119208212
Tachyon and Quintessence in Brane-Worlds
Using tachyon or quintessence fields along with a barotropic fluid on the brane we examine the different cosmological stages in a Friedmann-Robertson-Walker universe, from the first radiation scenario to the later era dominated by cosmic string networks. We introduce a new algorithm to generalize previous works on exact solutions and apply it to study tachyon and quintessence fields localized on the brane. We also explore the low and high energy regimes of the solutions. Besides, we show that the tachyon and quintessence fields are driven by an inverse power law potential. Finally, we find several simple exacts solutions for tachyon and/or quintessence fields.
119269872
SELF-INTERACTING HOLOGRAPHIC DARK ENERGY
We investigate a spatially flat Friedmann–Robertson–Walker (FRW) universe where dark matter exchanges energy with a self-interacting holographic dark energy (SIHDE). Using the χ2-statistical method on the Hubble function, we obtain a critical redshift that seems to be consistent with both BAO and CMB data. We calculate the theoretical distance modulus for confronting with the observational data of SNe Ia for small redshift z ≤ 0.1 and large redshift 0.1 ≤ z ≤ 1.5. The model gets accelerated faster than the ΛCDM one and it can be a good candidate to alleviate the coincidence problem. We also examine the age crisis at high redshift associated with the old quasar APM 08279+5255.
122190148
A mass-selecting apparatus to measure the energy loss of fission fragments in gases
Abstract We describe an apparatus combining solid-state and gas ionization chamber techniques to measure — for both fragments released in a fission event — the energy lost in a given gaseous range and the residual energy. This device allows to measure the energy loss in gases of fission fragments selecting their masses The performances of the apparatus are discussed referring to the data obtained by slowing down fission fragments from 252 Cf in gaseous argon.
122896950
Measurement of parity nonconserving neutron spin rotation in lanthanum
The rotation, phi/sub pnc/, of a neutron beam polarization vector due to parity nonconserving forces is measured in a lanthanum target. It is found that phi/sub pnc//l = -(21.9 +- 2.9) x 10- /sup 5/ rad/cm, where the negative sign corresponds to a left-handed rotation of the neutron spin about its momentum.