Lepton asymmetries present in the early universe can source helical hypermagnetic fields through the chiral plasma instability. If these hypermagnetic fields survive until the electroweak phase transition, they source a contribution to the baryon asymmetry of the universe. In this talk I will explain how this phenomenon can, one the one hand, be used to set the to date strongest bounds on primordial lepton flavour asymmetries and on the other hand, can play a key role in viable baryogenesis models.
Whether neutrinos are Majorana or Dirac particles is an open question. Theoretically, it is also possible that neutrinos are pseudo-Dirac, which are fundamentally Majorana fermions, but essentially act like Dirac fermions in most experimental settings due to extremely small active-sterile mass splitting. However, they can be differentiated through active-sterile oscillations with an astrophysical baseline. In this talk, we will show that the recent identification of ultra-high energy neutrino sources by the IceCube Neutrino Observatory provides us with such an astrophysical baseline, thus improving the reach of terrestrial experiments by more than a billion for the mass-squared difference.
We study an infinite family of Massive Type IIA backgrounds that holographically describe the twisted compactification of N=(1,0) six-dimensional SCFTs to four dimensions. The analysis of the branes involved suggests a four dimensional linear quiver QFT, that deconstructs the theory in six dimensions. For the case in which the system reaches a strongly coupled fixed point, we calculate some observables that we compare with holographic results. Two quantities measuring the number of degrees of freedom for the flow across dimensions are studied.
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𝑉_{𝑢𝑏} is the smallest and least known of all CKM matrix elements; it's currently determined primarily through the exclusive process B \to \pi \ell \bar{
u}. I will present progress toward a lattice QCD determination of the 𝑉_{𝑢𝑏} matrix element from a novel transition -- the B \to \pi \pi \ell \bar{
u} process, where the π π system is in a P-wave and features the \rho(770) resonance as an enhancement. The calculation is performed an ensemble with 𝑁_𝑓=2+1 isotropic clover fermions wiht 𝐿≈3.6 fm and a pion mass of 320 MeV; for the b-quark we use the anisotropic clover action. After a brief overview of the theoretical framework, I will discuss some preliminary results.