# Differences

This shows you the differences between two versions of the page.

joint [2018/05/16 12:28] alessio |
joint [2019/01/14 11:18] (current) manuel |
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====Seminar calendar==== | ====Seminar calendar==== | ||

+ | |||

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

+ | |||

+ | == 14th March 2019: Journal Club == | ||

+ | |||

+ | TBA | ||

+ | |||

+ | == 7th March 2019: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

+ | |||

+ | Xuewen Liu (Institute of Theoretical Physics, CAS, Peking) - TBA | ||

+ | |||

+ | == 28th February 2019: Journal Club == | ||

+ | |||

+ | TBA | ||

+ | |||

+ | == 21st February 2019: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

+ | |||

+ | Stefano Savastano (University of Bologna) - TBA | ||

+ | |||

+ | |||

+ | == 14th February 2019: Journal Club == | ||

+ | |||

+ | TBA | ||

+ | |||

+ | == 7th February 2019: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

+ | |||

+ | Ana Marta Pinho (ITP, Universität Heidelberg) - TBA | ||

+ | |||

+ | |||

+ | == 31st January 2019: Journal Club == | ||

+ | |||

+ | TBA | ||

+ | |||

+ | == 24th January 2019: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

+ | |||

+ | Salvador Ramirez (ITP, Universität Heidelberg) - TBA | ||

+ | |||

+ | |||

+ | == 17th January 2019: Journal Club == | ||

+ | |||

+ | TBA | ||

+ | |||

+ | == 10th January 2019: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

+ | |||

+ | Xuewen Liu (Institute of Theoretical Physics, CAS, Peking) - Cultural Tunch | ||

+ | |||

+ | |||

+ | == 3rd January 2019: Journal Club == | ||

+ | |||

+ | Christmas break | ||

+ | |||

+ | == 27th December 2018: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

+ | |||

+ | Christmas break | ||

+ | |||

+ | == 20th December 2018: Journal Club == | ||

+ | |||

+ | Collective Discussions | ||

+ | |||

+ | == 13th December 2018: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

+ | |||

+ | Collective Discussions | ||

+ | |||

+ | == 6th December 2018: Journal Club == | ||

+ | |||

+ | Jiaming Zhao \\ | ||

+ | |||

+ | Cosmological parameter constraints for Horndeski scalar-tensor gravity \\ | ||

+ | Johannes Noller, Andrina Nicola \\ | ||

+ | ePrint: arXiv: 1811.12928 \\ | ||

+ | |||

+ | Guillem Domenèch \\ | ||

+ | |||

+ | Early Dark Energy Can Resolve The Hubble Tension \\ | ||

+ | Vivian Poulin, Tristan L. Smith, Tanvi Karwal, Marc Kamionkowski \\ | ||

+ | ePrint: arXiv: 1811.04083 | ||

+ | |||

+ | == 29th November 2018: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

+ | |||

+ | Collective Discussions | ||

+ | |||

+ | == 22nd November 2018: Journal Club == | ||

+ | |||

+ | Julius Wons \\ | ||

+ | |||

+ | Primordial Black Holes With Multi-Modal Mass Spectra \\ | ||

+ | Bernard Carr, Florian Kuhnel \\ | ||

+ | ePrint: arXiv: 1811.06532 \\ | ||

+ | |||

+ | Salvador Ramirez \\ | ||

+ | |||

+ | Current Signs of Dynamical Dark Energy \\ | ||

+ | Joan Sola Peracaula, Adria Gomez-Valent, Javier de Cruz Perez \\ | ||

+ | ePrint: arXiv: 1811.03505.pdf \\ | ||

+ | |||

+ | == 15th November 2018: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

+ | |||

+ | Julius Wons (ITP, Universität Heidelberg) - "Are primordial standard clocks really standard?" | ||

+ | |||

+ | Excited heavy fields during the creation of the primordial curvature perturbation leave oscillatory patterns in the power spectrum. These patterns can be used to distinguish between different primordial scenarios (inflation, bounce, ...) and are therefore called primordial standard clocks. I will show that this is in general not true if the mass of the heavy field is time dependent or when having non-canonical kinetic terms. | ||

