Programm für das Sommersemester 2023
Tuesdays, 14:00 Uhr s.t.
Institut für Physik
Lorentz room (Staudingerweg 7, 5th floor)
18.04.23  Anna Socha, Warsaw U.  
According to the standard model of cosmology, the Universe at its very beginning underwent a phase of rapid expansion, followed by a reheating period. During this epoch, the energy density, initially accumulated in the coherent oscillations of the inflaton field, was injected into the visible sector, eventually setting the initial conditions for the hot Big Bang. In this talk, I will discuss perturbative production of the Standard Model (SM) particles adopting a nonstandard postinflationary scenario with a generic equationofstate parameter \(\bar{w}\). To specify the inflaton dynamics, I will employ the \(\alpha\)attractor Tmodel of inflation, such that \(\phi\) has a monomial potential \(V(\phi) \propto \phi^{2n}\) about the minimum. Moreover, I will explore the Higgs bosoninduced reheating, assuming that it is achieved through a cubic inflatonHiggs coupling \(\phi \mathcal{H}^2\). In the presence of such interaction, the Higgs field acquires a \(\phi\)dependent mass which generates a vacuum expectation value that oscillates in time and breaks the electroweak gauge symmetry. Interestingly, the nonzero Higgs mass leads to a timedependent inflaton decay rate and generates a phasespace suppression of the reheating efficiency. This, in turn, has nontrivial consequences for the reheating dynamics, modifying the evolution of the SM radiation energy density or the duration of the reheating phase. Furthermore, the implications of the nonstandard reheating for the dark sector will be discussed, exemplified by the UV freezein dark matter model.  
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)  

25.04.23  Fabrizio Rompineve, CERN  
A population of relativistic QCD axions can be produced in the early Universe, via scatterings with Standard Model particles. This can be searched for in cosmological datasets, which therefore provide the opportunity to discover/constrain the QCD axion, independently of astrophysical and/or laboratory probes.
In this talk, after reviewing the subject, I present an improved calculation of the relic abundance of such “hot” axions from scatterings with pions below the QCD crossover, as well as the resulting upper bound on the QCD axion mass. I then discuss the exciting outlook of upcoming cosmological surveys, which may probe otherwise unexplored regions of the QCD axion parameter space. I highlight the need of a nonperturbative calculation of axion production rates throughout the QCD crossover, to fully exploit the reach of such datasets.  
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)  

02.05.23  Jose Zurita, IFIC Valencia  
In the last years there has been a renewed interest in the particle physics theoretical and experimental communities on the study of exotic (nonstandard) signatures at colliders, including LongLived Particles (LLPs).
In this talk I will first give a brief overview of the theoretical motivations for longlived particles. Later I will illustrate the impact of LLPs in the current LHC physics programme, including new LHC detectors specifically hunting for LLPs (MoEDAL, FASER, SND@LHC), detector proposals under consideration (MATHUSLA, ANUBIS, FPF) and relevant upgrades to the ATLAS, CMS and LHCb experiments. Finally, I will present snapshots of novel signatures and the implications of LLP searches in the context of neutrino, axion, dark matter and Higgs physics.  
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)  

16.05.23  Anne Spiering, Bohr Inst  
The direct integration of Feynman integrals can be a daunting task, in particular for increasing numbers of loops and external particles. The “symbol bootstrap” has proven to be a powerful tool in the calculation of certain polylogarithmic Feynman integrals and scattering amplitudes that bypasses this direct integration. In this approach one first writes an ansatz for the symbol of the integral and then fixes its degrees of freedom by imposing known mathematical and physical properties of the final result. In this talk I will discuss a generalisation of this approach to an elliptic case: the 12point twoloop doublebox integral. The bootstrapping ansatz is obtained from an elliptic generalisation of the socalled Schubert problem, and after imposing a sufficient number of constraints on this ansatz, we obtain a compact oneline formula for the (2,2)coproduct of the doublebox integral.  
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)  

