We study the physics potential of the detection of the Cosmic Neutrino Background via neutrino capture on tritium, taking the proposed PTOLEMY experiment as a case study. With the projected energy resolution of ∆ ∼ 0.15 eV, the experiment will be sensitive to neutrino masses with degenerate spectrum, m 1 m 2 m 3 = m ν 0.1 eV. These neutrinos are non-relativistic today; detecting them would be a unique opportunity to probe this unexplored kinematical regime. The signature of neutrino capture is a peak in the electron spectrum that is displaced by 2m ν above the beta decay endpoint. The signal would exceed the background from beta decay if the energy resolution is ∆ 0.7 m ν . Interestingly, the total capture rate depends on the origin of the neutrino mass, being Γ D 4 and Γ M 8 events per year (for a 100 g tritium target) for unclustered Dirac and Majorana neutrinos, respectively. An enhancement of the rate of up to O(1) is expected due to gravitational clustering, with the unique potential to probe the local overdensity of neutrinos. Turning to more exotic neutrino physics, PTOLEMY could be sensitive to a lepton asymmetry, and reveal the eV-scale sterile neutrino that is favored by short baseline oscillation searches. The experiment would also be sensitive to a neutrino lifetime on the order of the age of the universe and break the degeneracy between neutrino mass and lifetime which affects existing bounds.

We show that maximally helical hypermagnetic fields produced during pseudoscalar inflation can generate the observed baryon asymmetry of the universe via the B + L anomaly in the Standard Model. We find that most of the parameter space of pseudoscalar inflation that explains the cosmological data leads to baryon overproduction, hence the models of natural inflation are severely constrained. We also point out a connection between the baryon number and topology of the relic magnetic fields. Both the magnitude and sign of magnetic helicity can be detected in future diffuse gamma ray data. This will be a smoking gun evidence for a link between inflation and the baryon asymmetry of the Universe.PACS numbers: 98.80.Cq, 12.15.-y.

Superstring theory and other supersymmetric theories predict the existence of relatively light, weakly interacting scalar particles, called moduli, with a universal form of coupling to matter. Such particles can be emitted from cusps of cosmic strings, where extremely large Lorentz factors are achieved momentarily. Highly boosted modulus bursts emanating from cusps subsequently decay into gluons, they generate parton cascades which in turn produce large numbers of pions and then neutrinos. Due to very large Lorentz factors, extremely high energy neutrinos, up to the Planck scale and above, are produced. For some model parameters, the predicted flux of neutrinos with energies 10 21 eV is observable by JEM-EUSO and by the future large radio detectors LOFAR and SKA.

The anomalous conversion of leptons into baryons during leptogenesis is shown to produce a right-handed helical magnetic field; in contrast, the magnetic field produced during electroweak baryogenesis is known to be left-handed. If the cosmological medium is turbulent, the magnetic field evolves to have a present day coherence scale ∼ 10 pc and field strength ∼ 10 −18 Gauss. This result is insensitive to the energy scale at which leptogenesis took place. Observations of the amplitude, coherence scale, and helicity of the intergalactic magnetic field promise to provide a powerful probe of physics beyond the Standard Model and the very early universe.

Superconducting cosmic strings can give transient electromagnetic signatures that we argue are most evident at radio frequencies. We investigate the three different kinds of radio bursts from cusps, kinks, and kink-kink collisions on superconducting strings. We find that the event rate is dominated by kink bursts in a range of parameters that are of observational interest, and can be quite high (several a day at 1 Jy flux) for a canonical set of parameters. In the absence of events, the search for radio transients can place stringent constraints on superconducting cosmic strings.