+ | |||

+ | |||

+ | == 8th November 2018: Journal Club == | ||

+ | |||

+ | Manuel Wittner \\ | ||

+ | |||

+ | On the Cosmological Implications of the String Swampland \\ | ||

+ | Prateek Agrawal, Georges Obied, Paul J. Steinhardt, Cumrun Vafa \\ | ||

+ | ePrint: arXiv: 1806.09718 \\ | ||

+ | |||

+ | Stefano Savastano \\ | ||

+ | |||

+ | The Primordial Black Hole Dark Matter - LISA Serendipity \\ | ||

+ | N. Bartolo, V. De Luca, G. Franciolini, M. Peloso, A. Riotto \\ | ||

+ | ePrint: arXiv: 1810.12218 \\ | ||

+ | |||

+ | Xue-Wen Liu \\ | ||

+ | |||

+ | The End of Cosmic Growth \\ | ||

+ | Eric V. Linder, David Polarski \\ | ||

+ | ePrint: arXiv: 1810.10547 \\ | ||

+ | |||

+ | |||

+ | == 1st November 2018: NO Journal Club/Tunch == | ||

+ | |||

+ | Public Holiday | ||

+ | |||

+ | |||

+ | |||

+ | == 25th October 2018: Journal Club == | ||

+ | |||

+ | Dario Bettoni \\ | ||

+ | |||

+ | Dark energy after GW170817, revisited \\ | ||

+ | Edmund J. Copeland, Michael Kopp, Antonio Padilla, Paul M. Saffin, Constantinos Skordis \\ | ||

+ | e-Print: arXiv:1810.08239 | ||

+ | |||

+ | Ana Marta Pinho \\ | ||

+ | |||

+ | H0 Tension: Response to Riess et al arXiv:1810.03526 \\ | ||

+ | Tom Shanks, Lucy Hogarth, Nigel Metcalfe \\ | ||

+ | e-Print: arXiv:1810.07628 | ||

+ | |||

+ | |||

+ | == 18th October 2018: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

+ | |||

+ | Manuel Wittner (ITP, Universität Heidelberg) - Cultural Tunch | ||

+ | |||

+ | |||

+ | __**Summer term 18:**__ | ||

== 19th July 2018: Journal Club == | == 19th July 2018: Journal Club == | ||

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+ | == 11th July 2018: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

- | == 12th July 2018: Selected topics in theory and observations of Dark Energy (Tunch) == | + | Akshay Rana (University of Delhi, India)- "Novel ways to constrain Graviton mass and spatial curvature" |

- | Tunch available () | + | In cosmology, it always remains a topic of great interest to constrain cosmological parameters |

+ | by using different approaches and observational probes to confirm their consistency. In the same | ||

+ | direction, I will present two novel ways that can be used to limit the mass of the Graviton and the spatial | ||

+ | curvature of the space. My talk will be focused on two different aspects of present precision cosmology, | ||

+ | | ||

+ | 1) Firstly, I will discuss about the graviton, which is a massless particle in GR while considered to be | ||

+ | massive in some alternative models of GR like; Massive gravity theories. I will present a novel | ||

+ | approach that can be used to put stringent constraints on its mass using galaxy clusters. | ||

+ | | ||

+ | 2) Similarly, the estimation of spatial curvature of the Universe is also one of the most fundamental | ||

+ | issue of modern cosmology. I will discuss a model-independent approach to test the curvature of | ||

+ | space by using statistical features of strong gravitational lensing. | ||

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- | == 28th June 2018: Selected topics in theory and observations of Dark Energy (Tunch) == | + | == 27th June 2018: Selected topics in theory and observations of Dark Energy (Tunch) == |

- | Tunch available () | + | Davi C. Rodrigues(Federal University of Espirito Santo, Brazil)-"Absence of a fundamental acceleration scale in galaxies" |

+ | The Radial Acceleration Relation confirms that a nontrivial acceleration scale a0 can be found from the internal dynamics of several galaxies. The existence of such a scale is not obvious as far as the standard cosmological model is concerned, and it has been interpreted as a possible sign of modified gravity. We consider 193 high-quality disk galaxies and, using Bayesian inference, we show that the probability of existence of a fundamental acceleration is essentially zero: the null hypothesis is rejected at more than 10σ. We conclude that a0 is of emergent nature. In particular, the MOND theory, a well-known alternative to dark matter that is based on the existence of a fundamental acceleration scale, or any other theory that behaves like it at galactic scales, is ruled out as a fundamental theory for galaxies at more than 10σ. | ||

