Name: Quantum Vacuum and Gravitation: Testing General Relativity in Cosmology
Start: 2017-03-13T08:00:00+01:00
End: 2017-03-24T19:00:00+01:00
Location: Mainz Institute for Theoretical Physics, Johannes Gutenberg University

Quantum Vacuum and Gravitation: Testing General Relativity in Cosmology

from Monday, March 13, 2017 (8:00 AM) to Friday, March 24, 2017 (7:00 PM)

Monday, March 13, 2017

9:00 AM Coffee
Coffee
9:00 AM - 10:00 AM
Room: 02.430

10:00 AM Welcome: Organizational Meeting
Welcome: Organizational Meeting
10:00 AM - 10:30 AM
Room: 02.430
10:30 AM Loop quantum cosmology and the cosmic microwave background - Ivan Agullo (Louisiana State University)
Loop quantum cosmology and the cosmic microwave background
- Ivan Agullo (Louisiana State University)
10:30 AM - 11:45 AM
Room: 02.430 Loop quantum cosmology has become a robust framework to describe the highest curvature regime of the early universe. In this theory, inflation is preceded by a bounce replacing the big bang singularity. I will summarize the theoretical framework, and explore the corrections to the inflationary predictions for the primordial spectrum of cosmological perturbations that this pre-inflationary, quantum gravity phase of the universe introduces. The impact of the bounce on non-Gaussianity and the exciting relation to the observed large scale anomalies in the CMB will be discussed.
11:45 AM Questions/Discussion
Questions/Discussion
11:45 AM - 12:00 PM
Room: 02.430

12:00 PM Lunch
Lunch
12:00 PM - 2:00 PM
Room: 02.430
2:00 PM Infrared dynamics of massive scalars from the complementary series in de Sitter space - Emil Ahkmedov
Infrared dynamics of massive scalars from the complementary series in de Sitter space
- Emil Ahkmedov
2:00 PM - 3:00 PM
Room: 02.430 We consinder loop IR effects in the $D$-dimensional de Sitter space. We study the real scalar $\phi^4$ theory from the complementary series, i.e. with the mass obeying $0 < m \leq \frac{D-1}{2}$ in units of the Hubble scale. We derive an equation which allows to perform the self--consistent resummation of the leading IR contributions from all loops to the two-point correlation function in the expanding Poincar\'{e} patch of de Sitter space. The equation is applicable only for masses higher than certain value, $m > \frac{\sqrt{3}}{4}\, \left(D-1\right)$: the restriction on the masses comes from the fact that for low enough masses there are large IR loop effects in the vertices. The resummation can be done for such density perturbations of the Bunch--Davies state, which violate the de Sitter isometry. We find solutions of the obtained equation. Some of the solutions have an explosive behavior.
3:00 PM Questions/Discussion
Questions/Discussion
3:00 PM - 3:15 PM
Room: 02.430

