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Beyond General Relativity, Beyond Cosmological Standard Model
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Faculty of Physics, University of Warsaw
Faculty of Physics, University of Warsaw
conference hall 0.03,
Faculty of Physics, University of Warsaw
ul. Pasteura 5, 02-093 Warszawa
Poland
Chunshan Lin
(Faculty of Physics, University of Warsaw)
Description
Cosmology provides us a unique arena where gravitation and quantum physics meet each other. It is also a unique probe of ultra-high energy physics beyond energies that can be achieved at colliders. This conference aims at bringing together top researchers in the field to present recent breakthroughs, discuss on what we have learnt and what challenges we are still facing. The focus of this event involves several interrelated areas, from fundamental gravity theory through cosmology to new physics beyond standard model of particle physics. It includes, but not limited to:
| (1) Physics of Primordial Universe; | (5) Black Hole Physics; |
| (2) Modified Gravity Theories; | (6) CMB and Large Scale Structure; |
| (3) Cosmological Constant Problem, Dark energy; | (7) Gravitational Waves; |
| (4) Dark matter, Baryon asymmetry; |
The registration has opened.
A message to phd students:
We will provide local accommodations for the phd students with accepted abstract submissions (contributed talk). Therefore, if you need local support, please register yourself and submit your abstract early.
Depending on our budget, we may provide accommodations for some small number of PhD students in poster session as well.
List of Invited speakers (alphabetical order)
- Celine Boehm
- Yi-fu Cai
- Mu-Chun Chen
- Xingang Chen
- Marco Cirelli
- Anne-Christine Davis
- Emanuela Dimastrogiovanni
- Matteo Fasiello
- Gregory Gabadadze
- Dumitru Ghilencea
- Elena Giusarma
- Andrzej Królak
- Michele Liguori
- Andrei Linde
- Shinji Mukohyama
- Antonio Padilla
- Clem Pryke
- Arttu Rajantie
- Graham Ross
- Misao Sasaki
- Géraldine Servant
- Alexander Vikman
- David Wands
- Yi Wang
- Marcus Werner
- Wei Xue
This is the summer session of a series of seasonal workshops on gravity and cosmology, held in the Faculty of Physics, University of Warsaw. The last winter session can be found here , and the spring session can be found here .
Local Organising Committee
Registration
Beyond General Relativity, Beyond Cosmological Standard Model
125
Participants
125
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Beyond I
Monday session
Conveners: Chunshan Lin (morning), Yi Wang (afternoon)-
08:00
Reception 55m
sandwiches, snacks, sweets, coffee, tea... are provided.
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08:55
openning remarks 5mSpeaker: Dr Chunshan Lin
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09:00
Observing the Universe with Gravitational Waves 45m
Detection of gravitational wave signals from mergers of black holes and neutron stars is one the most important discoveries of this century. I shall briefly present the phenomenon of gravitational radiation as predicted by Einstein's general relativity. I shall describe gravitational wave detectors and
methods of analyzing gravitational wave data. I shall review the observations made during the two observational runs of advanced LIGO and Virgo detector projects. I shall present the physical and astrophysical significance of these observations. I shall summarize the most recent observations of gravitational wave signals made during the third observational run of LIGO and Virgo detectors that is currently underway.Speaker: Prof. Andrzej Królak (the leader of Polgraw-Virgo group) -
09:45
Gravitational wave energy budget in strongly supercooled phase transitions 20m
I will discuss efficiency factors for the production of gravitational waves through bubble collisions and plasma-related sources in strong phase transitions, and the conditions under which the bubble collisions can contribute significantly to the signal. I will also show that generically the sound-wave period is much shorter than a Hubble time leading to a reduction of GW signal produced by sound waves and possibly suggesting a significant amplification of the turbulence-sourced signal. I will illustrate our findings in two examples, the Standard Model with an extra $|H|^6$ interaction and a classically scale-invariant $U(1)_{\rm B-L}$ extension of the Standard Model. The contribution to the GW spectrum from bubble collisions is found to be negligible in the $|H|^6$ model, whereas it can play an important role in parts of the parameter space in the scale-invariant $U(1)_{\rm B-L}$ model.
Speaker: Marek Lewicki (Kings College London) -
10:05
Echoes from Quantum Black Holes 20m
Exotic compact objects (ECOs) produce the same initial event detected by LIGO-Virgo collabo-ration as classical black holes (BHs), but various quantum gravity models feature the different following echoes. In particular, we investigate the echoes from the fluctuation-dissipation theorem [1, 2], which changes the dispersion relationship near the (would-be) horizon and results in a Boltzmann reflective boundary. We derive correspondent quasi-normal modes (QNMs) analytically. Further, wemodel the analytical and numerical echoes in the real time, which are consistent with each other. Last, we show that the superradiance is highly suppressed in the theorem.
Based on: Echoes from Quantum Black Holes(in prep.)
Fluctuation Dissipation theorem for Quantum Black Holes (in prep.)
Black Hole Echology arXiv:1803.02845v2Speaker: Qingwen Wang -
10:25
Strong gravitational radiation from a simple dark matter model 20m
A rather minimal possibility is that dark matter consists of the gauge bosons of a spontaneously broken symmetry. I will discuss the possibility of detecting the gravitational waves produced by the phase transition associated with such breaking. Concretely, I will focus on the scenario based on an 𝑆𝑈(2)_D group and argue that it is a case study for the sensitivity of future gravitational wave observatories to phase transitions associated with dark matter. This is because there are few parameters and those fixing the relic density also determine the effective potential establishing the strength of the phase transition. Particularly promising for LISA is the super-cool dark matter regime, with DM masses above 100 TeV, for which the gravitational wave signal is notably strong.