- | == 21st June 2018: Journal Club == | ||

- | Collective Journal Club | ||

+ | == 21st June 2018: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

+ | Elena Sellentin (Geneva University)- "Objective Bayesian analysis of neutrino masses and hierarchy" | ||

- | == 14th June 2018: Selected topics in theory and observations of Dark Energy (Tunch) == | + | Given the precision of current neutrino data, priors still impact noticeably the constraints on neutrino masses and their hierarchy. To avoid our understanding of neutrinos being driven by prior assumptions, we construct a prior that is mathematically minimally informative. Using the constructed uninformative prior, we find that the normal hierarchy is favoured but with inconclusive posterior odds of 5.1:1. Better data is hence needed before the neutrino masses and their hierarchy can be well constrained. We find that the next decade of cosmological data should provide conclusive evidence if the normal hierarchy with negligible minimum mass is correct, and if the uncertainty in the sum of neutrino masses drops below 0.025 eV. On the other hand, if neutrinos obey the inverted hierarchy, achieving strong evidence will be difficult with the same uncertainties. Our uninformative prior was constructed from principles of the Objective Bayesian approach. The prior is called a reference prior and is minimally informative in the specific sense that the information gain after collection of data is maximized. The prior is computed for the combination of neutrino oscillation data and cosmological data and still applies if the data improve. |

- | Tunch available () | ||

- | == 07th June 2018: Journal Club == | + | == 14th June 2018: Journal Club == |

Collective Journal Club | Collective Journal Club | ||

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- | == 31st May 2018: Selected topics in theory and observations of Dark Energy (Tunch) == | + | == 07th June 2018: Selected topics in theory and observations of Dark Energy (Tunch) == |

- | Tunch available () | + | Gerasimos Belegrinos (ITP, Universität Heidelberg)-"Why not two scalars? |

+ | " | ||

+ | Scalar-Tensor theories are arguably the largest known and most widely used models of modified gravity due to their combination of simplicity and extensive range of applications. The recent gravitational wave/ gamma ray bursts detection seems to indicate that a subclass of simplest Horndeski theories respects the constraints set on the gravitational waves speed. One way to go further is to take into account one additional scalar degree of freedom. In my work I consider to this purpose linear pertubation theory for a Biscalar-Tensor theory. The modified gravity quantities (effective gravitational constant, anisotropic stress-slip and weak lensing potential) are derived using the quasi-static approximation. In my talk I will present some of the results achieved that might have theoretical and observational interest. Finally I will present a way for testing an approximation performed while solving the modified growth rate. | ||

- | == 17th May 2018: Journal Club | + | == 31st May 2018: NO Journal Club/Tunch == |

+ | | ||

+ | Public Holiday | ||

+ | | ||

+ | | ||

+ | | ||

+ | == 24th May 2018: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

+ | | ||

+ | Caroline Heneka (SCUOLA NORMALE SUPERIORE, Pisa)-"The nature of modifications to gravity: 21cm to the rescue?" | ||

+ | | ||

+ | For this tunch I will briefly review some basics of both the global 21cm signal and 21cm intensity mapping at high redshifts (of reionization and beyond). I will continue to discuss the recent measurement of the global 21cm signal by EDGES, and conclude with the prospects of measuring general modifications of gravity with intensity mapping. | ||

+ | | ||

+ | == 17th May 2018: Journal Club == | ||

Collective Journal Club | Collective Journal Club | ||

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== 3rd May 2018: Selected topics in theory and observations of Dark Energy (Tunch) == | == 3rd May 2018: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

- | Tunch available () | + | Group Discussion |

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arXiv 1804.09206 | arXiv 1804.09206 | ||

+ | |||

+ | __**Winter term 17/18:**__ | ||

== 27th March 2018: Selected topics in theory and observations of Dark Energy (Tunch) == | == 27th March 2018: Selected topics in theory and observations of Dark Energy (Tunch) == | ||

- | Tunch available () | + | Group Discussion |

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Alessio Spurio Mancini - Dark Energy after GW170817 - 1710.05901 | Alessio Spurio Mancini - Dark Energy after GW170817 - 1710.05901 | ||