3:15 PM Coffee
Coffee
3:15 PM - 3:45 PM
Room: 02.430
3:45 PM Electrodynamic Effects of Inflationary Gravitons - Drazen Glavan (University of Warsaw)
Electrodynamic Effects of Inflationary Gravitons
- Drazen Glavan (University of Warsaw)
3:45 PM - 4:45 PM
Room: 02.430 Photons are conformally coupled to gravity and therefore do not get produced due to cosmological expansion, while gravitons are not and do get produced a lot due to the expansion. Since gravitons couple universally to all matter fields they can induce sizeable effects for conformally coupled fields through loop corrections. I will present computations in two different gauges for the one-loop graviton corrections to photon vacuum polarization in de Sitter spacetime. This is used to quantum correct Maxwell equations, and I will present two cases, (i) correction to dynamical photons, and (ii) correction to the Coulomb force between two point charges. The corrections in both cases exhibit secular growth. Gauge dependence will be discussed.
4:45 PM Questions/Discussion
Questions/Discussion
4:45 PM - 5:00 PM
Room: 02.430
Tuesday, March 14, 2017
9:00 AM Cosmic Evolution and Large-Scale Structure - Matthias Bartelmann (Heidelberg University)
Cosmic Evolution and Large-Scale Structure
- Matthias Bartelmann (Heidelberg University)
9:00 AM - 10:15 AM
Room: 02.430 The evolution of cosmic structures, in particular in its late, non-linear phases, provides important clues on the evolution of the Universe as a whole. In view of possible, subtle deviations from general relativity and the cosmological standard model, non-linear cosmic structures as for example traced by the population of galaxy clusters may act as magnifiers to enhance small dynamical effects above observational thresholds. For drawing such conclusions, we need to understand cosmic structure formation in detail in particular on small scales and at late times. In the first half of this overview talk, I will review the cosmological standard model and the standard approach to the formation and evolution of cosmic structures. In the second half, I will discuss a new approach to cosmic structure formation based on a non-equilibrium, statistical field theory for correlated, classical particle ensembles. First applications of this theory show that it allows to calculate statistical properties of cosmic structures at low orders in perturbation theory even at small scales and deeply in the non-linear regime. The theory builds on first principles and is free of adjustable parameters.
10:15 AM Coffee
Coffee
10:15 AM - 10:45 AM
Room: 02.430
10:45 AM Cosmology with relativistic effects - Daniele Bertacca
Cosmology with relativistic effects
- Daniele Bertacca
10:45 AM - 11:45 AM
Room: 02.430 Since the 1970s, the size of galaxy catalogs has constantly increased in terms of solid-angle and redshift coverage as well as in sampling rate. The next generation of surveys will provide us with the possibility to measure galaxy clustering on scales comparable with the Hubble radius (for example: Euclid, DESI, SKAII, etc.). Theoretical analysis suggests that several relativistic effects might be detectable on these scales. In order to fully exploit the potential of the new datasets, it is therefore imperative to develop analysis tools that include these effects. I have developed a fully general relativistic formalism which recovers and generalizes previous results in the plane-parallel (at-sky) and Newtonian wide-angle approximations. These corrections become important on large scales both at low and high redshifts, and lead to new terms in the wide-angle correlations. Now we need to work out how to apply this formalism for real data and understand which cosmological parameters are particularly affected. This will be important for future surveys and to guide the development on the next generation of large astrophysical experiments.
11:45 AM Questions/Discussion
Questions/Discussion
11:45 AM - 12:15 PM
Room: 02.430

12:15 PM Lunch
Lunch
12:15 PM - 2:00 PM
Room: 02.430
2:00 PM Scale hierarchies and string cosmology - Ignatios Antoniadis (LPTHE Paris and AEC Bern)
Scale hierarchies and string cosmology
- Ignatios Antoniadis (LPTHE Paris and AEC Bern)
2:00 PM - 3:00 PM
Room: 02.430 I will discuss the problem of scale hierarchies in string phenomenology of particle physics and cosmology and propose ways to address it. In particular I will present a mechanism for supersymmetry breaking in the presence of a tiny (tunable) positive cosmological constant, discuss connections of supersymmetry breaking and inflation, and describe their phenomenological consequences.
3:00 PM Questions/Discussion
Questions/Discussion
3:00 PM - 3:15 PM
Room: 02.430

