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Wetterich Christof28/01/2019, 09:10
Quantum scale symmetry is the realization of scale invariance in a quantum field theory. No parameters with dimension of length or mass are present in the quantum effective action. Quantum scale symmetry is generated by quantum fluctuations via the presence of fixed points for running couplings. As for any global symmetry, the ground state or cosmological state may be scale invariant or not....
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Elias Kiritsis28/01/2019, 09:50
Holographic ideas are used to set-up cosmology along the Wilsonian paradigm. Cosmological solutions are investigated, and the connection between de Sitter and Anti de Sitter regimes in the supergravity landscape is probed.
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Hermann Nicolai28/01/2019, 13:30
In this talk I will describe an attempt to understand the
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fermion spectrum of the Standard Model (with three generations of quarks
and leptons, and no "extra baggage") from a more fundamental theory. One interesting possible consequence of this scheme is the emergence of new super-heavy dark matter candidates. -
Eliezer Rabinovici28/01/2019, 14:10
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Jinn-Ouk Gong28/01/2019, 15:20
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Steven Abel28/01/2019, 16:00
I report on recent work to embed the Standard Model within an asymptotically safe framework. This approach, which is based on gauge-Yukawa theories with interacting UV fixed points, focusses on providing a field theoretical UV completion to the SM along with radiative symmetry breaking. The framework yields several generic predictions.
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Anupam Mazumdar28/01/2019, 16:30
I will discuss some of the recent results obtained in ghost free infinite derivative theory of gravity, which suggests towards scale invariant, conformally flat for static and rotating non-singular metric solutions at both linear and non-linear level. From quantum perspective such class of theory provides a new scale in the infrared which points towards transmutation of scales from ultraviolet...
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Alberto Salvio29/01/2019, 08:30
Models with classical scale invariance (CSI) provides us with a dynamical origin for all masses (via dimensional transmutation) and can account for all evidence of beyond the standard model physics. Furthermore, a general theory with CSI is renormalizable (even in the gravity sector) and can solve the hierarchy problem. The price to pay is a classical ghost. The theory, however, admits...
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John Donoghue29/01/2019, 09:10
In work with Gabriel Menezes, we are exploring the use of quantum field theory for quantum gravity at all scales. Starting from a scale invariant action, our variant uses an extra Yang-Mills gauge interaction to induce the Einstein action in such a way that gravity is kept weakly coupled at all scales. We have explored the unusual field theoretic aspects of this theory, and so far have...
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Ariel Edery29/01/2019, 10:20
Recent work has shown that pure R^2 gravity (i.e. R^2 gravity with no extra R term) has a symmetry that is larger than scale symmetry and smaller than full Weyl symmetry. This has been dubbed restricted Weyl symmetry as it involves a Weyl transformation where the conformal factor has a constraint. Most importantly, this symmetry is spontaneously broken when the vacuum (background spacetime)...
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Damiano Anselmi29/01/2019, 10:50
A new quantization prescription is able to endow quantum field theory with a new type of "particle", the fakeon (fake particle), which mediates interactions, but cannot be observed. A massive fakeon of spin 2 (together with a scalar field) allows us to build a theory of quantum gravity that is both renormalizable and unitary, and to some extent unique. After presenting the general properties...
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Manfred Lindner (Max Planck Institut fuer Kernphysik, Heidelberg, Germany)29/01/2019, 13:30
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Bob Holdom29/01/2019, 14:10
We encounter these demons on the path towards a UV complete QFT of gravity and a horizonless replacement for black holes. The fate of the ghost and related issues are discussed in the strong coupling version of classically scale invariant quadratic gravity. We compare this story to QCD. The 2-2-hole solutions appearing in a classical approximation of the gravity theory are then discussed,...
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Dr Daniele Teresi (Università di Pisa), Satoshi Iso29/01/2019, 15:20
If the electroweak sector of the Standard Model is described by classically conformal dynamics, the early Universe evolution can be substantially altered. In particular, one generically has a significant period of super-cooling, often ended when quark condensates form at the QCD phase transition. This scenario is potentially rich in cosmological consequences, such as renewed possibilities...
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Kohei Kamada29/01/2019, 16:00
Higgs inflation with the nonminimal coupling to gravity \xi H^2 R is the unique model
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to realize inflation driven by the Standard Model Higgs field in a classically scale invariant way.
However, the reheating in that model is not understood well yet.
In particular, in the so-called “non-critical” regime, it turned out that there are violent instabilities
in the longitudinal mode at very... -
Kellog Stelle29/01/2019, 16:30
Including quadratic curvature terms in the gravitational action yields a renormalizable theory at the apparent cost of instability in the radiation field. One also
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needs to consider the effects upon classical solutions such as black holes. All vacuum solutions to Einstein’s theory remain good solutions to the higher derivative theory, so the Schwarzschild family carries over to the generalized... -
Javier Rubio30/01/2019, 08:30
I will review a scale-invariant extension of the Standard Model and gravity able to support inflation and dark energy and containing just an additional degree of freedom on top of the Standard Model content. This scenario has some interesting features such as i) the existence of a conserved current that effectively forbids the generation of isocurvature perturbations ii) an...
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Fedor Bezrukov30/01/2019, 09:10
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Dumitru Ghilencea30/01/2019, 10:20
Recent results in (quantum) scale invariance and its spontaneous breaking are presented. In flat spacetime, for a scale invariant theory the scalar potential is presented at three loops while keeping manifest scale symmetry. This is possible in a scale-invariant regularization (in $d=4-2\epsilon$) in which the Goldstone (dilaton) of this symmetry generates (spontaneously) the subtraction...
