Dark energy properties in DBI theory

Abstract

The Dirac-Born-Infeld (DBI) action from string theory provides several new classes of dark energy behavior beyond quintessence due to its relativistic kinematics. We constrain parameters of natural potentials and brane tensions with cosmological observations as well as showing how to design these functions for a desired expansion history. We enlarge the attractor solutions, including new ways of obtaining cosmological constant behavior, to the case of generalized DBI theory with multiple branes. An interesting novel signature of DBI attractors is that the sound speed is driven to zero, unlike for quintessence where it is the speed of light.

Recent Results from the LHCf Experiment

“…The energy spectrum of photons and the transverse momentum spectra of π 0 s were already published [9,10]. Figure 2 shows the transverse momentum spectrum of π 0 s measured by LHCf (black dots) with predictions of several hadronic interaction models (colored lines) [11][12][13][14][15]. The best agreement with LHCf data is given by EPOS1.99 in the models.…”

“…The black dots and the shaded area show LHCf data and the uncertainties. The color lines indicate the predictions by several hadron interaction models [11][12][13][14][15].…”

Studies of Muons in Extensive Air Showers from Ultra-High Energy Cosmic Rays Observed with the Telescope Array Surface Detector

“…In the energy range, the composition of the primary cosmic rays is consistent with proton within statistical and systematic errors by X max measurement using the TA FD [6][7][8][9], thus we use the MC for proton primaries. The experimental data is compared with the MC using the hadronic models QGSJET II-03, QGSJET II-04 [10], Epos 1.99 [11] and Sibyll 2.1 [12].…”

Measurement of the atmospheric muon neutrino energy spectrum with IceCube in the 79- and 86-String configuration

“…2. The theoretical flux predictions obtained for two hadronic interaction models (SYBILL-2.1 [15] and QGSJET-II [16]) are depicted together with the expected prompt flux according to the model by Enberg et al (ERS) [17]. The spectrum obtained using IceCube in the 59-string configuration (brown) is shown for comparison [6].…”