Speaker: Dr Camilo Garcia Cely (DESY) -
10:45
Coffee break 30m
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11:15
Gravitational Wave Cosmology -The Dawn has Arrived! 1h 15mSpeaker: Prof. Misao Sasaki (Kavli IPMU, the University of Tokyo)
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12:30
Lunch break 1h 30m
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14:00
Stochastic inflation: slow roll and beyond 45m
Quantum fluctuations play an essential role in the dynamics and phenomenology of inflation in the very early universe. Usually quantum fluctuations during inflation are studied perturbatively (often linearly) about a fixed classical background, but in the stochastic approach quantum fluctuations on small scales provide a stochastic contribution to the non-perturbative classical evolution on large (super-Hubble) scales. In particular the stochastic delta-N formalism can be used to study large density perturbations required to form primordial black holes. This relies on the separate universe viewpoint but does not necessarily require slow roll (though the system is particularly simple in slow roll). I will discuss some of the issues when applying the stochastic approach beyond slow-roll.
Speaker: Prof. David Wands -
14:45
Testing the Particle Dark Matter paradigm with future cosmological and astronomy surveys. 45m
The presence of dark matter strongly suggests that the laws of Physics as we know them are incomplete. In this talk I will summarise the directions which have been explored to determine the nature of dark matter (as well as their motivations), and discuss how future cosmological and astronomy surveys will help us to progress in this field.
Speaker: Prof. Celine Boehm -
15:30
Perturbatively renormalizable quantum gravity 20m
The Wilsonian renormalization group (RG) requires Euclidean signature. The conformal factor of the metric then has a wrong-sign kinetic term, which has a profound effect on its RG properties. In particular around the Gaussian fixed point, it supports a Hilbert space of renormalizable interactions involving arbitrarily high powers of the gravitational fluctuations. These interactions are characterised by being exponentially suppressed for large field amplitude, perturbative in Newton's constant but non-perturbative in Planck's constant. By taking a limit to the boundary of the Hilbert space, diffeomorphism invariance is recovered in the continuum quantum field theory. Thus the so-called conformal factor instability is the key that allows the construction of a genuine continuum limit for quantum gravity.
[1] Tim R. Morris. Renormalization group properties in the conformal sector: towards perturbatively renormalizable quantum gravity. JHEP, 08:024, 2018, 1802.04281.
[2] Matthew P. Kellett and Tim R. Morris. Renormalization group properties of the conformal
mode of a torus. Class. Quant. Grav., 35(17):175002, 2018, 1803.00859.
[3] Tim R. Morris. Perturbatively renormalizable quantum gravity. Int. J. Mod. Phys.,
D27(14):1847003, 2018, 1804.03834.
[4] Tim R. Morris. Quantum gravity, renormalizability and di?eomorphism invariance. SciPost
Phys., 5:040, 2018, 1806.02206.
[5] Tim R. Morris. to appear.Speaker: Tim Morris (Southampton University) -
15:50
coffee break 30m
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16:20
Understanding the dynamical nature of late-time cosmic acceleration from dark energy and f(T) modified gravity 45m
In this talk I will briefly introduce the present understanding about the cosmic acceleration at present from the perspective of phenomenological study. I will review the latest observational status of the late-time cosmic acceleration and then depict how to do the model building of dynamical dark energy. Afterwards, I will also give an introduction to a type of torsional based modified gravity, which can also realize the cosmic acceleration at present. This so-called f(T) gravity and beyond theories can be depicted in a language of effective field theory and thus we can examine certain operators that are most connected with various cosmological observations.
Speaker: Prof. Yi-fu Cai (University of Science and Technology of China) -
17:05
Cosmological implications of the electroweak vacuum instability 45m
When extrapolated to high energies, the Standard Model of particle physics predicts that the current vacuum state is metastable. Its predicted decay rate is currently extremely low, but it would have been much higher in the early Universe. Therefore the fact that the Universe survived its first moments places constraints on both the cosmological history and on particle physics. I will discuss and review these constraints, focussing particularly on the bounds that can be obtained for the non-minimal couplings between the Higgs field and spacetime curvature.
Speaker: Prof. Arttu Rajantie -
17:50
Is Vacuum Decay During Inflation Fatal? 20m
If the Standard Model vacuum is metastable, bubbles that form expand and convert the entire vacuum into a true vacuum state incompatible with observations. It is sometimes argued, however, that true vacuum bubbles forming during inflation are 'inflated away' and thus pose no danger to the present day universe, even if they form. I will argue that this point of view is incorrect - while the exponential expansion of spacetime does affect the evolution of true vacuum bubbles, they do not, in fact, collapse to nothing and can in fact survive to the present day. Consequently, the electroweak vacuum instability must be fixed or circumvented if high scale inflation is to take place, providing strong hints that there must be new physics before the Planck scale.
Speaker: Dr Stephen Stopyra (University College London) -
18:10
Could the H0 Tension be Pointing Toward the Neutrino Mass Mechanism? 20m
Within the framework of $\Lambda$CDM, the local determination of the Hubble constant disagrees -- at the 4.4$\sigma$ level -- with that inferred from the very accurate CMB observations by the Planck satellite. This clearly motivates the study of extensions of the standard cosmological model that could reduce such tension. Proposed extensions of $\Lambda$CDM that reduce this so-called Hubble tension require an additional component of the energy density in the Universe to contribute to radiation at a time close to recombination.
In this talk, I will show that pseudo-Goldstone bosons -- associated with the spontaneous breaking of global lepton number in type-I seesaw models -- lead to a non-standard early Universe evolution that can help to reduce the Hubble tension. I will show that current CMB observations can set a lower bound on the scale at which lepton number is broken as high as 1 TeV. Finally, I will argue that future CMB observations will test wide and relevant regions of parameter space of scenarios in which the spontaneous breaking of global lepton number is the mechanism behind the observed neutrino masses.
