Primordial Magnetic Fields in Cosmic Web and Galaxy Clusters

Magnetic fields are ubiquitous on astrophysical and cosmological scales: from planets and stars to galaxies and galaxy clusters. Different observational methods infer a field strength of the order of microGauss and coherence scales reaching a few tens of kiloparsecs in galaxy clusters. Despite their ubiquity, the origin of these fields still remains unknown. It is commonly assumed that the observed fields are originated from either astrophysical or cosmological (primordial) weak seed magnetic fields that undergo efficient growth during structure formation.

Relativistic superfluids, and the connection between finite density and spontaneous symmetry breaking for interacting scalar fields

We study the low-energy effective action for relativistic superfluids obtained by integrating out the heavy fields of a UV theory. A careful renormalization procedure is required if one is interested in deriving the effective theory to all orders in the light fields (but still to fixed order in the derivative expansion). The result suggests a general relation between finite density and spontaneous symmetry breaking for QFTs of interacting scalars with an internal global symmetry.

Towards the detection of nonclassical primordial waves

One of the cornerstones of inflationary cosmology is that the large
scale structure of the Universe has a quantum mechanical origin. This
invites the question of whether compelling observational evidence for
the quantum nature of the origin can be found. Primordial
gravitational waves are generated directly from quantum fluctuations
during inflation. Since they interact with matter very weakly, travel
through the Universe virtually unimpeded, it is expected that they
keep their nonclassicality until today. In this talk, I will present

Positivity Constraints on Lorentz-breaking EFTs

The coefficients of the operators of an effective field theory (EFT) are constrained to satisfy certain inequalities, under the (mild) assumption that the UV completion satisfies general requirements of causality and unitarity. We begin the extension of these ideas to theories where the Lorentz symmetry is spontaneously broken, as it happens in cosmology and condensed matter physics. Constraints are derived using dispersive arguments for the 2-point function of conserved currents and of the stress-energy tensor.

Quantum effects on the inner (Cauchy) horizon of rotating black holes

All black holes in the Universe are believed to be rotating. This poses interesting questions, since rotating black hole solutions of Einstein’s equations of General Relativity possess a so-called Cauchy horizon in their interior, which threatens the predictability of Einstein’s theory. However, these exact solutions may not model sufficiently accurately black holes in Nature, which have classical matter in their neighbourhood and, furthermore, are inevitably surrounded by a quantum vacuum (which is responsible for Hawking radiation).

Unveiling Positrons in Galactic Cosmic Rays

The spectrum of positrons in cosmic rays is currently measured with unprecedented precision by AMS-02 up to TeV energies, and represents an unique probe for the local properties of our Galaxy. Currently, its interpretation is still debated, especially for the excess above 10 GeV which suggests the presence of a local, primary source.
Recently, the observation of extended gamma-ray halos around Galactic pulsars has opened a new window to constrain the acceleration and propagation of positrons in our Galaxy.


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