- | == 18th July : Journal Club == | + | __**Summer term 17:**__ |

+ | | ||

+ | == 18th July 2017: Journal Club == | ||

- | == 11th July : Selected topics in theory and observations of Dark Energy (Tunch) == | + | == 11th July 2017: Selected topics in theory and observations of Dark Energy (Tunch) == |

Martin Pauly (ITP, Heidelberg) - "Predictions of renormalized Higgs inflation" | Martin Pauly (ITP, Heidelberg) - "Predictions of renormalized Higgs inflation" | ||

Abstract: Higgs inflation is a model, that allows to explain inflation with the standard model degrees of freedom by introducing an additional coupling between the Higgs field and gravity. In this talk, I am going to explore the influence of the running of the standard model couplings on the observational predictions of Higgs inflation. In particular, the running of the Higgs-self-coupling and sudden changes in that coupling will be important. These sudden changes can be induced by the effective-field-theory nature of Higgs inflation. I will show that as long as the coupling stays sufficiently large in the inflationary region the predictions are insensitive to the running and become sensitive once the coupling approaches the critical point. | Abstract: Higgs inflation is a model, that allows to explain inflation with the standard model degrees of freedom by introducing an additional coupling between the Higgs field and gravity. In this talk, I am going to explore the influence of the running of the standard model couplings on the observational predictions of Higgs inflation. In particular, the running of the Higgs-self-coupling and sudden changes in that coupling will be important. These sudden changes can be induced by the effective-field-theory nature of Higgs inflation. I will show that as long as the coupling stays sufficiently large in the inflationary region the predictions are insensitive to the running and become sensitive once the coupling approaches the critical point. | ||

- | == 4th July : Journal Club == | + | == 4th July 2017: Journal Club == |

Caroline Heneka \\ | Caroline Heneka \\ | ||

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arXiv:1705.04861 | arXiv:1705.04861 | ||

- | == 27th June : Selected topics in theory and observations of Dark Energy (Tunch) == | + | == 27th June 2017: Selected topics in theory and observations of Dark Energy (Tunch) == |

Cornelius Rampf (ITP, Heidelberg University ) - "Shell-crossing in quasi one-dimensional flow " | Cornelius Rampf (ITP, Heidelberg University ) - "Shell-crossing in quasi one-dimensional flow " | ||

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Abstract: So far exact analytic solutions to the cosmological fluid equations existed for initial data that only depend on one space variable. Exact solutions (until shell-crossing) play an important role in cosmology, not only because they are simple but because the breakdown of smooth 3D solution through the development of infinite density caustics begins generically as an almost 1D phenomenon with the formation of pancakes. I present recent work on quasi-one-dimensional (Q1D) flow that depends on all three coordinates but differs only slightly from a strictly 1D flow, thereby allowing a perturbative treatment of shell-crossing using the Euler-Poisson equations written in Lagrangian coordinates. The signature of shell-crossing is then just the vanishing of the Jacobian of the Lagrangian map, a regular perturbation problem. In essence, the problem of the first shell-crossing, which is highly singular in Eulerian coordinates, has been desingularized by switching to Lagrangian coordinates, and can then be handled by perturbation theory. All-order recursion relations are obtained for the time-Taylor coefficients of the displacement field, and it is shown that the Taylor series has an infinite radius of convergence. This allows the determination of the time and location of the first shell-crossing, which is generically shown to be taking place earlier than for the unperturbed 1D flow. | Abstract: So far exact analytic solutions to the cosmological fluid equations existed for initial data that only depend on one space variable. Exact solutions (until shell-crossing) play an important role in cosmology, not only because they are simple but because the breakdown of smooth 3D solution through the development of infinite density caustics begins generically as an almost 1D phenomenon with the formation of pancakes. I present recent work on quasi-one-dimensional (Q1D) flow that depends on all three coordinates but differs only slightly from a strictly 1D flow, thereby allowing a perturbative treatment of shell-crossing using the Euler-Poisson equations written in Lagrangian coordinates. The signature of shell-crossing is then just the vanishing of the Jacobian of the Lagrangian map, a regular perturbation problem. In essence, the problem of the first shell-crossing, which is highly singular in Eulerian coordinates, has been desingularized by switching to Lagrangian coordinates, and can then be handled by perturbation theory. All-order recursion relations are obtained for the time-Taylor coefficients of the displacement field, and it is shown that the Taylor series has an infinite radius of convergence. This allows the determination of the time and location of the first shell-crossing, which is generically shown to be taking place earlier than for the unperturbed 1D flow. | ||