23.05.23  Felipe Llanes Estrada, Madrid U.  
The Electroweak Symmetry Breaking Sector of the Standard Model is an active field where new physics is sought. In the absence of new higherenergy particles at colliders, Effective Field Theories in terms of the Standard Model particles (longitudinal gauge
and Higgs bosons) seem a natural tool. New physics could then manifest itself as new forces modifying the couplings of those particles.
Should such new forces be found, they could be used to confront (falsify?) the popular SMEFT: as it is not the most general possible EFT, we have managed to produce correlations among the parameters of the embedding HEFT that can be tested if that new physics is describable by SMEFT. We have also extended HEFT via the Inverse Amplitude Method to be able to address resonances in the electroweak sector directly from the lowenergy particles and eventual BSM couplings, thus maintaining agnosticism about the nature of the eventual new physics,
and I will discuss the systematic uncertainties of the unitarization procedure.
Based on various works, e.g.
https://inspirehep.net/literature/2120028 https://inspirehep.net/literature/2154526
https://inspirehep.net/literature/1826204 https://inspirehep.net/literature/1345172
https://inspirehep.net/literature/1310013  
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)  

30.05.23  Christian Ecker, Frankfurt U.  
According to the inflationary theory of cosmology, most elementary particles in the current universe were created during a period of reheating after inflation. In this talk I will show how to selfconsistently couple the Einsteininflaton equations to a strongly coupled quantum field theory (QFT) that is described by holography. I will then use a specific example to demonstrate that this setup leads to an inflating universe, a reheating phase and finally a universe dominated by the QFT in thermal equilibrium.
This talk is based on arXiv:2302.06618.  
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)  

06.06.23  Bibhushan Shakya, DESY  
The Standard Model Higgs becomes tachyonic at high energy scales according to current measurements. This unstable regime of the Higgs potential can be realized in the early Universe during high scale inflation, potentially with catastrophic consequences. In this talk, we will discuss a crucial inherent feature of such configurations that has so far remained ignored: Higgs particle production out of vacuum induced by the rapidly evolving Higgs field, which gets exponentially enhanced due to the tachyonic instability. We will discuss various theoretical and observational implications of this effect.  
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)  

13.06.23  Thomas Thiemann, Erlangen Nürnberg  
The Hamiltonian approach to quantum gravity initiated by Bergman, Dirac, DeWitt, Komar, Wheeler et al has a long tradition and many quantum gravity programmes rest on it. While there has been progress in the past, the current theory is still not predictive because the EinsteinHilbert Lagrangian is not even polynomial in the metric field which triggers many quantisation ambiguities. To eliminate those, renormalisation methods suggest themselves, preferrably directly in the Hamiltonian rather than the path integral language. After an introduction to those concepts, in this talk we present such a Hamiltonian renormalisation scheme which is derived from Wilson's notion of nonperturbative renormalisation of path integrals together with methods from constructive QFT. As a test we study Hamiltonian renomalisation of parametrised field theory in 2D which is a toy model for 4D quantum gravity in the sense that both theories are subject to the hypersurface deformation algebroid shared by all generally covariant field theories.  
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)  

20.06.23  Thomas Becher, Bern  
In cross sections involving angular cuts, intricate patterns of enhanced higherorder corrections known as nonglobal logarithms arise. These corrections do not exponentiate and to resum them to all orders one has to resort to numerical techniques. The resummation of the leading nonglobal logarithms was achieved twenty years ago, but higherlogarithmic resummations remained elusive. In my talk, I will show how such resummation can be performed using renormalization group methods in effective field theory. I will demonstrate how the associated evolution equations can be implemented into a MonteCarlo framework and will present first numerical results for higherlogarithmic resummations at both lepton and hadron colliders.  
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)  

27.06.23  Maria Anayeli Ramirez Ortiz, Milano Bicocca  
The AdS3/CFT2 correspondence provides the best arena to test the holographic duality. This is because there is a better understanding of how to quantise strings on AdS3, compared with the higher dimensional cases, and the relative tractability of twodimensional CFTs. In spite of this, little effort has been made to construct and classify supersymmetric AdS3 solutions. With a focus in their CFT interpretation, in this talk I will show you new AdS3 solutions in massive type IIA supergravity preserving small N=(4,0) supersymmetry. From the geometry, we engineer the dual CFT with wellknown tools and propose a duality with a precise family of quivers. Additionally, we compute field theory and holographic central charges showing a clean matching in both descriptions.  
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)  