Speaker: Miguel Escudero (King's College London)
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Beyond IIConveners: Prof. Celine Boehm (morning), Marcus Werner (afternoon)
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Hunting Axion Dark Matter with New Techniques 20m
Identification of dark matter has been an outstanding problem in physics for decades, and axion (or axion like partciles) is its candidate with great motivations. A number of observations and experiments have tried to detect axion by using the axion-photon conversion by assuming the axion is coupled to photon, while no signal yet to be found. In this talk, I will discuss new techniques to search for axion dark matter (ADM) by focusing on another phenomena, birefringence, which is caused by the same coupling. The polarimetry observation of protoplanetary disks puts the best constraint on ADM for fuzzy dark matter mass (m = 10^{-22}eV). I also propose to use gravitational wave interferometer like LIGO for ADM search by installing a new detector which does not affect the detection of gravitational waves.
Speaker: Tomohiro Fujita (Kyoto University) -
10:20
coffee break 30m
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10:50
Searching for Dark Matter across different Scales 45m
In this talk, I will discuss the methods to search for dark matter or dark sector particles having the masses from GeV to the Solar Mass. We can probe their properties by colliders, neutrino or gamma ray experiments.
Speaker: Dr Wei Xue -
11:35
Light Dark Matter from Inelastic Cosmic Ray Collisions 20m
Direct detection experiments relying on nuclear recoil signatures lose sensitivity to sub-GeV dark matter for typical galactic velocities. This sensitivity is recovered if there exists another source of flux with higher momenta. Such an energetic flux of light dark matter could originate from the decay of mesons produced in inelastic cosmic ray collisions. I present in this talk the dark matter flux expected from such cosmic beam dump experiment and the resulting limits on the model parameters using direct detection experiments such as XENON1T and the projected LZ. A particular model involving a hadrophilic scalar mediator is also considered and I show how the limits compare with dedicated beam dump experiments such as MiniBooNE.
Speaker: Miguel D. Campos (King's College London) -
11:55
Dark matter and baryon-number generation in quintessential inflation via hierarchical right-handed neutrinos 20m
Incorporating three generations of right-handed Majorana neutrinos to quintessential inflation, we construct a model which simultaneously explains inflation, dark energy, dark matter and baryogenesis. These right-handed neutrinos have hierarchical masses $M_3 \sim 10^{13}$GeV, $M_2 \sim 10^{11}$GeV, $M_1 \sim 10$keV and are produced by gravitational particle production in the kination regime after inflation. The heaviest, the intermediate, and the lightest account for reheating, CP violation of leptogenesis, and dark matter, respectively. We consider various constraints from particle experiments and cosmological observations. If we adopt the Randall-Sundrum brane-world scenario, these constraints on parameters are satisfied without fine-tuning.
This talk is based on 1905.12423.
Speaker: Soichiro Hashiba -
12:15
Poster session 30m
1 minute 1 slide oral presentation;
Speakers: Aya IYONAGA, Bryce Cyr, Daniel Kristoffer Blixt, Emmanuel Frion, Francesco Pace, Jaksa Osinski, Jan Olle, Juho Lankinen, Laura Iacconi, Manuel Hohmann, Matteo Cinus, Michael Kenna-Allison, Mohammad Malekjani, SAMIR IRAOUI, Sebastián Bahamonde Beltrán, Tays Miranda de Andrade, Xin Ren, Yin Lu, Yun-Long Zhang -
12:45
Lunch break 1h 15m
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14:00
Gravity and cosmology beyond Einstein 1h 15m
I will give an introductory review talk on extensions of general relativity, covering the following contents.
1. Introduction
2. General relativity and Lovelock gravity
3. PPN formalism
4. EFT approach
5. Massive gravity
6. SummarySpeaker: Prof. Shinji Mukohyama -
15:15
Einstein-Gauss-Bonnet gravity in four space-time dimensions 20m
Lovelock's theorem asserts that the most general theory of gravity in D=4 space-time dimensions is given by the action containing the Einstein-Hilbert term and a cosmological constant. Already in D=5 an additional term is possible - the Gauss-Bonnet action - which in D=4 turns into a total derivative not contributing to dynamics. In general, the contribution of the Gauss-Bonnet action to Einstein equation is proportional to (D-4). Here I will present an idea of multiplying the Gauss-Bonnet action by 1/(D-4) and defining the four-dimensional case as a smooth D->4 limit of the Einstein equation. Thus defined the theory propagates only the graviton and it satisfies the criteria of Lovelock's theorem, but bypasses its results. This theory has several novel predictions, including the corrections to the dispersion relation of cosmological tensor and scalar modes and singularity resolution for spherically symmetric solutions.
Speaker: Dr Drazen Glavan -
15:35
coffee break 30m
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16:05
Gravitational Effects of Disformal Couplings 45mSpeaker: Prof. Anne-Christine Davis (DAMTP, Cambridge University)
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16:50
Resolving the strong coupling problem in massive gravity 45m
Theories of massive gravity and their generalizations have been used for the description of the late time and early universe cosmologies. These theories however are strongly coupled at a certain low energy scale. We show how this problem can be avoided by embedding massive gravity and its generalizations into higher dimensional theories.
