Event Category: 4D Seminar

4D Seminar series:
Monday at 2:30 on campus

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Abstract: The asymmetry between matter and antimatter is one of the big outstanding questions of particle physics and cosmology. In this talk, I will argue that electroweak baryogenesis is an interesting mechanism to generate the baryon asymmetry. The new physics needed for electroweak baryogenesis come into play at a relatively low scale and can thus be tested in experiment. I … Read More

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The search for new, sub-GeV particles has become the center of much interest. In a first part, I will consider light dark states that share a direct coupling with the photon through higher dimensional operators (“photon portal”). The prospects of detecting such states at the intensity frontier will be confronted with low-energy precision tests as well as with cosmological and … Read More

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Abstract: In this talk I will present new constraints on U(1)Lμ−Lτ symmetry. In pulsar binaries, such U(1)Lμ−Lτ vectors induce an anomalously fast decay of the orbital period through the emission of dipole radiation. I’ll show the range of different pulsar binaries, finding the most powerful constraints for vector masses below O(10−18eV). For merging binaries the presence of muons in neutron … Read More

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Functional methods, in particular efficient reorganization of the one-loop effective action, have in recent years made a reappearance in simplifying the problem of computing matching and running effects in Lorentz-invariant EFTs such as the SMEFT. This has lead to the appearance of universal one-loop effective actions, where many such effects are now known in closed form for arbitrary field-content. Similar … Read More

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Abstract: I will discuss a production scenario for QCD axion dark matter where the Peccei-Quinn phase transition occurs at a temperature far below the symmetry breaking scale. Both early cosmic string network dynamics and parametric resonance contribute to the axion population. The observed dark matter abundance is reproduced even if the decay constant is much lower than 10^11 GeV. I … Read More

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Abstract: Soft Collinear Effective Theory (SCET) can be made compatible with supersymmetry, and such a theory can be conveniently formulated in “Collinear Superspace”. In this talk I will introduce a new set of effective field theory rules for constructing Lagrangians in collinear superspace. This new formalism represents a general way to derive on-shell superspace Lagrangians directly from the symmetries of … Read More

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Abstract: We propose a novel explanation for the smallness of the observed cosmological constant (CC). Regions of space with a large CC are short lived and are dynamically driven to crunch soon after the end of inflation. Conversely, regions with a small CC are metastable and long lived and are the only ones to survive until late times. While the … Read More

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Abstract: Millisecond pulsars are known to be very stable clocks, whose fluctuations in the periods of pulses observed over decades do not accumulate. We use the stability of these astrophysical clocks to derive prospects for detecting transiting dark matter substructure from frequency dependent fluctuations in the pulsar period over a 30 year timescale. We apply our results to deterministic and … Read More