As an extension of ΛCDM, the decaying vacuum model (DV) describes the dark energy as a varying vacuum whose energy density decays linearly with the Hubble parameter in the late-times, ρ Λ (t) ∝ H(t), and produces the matter component. We examine the high-z cosmic age problem in the DV model, and compare it with ΛCDM and the Yang-Mills condensate (YMC) dark energy model. Without employing a dynamical scalar field for dark energy, these three models share a similar behavior of late-time evolution. It is found that the DV model, like YMC, can accommodate the high-z quasar APM 08279+5255, thus greatly alleviates the high-z cosmic age problem. We also calculate the Statefinder (r, s) and the Om diagnostics in the model. It is found that the evolutionary trajectories of r(z) and s(z) in the DV model are similar to those in the kinessence model, but are distinguished from those in ΛCDM and YMC. The Om(z) in DV has a negative slope and its height depends on the matter fraction, while YMC has a rather flat Om(z), whose magnitude depends sensitively on the coupling. *

Co9S8@S,N-doped carbon materials derived from S,N-containing Co-MOFs exhibited superior performance as bifunctional oxygen electrocatalysts and supercapacitor electrode materials.

We study the impact of a running index α t on the spectrum of relic gravitational waves (RGWs) over the whole range of frequency (10 −18 ∼ 10 10 ) Hz and reveal its implications in RGWs detections and in cosmology. Analytical calculations show that, although the spectrum of RGWs on low frequencies is less affected by α t = 0, but, on high frequencies, the spectrum is modified substantially. Investigations are made toward potential detections of the α t -modified RGWs for several kinds of current and planned detectors. The Advanced LIGO will likely be able to detect RGWs with α t ≥ 0 for inflationary models with the inflation index β = −1.956 and the tensor-scalar ratio r = 0.55. The future LISA can detect RGWs for a much broader range of (α t , β, r), and will have a better chance to break a degeneracy between them. Constraints on α t are estimated from several detections and cosmological observations. Among them, the most stringent one is from the bound of the Big Bang nucleosynthesis (BBN), and requires α t < 0.008 rather conservatively for any reasonable (β, r), preferring a nearly power-law spectrum of RGWs. In light of this result, one would expect the scalar running index α s to be of the same magnitude as α t , if both RGWs and scalar perturbations are generated by the same scalar inflation.

According to the CMB observations, Mielczarek ([40]) evaluated the reheating temperature, which could help to determine the history of the Universe. In this paper, we recalculate the reheating temperature using the new data from WMAP 7 observations. Based on that, we list the approximate solutions of relic gravitational waves (RGWs) for various frequency bands. With the combination of the quantum normalization of RGWs when they are produced and the CMB observations, we obtain the relation between the tensor-to-scalar ratio r and the inflation index β for a given scalar spectral index ns. As a comparison, the diagram r − β in the slow-roll inflation model is also given. Thus, the observational limits of r from CMB lead to the constraints on the value of β. Then, we illustrate the energy density spectrum of RGWs with the quantum normalization for different values of r and the corresponding β. For comparison, the energy density spectra of RGWs with parameters based on slow-roll inflation are also discussed. We find that the values of ns affect the spectra of RGWs sensitively in the very high frequencies. Based on the current and planed gravitational wave detectors, we discuss the detectabilities of RGWs.PACS number: 98.80.Es, 98.80.Cq

We have constructed a new timescale, TT(IPTA16), based on observations of radio pulsars presented in the first data release from the International Pulsar Timing Array (IPTA). We used two analysis techniques with independent estimates of the noise models for the pulsar observations and different algorithms for obtaining the pulsar timescale. The two analyses agree within the estimated uncertainties and both agree with TT(BIPM17), a post-corrected timescale produced by the Bureau International des Poids et Mesures (BIPM). We show that both methods could detect significant errors in TT(BIPM17) if they were present. We estimate the stability of the atomic clocks from which TT(BIPM17) is derived using observations of four rubidium fountain clocks at the US Naval Observatory. Comparing the power spectrum of TT(IPTA16) with that of these fountain clocks suggests that pulsar-based timescales are unlikely to contribute to the stability of the best timescales over the next decade, but they will remain a valuable independent check on atomic timescales. We also find that the stability of the pulsar-based timescale is likely to be limited by our knowledge of solar-system dynamics, and that errors in TT(BIPM17) will not be a limiting factor for the primary goal of the IPTA, which is to search for the signatures of nano-Hertz gravitational waves.

A facile method was developed to synthesize ultrafine Ni–Co alloy nanoparticles embedded into 3D porous graphitic carbon, an excellent electrode material for supercapacitors.

In the non-standard model of relic gravitational waves (RGWs) generated in the early universe, the theoretical spectrum of is mainly described by an amplitude r and a spectral index β, the latter usually being determined by the slope of the inflation potential. Pulsar timing arrays (PTAs) data have imposed constraints on the amplitude of strain spectrum for a power-law form as a phenomenological model. Applying these constraints to a generic, theoretical spectrum with r and β as independent parameters, we convert the PTAs constraint into an upper bound on the index β, which turns out to be less stringent than those upper bounds from BBN, CMB, and LIGO/VIRGO, respectively. Moreover, it is found that PTAs constrain the non-standard RGWs more stringent than the standard RGWs. If the condition of the quantum normalization is imposed upon a theoretical spectrum of RGWs, r and β become related. With this condition, a minimum requirement of the horizon size during inflation is greater than the Planck length results in an upper bound on β, which is comparable in magnitude to that by PTAs. When both PTAs and the quantum normalization are applied to a theoretical spectrum of RGWs, constraints can be obtained for other cosmic processes of the early universe, such as the reheating, a process less understood observationally so far. The resulting constraint is consistent with the slow-roll, massive scalar inflation model. The future SKA will be able to constrain RGWs further and might even detect RGWs, rendering an important probe to the very early universe.

CoNi alloy nanoparticles incorporated into S,N-doped carbon structure was obtained by pyrolysis treatment of 2D S,N-containing Co/Ni MOFs nanosheets, as electrode material exhibiting high supercapacitor performance.