3:15 PM Coffee
Coffee
3:15 PM - 3:45 PM
Room: 02.430
3:45 PM Cosmology with arbitrary spin coherent fields - Antonio L. Maroto (Universidad Complutense de Madrid)
Cosmology with arbitrary spin coherent fields
- Antonio L. Maroto (Universidad Complutense de Madrid)
3:45 PM - 4:45 PM
Room: 02.430 Coherent scalar fields play a fundamental role in the description, not only of the inflationary epoch, but also as dark matter candidates such as the axion or in dark energy models. In this talk we will explore the potential role that coherent fields of higher spin could play in cosmology. We will present a general result showing that rapidly evolving coherent fields preserve the isotropy of the background expansion. We will also consider models of coherent bosonic dark matter, providing an explicit example of ultralight vector dark matter and showing the distinctive features at the perturbations level with respect to the scalar case and to conventional cold dark matter.
4:45 PM Questions/Discussion
Questions/Discussion
4:45 PM - 5:00 PM
Room: 02.430
Wednesday, March 15, 2017
9:00 AM CMB Anomalies 25 years after COBE - glenn starkman (Case Western Reserve University)
CMB Anomalies 25 years after COBE
- glenn starkman (Case Western Reserve University)
9:00 AM - 10:15 AM
Room: 02.430 Several unexpected features have been observed in the temperature of the microwave sky at large angular scales, from COBE to WMAP and Planck. These include lack of both variance and correlation on the largest angular scales; alignment of the lowest multipole moments with one another and with the motion and geometry of the Solar System; lack of variance in the northern hemisphere, or a hemispherical power asymmetry or dipolar power modulation; a preference for odd parity modes; and an unexpectedly large cold spot in the Southern hemisphere. The individual p-values of the significance of several of these features are in the per mille to per cent level, compared to the expectations of the best-fit inflationary ΛCDM model. There are no good physical models for these anomalies. Rather than focus on a debate about the validity of a posteori statistics, or the relative merits of one statistical measure or another, we will discuss how we can make progress by: (a) considering how the existence of measured anomaly alters the predictions of ΛCDM for other observables; (b) making predictions from reasonable phenomenological expectations for the physics contents of measured anomalies.
10:15 AM Coffee
Coffee
10:15 AM - 10:45 AM
Room: 02.430
10:45 AM Do we understand the cosmic dipole? - Dominik Schwarz (Bielefeld University)
Do we understand the cosmic dipole?
- Dominik Schwarz (Bielefeld University)
10:45 AM - 11:45 AM
Room: 02.430 An important assumption of modern cosmology is that the CMB dipole is due to the proper motion of the solar system wrt the CMB. This fixes a reference frame for many observations, e.g. the Hubble diagram of SN1a. Planck observations of the largest multipole moments are consistent with the proper motion hypothesis, but also allow for sizeable non-kinetic contributions to the CMB dipole. The proper motion hypothesis can also be tested at any other wavelength, given good sky coverage and statistics are available. This is the case for modern radio point source catalogues. These allow us to measure the dipole distribution of radio sources at mean redshift of z ~ 1. The radio dipole can be measured at different radio frequencies and is compared to the CMB dipole. First results at three different frequency bands (at three different instruments) indicate an excess wrt to the expected signal based on the propor motion hypothesis only. The radio dipole directions are consistent with the CMB dipole direction at all three frequencies. Together with the alignment of low-l CMB multipole moments with the CMB dipole, I argue that this is further evidence that the largest angular scales of the Universe are not properly understood so far.
11:45 AM Questions/Discussion
Questions/Discussion
11:45 AM - 12:15 PM
Room: 02.430

12:15 PM Lunch
Lunch
12:15 PM - 2:00 PM
Room: 02.430
2:00 PM Recent developments in the inflationary scenario - Alexei Starobinsky (Landau Institute for Theoretical Physics)
Recent developments in the inflationary scenario
- Alexei Starobinsky (Landau Institute for Theoretical Physics)
2:00 PM - 3:00 PM
Room: 02.430 I consider reconstruction of inflationary models in GR and f(R) gravity using information on the power spectrum of scalar perturbations only, ambiguity in this procedure and how it can be fixed by some aesthetic assumptions on the absence of new physical scales during and after inflation. Also discussed is the problem on the onset of inflation from generic classical curvature singularity preceding it, and which conditions are needed for this.
3:00 PM Questions/Discussion
Questions/Discussion
3:00 PM - 3:15 PM
Room: 02.430

