A modified Mottola-Wipf model with sphaleron and instanton fields

We modify the Mottola-Wipf O(3) sigma model by extending it with a Skyrme term. The resulting model supports a localised instanton solution, as well as sphaleron solution in the static limit.     

Electroweak baryogenesis from late neutrino masses

Electroweak baryogenesis, given a first-order phase transition, does not work in the standard model because the quark Yukawa matrices are too hierarchical. On the other hand, the neutrino mass matrix is apparently not hierarchical. In models with neutrino mass generation at low scales, the neutrino Yukawa couplings lead to large CP violation in the reflection probability of heavy leptons by the expanding Higgs bubble wall, and can generate the observed baryon asymmetry of the universe. The mechanism predicts new vectorlike leptons below the TeV scale and sizable mu --> e processes.     

Asymmetric dark matter from hidden sector baryogenesis

We consider the production of asymmetric dark matter during hidden sector baryogenesis. We consider a particular supersymmetric model where the dark matter candidate has a number density approximately equal to the baryon number density, with a mass of the same scale as the b, c and τ. Both baryon asymmetry and dark matter are created at the same time in this model. We describe collider and direct detection signatures of this model.     

Primordial magnetic fields and dynamos from parity violated torsion

It is well known that torsion induced magnetic fields may seed galactic dynamos, but the price one pays for that is the conformal and gauge invariance breaks and a tiny photon mass. More recently I have shown [L.C. Garcia de Andrade, Phys. Lett. B 468 (2011) 28] that magnetic fields decay in a gauge invariant non-minimal coupling theory of torsion is slow down, which would allow for dynamo action to take place. In this Letter, by adding a parity violation term of the type _Rμνρσ?^μνρσ$R_{\mu \nu \rho \sigma }{?}^{\mu \nu \rho \sigma }$ to the non-coupling term, a magnetic dynamo equation is obtained. From dynamo equation it is shown that torsion terms only appear in the dynamo equation when diffusion in the cosmic plasma is present. Torsion breaks the homogeneity of the magnetic field in the universe. Since Zeldovich anti-dynamo theorem assumes that the spacetime should be totally flat, torsion is responsible for violation of anti-dynamo theorem in 2D spatial dimensions. Contrary to previous results torsion induced primordial magnetic fields cannot seed galactic dynamos since from torsion and diffusion coefficient the decaying time of the magnetic field is 10⁶yrs${10}^{6}yrs$, which is much shorter than the galaxy age.     

Out-of-plane spin polarization from in-plane electric and magnetic fields

We show that the joint effect of spin-orbit and magnetic fields leads to a spin polarization perpendicular to the plane of a homogeneous two-dimensional electron system with Rashba spin-orbit coupling and in-plane parallel dc magnetic and electric fields, for angle-dependent impurity scattering or nonparabolic energy spectrum, while only in-plane polarization persists for simplified models. We derive Bloch equations, describing the main features of recent experiments, including the magnetic field dependence of static and dynamic responses.     

Helical magnetic structures in cubic perovskites

One-dimensional helical structures with a finite Hund interaction have been considered in detail. The analytical expressions for the electron spectrum of charge carriers in simplest one-dimensional and three-dimensional helical structures in a simple cubic lattice, which simulates the manganese sublattice in the crystal structure of perovskite, have been derived in the tight-binding approximation. It has been shown that this approach can explain qualitatively the formation of the antiferromagnetic A structure in LaMnO₃.     

Metric-torsion decay of non-adiabatic chiral helical magnetic fields against chiral dynamo action in bouncing cosmological models

Metric-torsion effects on chiral massless fermions are investigated in the realm of the adiabatic amplification of cosmological magnetic fields (CMFs) in a general relativistic framework and in the framework of Einstein–Cartan (EC) bouncing cosmologies. In GR the chiral effect is proportional to the Hubble factor and the solution of the dynamo equation leads to an adiabatic magnetic field, while in Einstein–Cartan bouncing cosmology we have non-adiabatic magnetic fields where the breaking of adiabaticity is given by a torsion term. Using a EWPT magnetic field of the order of \(B_{\text {seed}}\sim {10^{24}}\) G at 5 pc scale, we obtain a CMF in EC of the order of \(10^{-10}\) G, which is still able to seed a galactic dynamo which amplifies this field up to galactic magnetic fields of four orders of magnitude, which is a mild dynamo. In the case of massive chiral fermions it is shown that torsion actually attenuated the convective dynamo term in the dynamo equation obtained from the QED of an electron–positron pair \(e^{-}e^{+}\). Chiral effects on general relativity may lead to strong magnetic fields of the order of \(\sim {10^{18}}\) G at the early universe resulting from pure metric effects. Strong magnetic fields of the order of \(B_{\text {metric}-\text {torsion}}\sim {10^{8}}\) G may be obtained from very strong seed fields. At 1 Mpc scale of the present universe a galactic dynamo seed of the order of \(10^{-19}\) G is found. It is shown in this paper that chiral dynamo effects in the expanded universe can be obtained if one takes into account the speed of the cosmic plasma.     

Dark sector production and baryogenesis from not quite black holes

Primordial black holes have been considered attractive dark matter candidates,whereas some of the pre-dictions rely heavily on the near-horizon physics that rem...     

Complex hybrid inflation and baryogenesis

We propose a hybrid inflation model with a complex waterfall field which contains an interaction term that breaks the U(1) global symmetry associated with the waterfall field charge. We show that the asymmetric evolution of the real and imaginary parts of the complex field during the phase transition at the end of inflation translates into a charge asymmetry. The latter strongly depends on the vacuum expectation value of the waterfall field, which is well constrained by diverse cosmological observations.     

Cosmological magnetic fields

Magnetic fields are observed not only in stars, but in galaxies, clusters, and even high redshift Lyman-α systems. In principle, these fields could play an important role in structure formation and also affect the anisotropies in the cosmic microwave background radiation (CMB). The study of cosmological magnetic fields aims not only to quantify these effects on large-scale structure and the CMB, but also to answer one of the outstanding puzzles of modern cosmology: when and how do magnetic fields originate? They are either primoridial, i.e. created before the onset of structure formation, or they are generated during the process of structure formation itself.     

Fluctuating magnetic fields

Some problems pertaining to the behaviour of a classical spin under the influence of a random Gaussian magnetic field are discussed. It is shown that, in agreement with simple expectations, the magnetic moment is effectively decreased to lowest order. Various physical applications and connections with group theory are pointed out.     

Reflection of neutrons from a magnetic film placed in static and oscillating magnetic fields

Measurements of polarized-neutron reflection from magnetic films placed in a static magnetic field and in an oscillating magnetic field perpendicular to it are described. The process of diffuse neutron scattering involving energy transfer from a RF electromagnetic field to neutrons has been studied. Neutron magnetic resonance has been detected, and splitting of the polarized beam of neutrons reflected from a film has been discovered.