Speaker: Prof. Gregory Gabadadze -
17:35
Massive Gravity on a Brane 20m
dRGT theory is the unique ghost-free theory of massive gravity and it realizes a full nonlinear completion of the linear Fierz-Pauli theory for a massive spin-2 field. In addition to being an interesting field theoretic modification of General Relativity, it could potentially explain the late-time cosmic acceleration of our universe as an alternative to a small cosmological constant. However, dRGT is an effective field theory with a very low strong coupling scale $\Lambda_3 \sim (1000 km)^{-1}$ and in order to have a consistent modification of gravity that is compatible with short distance tests of GR, the theory must be UV completed in some way. It seems that a UV completion analogous to the Higgs mechanism for massive non-Abelian gauge theory will not work in flat space but there does exist a known mechanism for dynamically generating mass for the graviton in AdS space. We utilize this mechanism in a Randall-Sundrum-like scenario where our world is a flat boundary of a cutoff AdS space. The dRGT action is on the boundary and the bulk has gravity coupled to scalar fields that dynamically gains a mass. This massive graviton then has a 'zero-mode' which plays the role of the graviton on the brane and it's effective 4d dynamics are such that they raise the cut-off of massive gravity from $(1000 km)^{-1} \sim 10^{-19} MeV$ to as high as $10^{19} MeV$.
Speaker: Daniel Older -
17:55
Cosmology of models with spontaneous scalarization: instability and a cure. 20m
I will discuss scalar-tensor models of gravity, which predict the spontaneous scalarization of neutron stars or/and black holes. In the cosmological setup, the scalar field responsible for scalarization is subject to a tachyonic instability during inflation as well as at other cosmological stages, depending on the model. The instability poses a problem for viability of such models. I will show that for the case of scalarization with the Gauss-Bonnet term, a catastrophic instability develops during inflation within a period of time much shorter than the minimum required duration of inflation. As a result, the standard cosmological dynamics is not recovered. On the other hand, in the case of standard scalarization by Damour-Esposito-Farese, it is possible to make a simple modification of the original model by coupling the scalar to the inflaton field. For generic couplings the scalar (including its perturbations) relaxes to zero with an exponential accuracy by the beginning of the hot stage.
Speaker: Dr Eugeny Babichev (Paris-Sud University) -
18:15
Role of matter in modified gravity: a search for new interactions 20m
Modified gravity theories are typically constructed in the Jordan frame, where the matter follows the geodesics of the metric. This is nothing more than a choice of field variable that leaves the observables intact. However recent developments in classical field theory revealed that fixing variables may affect how the fundamental assumptions in the theory building process are represented. For instance, the construction of "beyond-Horndeski" theories in the Jordan frame representation requires an intricate constraint analysis to exploit degeneracies, while using different variables one can obtain arguably simpler formulations within the framework of standard (i.e. Horndeski) scalar-tensor theory.
In this talk, I will adopt Bekenstein's perspective of multiple geometries and consider two applications where a generic matter coupling unveils new interactions: i. a massive spin--2 theory; ii. a vector-tensor theory with an Abelian gauge field.
Speaker: Dr Emir Gumrukcuoglu (Institute of Cosmology and Gravitation, Portsmouth)
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Beyond IIIConvener: Prof. Zygmunt Lalak
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Scale invariance, Stueckelberg breaking of Weyl gravity and inflation 45m
Weyl conformal geometry may play a role in early cosmology where effective theory at short distances becomes conformal. We consider the original Weyl gravity action, quadratic in the scalar curvature and in the Weyl tensor of Weyl conformal geometry; this action is invariant under Weyl scaling gauge transformations. In the absence of matter fields, we show that Weyl action has spontaneous breaking of this symmetry: the Weyl gauge field (of local scale transformations) becomes massive (mass ~ Planck scale) after absorbing a compensator (dilaton), in a gravitational Stueckelberg mechanism. As a result, one obtains the Einstein-Hilbert action, a positive cosmological constant and the Proca action for the massive Weyl gauge field ("photon"). The Einstein-Hilbert action is then just a "low energy" limit of Weyl quadratic gravity which thus avoids its long-held previous criticisms, while Planck scale is an emergent scale of this symmetry breaking (where Weyl geometry becomes Riemannian). The results remain valid in the presence of matter with non-minimal coupling. Successful inflation in Weyl gravity is possible, with results close to the Starobinsky model. Based on arXiv:1812.08613, 1904.06596.
Speaker: Prof. Dumitru Ghilencea (IFIN) -
09:30
Quantum scale invariance, hierarchy generation and inflation 45m
Global and local Weyl invariant theories can solve the hierarchy problem and generate all mass scales spontaneously, initiated by a dynamical process of “inertial spontaneous symmetry breaking” that does not involve a potential. I will discuss how inflation readily occurs in a scale invariant version of Starobinsky (R2) inflation and how an hierarchy of mass scales may be generated, stable against both Standard Model and gravitational quantum corrections.
Speaker: Prof. Graham Ross (Oxford University) -
10:15
Beyond Standard Model and Asymptotically Safe Gravity 20m
Einstein gravity cannot be quantised using standard Quantum Field Theory techniques. Hence to describe gravity on quantum level then either a new, special quantisation prescription should be proposed or General Relativity should be replaced by another theory which can be properly quantised. If the first option is true, then General Relativity should possess an interacting UV fixed point (as an asymptotically safe theory) and then GR becomes a fundamental Quantum Field Theory to arbitrary scales. There are many hints that indeed it is so.
On the other hand there are many proposals on how to extend the Standard Model, designed to deal with its fundamental inconsistencies. Since no new particles have been detected experimentally so far, the models which add only one more scalar particle and possibly right-chiral neutrinos are favoured. One of such models is the Conformal Standard Model.
If there are no intermediate scales between electroweak and Planck scale then these type of models supplemented with asymptotically safe gravity can be valid up to arbitrarily high energies and give a complete description of particle physics and gravitational phenomena.
This assumption restricts the mass of the second scalar particle to 300 +/-28 GeV and the mass of Higgs boson at 125 +/- few GeV. This has also impact on the multiple Higgs inflation scenarios.
