Tuesdays 10:30 - 11:30 | Fridays 11:30 - 12:30
Showing votes from 2020-03-17 11:30 to 2020-03-20 12:30 | Next meeting is Tuesday Aug 5th, 10:30 am.
We advocate an idea that some mysterious explosions, the so-called sky-quakes, which have been known for centuries could be a manifestation of the dark matter Axion Quark Nuggets (AQN) when they propagate in the Earth's atmosphere. We specifically study the event which occurred on July 31-st 2008 and was properly recorded by the dedicated Elginfield Infrasound Array (ELFO) near London, Ontario, Canada. The infrasound detection was accompanied by non-observation of any meteors by an all-sky camera network. Our interpretation is based on the AQN dark matter model which was originally invented with a completely different purpose---to explain the similarity of the dark and visible cosmological matter densities $\Omega_{\rm dark}\sim \Omega_{\rm visible}$. Our estimates for the infrasonic frequency $\nu\simeq 5$ Hz and overpressure $\delta p\sim 0.3$ Pa are consistent with the ELFO record. We propose a detection strategy for a systematic study to search for such explosions originating from AQNs by using Distributed Acoustic Sensing and briefly mention other possible detection methods. Specific signals from AQN tracks may also be detected by an existing network of seismic stations.
The clustering of local extrema including peaks and troughs will be exploited to assess Gaussianity, asymmetry and the footprint of cosmic strings network on the CMB random field observed by {\it Planck} satellite. The number density of local extrema reveals some non-resolved shot noise in {\it Planck} maps. The \texttt{SEVEM} data has maximum number density of peaks, $n_{pk}$, and troughs, $n_{tr}$, compared to other observed maps. The cumulative of $n_{pk}$ and $n_{tr}$ above and below a threshold, $\vartheta$, for all {\it Planck} maps except for the 100GHz band are compatible with the Gaussian random field. The unweighted Two-Point Correlation Function (TPCF), $\Psi(\theta;\vartheta)$, of the local extrema illustrates significant non-Gaussianity for angular separation $\theta\le 15'$ for all available thresholds. Our results show that to put the feasible constraint on the amplitude of the mass function based on the value of $\Psi$ around the {\it Doppler peak} ($\theta\approx 70'-75'$), we should consider $\vartheta\gtrsim+1.0$. The scale independent bias factors for peak above a threshold for large separation angle and high threshold level are in agreement with that of expected for a pure Gaussian CMB. Unweighted TPCF of local extrema demonstrates a level of rejecting Gaussian hypothesis in \texttt{SMICA}. Genus topology also confirms the Gaussian hypothesis for different component separation maps. Tessellating CMB map with disk of size $6^{\circ}$ based on $n_{pk}$ and $\Psi_{pk-pk}$ demonstrate statistical symmetry in {\it Planck} maps. Combining all maps and applying the $\Psi_{pk-pk}$ puts the upper bound on the cosmic string's tension: $G\mu^{(up)} \lesssim 5.00\times 10^{-7}$.
Accurate cosmological simulations that include the effect of non-linear matter clustering as well as of massive neutrinos are essential for measuring the neutrino mass scale from upcoming galaxy surveys. Typically, Newtonian simulations are employed and the neutrino distribution is sampled with a large number of particles in order to beat down the shot noise. Here we perform very efficient simulations with light massive neutrinos which require virtually no extra cost over matter-only simulations, and furthermore do not require tracer particles for the neutrinos. Instead, we use a weak-field dictionary based on the recently developed Newtonion motion approach, where Newtonian simulations for matter are paired with a linear relativistic Boltzmann code to allow for an absorption of the neutrino evolution into a time-dependent coordinate transformation. For this, only minimal modifications in existing N-body codes are required, which we have explicitly implemented in $\textit{gevolution}$ and $\textit{gadget-2}$. Our fast method determines the non-linear matter power spectrum to permille-level precision when compared against state-of-the-art simulations that have been performed for $0.1\,{\rm eV} \leq \sum m_\nu \leq 0.3\,$eV.
We develop a new embedding-space formalism for AdS$_4$ and CFT$_3$ that is useful for evaluating Witten diagrams for operators with spin. The basic variables are Killing spinors for the bulk AdS$_4$ and conformal Killing spinors for the boundary CFT$_3$. The more conventional embedding space coordinates $X^I$ for the bulk and $P^I$ for the boundary are bilinears in these new variables. We write a simple compact form for the general bulk-boundary propagator, and, for boundary operators of spin $\ell \geq 1$, we determine its conservation properties at the unitarity bound. In our CFT$_3$ formalism, we identify an $\mathfrak{so}(5,5)$ Lie algebra of differential operators that includes the basic weight-shifting operators. These operators, together with a set of differential operators in AdS$_4$, can be used to relate Witten diagrams with spinning external legs to Witten diagrams with only scalar external legs. We provide several applications that include Compton scattering and the evaluation of an $R^4$ contact interaction in AdS$_4$. Finally, we derive bispinor formulas for the bulk-to-bulk propagators of massive spinor and vector gauge fields and evaluate a diagram with spinor exchange.