The geometry of field space governs on-shell scattering amplitudes. We formulate a geometric description of effective field theories which extends previous results for scalars and gauge fields to fermions. The field-space geometry reorganizes and simplifies the computation of quantum loop corrections. Using this geometric framework, we calculate the fermion loop contributions to the...
The common claim that vacuum is filled with virtual particles buzzing in and out of existence, has always bother me.
I will here argue for why I do not think this is a correct interpretation of the mathematics of QFT.
Note that I am not questioning any of the mathematics of QFT, merely the metaphysical interpretation often presented.
Taking axion inflation as an example, we consider a scenario where the inflaton is coupled solely to a pure SU(3) Yang-Mills sector. In the low-energy phase of this sector, glueball states are formed. If non-renormalizable operators are considered, these glueballs may become unstable and reheat the standard model fields. Yet, for a certain parameter range, C-parity can protect part of the...
The Swampland Distance Conjecture states that at infinite distance in the scalar moduli space an infinite tower of particles become exponentially massless. I will review this topic, and its evidence from dualities. I will give an example in the context of heterotic string compactifications.
Threshold resummation is a key complement to perturbative QCD for predicting cross-sections at hadron colliders. Logarithms that grow large in the threshold limit, when emitted gluons are soft, are included to all orders in the strong coupling, thus stabilizing the theoretical predictions. Resummation of these logarithms has been studied extensively, e.g. reaching next-to-next-to-leading...
In this talk, I will show recent GAMBIT global fits of SUSY scenarios. These combine many collider searches performed during Run 2 of the LHC to constrain the electro-weak sector of the MSSM, both with and without an additional light gravitino. Fits will show parameter regions where the combination of collider searches displays behaviour that would not be trivial to see from studying search...
Primordial Black Holes is a particular candidate for Dark Matter. In this talk I will present the case for, and against, Primordial Black Holes and the limits we can set on them today.
In addition, I will discuss how their existence could be probed by considering how Black Holes of asteroid like mass could affect the Neutron Star population at the center of the Milky Way.
We consider the instabilities of field perturbations around a homogeneous background color-electric and/or -magnetic field in SU(2) pure gauge theory. We investigate a number of distinct cases of background magnetic and electric fields, and compute the dispersion relations in the linearised theory, identifying stable and unstable momentum modes. In the case of a net homogenous non-abelian...
Particle physics simulations and modelling of infectious diseases in a pandemic share computational challenges due to their heavy Monte Carlo models. Both types of models need to fit large numbers of parameters to data, making the calibration process time-consuming.
In particle physics, we use the GAMBIT software to compare Beyond Standard Model theories to data from experiments. In this...
The talk will aim at an introduction to the topic of gravitational wave echoes, which are gravitational waves reflected from the surface of black holes (then by mechanism of some quantum effect), or some alternative to black holes known as Exotic Compact Objects (ECO).
Gaussian processes regression provides a principled Bayesian approach to regression problems. But many applications of GP regression are hampered by the fact that the training time for a naive GP implementation scales as the number of data points cubed. In this talk I will present a new software package, GPTreeO, that enables continual learning with GPs, i.e. a GP regression model that...
The search for gravitational waves has literally opened up a new window into
the universe, not the least as a means to probe new physics beyond the
standard model. In this talk I provide some examples, with a strong personal
bias, how this statement applies to a very broad range of frequencies.
The confirmed nHz cosmological background signal, is for example consistent
with a dark...
In this talk, we will present an introduction to strongly interacting massive particles (SIMPs) as dark matter candidates. In general, the SIMP scenario can have different realizations; however, we will mostly concentrate on the dark sector described by QCD-like theories. We will discuss the basics of various scenarios and motivate the necessity of next-to-leading-order calculations in the...
General relativity has proven to be a highly successful theory of gravity since its inception. The theory has passed numerous experimental tests in different regimes. Observable gravitational waves (GWs) originate from regions of spacetime where gravity is extremely strong, making them a unique tool for testing GR, in previously inaccessible regions of large curvature, relativistic speeds, and...
Guest lecture by professor emeritus Harald Yndestad
I present recent work [1] on a new numerical approach to solving classical initial boundary value problems on the level of the system action, which is discretized in a way in which space-time symmetries remain preserved.
[1] W.A. Horowitz, J. Nordström, A. Rothkopf arXiv:2404.18676
I will present some work that Gerhard has done on simulations of real-time quantum fields using the 2PI effective action formalism.
Update from the LIGO-Virgo-KAGRA collaborations 4th observing run.
