# Differences

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joint [2019/05/15 14:43] 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) == | ||

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+ | 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 ]] \\ | ||

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+ | 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 ]] \\ | ||

+ | |||

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

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

+ | | ||

+ | 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. | ||

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

- | TBA | + | Adrià Gomez-Valent \\ |

+ | | ||

+ | 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 ]] | ||

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