- | == 20th June : Journal Club == | + | == 20th June 2017: Journal Club == |

Caroline Heneka \\ | Caroline Heneka \\ | ||

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arXiv:1706.05205 | arXiv:1706.05205 | ||

- | == 13th June : Selected topics in theory and observations of Dark Energy (Tunch) == | + | == 13th June 2017: Selected topics in theory and observations of Dark Energy (Tunch) == |

Santiago Casas (ITP, Heidelberg University) - "Non-linear structure formation" | Santiago Casas (ITP, Heidelberg University) - "Non-linear structure formation" | ||

- | == 6th June : NO Journal Club on this day == | + | == 6th June 2017: NO Journal Club on this day == |

- | == 30th May : Selected topics in theory and observations of Dark Energy (Tunch) == | + | == 30th May 2017: Selected topics in theory and observations of Dark Energy (Tunch) == |

Javier Rubio (ITP, Heidelberg University) - "Scale invariance: connecting inflation and dark energy" | Javier Rubio (ITP, Heidelberg University) - "Scale invariance: connecting inflation and dark energy" | ||

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Abstract: Inflation and dark energy share many essential properties. I will show that these two eras can be accommodated into a common framework based on scale invariance. I will discuss the phenomenological consequences of two scenarios based on i) exact scale symmetry and ii) broken scale invariance with symmetry resurgence at UV and IR fixed points. | Abstract: Inflation and dark energy share many essential properties. I will show that these two eras can be accommodated into a common framework based on scale invariance. I will discuss the phenomenological consequences of two scenarios based on i) exact scale symmetry and ii) broken scale invariance with symmetry resurgence at UV and IR fixed points. | ||

- | == 23rd May : Journal Club == | + | == 23rd May 2017: Journal Club == |

Henrik Nersisyan \\ | Henrik Nersisyan \\ | ||

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- | == 16th May : Selected topics in theory and observations of Dark Energy (Tunch) == | + | == 16th May 2017: Selected topics in theory and observations of Dark Energy (Tunch) == |

Alefe Almeida(ITP, Heidelberg University) - " A method for evaluating models that use galaxy rotation curves to derive matter density profiles" | Alefe Almeida(ITP, Heidelberg University) - " A method for evaluating models that use galaxy rotation curves to derive matter density profiles" | ||

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Abstract: There are some approaches, either based on GR or modified gravity that use galaxy rotation to derive the matter density of the corresponding galaxy. In this work, we proposed a test for evaluating them. | Abstract: There are some approaches, either based on GR or modified gravity that use galaxy rotation to derive the matter density of the corresponding galaxy. In this work, we proposed a test for evaluating them. | ||

- | == 9th May Journal Club == | + | == 9th May 2017: Journal Club == |

Kevin Wolz | Kevin Wolz | ||

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arXiv:1701.08724 | arXiv:1701.08724 | ||

- | == 25th April : Selected topics in theory and observations of Dark Energy (Tunch) == | + | == 25th April 2017: Selected topics in theory and observations of Dark Energy (Tunch) == |

Yves Dirian (Geneva University ) - "A numerical relativity scheme for cosmological simulations" | Yves Dirian (Geneva University ) - "A numerical relativity scheme for cosmological simulations" | ||

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Abstract: I present a new 3+1 integration scheme which allows one to pass an adaptation of the robustness test to the cosmological context, at least in the case of General Relativity with a pressureless perfect fluid field. As an interesting by-product of this construction, a novel constraint-damping method is obtained. | Abstract: I present a new 3+1 integration scheme which allows one to pass an adaptation of the robustness test to the cosmological context, at least in the case of General Relativity with a pressureless perfect fluid field. As an interesting by-product of this construction, a novel constraint-damping method is obtained. | ||

- | == 18th April : Journal Club == | + | == 18th April 2017: Journal Club == |

Viviana Niro | Viviana Niro |