Cosmological simulations play an important role in the interpretation of astronomical data, in particular in comparing observed data to our theoretical expectations. However, to compare data with these simulations, the simulations in principle need to include gravity, magneto-hydrodyanmics, radiative transfer, etc. These ideal large-volume simulations (gravo-magneto-hydrodynamical) are incredibly computationally expensive which can cost tens of millions of CPU hours to run. In this paper, we propose a deep learning approach to map from the dark-matter-only simulation (computationally cheaper) to the galaxy distribution (from the much costlier cosmological simulation). The main challenge of this task is the high sparsity in the target galaxy distribution: space is mainly empty. We propose a cascade architecture composed of a classification filter followed by a regression procedure. We show that our result outperforms a state-of-the-art model used in the astronomical community, and provides a good trade-off between computational cost and prediction accuracy.

SHiP is a new proposed facility at CERN SPS, which is used to explore the hidden sector. In order to study the hidden sector, the charged particle shall be measured with high precision, so that the decay of hidden particle may be reconstructed. Spectrometer Straw Tracker is a detector which measure the trajectory and the momentum of the charged particle. Straw tube is one of the main components of the detector. Since the straw tube is subjected to external force, such as gravity, the installation will not be ideal. Sagging is expected to exist. In my work, the effect on track reconstruction performance due to sagging is investigated by using the developing software package from SHiP. Modification is implemented to the package and two cases are studied, which are all straw tubes have same amount of sagging and different straw tubes may have different amount of sagging. It is found that the performance is decreased under the exist of sagging. The case with different amount of sagging will decrease the performance significantly, even if the amount of sagging is less serious.  The spatial and momentum resolution also show different trends on performance under the exist of sagging.

Over the few decades, many theories were established for different kinds of celestial bodies. However, due to recent observations, it is believed that more than a quarter of our universe are made of dark matter. Although the nature of dark matter is still a mystery nowadays, we still want to see how dark matter will affect different parameters of celestial bodies (e.g. density, pressure, velocity) by making some assumptions on dark matter.

Astronomers believe that the matter content of the universe is dominated by dark matter (DM), which are weakly interacting and massive, but their properties are largely unknown. The search for astronomical DM, although difficult, remains one of the major goals in the astrophysics particle physics. There is recent rising interest in DM admixed stellar objects, such as stars and compact stars. In particular, DM admixed white dwarfs (DMAWD) and their thermonuclear explosions were one of the possible models for sub-luminous Type Ia supernovae. In this talk, we would present a model of DMAWD with DM as ideal fermi gas. Numerical calculation of their effect to the equilibrium structure of DMAWD, and the simulations of their thermonuclear explosions are presented and briefly discussed. We find that DMAWD with DM particles mass around 0.1GeV could produce DMAWD with comparable order of NM and DM mass and radius. The NM with mass usually lower than that of typical Type Ia supernovae, could produce less Nickel-56 under thermonuclear explosions, and hence could be a possible model of sub-luminous type Ia supernovae.

Study of magnetic monopoles and monopolium is performed in Monte Carlo(MC) level. Monopoles events in Heavy ion (Pb-Pb) collision at 5.02 TeV are interested, and are generated with SuperChic 3.03. Dirac coupling and beta_g coupling are implemented in both monopole pair production and monopolium production. MC events reconstruction at CMS detector are performed by GEANT4. No evidence of existence of monopole or monopolium is found under analysis with forward triggered data and non colliding data at monopole mass 500GeV.

On 17th August, 2017, the Fermi Gamma-ray Burst Monitor captured a significant gamma ray burst on sky, followed by a gravitational wave (GW) detection with a successful registration as an binary neutron star (BNS) coalescences from LIGO in a few minutes (now called the GW170817). The estimated close distance (~40Mpc) from Earth and overlapping localization region of two events fostered a broadband emission follow up by various parties and telescopes, resulted in a successful detection in the electromagnetic counterpart after 11 hours and symbolized the beginning of the era of multi-messenger astronomy. With a large camera and wide field of view, the Large Synoptic Survey Telescope (LSST) would be one of the most efficient candidates for GW follow-up in next decade. Our goal is to evaluate the efficiency of GW follow-up on BNS merge using the LSST normal strategy and demonstrate that the Target-of-Opportunity (TOO) strategy has higher efficiency in searching the optical counterpart using GW trigger.

Taylor series expansion is a well-developed mathematical tool to solve differential equations which appears in all fields of physics. However, solving differential equation or some perturbation problem with series solution is relatively easy, computing the solution as finite series usually has a small converging range even with high order correction. In fact, the first few terms of the series already contain useful information about the whole series. Therefore, if we can smartly rearrange the terms, we may extract more accurate solution with fewer terms, which we call Series Acceleration. In this talk, I would like to introduce some acceleration methods include Shank's Transformation, Aitken method and Pade approximants.

The superconformal algebra’s vector field representation of a N = (2,0) superconformal theory in 6D is reviewed and extended to 10D. Some constraints on the expression of the vector fields are derived.

Multiple theories predict the presence of cosmic strings with different mass densities μ . A number of ways to constrain μ have been developed. In this project, we derived an equation governing the perturbation of a rotating black hole pierced by a straight, infinitely long cosmic string along its axis of rotation, from which the quasinormal mode frequencies were calculated. These results were used to put a constraint on μ for a Black-hole-string system through the analysis of its ringdown signals.

Strongly-lensed gravitational waves events can generate multiple signals that are different in amplitude and time separation. We assume the strongly-lensed signals are sub-threshold that are buried in the noise background. We present a GstLAL-based pipeline to search for the sub-threshold signal using reduced template banks for each targeted specific gravitational events. We apply the pipeline to all the event from Advanced LIGO’s first and second observing run, O1 and O2. We show that pipeline can effectively reduce the noise background and hence improve the signifiernce of (near-) sub-threshold triggers. Finally, the sensitive distance can be

Neutrino is fermion that only interacts via gravity and weak interaction. It is electrically neutral and its rest mass is nearly negligible.This greatly increase the difficulty for researchers to detect it. However, it has large abundance so it may still play an important role in universe evolution. Thus, we study the effect of neutrino on cosmic expansion and structure formation in this project

We consider the possibilities of directional variation of the cosmolog-ical parameters. By using MCMC, we fit the Planck CMB temperature angular power spectrum for twelve different half-skies, centering on twelve different directions, to search for directional dependences of the standard cosmological parameters. The results show that there are more than 3σdeviations of the parameters between different directions. The directional distributions ofns,H0, and cosmological baryon and dark matter densities Ωbh2, Ωch2all follow a dipole form Acosθ+B, where θ is the angle to thebest-fit dipole axis, with the values of Adeviating by 2-4σfrom zero. Thebest-fit dipole axes forns, Ωch2,H0, andτall align within 1σ uncertain-ties, pointing to the direction ofV≡(b=−48.7±20.4◦,l= 170.8±49.2◦).The dipole axes for Ωbh2and ln(1010As) are also aligned with each other,but they are perpendicular toV. Our results suggest either significant deviation from the standard ΛCDM cosmology, or previously unknown systematic errors in the s