Skip to main content
Back

Xinpeng Wang

Xinpeng Wang

Affiliation

Kavli IPMU, The University of Tokyo

Supervisors

  • Masahiro Takada (Kavli IPMU
  • the University of Tokyo)
  • Misao Sasaki (Kavli IPMU
  • the University of Tokyo)

Short bio

I am a PhD student at the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU). Prior to this, I earned my bachelor’s degree in Applied Physics from Tongji University, where I worked on population analyses of primordial black holes as a possible explanation for a subset of the gravitational-wave events detected by LIGO–Virgo–KAGRA. This experience sparked my interest in the phenomenology of the very early universe.
Since the beginning of my PhD, my research has focused on exploring detectable signatures originating from the early universe, particularly in the contexts of inflation, dark matter, and gravitational waves. Through the Enrico Fermi Fellowship, I aim to connect theoretical studies of the dark universe with ongoing and future observations to study the challenges to our current picture of the universe.

Bridging Theory and Observation to Illuminate the Dark Universe

Most of the Universe is invisible. Dark matter and dark energy dominate the cosmos, yet their true nature remains a mystery. Dark matter interacts only very weakly with the particles we are familiar with, while dark energy appears to drive the accelerated expansion of the Universe. We still do not know what they are made of or what physical mechanism is responsible for them. Yet the Universe itself acts as the largest and most extreme laboratory we can access. By studying the cosmos, we can probe physical processes far beyond what is possible on Earth. Understanding this “dark universe” is therefore one of the central challenges of modern physics.

Xinpeng Wang's project image
The timeline of the Universe showing how our universe evolves from the inflationary era into the atoms, stars, galaxies, and large-scale structures we're familiar with today. (Credit: Ben Gibson / NASA / Pablo Carlos Budassi / Big Think)

In recent years, new observational tools have opened an unprecedented window into the cosmos. Gravitational wave detectors can listen to ripples in spacetime, cosmic microwave background experiments measure the faint afterglow of the Big Bang, and large galaxy surveys map the structure of the Universe across billions of years. Together, these observations allow us to test ideas about the early Universe and the physics behind dark matter and cosmic acceleration with remarkable precision.

At the same time, current observations have revealed several puzzling tensions. In particular, key cosmological parameters inferred from early-universe probes and measured using late-universe methods do not always agree, suggesting that our standard picture of the Universe may be incomplete. Resolving these discrepancies requires both more precise observations and better theoretical modeling that can identify clear, testable signatures of new physics.

Xinpeng Wang's project image 2
The focal plane of the Subaru Prime Focus Spectrograph (PFS). The cluster of small white dots in the center represents ~2400 optical fibers spread across the telescope’s field of view. Each fiber is positioned by the fiber positioner to capture light from an astronomical object in the sky. (Credit: Kavli IPMU / NAOJ)

My research, therefore, aims to connect theoretical models of the early Universe with cutting-edge observations to identify signatures that could reveal new physics. I investigate how processes in the primordial Universe, such as cosmic inflation or the formation of exotic objects like primordial black holes, could leave observable signals today. To test these ideas, I will work with data from the Subaru Prime Focus Spectrograph (PFS) survey, which maps galaxies at high redshifts and helps constrain the expansion and growth history of the Universe. Combining these measurements with cosmic microwave background data and other surveys will allow us to test whether new physics is needed to describe our Universe.