Superconducting cosmic strings naturally emit highly boosted charge carriers from cusps. This occurs when a cosmic string or a loop moves through a magnetic field and develops an electric current. The charge carriers and the products of their decay, including protons, photons and neutrinos, are emitted as narrow jets with opening angle θ ∼ 1/γ c , where γ c is the Lorentz factor of the cusp. The excitation of electric currents in strings occurs mostly in clusters of galaxies, which are characterized by magnetic fields B ∼ 10 −6 G and a filling factor f B ∼ 10 −3 .Two string parameters determine the emission of the particles: the symmetry breaking scale η, which for successful applications should be of order 10 9 -10 12 GeV, and the dimensionless parameter i c , which determines the maximum induced current as J max = i c eη and the energy of emitted charge carriers as ǫ X ∼ i c γ c η, where e is the electric charge of a particle. For the parameters η and B mentioned above, the Lorentz factor reaches γ c ∼ 10 12 and the maximum particle energy can be as high as γ c η ∼ 10 22 GeV. The diffuse fluxes of UHE neutrinos are close to the cascade upper limit, and can be detected by future neutrino observatories. The signatures of this model are: very high energies of neutrinos, in excess of 10 20 eV, correlation of neutrinos with clusters of galaxies, simultaneous appearance of several neutrino-produced showers in the field of view of very large detectors, such as JEM-EUSO, and 10 TeV gamma radiation from the Virgo cluster. The flux of UHE protons from cusps may account for a large fraction of the observed events at the highest energies.

We reconsider the effect of electromagnetic radiation from superconducting strings on cosmic microwave background (CMB) µ-and y-distortions and derive present (COBE-FIRAS) and future (PIXIE) constraints on the string tension, µs, and electric current, I. We show that absence of distortions of the CMB in PIXIE will impose strong constraints on µs and I, leaving the possibility of light strings (Gµs 10 −18 ) or relatively weak currents (I 10 TeV).

We show that radio bursts from cusps on superconducting strings are linearly polarized, thus, providing a signature that can be used to distinguish them from astrophysical sources. We write the event rate of string-generated radio transients in terms of observational variables, namely, the event duration and flux. Assuming a canonical set of observational parameters, we find that the burst event rate can be quite reasonable, e.g., order ten a year for Grand Unified strings with 100 TeV currents, and a lack of observed radio bursts can potentially place strong constraints on particle physics models.PACS numbers: 98.80. Cq, 11.27.+d, 95.85.Bh, 95.85.Fm Cosmic strings are possible relics from the early Universe. Their discovery would substantiate our hot big bang cosmological model and also provide tremendous insight into the nature of fundamental interactions.There are a number of different ways to look for cosmic strings, mostly based on their gravitational interactions, and negative searches so far impose constraints on particle physics models and cosmology. If the strings are superconducting [1], their electromagnetic emission provides yet another signature that can be used to search for them. The electromagnetic emission from a cosmic string loop is not steady and can have sharp bursts that can be seen as transient events. In Ref.[2], it was pointed out that it might be fruitful to look for superconducting strings by searching for bursts at radio wavelengths. There is a simple reason for choosing to look in the radio band. Cosmic strings are large objects and their fundamental frequency of emission is very low. The power emitted at higher frequencies generally falls off with increasing harmonic. Thus, there is more power emitted in the radio than in other bands such as the optical. Also, as we shall see in Sec. I, the emission in the burst is beamed, with the beam being widest at lower frequencies. Thus, the event rate in radio bursts can be expected to be larger than those at higher frequencies. On the other hand, propagation effects in the radio band are stronger, and these have to be included when evaluating the signature.Besides superconducting cosmic strings, there are other strong motivations for looking at transient radio phenomenon from pulsars, supernovae, black hole evaporation, gamma-ray bursts, active galactic nuclei, and extra-terrestrial life. A radio burst from a superconducting cosmic string will have to be distinguished among bursts from other potential astrophysical sources. With this in mind, we recalculate the characteristics of the string burst and show that it is linearly polarized in a direction that is independent of the frequency.The feasibility of observations depends on the event * Electronic address: ycai21@asu.edu † Electronic address: Eray.Sabancilar@asu.edu ‡ Electronic address: tvachasp@asu.edu rates for radio bursts. Here, we focus on evaluating the event rate in variables that are most useful to observers. The burst at source occurs with a certain duration and flux. However...