3:15 PM Coffee
Coffee
3:15 PM - 3:45 PM
Room: 02.430
3:45 PM Testing primordial non-Gaussianity with CMB and LSS data - Michele Liguori (Univ. of Padova)
Testing primordial non-Gaussianity with CMB and LSS data
- Michele Liguori (Univ. of Padova)
3:45 PM - 4:45 PM
Room: 02.430 Primordial non-Gaussianity (NG) is a powerful probe of Inflation, able to test extra-interactions and extra-degrees of freedom in scenarios beyond the simplest, standard single-field slow-roll paradigm.The most important observational signature of primordial NG is a non-vanishing bispectrum (3-point function in Fourier/harmonic space) of the primordial perturbation field. After showing the link between different bispectrum shapes and corresponding inflationary scenarios, I will describe current bispectrum constraints obtained from the analysis of Planck CMB data. I will then discuss future potential improvements over Planck results, coming from the next generation CMB and galaxy surveys, and their implications. I will conclude by showing the limits that can be in principled achieved in more futuristic experimental scenarios, exploiting 21 cm and CMB spectral distortion fluctuations.
4:45 PM Questions/Discussion
Questions/Discussion
4:45 PM - 5:00 PM
Room: 02.430
Thursday, March 16, 2017
9:00 AM What is the Quantum Matter with Black Holes? - Emil Mottola (Los Alamos National Laboratory)
What is the Quantum Matter with Black Holes?
- Emil Mottola (Los Alamos National Laboratory)
9:00 AM - 10:45 AM
Room: 02.430 Classical General Relativity (GR) together with conventional equations of state suggest that in complete gravitational collapse a singular state of matter with infinite density could be reached finally, to what is popularly called a "black hole." In addition to its interior singularities, the characteristic feature of a black hole is its apparent horizon, the surface of finite area at which outwardly directed light rays are first trapped. The loss of information to the outside world this implies gives rise to additional difficulties with well-established principles of quantum mechanics and statistical physics. I will overview the historical and most recent approaches to these problems, as well as the status of the gravitational vacuum condensate star proposal we have made in 2001, with a p= - rho interior is actually realized in Schwarzschild's second paper over a century ago. The redshifted surface tension of the condensate star surface is given by $\tau_s = \Delta \kappa/8 \pi G$, where $\Delta \kappa= 1/R_s$ is the difference of equal and opposite surface gravities between the exterior and interior Schwarzschild solutions. The First Law, $dM = dE_v + \tau_s\, dA$ is recognized as a purely mechanical classical relation at zero temperature and zero entropy, describing the volume energy and surface energy change respectively. Since there is no event horizon, the Schwarzschild time $t$ of such a non-singular gravitational condensate star is a global time, fully consistent with unitary time evolution in quantum theory. The $p=-\bar\rho$ interior acts as a defocusing lens for light passing through the condensate, leading to imaging characteristics distinguishable from a classical black hole. Further observational test of gravitational condensate stars vs. black holes is the {\it discrete} surface modes of oscillation and echoes which should be detectable by their gravitational wave signatures.
10:45 AM Gravitational-wave signatures of exotic compact objects and of quantum corrections at the horizon scale - Paolo Pani (Sapienza University of Rome & INFN Roma1 - IST, Lisbon)
Gravitational-wave signatures of exotic compact objects and of quantum corrections at the horizon scale
- Paolo Pani (Sapienza University of Rome & INFN Roma1 - IST, Lisbon)
10:45 AM - 11:45 AM
Room: 02.430 Gravitational wave (GW) astronomy allows us for unprecedented tests of the nature of compact objects. In this context, I will discuss two signatures of new physics at the horizon scale: GW "echoes" in the postmerger ringdown phase of a binary coalescence, and the tidal deformability of exotic compact objects as measured from the inspiral premerger phase. In the first case, the ringdown waveform of exotic ultracompact objects is initially identical to that of a black hole, and putative corrections at the horizon scale appear only later as a modulated and distorted train of echoes of the modes of vibration associated with the photon sphere. As for the second case, I will discuss the tidal Love numbers of different families of boson stars, gravastars, wormholes, and other toy models for quantum corrections at the horizon scale, showing that they display a universal logarithmic dependence on the location of the surface in the black-hole limit. I will discuss the ability of present and future GW detectors to measure these effects. Both LIGO, ET and LISA can impose interesting constraints on boson stars, while LISA is able to probe even extremely compact objects like gravastars. We argue that these effects provide a smoking gun of new physics at the horizon scale, and that future GW measurements of a binary coalescence provide a novel way to test black holes and general relativity in the strong-field regime.
11:45 AM Questions/Discussion
Questions/Discussion
11:45 AM - 12:15 PM
Room: 02.430

12:15 PM Lunch
Lunch
12:15 PM - 2:00 PM
Room: 02.430
2:00 PM Remarks on non-singular black hole models - Valeri Frolov (University of Alberta, Edmonton, Canada)
Remarks on non-singular black hole models
- Valeri Frolov (University of Alberta, Edmonton, Canada)
2:00 PM - 3:00 PM
Room: 02.430 We discuss spherically symmetric metrics which represent non-singular black holes in four- and higher-dimensional spacetimes. We first consider static metrics, which obey the following conditions: (i) Regularity at the center and (ii) Validity of the limiting curvature condition. We describe the Hayward model and its generalizations, which obey these properties. After this we discuss quantum radiation of a massless scalar field from an evaporating spherically symmetric non-singular black hole with finite lifetime. We demonstrate that in a general case there exists a huge outburst of the quantum radiation, emitted from the black hole interior from the domains close to the inner horizon. We discuss a relation of this phenomenon with the mass inflation effect. Finally, we shall make remarks on attempts to solve this problem and to provide self-consistency of the non-singular model in the quantum domain.
3:00 PM Questions/Discussion
Questions/Discussion
3:00 PM - 3:15 PM
Room: 02.430

