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We show a text-book potential for single-field inflation, namely, the Coleman-Weinberg model can induce double inflation and formation of primordial black holes (PBHs), because fluctuations that leave the horizon near the end of first inflation are anomalously enhanced at the onset of second inflation when the time-dependent mode turns to a growing mode rather than a decaying mode. The mass of PBHs produced in this mechanism lies in several discrete ranges depending on the model parameters. We also calculate the effects of non-Gaussian statistics due to higher-order interactions on the abundance of PBHs, which turns out to be small.

Abstract. Thermal history of the universe after big-bang nucleosynthesis (BBN) is well understood both theoretically and observationally, and recent cosmological observations also begin to reveal the inflationary dynamics. However, the epoch between inflation and BBN is scarcely known. In this paper we show that the detection of the stochastic gravitational wave background around 1Hz provides useful information about thermal history well before BBN. In particular, the reheating temperature of the universe may be determined by future space-based laser interferometer experiments such as DECIGO and/or BBO if it is around 10 6−9 GeV, depending on the tensor-toscalar ratio r and dilution factor F .Probing reheating temperature of the universe with gravitational wave background 2

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We use 47 gravitational wave sources from the Third LIGO–Virgo–Kamioka Gravitational Wave Detector Gravitational Wave Transient Catalog (GWTC–3) to estimate the Hubble parameter H(z), including its current value, the Hubble constant H 0. Each gravitational wave (GW) signal provides the luminosity distance to the source, and we estimate the corresponding redshift using two methods: the redshifted masses and a galaxy catalog. Using the binary black hole (BBH) redshifted masses, we simultaneously infer the source mass distribution and H(z). The source mass distribution displays a peak around 34 M ⊙, followed by a drop-off. Assuming this mass scale does not evolve with the redshift results in a H(z) measurement, yielding H 0 = 68 − 8 + 12 km s − 1 Mpc − 1 (68% credible interval) when combined with the H 0 measurement from GW170817 and its electromagnetic counterpart. This represents an improvement of 17% with respect to the H 0 estimate from GWTC–1. The second method associates each GW event with its probable host galaxy in the catalog GLADE+, statistically marginalizing over the redshifts of each event’s potential hosts. Assuming a fixed BBH population, we estimate a value of H 0 = 68 − 6 + 8 km s − 1 Mpc − 1 with the galaxy catalog method, an improvement of 42% with respect to our GWTC–1 result and 20% with respect to recent H 0 studies using GWTC–2 events. However, we show that this result is strongly impacted by assumptions about the BBH source mass distribution; the only event which is not strongly impacted by such assumptions (and is thus informative about H 0) is the well-localized event GW190814.

The three-year WMAP(WMAP3), combined with other cosmological observations from galaxy clustering and Type Ia Supernova (SNIa), prefers a non-vanishing running of the primordial spectral index independent of the low CMB multipoles. Motivated by this feature we study cosmological constraint on the neutrino mass, which severely depends on what prior we adopt for the spectral shape of primordial fluctuations, taking possible running into account. As a result we find a more stringent constraint on the sum of the three neutrino masses, mν < 0.76eV (2 σ), compared with mν < 0.90eV (2 σ) for the case where power-law prior is adopted to the primordial spectral shape. PACS number(s): 98.80.CqThe three year Wilkinson Microwave Anisotropy Probe observations (WMAP3) [1,2,3,4, 5] have marked another milestone on the precision cosmology of the Cosmic Microwave Background (CMB) Radiation. The simplest six-parameter power-law ΛCDM cosmology is in remarkable agreement with WMAP3 together with the large scale structure(LSS) of galaxy clustering as measured by 2dF [6] and SDSS [7] and with the Type Ia Supernova (SNIa) as measured by the Riess "gold" sample [8] and the first year SNLS [9]. This agreement between the above "canonical" cosmological model and observations can be used to test a number of possible new physics, such as the equation of state of dark energy, neutrino masses, time variation of fundamental constants, etc.Among them, the constraint on the neutrino or hot dark matter mass can be obtained from the freestreaming modification of the transfer function of the matter power spectrum. We should note, however, that if one allowed any shape of primordial spectrum, the freestreaming effect could easily be compensated by some nontrivial shape of the primordial spectrum, so that one cannot obtain sensible limit on the neutrino mass. That is, we can obtain a nontrivial bound on neutrino mass if and only if we adopt some prior on the shape of primordial power spectrum such as a simple power-law. From the above argument, we expect that as we allow more degrees of freedom on the primordial spectrum beyond a power-law, the constraint on the neutrino mass would be less stringent in general.As for the shape of the primordial power spectrum, it is noteworthy that a significant deviation has been observed by WMAP3 from the simplest Harrison-Zel'dovich spectrum, and that this feature is more eminent with the combination of all the currently available CMB, LSS and SNIa (dubbed the case of "All" in [5]). Moreover, a nontrivial negative running of the scalar spectral index α s , whose existence was studied even before WMAP epoch [10,11], was favored by the first-year WMAP papers [12,13,14]. But its preference was somehow diminished as corrections to the likelihood functions were made [15].However, the new WMAP3 data prefers again a negative running in the "All" combination [5].If confirmed, a nonvanishing running of α s would not only constrain inflationary cosmology significantly [16,17,18,19,20,21], but also affect the cosmological c...

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We probe the scale dependence of the primordial spectrum in the light of the three-year WMAP (WMAP3) alone and WMAP3 in combination with the other cosmological observations such as galaxy clustering and Type Ia Supernova (SNIa). We pay particular attention to the combination with the Lyman α (Lyα) forest. Different from the first-year WMAP (WMAP1), WMAP3's preference on the running of the scalar spectral index on the large scales is now fairly independent of the low CMB multipoles ℓ. A combination with the galaxy power spectrum from the Sloan Digital Sky Survey (SDSS) prefers a negative running to larger than 2σ, regardless the presence of low ℓ CMB (2 ≤ ℓ ≤ 23) or not. On the other hand if we focus on the Power Law ΛCDM cosmology with only six parameters (matter density Ωmh 2 , baryon density Ω b h 2 , Hubble Constant H0, optical depth τ , the spectral index, ns, and the amplitude, As, of the scalar perturbation spectrum) when we drop the low ℓ CMB contributions WMAP3 is consistent with the Harrison-Zel'dovich-Peebles scale-invariant spectrum (ns = 1 and no tensor contributions) at ∼ 1σ. When assuming a simple power law primordial spectral index or a constant running, in case one drops the low ℓ contributions (2 ≤ ℓ ≤ 23) WMAP3 is consistent with the other observations better, such as the inferred value of σ8. We also find, using a spectral shape with a minimal extension of the running spectral index model, LUQAS+ CROFT Lyα and SDSS Lyα exhibit somewhat different preference on the spectral shape.PACS number(s): 98.80.Es, 98.80.Cq