Whats more various theories of gravity gives various predictions for the Higgs boson masses. Hence then by accurate measurements we can investigate the quantum gravity in LHC.
Talk based on the articles: https://arxiv.org/abs/1810.08461, arXiv:1712.03778 and unpublished results in collaboration with Frederic Grabowski and prof. Krzysztof A. Meissner.
Speaker: Mr Jan Kwapisz (Faculty of Physics, University of Warsaw) -
10:35
coffee break 30m
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Flavor, CP, and Baryons 45m
I will review flavor models based on non-Abelian discrete symmetries, motivated by neutrino oscillation data. I will discuss how CP violation, a necessary condition for baryogenesis, can be entirely group theoretical in origin in certain class of the non-Abelian discrete groups. I will then describe a proposal where successful baryogenesis can be achieved through flavon decays.
Speaker: Prof. Mu-Chun Chen (University of California, Irvine) -
11:50
Self-stopping relaxion 45m
I will review the mechanism of cosmological relaxation of the electroweak scale and will discuss relaxion particle production during the evolution of the relaxion field, an effect which had been so far ignored in the relaxion literature. I will present its implications on the relaxion mechanism in general.
Speaker: Prof. Géraldine Servant (DESY) -
12:35
Neutrino Cosmology - Weighing the Ghost Particle with the Universe 45m
Over the past decades, the high-precision cosmological data have significantly improved our understanding of the Universe, contributing greatly to the establishment of the standard model of cosmology. However these results have also opened new questions in both fundamental physics and astrophysics. One of the great mystery of the universe is that more than 80% of the matter in our Universe is made up of material that is invisible (dark matter). This component has important consequences in the evolution of the Universe and in the structure formation processes. While the major contribution to the dark matter should arise from cold dark matter (CDM), a small component of hot dark matter (HDM) can also be present. A natural candidate for the HDM is neutrino. Neutrinos physics is one of the most fascinating research areas that has stemmed from the interplays between cosmology, astrophysics and particle physics. Cosmology provides an independent tool for the investigation of neutrino properties since it is sensitive to the absolute scale of neutrino masses. Measuring the masses of these particles would be of extreme value to unravel the departure from the Standard Model (SM) of Particle Physics. A robust detection of neutrino masses is among the key goals of upcoming Cosmic Microwave Background (CMB) and Large-Scale Structure (LSS) surveys. In this talk, I will review the main physical effects of massive neutrinos on cosmological observable and summarize recent progress on neutrino mass constraints obtained by combining different cosmological measurements. I will also show a new approach to produce fast non-standard cosmological simulations with massive neutrinos by applying deep learning algorithms.
Speaker: Dr Elena Giusarma (Flatiron Institute, New York)
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Address: plac Zamkowy 8/Plac Zamkowy, 00-277 Warszawa
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banquet 3h
Restauracja Pod Gigantami
Address: al. Ujazdowskie 24, 00-535 Warszawa
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Beyond IVConveners: Prof. Misao Sasaki (morning), Prof. Yifu Cai (afternoon)
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Reverse Engineering the Universe 1h 15m
I will give a brief review of inflationary cosmology, including its motivation, observational status, the problem of initial conditions, and the string landscape scenario. I will also describe the problems with hilltop inflation and then I will show that the theory of alpha-attractors and D-brane inflation together can completely cover the range or values of n_s and r favored by Planck 2018.
Speaker: Andrei Linde (Stanford University) -
10:00
Probing the Inflationary Field Content with Primordial Gravitational Waves and more. 20m
The inflationary paradigm, already in its simplest disguises, has been spectacularly successful when it comes to agreement with observations. However, there’s a lot we do not yet know about inflation:
- what is its energy scale?
- how about its particle content?
- how did inflation begin?
…New cosmological probes (at all scales, from CMB to interferometers) will soon put some of our best ideas to the test.
The answers to these questions are bound to be transformative of our understanding of cosmology and, possibly, also particle physics. A high-scale inflation, for example, would automatically be a portal to otherwise unaccessible energy scales.
In this talk I will review some recent work on the inflationary particle content and then focus on a model that includes a pseudo scalar field coupled with SU(2) gauge fields. This setup can generate a chiral gravitational waves signal. I will then detail on how the parameter space of the theory supports a blue tensor spectrum and large tensor as well as mixed non-Gaussianities.Speaker: Matteo Fasiello (ICG Portsmouth) -
10:20
coffee break 30m
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The Search for Inflationary B-modes with the BICEP/Keck Telescopes 45m
The LCDM cosmological model fits a wealth of observational data extremely well but assumes a very specific type of initial conditions (near-scale-invariant, Gaussian, adiabatic perturbations). Inflationary theories can naturally produce these initial conditions, while also generically predicting a background of gravitational waves---which have so far not been detected. There are a wide range of inflationary models which make different predictions for the strength of the gravitational wave background, which is customarily characterized by the scalar-to-tensor ratio $r$. Primordial gravitational waves will have left an imprint in the polarization pattern of the cosmic Microwave Background (CMB) which we can potentially detect as a curl component, or B-mode, in the pattern at degree angular scales. The BICEP/Keck series of experiments are small aperture refracting telescopes specifically designed to search for this signal. The latest BK15 results use measurements at 95, 150 and 220GHz, in conjunction with additional bands from WMAP and Planck, to constrain the foreground signal and set the limit $r<0.07$ (95% confidence). I will describe the current instruments, data and analysis, and also the major BICEP Array upgrade which is projected to reach sensitivity of $\sigma(r)\sim0.003$ within the next five years.
