Ruprecht Karls Universit├Ąt Heidelberg

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joint [2018/07/03 10:40]
henrik
joint [2018/10/18 11:15] (current)
marta [Seminar calendar]
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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 ==+== 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

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