CPLUOS Astrophysics team meeting

Asia/Seoul
물리학과

물리학과

Zoom Meeting https://uos-ac-kr.zoom.us/j/8264902652 Meeting ID: 826 490 2652
Description

https://uos-ac-kr.zoom.us/j/8264902652

    • 16:30 17:30
      COSMOLOGY
      • 16:30
        Hyeonmo's report - FDM vs CDM Halo Collision 10m
        Speaker: Hyeonmo Koo (University of Seoul)

        FDM vs CDM Halo Collision

        • Setup of the Head-on Collision simulation of CDM Halos
      • 16:40
        Young's report. FoF and MST algorithm 10m
        Speaker: Young Ju

        FoF and MST algorithm

        • Controlled data
          • 1. Changing cut-length and check the number of clusters
            • n=50 : Giant cluster
            • MGS
            • FoF
            • MST
            • DBSCAN
            • Hierarchical
            • 1. MGS and DBSCAN is similar
            • 2. FoF and MST have isolated galaxies
            • 3. MST does not make a giant cluster
            • MGS actually is consists of 2 stage. The pre-mgs stage calculate the number density by  using pre-fResolution
            • Change pre-fResolution and check the number of clusters
              • Pre-fResolution = 10
              • Pre-fResolution = 5
      • 16:50
        CHOA(Cosmology of High-Order Statistics) 10m
        Speaker: Sumi Kim (University of Seoul)

        CHOA(Cosmology of High-Order Statistics)

        • 4pcf (connected) 0%
        • 2pcf 100% → Disconnected part 3*2pcf^2
        • Will connected be 0? = Will encore remove disconnected part?
        • Test at the encore code
          • Fixed distance 4
            • Test at the encore code → Can this connected be a noise?
            • Seems decreasing after averaging multiple calculations, so the connected value can be concluded as noise
        • Test at the encore code 2
          • Non-fixed distance
            • Given power spectrum(Power box) → Calculates every available distance
            • 4pcf (connected) 0% 2pcf 100%(Disconnected part)
            • Will connected be 0? = Will encore remove disconnected part?
            • In multiple calculation, mean value is larger than standard deviation value, so encore code doesn't remove the disconnected part well
        • For next
          • Doing test and calculating mocks of our new code
          • Seeing other distance ranges
      • 17:00
        CLML 10m

        Cosmology with Large scale structure using Machine Learning

        Speaker: Se Yeon Hwang

        CLML(Cosmology with Large scale structure using Machine Learning)

        • Outlook
          • Started on the machine learning!(arXIv : 1908.10590) which is using 3d convolution network
            • input(3d density field of dark matter halo) → CNN CNN CNN Fully connected Fully connected Fully connected → output(Ω_m, σ_8 → Cosmological parameter)
        • Data
          • xyz position of dark matter halo
            • Box size = 256(Mpc/h)
            • Number of particles = 256^3
          • 3d histogram of 32 voxels(density field)
            • 1 voxel have 8(Mpc/h) information
        • Change for the data
          • 128
            • Boxsize = 256(Mpc/h)
            • Number of particles = 128^3
          • 256
            • Boxsize = 256(Mpc/h)
            • Number of particles = 256^3
          • 512
            • Boxsize = 256(Mpc/h)
            • Number of particles = 512^3
        • Data
          • Number of halo
            • The number of halo(128) : 9225
            • The number of halo(256) : 74646
            • The number of halo(512) : 504649
          • Halo mass
            • Ω_m = 0.33, σ_8 = 0.62
            • ρ = N(↑)*M(↓)/V
          • 1 voxel have 2(Mpc/h) information using 32 voxel(then one side should be 64(Mpc/h)
            • Short version
              • Only using 0(Mpc/h) < x, y, z < 64 (Mpc/h)
              • Including only 0~64 information
            • Cut version
              • At each side : [0, 64] [64, 128] [128, 192] [192 256] >> 32 voxel histogram
              • Including all information of the box scale
              • Total 64(4^3) for one cosmology
        • Data set
          • 128_short, 256_short, 512_short, 128_cut, 256_cut, 512_cut
        • Model
          • Model 1
          • Model 2
          • Model 3
          • Model 4
        • Conclusion
          • Don't sure about what is going on.
          • There are possibility of my mistakes + possibility of different results each time when run it even
          • Used same model and same data(I have to check)
        • Next step
          • Wil try running with different cosmology + same seed
          • Also, have to understand about mathematics on how each layer works
      • 17:10
        Hannah's Report - Weak Lensing with Machine Learning 10m
        Speaker: Hannah Jhee (University of Seoul)

        Weak Lensing with Machine Learning

        • Loss Function Issues
          • Implementing BCE loss gives NaN loss → Due to the exponential from sigmoid?
          • Therefore it is recommended to use tf built-in loss, or transform your loss function to prevent NaN.
          • tf.keras.losses.BinaryCrossEntropy(from_logits=True→False) after eliminating the last Activation Layer(sigmoid) in Discriminator
        • Tests on Learning Rates
          • Kernel size = 20
        • Tests on Kernel Sizes
          • Learning Rate = 1e-6
          • Learning Rate = 2e-5
          • Learning Rate = 1e-5
      • 17:20
        Dr.Sabiu's Report - N-PCF 10m
        Speaker: Dr Cristiano Sabiu (University of Seoul)
    • 17:30 17:40
      Discussion 10m