Speaker: Prof. Clem Pryke -
11:35
Testing primordial Non-Gaussianty: perspectives beyond Planck 45m
Tests of primordial non-Gaussianity (PNG) are a powerful tool to shed light on the physics of the Early Universe. Currently, the best limits on PNG come from Planck measurements of Cosmic Microwave Background (CMB) temperature and polarization anisotropies, which nearly saturated the CMB constraining power. After briefly reviewing current Planck PNG bounds for a variety of models, I will discuss how these could be further improved in the future using different probes, such as galaxy clustering, or CMB B-mode polarization and spectral distortions.
Speaker: Prof. Michele Liguori (University of Padova) -
12:20
Shift-symmetric orbital inflation: single field or multi-field? 20m
Multi-field inflation with curved field manifold attracts a lot of attention recently. From theoretical aspect, this class of models may be more naturally realized in the UV completion of inflation. From observational point of view, however, the current constraints on primordial non-Gaussianity and isocurvature perturbation already/marginally ruled out many of these models. In this talk I will introduce a new class of two-field inflationary attractors, known as ‘shift-symmetric orbital inflation’. It is strongly multi-field, but the phenomenology still mimics single-field inflation, since in the end only one degree of freedom (the one with isocurvature origin) is responsible for the prediction of primordial perturbations. This new regime of multi-field attractors provides a different perspective to explore UV completion of inflation, which is free from the problems faced by single field models.
Speaker: Mr Dong-Gang Wang (Leiden University) -
12:40
lunch break 1h 20m
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14:00
Updates on the Cosmological Collider Physics 45m
We review quasi-single field inflation and the cosmological collider physics, emphasizing on recent progress. The cosmological collider is a model-independent way of extracting the mass and spin information of heavy particles at the energy scale of inflation. The same mechanism can also be used as a direct probe of the expansion history of the universe. After the introduction, we survey the recent progress including neutrino physics, particle scanner, superheavy dark matter, tests of particle symmetries and the tension of today's Hubble parameter measurements.
Speaker: Prof. Yi Wang (Hong Kong University of Science and Technology) -
14:45
Primordial Standard Clocks as Direct Probes of the Scenario of the Primordial Universe 45m
How to model-independently distinguish the inflation scenario from alternatives to inflation is an important challenge in modern cosmology. In this talk, we show that massive fields in the primordial universe function as standard clocks and imprint clock signals in the density perturbations, which directly record the scale factor of the universe as a function of time, a(t). This function is the defining property of any primordial universe scenario, so can be used to identify the inflation scenario, or one of its alternatives, in a model-independent fashion. The signals also encode the mass and spin spectra of the particle physics at the energy scale of the primordial universe.
Speaker: Prof. Xingang Chen (Harvard University) -
15:30
Stability of de Sitter spacetime against the backreaction of the infrared modes of scalar fields 20m
We study the back-reaction of the infrared modes of an O(N) scalar theory in a classical de Sitter background. We use the nonperturbative renormalization group methods to extract analytically the flow of the Hubble constant as the gravitationally enhanced long wavelength modes are integrated out. For a massless theory, the interactions tend to renormalize negatively the Hubble constant, thus drawing energy from the classical gravitational field. This phenomenon saturates however, and unbounded loop corrections are screened by nonperturbative effects which stabilise the geometry.
Based on : G. Moreau and J. Serreau, Phys. Rev. Lett. 122 (2019) no.1, 011302, Phys. Rev. D 99 (2019) no.2, 025011
Speaker: Gabriel Moreau (Université Paris Diderot) -
15:50
coffee break 30m
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Monodromy inflation and an emergent mechanism for stabilising the cosmological constant 45m
We show how a pair of field theory monodromies in which the shift symmetry is broken by small, well motivated deformations, naturally incorporates a mechanism for cancelling off radiative corrections to the cosmological constant. The lighter monodromy sector plays the role of inflation as well as providing a rigid degree of freedom that acts as a dynamical counterterm for the cosmological constant. The heavier monodromy sector includes a rigid dilaton that forces a global constraint on the system and the cancellation of vacuum energy loops occurs at low energies via the sequestering mechanism. This suggests that monodromy constructions in string theory could be adapted to incorporate mechanisms to stabilise the cosmological constant in their low energy descriptions.
Speaker: Prof. Tony Padilla (University of Nottingham) -
17:05
Primordial-Black-Holes-as-CDM Scenario and Gravitational Waves 20mSpeaker: Misao Sasaki
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17:25
Cosmic Inflation and Dark Energy from the Electroweak Phase Transition 20m
Cosmic inflation is a period of accelerated expansion in the Early Universe. Inflation is the most compelling proposal for the formation of of the observed structures in the Universe like galaxies and galactic clusters. It also makes the Universe uniform and spatially flat in agreement with observations. To drive inflation an exotic substance is needed, with pressure negative enough to cause the expansion of the Universe to accelerate, when this substance is dominant. Observations suggest that the late Universe is also undergoing accelerated expansion, which is assumed to be due to another exotic substance called dark energy. Can this be the one and the same with the substance behind inflation? In this talk I present a novel idea, in which inflation leaves behind a minute potential density, which can become the dark energy observed today. The field responsible for inflation (inflaton), is trapped in a local minimum of its scalar potential until the electroweak phase transition. The transition releases the field and allows it to vary slowly down a shallow potential tail, becoming dark energy. This behaviour is facilitated by a suitable coupling between the inflaton field and the electroweak Higgs field. The model is successful without fine-tuning, because it makes use of the curious fact that the electroweak energy scale is roughly the geometric mean of the Planck scale and the dark energy scale.
Speaker: Dr Konstantinos Dimopoulos (Lancaster University) -
17:45
Complementary probes of cosmic inflation 20m
A rigorous constraint analysis on inflationary cosmology entails several probes which collectively survey an extensive range of energy scales. We complement the current cosmic microwave background data with an updated compilation of the cosmic abundance limits of primordial black holes, with which we infer stringent constraints on the runnings of the scalar spectral index. The constraints on the higher-order inflationary power spectrum parameters are notably improved by further including imminent measurements of the cosmic microwave background spectral distortions, clearly illustrating the effectiveness of joint large-scale and small-scale cosmological surveys.
