118344847
Differentiating CDM and Baryon Isocurvature Models with 21 cm Fluctuations
We discuss how one can discriminate models with cold dark matter (CDM) and baryon isocurvature fluctuations. Although current observations such as cosmic microwave background (CMB) can severely constrain the fraction of such isocurvature modes in the total density fluctuations, CMB cannot differentiate CDM and baryon ones by the shapes of their power spectra. However, the evolution of CDM and baryon density fluctuations are different for each model, thus it would be possible to discriminate those isocurvature modes by extracting information on the fluctuations of CDM/baryon itself. We discuss that observations of 21 cm fluctuations can in principle differentiate these modes and demonstrate to what extent we can distinguish them with future 21 cm surveys. We show that, when the isocurvature mode has a large blue-tilted initial spectrum, 21 cm surveys can clearly probe the difference.
119229900
Neutrino mass from cosmology: impact of high-accuracy measurement of the Hubble constant
Non-zero neutrino mass would affect the evolution of the Universe in observable ways, and a strong constraint on the mass can be achieved using combinations of cosmological data sets. We focus on the power spectrum of cosmic microwave background (CMB) anisotropies, the Hubble constant H0, and the length scale for baryon acoustic oscillations (BAO) to investigate the constraint on the neutrino mass, mν. We analyze data from multiple existing CMB studies (WMAP5, ACBAR, CBI, BOOMERANG, and QUAD), recent measurement of H0 (SHOES), with about two times lower uncertainty (5 %) than previous estimates, and recent treatments of BAO from the Sloan Digital Sky Survey (SDSS). We obtained an upper limit of mν < 0.2eV (95 % C.L.), for a flat ΛCDM model. This is a 40 % reduction in the limit derived from previous H0 estimates and one-third lower than can be achieved with extant CMB and BAO data. We also analyze the impact of smaller uncertainty on measurements of H0 as may be anticipated in the near term, in combination with CMB data from the Planck mission, and BAO data from the SDSS/BOSS program. We demonstrate the possibility of a 5σ detection for a fiducial neutrino mass of 0.1 eV or a 95 % upper limit of 0.04 eV for a fiducial of mν = 0 eV. These constraints are about 50 % better than those achieved without external constraint. We further investigate the impact on modeling where the dark-energy equation of state is constant but not necessarily -1, or where a non-flat universe is allowed. In these cases, the next-generation accuracies of Planck, BOSS, and 1 % measurement of H0 would all be required to obtain the limit mν < 0.05−0.06 eV (95 % C.L.) for the fiducial of mν = 0 eV. The independence of systematics argues for pursuit of both BAO and H0 measurements.
11074877
Constraining SuperWIMPy and Warm Subhalos with Future Submillilensing
Abstract We propose to observe QSO-galaxy strong lens systems to give a new constraint on the damping scale of the initial fluctuations. We find that the future observation of submilliarc scale astrometric shifts of the multiple lensed images of QSOs would find ∼ 10 ( 3 – 9 ) M ⊙ subhalos inside the macrolens halo. The superweakly interacting massive particles (superWIMPs) produced from a WIMP decay and the warm dark matter (WDM) particles that predict a comoving damping scale larger than ∼ 2 kpc can be constrained if ∼ 10 3 M ⊙ subhalos are detected.
14635411
Bigger Rip with no dark energy
Abstract By studying a modified Friedmann equation which arises in an extension of general relativity which accommodates a time-dependent fundamental length L ( t ), we consider cosmological models where the scale factor diverges with an essential singularity at a finite future time. Such models have no dark energy in the conventional sense of energy possessing a simple pressure–energy relationship. Data on supernovae restrict the time from the present until the Rip to be longer than the current age of the Universe.
8518266
On the determination of neutrino masses and dark energy evolution from the cross-correlation of CMB and LSS
We discuss the possibilities of the simultaneous determination of the neutrino masses and the evolution of dark energy from future cosmological observations such as cosmic microwave background (CMB), large scale structure (LSS) and the cross-correlation between them. Recently it has been discussed that there is a degeneracy between the neutrino masses and the equation of state for dark energy. It is also known that there are some degeneracies among the parameters describing the dark energy evolution. We discuss the implications of these for the cross-correlation of CMB with LSS in some detail. Then we consider to what extent we can determine the neutrino masses and the dark energy evolution using the expected data from CMB, LSS and their cross-correlation.
19015148
Correlated Isocurvature Fluctuation of Quintessence and Curvaton Scenario
We consider cosmic microwave background (CMB) anisotropy in models with quintessence taking into account of isocurvature fluctuation in the quintessence. It is shown that, if the primordial fluctuation of the quintessence has a correlation with the adiabatic density fluctuations, CMB angular power spectrum $C_l$ at low multipoles can be suppressed. Possible scenario of generating correlated mixture of the quintessence and adiabatic fluctuations is also discussed.
14617932
CONFORMAL ANOMALY OF STRING THEORY IN THE HARMONIC GAUGE
Considering the conformal anomaly in an effective action, the critical dimension of string theory can be determined in the harmonic gauge, in which it had been previously reported to be indefinite. In this gauge, there is no anomaly for the ghost number symmetry. This can be naturally understood in terms of the Faddeev-Popov conjugation in the theory.
11103294
Level truncation analysis of exact solutions in open string field theory
We evaluate vacuum energy density of Schnabl's solution using the level truncation calculation and the total action including interaction terms. The level truncated solution provides vacuum energy density expected both for tachyon vacuum and trivial pure gauge. We discuss the role of the phantom term to reproduce correct vacuum energy.
119022863
BRS Invariance of Unoriented Open-Closed String Field Theory.
We present the full action for the unoriented open-closed string field theory which is based on the \alpha=p^+ HIKKO type vertices. The BRS invariance of the action is proved up to the terms which are expected to cancel the anomalous one-loop contributions. This implies that the system is invariant under the gauge transformations with open and closed string field parameters up to the anomalies.
119301405
Homotopy operators and identity-based solutions in cubic superstring field theory
We construct a class of nilpotent operators using the BRST current and ghost fields in superstring theory. The operator can be realized in cubic superstring field theory as a kinetic operator in the background of an identity-based solution. For a particular type of the deformed BRST operators, we find a homotopy operator and discuss its relationship to the cohomology in a similar way to the bosonic case, which has been elaborated by the authors.
120125275
Applications and Imaging Techniques of a Si/CdTe Compton Gamma-Ray Camera
Abstract By using a new Compton camera consisting of a silicon double-sided strip detector (Si-DSD) and a CdTe doublesided strip detector (CdTe-DSD), originally developed for the ASTRO-H satellite mission, an experiment involving imaging radioisotopes was conducted to study their feasibility for hotspot monitoring. In addition to the hotspot imaging already provided by commercial imaging systems, identification of various radioisotopes is possible thanks to the good energy resolution obtained by the semiconductor detectors. Three radioisotopes of 133 Ba (356 keV), 22 Na (511 keV) and 137 Cs (662 keV) were individually imaged by applying event selection in the energy window and the gamma-ray images were correctly overlapped by an optical picture. Detection efficiency of 1.68 ×10 −4 (effective area: 1.7×10 −3 cm 2 ) and angular resolution of 3.8 degrees were obtained by stacking five detector modules for a 662 keV gamma ray. The higher detection efficiency required in specific use can be achieved by stacking more detector modules.