3:15 PM Coffee
Coffee
3:15 PM - 3:45 PM
Room: 02.430

3:45 PM

3:45 PM - 5:00 PM
Room: 02.430
Friday, March 17, 2017
9:00 AM The Cosmic Microwave Background: what can we learn from the most precious cosmological data ? - Ruth Durrer (Universite de Geneve)
The Cosmic Microwave Background: what can we learn from the most precious cosmological data ?
- Ruth Durrer (Universite de Geneve)
9:00 AM - 10:15 AM
Room: 02.430 Most numbers in cosmology have been measured using the anisotropies and polarisation of the Cosmic Microwave Background (CMB). So far other data has mainly been used for consistency checks and very few inconsistent measurements exist. The reason for this is twofold: first the theory of the CMB is nearly linear and therefore quite simple. Secondly, the CMB spectrum peaks around frequencies which allow relatively precise observations from the ground and especially from space. In the first part of my talk I review the relatively simple physics behind CMB anisotropies and polarisation and show in some examples how it can be used to measure cosmological parameters. In a second part I outline ideas to go beyond present measurements which mainly constrain cosmological parameters and show how we can use the CMB to test General Relativity on cosmological scales. If there is time, I would also like to outline interesting new developments in the theory of Large Scale Structure observations and argue why we hope that future LSS surveys can compete with and complement CMB observations.
10:15 AM Coffee
Coffee
10:15 AM - 10:45 AM
Room: 02.430
10:45 AM Testing Infinite derivative gravity: Bounce and Cosmic inflation - Anupam Mazumdar (Lancaster)
Testing Infinite derivative gravity: Bounce and Cosmic inflation
- Anupam Mazumdar (Lancaster)
10:45 AM - 11:45 AM
Room: 02.430 I will be discussing infinite derivative theories of gravity as a perturbative effective field theory of gravity, which in the ultraviolet can become asymptotically free. I will discuss their classical and quantum properties around Minkowski and deSitter backgrounds. I will show how to resolve cosmological singularity problem and I will discuss perturbations around deSitter background. Action which resolves cosmological singularity also gives rise to an ultraviolet completion for Starobinsky inflation. Therefore, a non-singular bounce followed by a period of cosmic inflation can lead to a successful classical and quantum prediction for our Universe. There are some smoking gun signatures for tensor to scalar ratio which I will describe.
11:45 AM Questions/Discussion
Questions/Discussion
11:45 AM - 12:15 PM
Room: 02.430

12:15 PM Lunch
Lunch
12:15 PM - 2:00 PM
Room: 02.430
2:00 PM Recent progress in higher-derivative gravity theories - Ilya Shapiro (Universidade Federal de Juiz de Fora)
Recent progress in higher-derivative gravity theories
- Ilya Shapiro (Universidade Federal de Juiz de Fora)
2:00 PM - 3:00 PM
Room: 02.430 Recently there were some advances in the higher-derivative gravity theories and my purpose is to give the brief survey of our results. First of all, it was shown that the theory with six or more derivatives in the action, which has only complex ghost-like poles, has a unitary S-matrix in the Lee-Wick sense. Second, it was shown that in this class of theories the magnitudes of the masses of the ghost-like states can not be reduced by a gravitational version of the see-saw mechanism. Third, even if the masses are huge, there may be a chance to design an indirect texts for higher derivatives from the astrophysical observations.
3:00 PM Questions/Discussion
Questions/Discussion
3:00 PM - 3:15 PM
Room: 02.430

3:15 PM Coffee
Coffee
3:15 PM - 3:45 PM
Room: 02.430

3:45 PM

3:45 PM - 5:00 PM
Room: 02.430
Saturday, March 18, 2017
Sunday, March 19, 2017