Although technical trading rules have been widely used by practitioners in financial markets, their profitability still remains controversial. We here investigate the profitability of moving average (MA) and trading range break (TRB) rules by using t
he Shanghai Stock Exchange Composite Index (SHCI) from May 21, 1992 through December 31, 2013 and Shenzhen Stock Exchange Composite Index (SZCI) from April 3, 1991 through December 31, 2013. The $t$-test is adopted to check whether the mean returns which are conditioned on the trading signals are significantly different from unconditioned returns and whether the mean returns conditioned on the buy signals are significantly different from the mean returns conditioned on the sell signals. We find that TRB rules outperform MA rules and short-term variable moving average (VMA) rules outperform long-term VMA rules. By applying Whites Reality Check test and accounting for the data snooping effects, we find that the best trading rule outperforms the buy-and-hold strategy when transaction costs are not taken into consideration. Once transaction costs are included, trading profits will be eliminated completely. Our analysis suggests that simple trading rules like MA and TRB cannot beat the standard buy-and-hold strategy for the Chinese stock exchange indexes.
We revisit the possibility and detectability of a stochastic gravitational wave background (SGWB) produced by a cosmological population of newborn neutron stars (NSs) with r-mode instabilities. We show that the resultant SGWB is insensitive to the ch
oice of CSFR models, but depends strongly on the evolving behavior of CSFR at low redshifts. Our results show that the dimensionless energy density $Omega_{rm{GW}}$ could have a peak amplitude of $simeq (1-3.5) times10^{-8}$ in the frequency range $(200-1000)$~Hz. However, such a high mode amplitude is unrealistic as it is known that the maximum value is much smaller and at most $10^{-2}$. A realistic estimate of $Omega_{rm{GW}}$ should be at least 4 orders of magnitude lower ($sim 10^{-12}$), which leads to a pessimistic outlook for the detection of r-mode background. We consider different pairs of terrestrial interferometers (IFOs) and compare two approaches to combine multiple IFOs in order to evaluate the detectability of this GW background. Constraints on the total emitted GW energy associated with this mechanism to produce a detectable stochastic background are $sim 10^{-3} M_{odot} c^2$ for two co-located advanced LIGO detectors, and $2 times 10^{-5} M_{odot} c^2$ for two Einstein Telescopes. These constraints may also be applicable to alternative GW emission mechanisms related to oscillations or instabilities in NSs depending on the frequency band where most GWs are emitted.
Galaxy clusters have their unique advantages for cosmology. Here we collect a new sample of 10 lensing galaxy clusters with X-ray observations to constrain cosmological parameters.The redshifts of lensing clusters lie between 0.1 and 0.6, and the red
shift range of their arcs is from 0.4 to 4.9. These clusters are selected carefully from strong gravitational lensing systems which have both X-ray satellite observations and optical giant luminous arcs with known redshift. Giant arcs usually appear in the central region of clusters, where mass can be traced with luminosity quite well. Based on gravitational lensing theory and cluster mass distribution model we can derive an Hubble constant independent ratio between two angular diameter distances. One is the distance of lensing source and the other is that between the deflector and the source. Since angular diameter distance relies heavily on cosmological geometry, we can use these ratios to constrain cosmological models. Meanwhile X-ray gas fractions of galaxy clusters can also be a cosmological probe. Because there are a dozen parameters to be fitted, we introduce a new analytic algorithm, Powells UOBYQA (Unconstrained Optimization By Quadratic Approximation), to accelerate our calculation. Our result proves that this algorithm is an effective fitting method for such continuous multi-parameter constraint. We find an interesting fact that these two approaches are sensitive to $Omega_{Lambda}$ and $Omega_{M}$ separately. Combining them we can get quite good fitting values of basic cosmological parameters: $Omega_{M}=0.26_{-0.04}^{+0.04}$, and $Omega_{Lambda}=0.82_{-0.16}^{+0.14}$ .
The cosmic coincidence problem is a serious challenge to dark energy model. We suggest a quantitative criteria for judging the severity of the coincidence problem. Applying this criteria to three different interacting models, including the interactin
g quintessence, interacting phantom, and interacting Chaplygin gas models, we find that the interacting Chaplygin gas model has a better chance to solve the coincidence problem. Quantitatively, we find that the coincidence index C for the interacting Chaplygin gas model is smaller than that for the interacting quintessence and phantom models by six orders of magnitude.
String cosmology models predict a relic background of gravitational wave produced during the dilaton-driven inflation. Its spectrum is most likely to be detected by ground gravitational wave laser interferometers (IFOs), like LIGO, Virgo, GEO, as the
energy density grows rapidly with frequency. We show the certain ranges of the parameters that underlying string cosmology model using two approaches, associated with 5% false alarm and 95% detection rate. The result presents that the approach of combining multiple pairs of IFOs is better than the approach of directly combining the outputs of multiple IFOs for LIGOH, LIGOL, Virgo and GEO.
We consider the evolution of the vacuum energy in the DGP model according to the holographic principle under the assumption that the relation linking the IR and UV cut-offs still holds in this scenario. The model is studied when the IR cut-off is cho
sen to be the Hubble scale $H^{-1}$, the particle horizon $R_{rm ph}$ and the future event horizon $R_{rm eh}$, respectively. And the two branches of the DGP model are also taken into account. Through numerical analysis, we find that in the cases of $H^{-1}$ in the (+) branch and $R_{rm eh}$ in both branches, the vacuum energy can play the role of dark energy. Moreover, when considering the combination of the vacuum energy and the 5D gravity effect in both branches, the equation of state of the effective dark energy may cross -1, which may lead to the Big Rip singularity. Besides, we constrain the model with the Type Ia supernovae and baryon oscillation data and find that our model is consistent with current data within $1sigma$, and that the observations prefer either a pure holographic dark energy or a pure DGP model
Power-law cosmologies, in which the cosmological scale factor evolves as a power law in the age, $a propto t^{alpha}$ with $alpha ga 1$, regardless of the matter content or cosmological epoch, is comfortably concordant with a host of cosmological obs
ervations.} {In this article, we use recent measurements of the X-ray gas mass fractions in clusters of galaxies to constrain the $alpha$ parameter with curvature $k = pm1, 0$. We find that the best fit happens for an open scenario with the power index $alpha = 1.14 pm 0.05$, though the flat and closed model can not be rule out at very high confidence level.} {Our results are in agreement with other recent analyses and show that the X-ray gas mass fraction measurements in clusters of galaxies provide a complementary test to the power law cosmology.
