Unified Dark Matter in Scalar Field Cosmologies

Considering the general Lagrangian of k-essence models, we study and classify them through variables connected to the fluid equation of state parameter w_\kappa. This allows to find solutions around which the scalar field describes a mixture of dark matter and cosmological constant-like dark energy, an example being the purely kinetic model proposed by Scherrer. Making the stronger assumption that the scalar field Lagrangian is exactly constant along solutions of the equation of motion, we find a general class of k-essence models whose classical trajectories directly describe a unified dark matter/dark energy (cosmological constant) fluid. While the simplest case of a scalar field with canonical kinetic term unavoidably leads to an effective sound speed c_s=1, thereby inhibiting the growth of matter inhomogeneities, more general non-canonical k-essence models allow for the possibility that c_s << 1 whenever matter dominates

Cosmic Microwave Background Anisotropies up to Second Order

These lecture notes present the computation of the full system of Boltzmann equations describing the evolution of the photon, baryon and cold dark matter fluids up to second order in perturbation theory, as recently studied in (Bartolo, Matarrese & Riotto 2006, 2007). These equations allow to follow the time evolution of the cosmic microwave background anisotropies at all angular scales from the early epoch, when the cosmological perturbations were generated, to the present, through the recombination era. The inclusion of second-order contributions is mandatory when one is interested in studying possible deviations from Gaussianity of cosmological perturbations, either of primordial (e.g. inflationary) origin or due to their subsequent evolution. Most of the emphasis in these lectures notes will be given to the derivation of the relevant equations for the study of cosmic microwave background anisotropies and to their analytical solutions

Superfield theories on S 3 and their localization

We consider the superfield formulation of supersymmetric gauge and matter field theories on a three-dimensional sphere with rigid $\mathcal{N}$ = 2 supersymmetry, as well as with $\mathcal{N}$ > 2. The construction is based on a supercoset SU(2 | 1)/U(1) containing S 3 as the bosonic subspace. We derive an explicit form of SU(2 | 1)/U(1) supervielbein and covariant derivatives, and use them to construct classical superfield actions for gauge and matter supermultiplets in this superbackground. We then apply superfield methods for computing one-loop partition functions of these theories and demonstrate how the localization technique works directly in the superspace

Spectroscopy of Low Energy Neutrinos from the Sun

Two methods are discussed for the solar neutrino spectroscopy in the sub-MeV region: absorption in a loaded liquid scintillator and elastic scattering in a TPC. The different neutrino oscillation solutions predict a strong effect in this energy region where the largest fraction (\sim 98%) of solar neutrinos lies. Both projects have reached the stage where they have to prove their capability to attain a background low enough for solar neutrino detection

A novel architecture for DAQ in multi-channel, large volume, long drift Liquid Argon TPC

Recently a large interest has been shown for multi-ton Liquid Argon Time-Projection-Chambers (LAr-TPC). The physics issues are very challenging, but the technical problem of long drifts and adequately long life-time of free electrons are not solved at all so far. Also one should take into account the extremely large number of channels required for such large volumes. In this paper we propose an architecture for DAQ that is based on recent developments in consumer electronics that made available, at a quite interesting price, components aimed to high-resolution delta-sigma conversion. This type of ADC is not at all popular in HEP experiments where normally signals related to events, well defined in time (triggered), should be converted and recorded. In the LAr-TPC however we have to deal rather with waveforms that should be converted and recorded continuously, that is the paramount case of delta-sigma ADC application

Possibly Large Corrections to the Inflationary Observables

We point out that the theoretical predictions for the inflationary observables may be generically altered by the presence of fields which are heavier than the Hubble rate during inflation and whose dynamics is usually neglected. They introduce corrections which may be easily larger than both the second-order contributions in the slow-roll parameters and the accuracy expected in the forthcoming experiments

B-mode polarization of the CMB from the second-order photon quadrupole

We study a new contribution to the polarization of the Cosmic Microwave Background induced at the epoch of recombination by the second-order quadrupole moment of the photon distribution. At second order in perturbation theory the quadrupole moment is not suppressed by the inverse of the optical depth in the tight coupling limit, as it happens at first order in perturbation theory. We concentrate on the B-mode CMB polarization and find that such a novel contribution constitutes a contamination in the detection of the primordial tensor modes if the tensor to scalar ratio r is smaller than a few x 10^{-5}. The magnitude of the effect is larger than the B-mode due to secondary vector/tensor perturbations and the analogous effect generated during the reionization epoch, while it is smaller than the contamination produced by the conversion of polarization of type E into type B, by weak gravitational lensing. However the lensing signal can be cleaned, making the secondary modes discussed here the actual contamination limiting the detection of small amplitude primordial gravitational waves if r is below \simeq 10^{-5}

|q/p| Measurement from B0->D*l nu Partial Reconstruction

We present a new measurement of CP violation induced by B0 B0bar oscillations, based on the full data set collected by the BaBar experiment at the PEPII collider. We use a sample of about 6 million B0->D* l nu decays selected with partial reconstruction of the D* meson. The charged lepton identifies the flavor of the first B meson at its decay time, the flavor of the other B is determined by kaon tagging. We determine the parameter dCP = 1 - |q/p| = (0.29+-0.84+1.78/-1.61) 10^-3

Order and anarchy hand in hand in 5D SO(10)

We update a five-dimensional SO(10) grand unified model of fermion masses and mixing angles originally proposed by Kitano and Li. In our setup Yukawa couplings are anarchical and quark and lepton sectors are diversified by the profiles of the fermion zero modes in the extra dimension. The breaking of SO(10) down to SU(5)×U(1) X provides the key parameter that distinguishes the profiles of the different SU(5) components inside the same 16 representation. With respect to the original version of the model, we extend the Higgs sector to explicitly solve the doublet-triplet splitting problem through the missing partner mechanism and we perform a fit to an idealized set of data. By scanning the Yukawa couplings of the model we find that, for large tan β , both normal and inverted ordered neutrino spectrum can be accommodated. However, while the case of inverted order requires a severe fine tuning of the Yukawa parameters, the normal ordering is compatible with an anarchical distribution of Yukawa couplings. Thus, in a natural portion of the parameter space, the model predicts a normal ordered neutrino spectrum, the lightest neutrino mass below 5 meV, and | m ββ | in the range 0.1-5 meV. No particular preference is found for the Dirac CP phase in the lepton sector while the right-handed neutrino masses are too small to explain the baryon asymmetry of the universe through thermal leptogenesis

An Equivalent Gauge and the Equivalence Theorem

I describe a novel covariant formulation of massive gauge theories in which the longitudinal polarization vectors do not grow with the energy. Therefore in the present formalism, differently from the ordinary one, the energy and coupling power-counting is completely transparent at the level of individual Feynman diagrams, with obvious advantages both at the conceptual and practical level