
 +
 +The QCD axion is arguably the most prominent solution to the
 +strong CP problem. On the other hand, string theory as a candidate for an
 +underlying theory beyond the standard model offers a plethora of
 +axion-like fields, one of which could indeed play the role of the QCD
 +axion. In general, however, it seems difficult to construct stringy
 +models that contain a QCD axion in the preferred parameter range. In
 +this tunch I am going to elaborate on the difficulties one has to
 +overcome when constructing stringy axion models and on the
 +phenomenological consequences of such models for the QCD axion and the
 +early universe.
 +
 +== 13th January 2021: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Martin Kärcher - Riemann-Einstein-Inverse Gravity
 +
 +The current FLRW-model makes use of a cosmological constant
 +which enters the Einstein field equations in order to explain
 +observations of an accelerated expansion of the Universe. However, the
 +cosmological constant is not flawless and brings some issues along the
 +way, for example, the fine-tuning problem. There exists a whole realm of
 +alternatives to the FLRW-model, trying to fit observations without the
 +necessity of a cosmological constant.
 +I investigated a specific modification of General Relativity by adding a
 +scalar to the action, build from the inversion of the Einstein tensor
 +and the Riemann tensor (similar to this reference
 +arxiv.org/abs/2006.04209). I carried out a linearized stability analysis
 +for the two cases in which I searched for critical points in the
 +accelerating regime. To wrap up the overview of the dynamical system,
 +numerical solutions were derived.
 +
 +== 16th December 2020: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Victor Bosca - Modelling accurately the microlensing of supernovae in a lumpy universe
 +
 +Needless to say that the nature of dark matter is one of the
 +biggest questions of modern physics. The possibility that dark matter is
 +(at least partially) made of compact objects is a very appealing idea.
 +One way to probe compact objects, such as primordial black holes, beyond
 +the Solar mass is via supernova lensing. In this project we model the
 +probability density function of microlensing magnification P(A|f), given
 +that a fraction f of dark matter is made of compact objects. We include
 +many effects, such as the complex distribution of dark matter in haloes,
 +the subtle effect of lens-lens coupling and the finite size of sources.
 +
 +== 02nd December 2020: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Cristian Moreno Pulido - Renormalized ρ vac without m^4 terms
 +
 +The cosmological constant (CC) term, Λ, in Einstein's equations has been for some three decades a fundamental buildingblock of the concordance or standard ΛCDM model of cosmology. Even though the model is not free of fundamental problems, they have not been circumvented by any alternative dark energy proposal either. However, an interesting alternative is that the vacuum energy is a "running quantity" in quantum field theory in curved spacetime. Several works have shown that this is option can compete with the ΛCDM with a rigid Λ term. The so-called, "running vacuum models" (RVM) are characterized by a vacuum energy density, ρvac, which is evolving with time as a series of even powers of the Hubble parameter and its time derivatives. This form has been motivated by renormalization group arguments in previous works. In this talk we show how to compute the renormalized energy-momentum tensor with the help of adiabatic regularization procedure as it has been done in arXiv/2005.03164 (Eur.Phys.J.C(2020)80:692). The final result is a RVM-like form of the vacuum energy, with ρvac(H) being a constant term plus others ∼H2 and ∼H4. Besides, it does not carry dangerous terms proportional to m4, the quartic powers of the masses of the fields, which are a well-known source of exceedingly large contributions.
 +
 +== 25th November 2020: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Alejandro Hernandez - Palatini-type gravity and dark matter in galaxies  
 +
 +From the weak field limits of Palatini f(R) gravity and Eddington-inspired-Born-Infeld gravity (EiBI), we test the possibility of these theories to  either replace dark matter or change the amount of dark matter in galaxies. We consider the SPARC galaxy sample. However, instead of considering individual galaxy fits, we use here a normalized missing velocity approach, as here detailed. The method is based on the data density in the plane rn × δv, where rn is the normalized galaxy radius and δv stands for the normalized difference between the observed and the baryonic circular velocity. As here discussed, this plane is useful for testing the dark matter or non-Newtonian model contribution to the rotation curve, it commonly depends on one less model parameter (due to the normalization), it reduces the dependence on baryonic details of individual galaxies (since only the average sample behavior is tested) and promptly yields the model overall behaviour: providing hints on which type of galaxies the proposed model has most difficulties on addressing; or if the proposed model is simply not compatible with observational data. For the models here tested, we show that:
 +i) considering their theoretical basis: a. These models can enhance thin disk stability, and b. the NFW dark matter halo cannot be in general used with them, since it implies an unbounded force;
 +ii) without any kind of dark matter, these models are in general incompatible with galaxy rotation curve data (they would require unrealistic stellar disks);
 +iii) (expectation) if used together with a phenomenologically successful dark matter halo (the Burkert profile), the models are compatible with null or close to null non-Newtonian behaviour in galaxies; that is, we find no evidence that the
 +non-Newtonian corrections could improve the Burkert profile success.
 +
 +== 18th November 2020: Journal Club ==
 +
 +Raquel Fazolo
 +
 +Interacting Dark Energy in a closed universe \\
 +Eleonora Di Valentino, Alessandro Melchiorri, Olga Mena, Supriya Pan, Weiqiang Yang \\
 +[[ https://arxiv.org/abs/2011.00283 | view arXiv ]]
 +
 +
 +
 +== 11th November 2020: Journal Club ==
 +
 +David Camarena
 +
 +Two-point statistics without bins: A continuous-function generalization
 +of the correlation function estimator for large-scale structure \\
 +Kate Storey-Fisher, David W. Hogg \\
 +[[ https://arxiv.org/abs/2011.01836 | view arXiv ]]
 +
 +
 +
 +__**Summer term 20:**__
 +
 +== 8th July 2020: Selected topics in theory and observations of Dark Energy (Tunch) ==
 +
 +Adrià Gómez-Valent - Boosting MonteCarlo sampling with a non-Gaussian fit
 +
 +We propose a new method, called MonteCarlo Posterior Fit, to boost the MonteCarlo sampling of likelihood (posterior) functions. The idea is to approximate the posterior function by an analytical multidimensional non-Gaussian fit. The many free parameters of this fit can be obtained by a smaller sampling than is needed to derive the full numerical posterior. In the examples that we consider, based on supernovae and cosmic microwave background data, we find that one needs an order of magnitude smaller sampling than in the standard algorithms to achieve comparable precision. This method can be applied to a variety of situations and is expected to significantly improve the performance of the MonteCarlo routines in all the cases in which sampling is very time-consuming. Finally, it can also be applied to Fisher matrix forecasts, and can help solve various limitations of the standard approach.
 +
 +This discussion is based [[ https://arxiv.org/pdf/2007.02615.pdf | view arXiv ]] \\ 
  
 __**Winter term 19/20:**__ __**Winter term 19/20:**__
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