Based on arXiv:1904.09590.
Speaker: Jurgen Mifsud (Korea Astronomy and Space Science Institute) -
18:05
Constant roll warm inflation 20m
I will present the idea of combinig the constant roll inflation with the warm inflationary paradigm, which comes from the strong particle production during inflation. I will show how to solve such a system and I will rpesent fundamental applications of this theory: from inflation to primordial black holes production
Speaker: Dr Michal Artymowski (Jagiellonian University)
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Beyond VConveners: Alexander Vikman (afternoon), Shinji Mukohyama (morning)
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Weyl Symmetry for Dark Matter and Dark Energy 45m
I will start by reviewing the mimetic formulation for irrotational fluid-like Dark Matter. It turned out that the latter can be described by a Weyl-invariant higher-derivative scalar-tensor theory beyond the Horndeski class of theories. Then I will proceed by discussing a novel vector extension of the mimetic construction. This novel vector-tensor theory provides a Weyl-invariant higher-derivative and generally covariant description for the unimodular gravity.
Speaker: Prof. Alexander Vikman -
09:30
Nonlocal Quantum Gravity 20m
We present a weakly nonlocal gravitational theory unitary and finite at quantum level in the quantum field theory framework. As a consequence of finiteness, there is no Weyl anomaly and the theory turns out to be conformal invariant at classical as well at quantum level. Therefore, nonlocal quantum gravity is a conformal invariant theory in the spontaneously broken phase of the Weyl symmetry. As an application, Weyl conformal symmetry solves the black hole's singularity issue and cosmological singularity problem, otherwise unavoidable in a generally covariant local or non-local gravitational theory. Following and extending the seminal paper by Narlikar and Kembhavi, we provide explicit examples of singularity-free black hole exact solutions. The absence of divergences is based on the finiteness of the curvature invariants and on showing that the new types of black holes are geodesically complete. Indeed, no massive or massless particle can reach the former singularity in a finite amount of proper time or of affine parameter.
Speaker: Leonardo Modesto (SUSTech) -
09:50
Scalar-tensor theories beyond Riemannian 20m
We discuss scalar-tensor theories based on a non-Riemannian geometry, called the metric-affine geometry, where the metric and the connection are treated as independent variables. In the metric-affine formalism, the Einstein-Hilbert action enjoys an additional local symmetry, the projective symmetry, under a shift of the connection. We find that the projective symmetry can provide an Ostrogradky ghost-free structure of general scalar-tensor theories. The ghostly sector of the second-order derivative of the scalar is absorbed into the projective gauge mode when the unitary gauge can be imposed. We also find that, up to the quadratic order of the connection, the most general projective invariant theory is equivalent to the U-degenerate theory when the connection is integrated out and, if we further assume the Galileon-type self-interactions, the theory is equivalent to DHOST theory.
[1] Katsuki Aoki and Keigo Shimada, Galileon and generalized Galileon with projective invariance in a metric-affine formalism, 1806.02589.
[2] Katsuki Aoki and Keigo Shimada, Scalar-metric-affine theories: Can we get ghost-free theories from symmetry?, 1904.10175.Speaker: Katsuki Aoki (Yukawa Institute for Theoretical Physics, Kyoto University) -
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coffee break 30m
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Metric Optical Geometry and Beyond 45m
Optical geometry is a spatial formalism for light propagation in Lorentzian spacetimes. This provides a geometrically interesting and useful framework for gravitational lensing, which is usually treated in terms of the quasi-Euclidean standard approximation instead. In this talk, I will first consider Riemannian optical geometry, and review basic results as well as recent work using the Gauss-Bonnet theorem and curve-shortening flow. In particular, the first isoperimetric inequality in this context will be presented. Then going beyond metric geometry, I will consider possible extensions to Randers-Finsler optical geometry, which arises for stationary spacetimes, and show a connection with the magnetoelectric effect. Finally, a framework for optics in non-metric spacetimes will be discussed.
Speaker: Prof. Marcus Werner (YITP, Kyoto University) -
11:25
Constraining primordial gravitational waves from inflation 45m
I discuss the prospects for constraining gravitational waves from non-minimal inflationary models using: (i) the large scale structure, through the so-called "fossil" signatures; (ii) cross-correlations of tracers of the large scale structure with secondary CMB anisotropies from kinetic and polarized Sunyaev–Zel'dovich effects. I show how these different routes for testing primordial gravitational waves will help us learn more about the early universe.
Speaker: Prof. Emanuela Dimastrogiovanni -
12:10
Possible resolution of a spacetime singularity with field transformations 20m
In this talk, we show that there is a class of spacetime curvature singularities which can be resolved with metric and matter field transformations. As an example, we consider an anisotropic power-law inflation model with gauge and scalar fields in which a space-like curvature singularity exists at the beginning of time. First, we provide a transformation of the metric to the flat geometry. The transformation is regular in the whole region of spacetime except for the singularity. In general, matter fields are still singular after such a metric transformation. However, we explicitly show that there is a case in which the singular behavior of the matter fields can be completely removed by a field re-definition. Since the action is invariant under any metric and matter field transformations, the regularity of the action at the original singularity is a necessary condition for the complete removal of a singularity.
