# Differences

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joint [2019/04/02 13:46] manuel [Seminar calendar] |
joint [2019/07/04 10:38] (current) marta [Seminar calendar] |
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__**Summer term 19:**__ | __**Summer term 19:**__ | ||

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+ | == 26th September 2019: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

TBA | TBA | ||

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+ | == 19th September 2019: Journal Club == | ||

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+ | TBA | ||

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+ | == 25th July 2019: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

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+ | TBA | ||

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+ | == 18th July 2019: Journal Club == | ||

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+ | TBA | ||

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+ | == 11th July 2019: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

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+ | Jakob Henrichs - TBA | ||

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+ | == 4th July 2019: Journal Club == | ||

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+ | Oliver Fabio Piattella \\ | ||

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+ | Can the quantum vacuum fluctuations really solve the cosmological constant problem? \\ | ||

+ | Gabriel R. Bengochea, Gabriel León, Elias Okon, Daniel Sudarsky \\ | ||

+ | [[ https://arxiv.org/abs/1906.05406 | view arXiv ]] | ||

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+ | == 25th June 2019, PW 12, Room 060 (NOTE UNUSUAL DATE AND LOCATION): Selected topics in theory and observations of Dark Energy (Tunch) == | ||

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+ | Adria Gomez-Valent (ITP, Universität Heidelberg) - "Quantifying the evidence for the current speed-up of the | ||

+ | Universe with low and intermediate-redshift data. A more | ||

+ | model-independent approach" | ||

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+ | According to cosmological low and intermediate-redshift | ||

+ | data, what is the statistical evidence in favor of the current | ||

+ | speed-up of the Universe? Although this question seems to be kind of | ||

+ | outdated, a quick review to the many papers that address this pivotal | ||

+ | question in the literature tells us that the answer is not obvious at | ||

+ | all. Determining the value of the deceleration parameter in the | ||

+ | context of particular cosmological models, concrete parametrizations | ||

+ | of the cosmographical quantities, or even using truncated | ||

+ | cosmographical expansions in which the truncation order is set in an | ||

+ | ad hoc way | ||

+ | can lead to biased estimations of the value of the deceleration | ||

+ | parameter at present, q0, and its uncertainty. In this talk, which is | ||

+ | based on arXiv:1810.02278, JCAP 05 (2019) 026, I present a new | ||

+ | determination of q0 obtained with data from the Pantheon+MCT | ||

+ | compilation of supernovae of Type Ia, cosmic chronometers and baryon | ||

+ | acoustic oscillations. I apply the so-called Weighted Function | ||

+ | Regression method to reconstruct q(z) more model-independently than | ||

+ | many analyses in the literature, improving in this way the usual | ||

+ | cosmograhical approach. We will see, for instance, that using only the | ||

+ | first two data sets the level of evidence for the current positive | ||

+ | acceleration of the universe is only moderate (using Jeffreys' scale | ||

+ | and jargon), contrary to the more than 17\sigma-evidence found in the | ||

+ | framework of the standard flat LCDM model. The level of evidence grows | ||

+ | up to the very strong one when BAO data are also considered, giving | ||

+ | rise to q0= -0.60 +- 0.10, with a deceleration-acceleration transition | ||

+ | redshift at z_t = 0.80 +- 0.10. The jerk is also reconstructed, | ||

+ | although unfortunately current data is unable to set stringent | ||

+ | constraints to this cosmographical parameter. | ||

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+ | == 19th June 2019, PW 12, Room 060 (NOTE UNUSUAL DATE AND LOCATION): Journal Club == | ||

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+ | Giorgio Laverda \\ | ||

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+ | Strong gravity signatures in the polarization of gravitational waves \\ | ||

+ | S. Shankaranarayanan \\ | ||

+ | [[https://arxiv.org/abs/1905.03943 | view arXiv ]] \\ | ||

+ | |||

+ | Julius Wons | ||

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+ | Gravitational wave standard sirens and cosmological parameter measurement \\ | ||

+ | Xin Zhang \\ | ||

+ | [[https://arxiv.org/abs/1905.11122 | view arXiv ]] \\ | ||

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+ | == 13th June 2019: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

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+ | Arvid Weyrauch & Manuel Wittner (ITP, Universität Heidelberg) - “Cosmology, philosophically speaking” (Collective Discussions) | ||

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+ | As researchers we tend to find answers using the scientific method. However, some questions may not have an answer but still spark a lot of different thoughts and perspectives. In this tunch, we will address some of these questions, from the nature of time to its beginning. | ||

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+ | == 6th June 2019: Journal Club == | ||

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+ | Leonardo Giani \\ | ||

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+ | Is Gravity Actually the Curvature of Spacetime? \\ | ||