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Andrey Shkerin (EPFL)30/01/2019, 11:00
Combining the quantum scale invariance with the absence of new degrees of freedom above the electroweak scale leads to stability of the latter against perturbative quantum corrections. Nevertheless, the hierarchy between the weak and the Planck scales remains unexplained. We argue that this hierarchy can be generated by a non-perturbative effect relating the low energy and the Planck-scale...
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Gerard 't Hooft30/01/2019, 14:00
In theories such as asymptotically safe gravity, conformal symmetry is treated as a symmetry for the ultra-violet limit of quantum gravity. However, gravity can be formulated as a theory where conformal symmetry is exact, but broken in the same way as in the Brout-Englert-Higgs-Kibble formalism, where local gauge symmetry is still exactly valid but realised in an apparently asymmetric manner....
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Christopher T. Hill30/01/2019, 15:30
Globally Weyl invariant theories have a conserved current that is generally the derivative of a scalar. In general expansion, this scalar flows to a constant, $K$, that serves as the order parameter of symmetry breaking, eg, the decay constant of the dilaton is proportional to \sqrt{K}. If we introduce the Weyl photon the dilaton is eaten and the photon acquires a mass proportional to K. The...
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Graham Ross30/01/2019, 16:10
Global and local Weyl invariant theories of scalars and gravity can generate all mass scales spontaneously, initiated by a dynamical process of “inertial spontaneous symmetry breaking” that does not involve a potential. We discuss how inflation readily occurs and how an hierarchy of mass scales may be generated and consider its stability against quantum corrections.
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Astrid Eichhorn31/01/2019, 09:00
I will review the key idea underlying the asymptotic-safety programme both in particle physics as well as quantum gravity. I will discuss mechanisms that can generate asymptotic safety and will provide an overview of models that could exhibit these mechanisms. After reviewing recent developments I will give a short outlook on future perspectives.
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Francesco Sannino31/01/2019, 09:40
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Archil Kobakhidze (The University of Sydney)31/01/2019, 10:50
I discuss a class of effective low-energy theories that incorporate nonlinearly realised scale invariance through the dilaton field. Radiatively stable mass hierarchies are realised in a natural (without fine-tuning) way in this class of models, with a generic prediction of a light dilaton field. The cosmological electroweak phase transition in this scenario is triggered by the QCD phase...
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Roberto Percacci31/01/2019, 14:10
I will review metric-affine theories of gravity and the occurrence of a Higgs mechanism that gives mass to the gravitational connection. I will then discuss the possibility of achieving quantum scale invariance at high energy in such theories.
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Jan Kwapisz31/01/2019, 15:20
There are many proposals 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 favored. One of them is the Conformal Standard Model, which proposes a coherent solution to the Standard Model drawbacks including...
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Masatoshi Yamada31/01/2019, 16:00
Classical scale invariance represents a promising framework for model building beyond the Standard Model. However, once coupled to gravity, any scale-invariant microscopic model requires an explanation for the origin of the Planck scale. In this talk, I will present a minimal example for such a mechanism and show how the Planck mass can be dynamically generated in a strongly coupled gauge...
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Dr Alexander Helmboldt (MPIK Heidelberg), Vedran Brdar (JGU Mainz)31/01/2019, 16:30
It was recently proposed that the electroweak hierarchy problem is absent if the generation of the Higgs potential stems exclusively from quantum effects of heavy right-handed neutrinos which can also generate active neutrino masses via the type-I seesaw mechanism. Hence, in this framework dubbed the "neutrino option", the tree-level scalar potential is assumed to vanish at high energies. Such...
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Kin-ya Oda01/02/2019, 09:10
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Pyungwon Ko01/02/2019, 09:50
Scale invariant extension of the SM with QCD-like strongly interacting hidden (dark) sector is interesting, since the dimensional transmutation and chiral symmetry breaking in the hidden sector could be the origin of electroweak symmetry breaking (EWSB), and all the masses of the SM particles as well as dark pions and dark baryons that could be good cold dark matter candidates. In this talk...
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Philip Mannheim01/02/2019, 10:50
The status of the chiral-invariant Nambu-Jona-Lasinio (NJL) four-fermi model is quite equivocal. It serves as the paradigm for dynamical symmetry breaking and yet it is not renormalizable. NJL only studied one loop graphs with point vertices, and needed to use an ultraviolet cutoff. We propose to dress the point vertices with scale invariant vertices with anomalous dimensions. We show that if...
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Deog-Ki Hong01/02/2019, 13:30
We study very light dilaton, arising from a scale-invariant ultraviolet theory of the Higgs sector in the standard model of particle physics. Imposing the scale symmetry below the ultraviolet scale of the Higgs sector, we alleviate the fine-tuning problem associated with the Higgs mass. When the electroweak symmetry is spontaneously broken radiatively à la Coleman-Weinberg, the dilaton...
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Sang Hui Im01/02/2019, 14:10
The clockwork mechanism provides a useful picture to understand extra dimensions via continuum limit of the scheme (continuum clockwork). The continuum clockwork can find its concrete realization in the general linear dilaton model (GLD). GLD can be defined by classical scale invariance in the presence of supersymmetry, which implies a non-trivial selection rule for radiative corrections to...
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Vedran Brdar
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D. Teresi
If the electroweak sector of the Standard Model is described by classically conformal dynamics, the early Universe evolution can be substantially altered. In particular, one generically has a significant period of super-cooling, often ended when quark condensates form at the QCD phase transition. This scenario is potentially rich in cosmological consequences, such as renewed possibilities...
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