Speaker: Prof. Atsushi Naruko -
12:30
lunch break 1h 30m
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Emergent inflation from a Nambu–Jona-Lasinio mechanism in gravity with non-dynamical torsion 20m
We discuss how inflation can emerge from a four-fermion interaction induced by torsion. Inflation can arise from coupling torsion to Standard Model fermions, without any need of introducing new scalar particles beyond the Standard Model. Within this picture, the inflaton field can be a composite field of the SM-particles and arises from a Nambu-Jona-Lasinio mechanism in curved space-time, non-minimally coupled with the Ricci scalar. The model we specify predicts small value of the r-parameter, namely r ~ 10−4 ÷ 10−2, which nonetheless would be detectable by the next generation of experiments, including BICEP 3 and the AliCPT projects.
Speaker: Antonino Marciano (Fudan University) -
14:20
Primordial Kerr Black Holes 20m
Primordial Black Holes (PBHs) are appealing candidates for dark matter in the universe but are severely constrained by theoretical and observational constraints. I will focus on the Hawking evaporation limits extended to Kerr Black Holes. These results have been obtained with a new to-be-published code entitled BlackHawk that I will briefly present. In particular, I will review the isotropic extragalactic gamma ray background constraint and show that the "window" in which PBHs can constitute all of the dark matter depends strongly on the PBH spin. Finally, I will give some tools that could be used to distinguish between Black Holes of primordial or stellar origin based on the Thorne limit on their spin.
Speaker: Mr Jérémy Auffinger (Institut d'Astrophysique de Paris) -
14:40
Hamiltonians & degrees of freedom in "Lorentz-violating" field theories 20m
Many classical field models which "violate Lorentz symmetry" do so via a vector or tensor field which takes on a vacuum expectation value, thereby spontaneously breaking the underlying Lorentz symmetry of the Lagrangian. To obtain a tensor field with this behavior, one can posit a smooth potential for this field, or one can enforce a non-zero tensor value via a Lagrange multiplier. In this talk, I will discuss the unexpected effects that can arise when one tries to construct a field model in this way. In particular, the number of degrees of freedom of the model is not necessarily reduced, compared to a theory with a smooth potential, when one "constrains" the field via a Lagrange multiplier; and for certain field theories with a potential, the equations of motion do not allow the field to evolve smoothly on and off of the vacuum manifold.
Speaker: Michael Seifert (Connecticut College) -
15:00
Minimalism in modified gravity 20m
It is generally believed that modification of GR inevitably introduce extra physical degree(s) of freedom. In this talk I argue that this is not the case by constructing modified gravity theories with two local physical degrees of freedom. After classifying such theories into two types, I show explicit examples and discuss their cosmology and phenomenology.
Speaker: Prof. Shinji Mukohyama -
15:20
coffee break 30m
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Information Missing Puzzle, Where Is Hawking's Error? 20m
We will discuss in our talk a picture for blackholes' inner structure and microscopic state in which matters falling into the horizon or consisting of them are oscillating around instead of accumulating statically on their central point, thus resolving the Schwarzschild singularity naturally. After quantizing, this picture not only blurs the horizon remarkably, but also provides an interpretation for the Bekenstein-Hawking entropy as measures of the number of consisting matters' oscillation modes. Since each microscopic blackhole has its own dynamic mass distribution and special $r_h$-$t$ curve when evaporating and distinguishable from each other, thermal features of the Hawking radiation are only averaged description of many such objects with equal mass and symmetry. As conclusion, we claim that Hawking' error in the information missing puzzle lies in taking the averaged ensemble behavior of many microscopic blackholes with equal mass and symmetry as features of a special microscopic one.
Speaker: Ding-Fang Zeng -
16:10
Macroscopic effects on neutralino dark matter depletion through large R-charge 20m
The presence of a large, non-vanishing background charge in the universe can interestingly have implications on symmetry restoration at high temperature. In theories with continuous global symmetries, like the R-symmetry of the MSSM, these can lead to important cosmological effects seemingly independent of the short-distance scale physics. Here we explore the effect of temporary R-symmetry violation on the density of neutralino dark matter in the presence of a large initial R-charge in the early universe. In particular, this behaviour may be important for models in which the dark matter experiences feeble annihilation rates with the primordial plasma, common in supersymmetric models.
Speaker: Matthew Talia (University of Sydney) -
16:30
Electroweak baryogenesis and dark matter from a complex singlet scalar 20m
We connect the electroweak (EW) baryogenesis and the dark matter physics in a complex singlet scalar S extension of the Standard Model. We impose the additional CP and Z_2 symmetries on the scalar potential. With the complex vacuum expectation value of S at the temperature higher than the EW phase transition, the CP symmetry is spontaneously broken and a strong first-order EW phase transition is easily realized. Together with a dimension-6 effective operator that gives new complex contributions to the top quark mass, we show that it is easy to yield the observed baryon asymmetry in our Universe. On the other hand, the CP and Z_2 symmetries are recovered after the EW phase transition. The lighter real state in S can be the dark matter candidate, and the strong constraints of CP violations can be avoided. With the scan of parameter space, we can find models which can explain the dark matter relic abundance and the baryon asymmetry simultaneously while satisfying all constraints.
Speaker: Da Huang (University of Warsaw) -
16:50
Current status of smooth quantum gravity 20m
Smooth QG is the attempt to use findings and infinite geometric constructions of differential geometry and topology in dimensions 3 and 4, to solve problems in physics, especially gravitational physics. The relation between general relativity and quantum mechanics is of particular interest. We report the recent result of G. Etesi that large exotic R4's are Ricci-flat and Koehler so that they are gravitational instantons. Also exotic smoothness structure of certain R4 determines realistic value of the cosmological constant, neutrino masses and some parameters of inflation. The smoothness is used to explore quantum regime of gravity via operator algebras and Riemannian curvature it generates.
https://arxiv.org/abs/1601.06436
https://arxiv.org/abs/1709.03314
https://arxiv.org/abs/1811.04464Speaker: Jerzy Krol (University of Silesia)
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