+ | Sebastian Bahamonde, Mir Faizal \\ | ||

+ | [[https://arxiv.org/abs/1905.04372 | view arXiv ]] \\ | ||

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+ | Ana Marta Pinho \\ | ||

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+ | Black hole shadow as a standard ruler in cosmology \\ | ||

+ | Oleg Yu. Tsupko, Zuhui Fan, Gennady S. Bisnovatyi-Kogan \\ | ||

+ | [[https://arxiv.org/abs/1905.10509 | view arXiv ]] \\ | ||

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+ | == 29th May 2019, PW 12, Room 060 (NOTE UNUSUAL DATE AND LOCATION): Selected topics in theory and observations of Dark Energy (Tunch) == | ||

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+ | Oliver Piattella (UFES, Brazil; visitor at ITP, Universität Heidelberg) - "Neutron stars masses in R^2 gravity" | ||

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+ | We investigate the mass-radius (M-R) relation for | ||

+ | neutron stars in f(R) = R + R^2 gravity. We adopt a spherically | ||

+ | symmetric metric and a SLy equation of state. We stress how in f(R) | ||

+ | gravity it is possible to define mass in many inequivalent ways which | ||

+ | are nonetheless all equivalent in General Relativity. We investigate | ||

+ | the role of the extra scalar degree of freedom in the definition of | ||

+ | the masses and in the features of the M-R relation. | ||

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+ | == 23rd May 2019: Journal Club == | ||

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+ | Adrià Gomez-Valent \\ | ||

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+ | Recasting H0 tension as OmegaM tension at low z \\ | ||

+ | Eoin Ó Colgáin \\ | ||

+ | [[https://arxiv.org/abs/1903.11743 | view arXiv ]] \\ | ||

+ | |||

+ | Leonardo Giani \\ | ||

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+ | How to Hide a Cosmological Constant \\ | ||

+ | S. Carlip \\ | ||

+ | [[https://arxiv.org/abs/1905.05216 | view arXiv ]] | ||

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+ | == 16th May 2019: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

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+ | Luca Amendola (ITP, Universität Heidelberg) - "Fisher matrix for multiple tracers (1904.00673)" | ||

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+ | I show how to obtain constraints on β, the ratio of the matter growth rate and the bias that quantifies the linear redshift-space distortions, that are independent of the cosmological model, using multiple tracers of large-scale structure. For a single tracer the uncertainties on β are constrained by the uncertainties in the amplitude and shape of the power spectrum, which is limited by cosmic variance. However, for two or more tracers this limit does not apply, since taking the ratio of power spectra cosmic variance cancels out, and in the linear (Kaiser) approximation one measures directly the quantity (1+β1μ2)2/(1+β2μ2)2, where μ is the angle of a given mode with the line of sight. I provide analytic formulae for the Fisher matrix for one and two tracers (up to quadrature) and quantify the signal-to-noise ratio needed to make effective use of the multiple-tracer technique. I also forecast the errors on β for a survey like Euclid. | ||

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+ | == 9th May 2019: Journal Club == | ||

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+ | Xuewen Liu \\ | ||

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+ | 21-cm observations and warm dark matter models \\ | ||

+ | Alexey Boyarsky, Dmytro Iakubovskyi, Oleg Ruchayskiy, Anton Rudakovskyi, Wessel Valkenburg \\ | ||

+ | [[https://arxiv.org/abs/1904.03097 | view arXiv ]] \\ | ||

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+ | == 2nd May 2019: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

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+ | Ana Marta Pinho (ITP, Universität Heidelberg) - "Cosmological Information Flow" | ||

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+ | The current state of Cosmology is a strong statistical preference for the LCDM model although with some unsolved problems. The recent data tensions raise now the doubt about the validity of the data pipeline and/or the LCDM model. Information theory provides some very useful tools that can measure the amount of information given by the data. Also these tools can be related to what it is commonly used in the literature as uncertainty measurements. In this talk I will present this on going work that tries to understand how information flows in the cosmological framework. | ||

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+ | == 25th April 2019: Journal Club == | ||

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+ | Ana Marta Pinho \\ | ||

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+ | Large Magellanic Cloud Cepheid Standards Provide a 1% Foundation for the Determination of the Hubble Constant and Stronger Evidence for Physics Beyond LambdaCDM \\ | ||

+ | Adam G. Riess, Stefano Casertano, Wenlong Yuan, Lucas M. Macri, Dan Scolnic \\ | ||

+ | [[https://arxiv.org/abs/1903.07603 | view arXiv ]] \\ | ||

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+ | Manuel Wittner \\ | ||

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+ | Probing modified gravity in cosmic filaments \\ | ||

+ | Alex Ho, Max Gronke, Bridget Falck, David F. Mota \\ | ||

+ | [[https://arxiv.org/abs/1807.07287 | view arXiv ]] \\ | ||

__**Winter term 18/19:**__ | __**Winter term 18/19:**__ |