Page 45 - Undergraduate Research Opportunities Program Proceedings 2017-18

School of Science
Department of Physics

We used ellipsometry to examine the thickness-temperature (h-T) relationship of two sets of pure polymer thin films,
P4TBS (poly(4-tert-butylstyrene)) and P4AS (poly(4-acetoxystyrene)) and three sets of their copolymers whose
compositions are 65.6%PTBS, 47.5%PTBS and 31.7%PTBS. From the h-T curve, the glass transition temperature Tg, the
starting and the ending temperature of glass transition T- and T+, the breadth of the transition ∆Tg and the thickness of
the surface liquid-like layer can be estimated. We investigated how the different compositions and total film thickness
influence the behavior of Tg, T-, T+, ∆Tg and the surface liquid-like layer to reveal the confinement effects of the
substrate on copolymer films.

Fuzzy Dark Matter

Supervisor: TYE Henry / PHYS
Student: HO Sui Lun / PHYS Course: UROP1100, Spring

The standard Cold Dark Matter model (CDM) interpretation of dark matter is successful in explaining large-scale
structure of our universe. Nevertheless, four major problems emerge in such model in the description of small-scale
structures. Fuzzy Dark Matter (FDM) model suggests an ultralight (m ~ 10 eV) scalar field to explain dark matter
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composition. The quantum effects in astronomical scale shown FDM model successfully preclude the problems faced by
CDM model. Observation shows a supermassive blackhole is a crucial central component of galaxies, leads to questions
on the effect of FDM model in the scenario of supermassive blackhole(SMBH) formation. The paper suggested a careful
study on the correlation between SMBH formation and FDM results in a mass constraint that disfavour FDM model. This
demonstrates that FDM model neither correlate nor contradict with SMBH formation. In addition, recent studies shed
light on possibility of dark matter not couple to baryonic matter in galactic scale, by discovering a galaxy lacking dark
matter. The paper suggest an upper bound for initial misalignment angle for the quantum fluctuation patch
corresponding to the dark-matter-lacking galaxy, through a spherical symmetric toy model with structure formation
scenario considered in expanding universe.

Supervisor: TYE Henry / PHYS
Student: LI Shing Yan / SSCI Course: UROP1100, Summer

We present a possible string theory explanation to an exponentially small cosmological constant. Through flux
compactification in Type IIB string theory, we obtain the Kähler uplift racetrack model. It shows that there is a statistical
preference of such cosmological constant within the string landscape, without much fine tuning. We emphasize the
difference between simple racetrack and multiple racetrack models. We also investigate the statistical distribution of
associated mass scales of the models from different mechanisms. The mass scales are as small as the cosmological
constant, and may correspond to ultra-light axions (ULAs), which are a candidate of dark matter in the model of fuzzy
dark matter.

Quantum Oscillations in Low Dimensional System
Supervisor: WANG Ning / PHYS
Student: KONG Kangyi / PHYS Course: UROP1100, Summer

This is a report exclusively for the UROP 1100 program “Quantum Oscillations in Low Dimensional System”. The aim of
this report is to summarize the studying progress of understanding the quantum statistical mechanics and solid state
physics in a progressive manner as a reference for future further studies and review. It will start with basic assumptions
in classical statistical mechanics. And then the thermodynamic properties of an ideal gas will be recovered. Combined

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