04.07.23  Pouria Mazloumi, MPP Munich  
In this talk, I will discuss different types of integrals over moduli space of punctured Riemann surfaces. First, I start with string scattering amplitudes and progress to the intersection number of twisted forms over the Riemann surface. I will discuss the equivalency between the two integrals and how this relation can be used to produce QFT (treelevel) amplitudes. In particular, I explore the double copy construction in amplitudes, which states that gravitational amplitudes can be expressed in terms of two sets of YangMills amplitudes i.e.gravity=(gauge X gauge). I will motivate a formal construction of double copy in terms of the twisted cohomology and explain its relation to other forms of the double copy such as BCJ double copy and color kinematic duality. I will finish by discussing the possibility of extending this formalism into the loop level in both string and QFT amplitudes.  
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)  

11.07.23  Cristina Benso, MPIK Heidelberg  
In our current understanding of the universe, the fundamental nature of one of its most abundant constituents, the dark matter (DM), is still a mystery. Among the many theorized candidates to play the role of DM, in this talk I will focus on sterile neutrinos with mass of O(keV) and in particular on their production in the early universe and phenomenology in terrestrial experiments today. The simplest mechanism able to produce sterile neutrino DM in the early universe is named DodelsonWidrow mechanism after its inventors. Although very fascinating due to its extreme simplicity, if we assume that sterile neutrinos constitute the entire abundance of DM today this vanilla solution is, on the one hand, far from the region of the parameter space in which near future experiments will be sensitive to such particles and, on the other hand, mostly excluded by Xray observations. After introducing the standard/vanilla scenario, I will discuss three minimal modifications to the standard scenario that change drastically the perspectives of detection of this DM candidate in the near future. They have to do with the following questions. What if before Big Bang Nucleosynthesis the universe evolved differently with respect to what is usually assumed? Should we consider the Xray bound to be absolute or model dependent? What if active neutrinos interact among each other also with nonstandard interactions?  
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)  

21.07.23  Elias Bernreuther, Fermilab  
Searches for longlived particles (LLPs) are a rapidly expanding
frontier at the LHC and other collider experiments. Still, many gaps
remain in the current search program, in particular for LLPs with masses
at the GeV or subGeV scale and with very large decay lengths. In this
talk, I will illustrate two different approaches to filling this gap by
discussing two models of light LLPs and their associated collider
signals. First, I will show that the dominant decay mode of vectorlike
leptons can be a very longlived pseudoscalar and a tau lepton and argue
that the muon chambers of CMS or ATLAS are ideal places to search for
this final state. Second, I will illustrate the excellent sensitivity of
Belle II to light LLPs with meterscale decay lengths using the example
of displaced vertex signals from strongly interacting dark sectors.  
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)  

25.07.23  Tin Sulejmanpasic, Durham U.  
I will introduce a formalism for abelian lattice gauge theories called the Modified Villain Action formalism, which has been popular in recent years for constructing abelian gauge theories with correct symmetries and anomalies of their continuum counterparts. I will then show that this formalism can be used to write down a \(U(1)\) ChernSimons theory on the lattice for even levels. The theory we construct suffers from the peculiar zero modes of the Gaussian differential operator which are infamous in the literature for plaguing the ChernSimons theory with unphysical modes. I will show that such modes are related to a peculiar subsystem symmetry of a spacetime lattice. This symmetry causes almost all Wilson loops to vanish. However Wilson looplike operators with striplike topology survive the pernicious symmetry and are topological, exactly like one expects in the continuum. Further the striplike topology of the loops is a lattice realization of a well known phenomenon in continuum called the framing anomaly. I will further argue, time permitting, that the pernicious symmetry is really a form of gauge symmetry, projecting out certain states from the Hilbert space, and that it is not associated with any physical significance.  
14:00 Uhr s.t., Lorentz room (Staudingerweg 7, 5th floor)  

22.09.23  Hidenori SONODA, Kobe University  
I would like to explain how the construction of a Wilson action in the exact renormalization group (ERG) formalism is related to diffusion equations for the fields. By making the diffusion equations gauge covariant, we have managed to linearize the BRST invariance of U(1) gauge theories. But with YM theories, the BRST invariance remains nonlinear, and we have not been able to solve the constraint. All this has been done in collaboration with Hiroshi Suzuki (Kyushu University).  
10 Uhr c.t., THEP seminar room (05427)  
Sonderseminar  

Koordination:  Kontakt: 
Max Ferré Anne Galda Sebastian Schenk  ferremax@unimainz.de agalda@unimainz.de sebastian.schenk@unimainz.de 