We present a new framework of grand unification that is equipped with an axion solution to the strong CP problem without a domain wall problem when the Peccei-Quinn (PQ) symmetry is spontaneously broken after inflation. Our grand unified theory (GUT) is based on a symmetry breaking pattern, SU(10)×SU(5)1→SU(5)V⊃SU(3)C×SU(2)L×U(1)Y, where SU(5)1 and a special embedding of SU(5)2⊂SU(10) are...
I will motivate the use of E6 grand unified theory and describe a
realistic E6 GUT which gives rise to novel possible intermediate stages.
I will present a set of simple KSVZ-type axion models, with a breaking scale similar to the GUT-scale, and which doesn't have a domain wall problem or fine-tuning in the initial misalignment angle. I will use this model to argue that it is experimentally difficult to distinguish whether PQ symmetry is broken before or after inflation. I will describe how GW probes could provide vital...
We present the recent progresses of a unified framework based on an affine SU(8) Lie algebra. This is found to be the minimal Lie algebra where three-generational SM fermions can transform differently. Accordingly, we describe how to generate the observed SM quark/lepton mass hierarchies and the CKM mixing patterns with one unique SM Higgs boson. We also discuss the gauge coupling unification...
We discuss heavy particles that can be used to pin down the faithful Standard Model (SM) gauge group and their patterns in the SM effective field theory (SMEFT). These heavy particles are not invariant under a specific $\mathbb{Z}_6$ subgroup of $SU(3)_c\times SU(2)_L \times U(1)_Y$, which however acts trivially on all the SM particles, hence the faithful SM gauge group remains undetermined....
I will present a recent work where we assessed the capability of Gravitational Wave (GW) experiments to probe the origin of the flavour sector of the Standard Model. Within the context of the Froggatt-Nielsen mechanism to generate the hierarchical patterns of fermion masses and mixing based on a gauged U(1) flavour symmetry, we investigated the formation of cosmic strings and the resulting GW...
The computation of bounce action in a phase transition involves solving partial differential equations, inherently introducing non-negligible uncertainty. Deriving characteristic temperatures and properties of this transition necessitates both differentiation and integration of the action, thereby exacerbating the uncertainty. In this work, we use polynomial fitting to approximate the action...
Symmetry breaking in the early universe is manifested in the form of cosmological
phase transitions, and more desirably first order ones, during which a stochastic
background of gravitational waves can be generated. I will discuss how to detect
such gravitational waves using future space-based detectors, and how future measurements of such signals help us learn about the underlying particle...
I will discuss Beyond Standard frameworks that can address the flavour problem and unification, including strategies for reconciling unification with distinct flavour structures between lepton and quark sectors.
We explore a class of axion models where an accidental U(1) Peccei-Quinn (PQ)
symmetry automatically arises from the interplay of vertical (grand-unified)
and horizontal (flavor) gauge symmetries. Focusing on a specific SO(10) or Pati-Salam realization, we analyze the quality of the PQ symmetry and demonstrate that
the model non-trivially reproduces the Standard Model flavor structure. A...
I introduce the appeal and remaining challenges of natural GUT and then discuss possible solutions to these problems. After that, I delve into the appeal and issues concerning scenarios of spontaneous supersymmetry breaking within natural grand unified theories.
I will talk about phonmenological consequencies induced by phase transitions occurred during inflation, including gravitational waves, primordial black holes, primordial non-gaussianity, baryogenesis, dark matter production.
I will introduce the basics and recent developments of cosmological collider physics, with a focus on the model-building aspects. In particular, I will describe the essential knowledge and techniques required for particle model builders to study the cosmological collider phenomenology of their favorite BSM new physics.
GUT phase transition is generally considered unobservable due to its ultra-high energy scale, and the monopole problem associated with GUT phase transition is one motivation of inflation. We propose that if a first-order GUT phase transition happens during inflation, the induced gravitational waves (GWs) are redshifted and deformed, and might be observed today in GW observatories. We review...
The ultimate dream of unification models consists in combining both gauge and Yukawa couplings into one unified coupling. This is achieved by using a supersymmetric exceptional E6 gauge symmetry together with asymptotic unification in compact five-dimensional space-time. The ultraviolet fixed point requires exactly three fermion generations: one in the bulk, and the two light ones localised on...
In this talk, we would like to discuss the breaking of multiple modular flavor symmetry by boundary conditions in flipped SU(5) unification model. We would also like to discuss the solution of SUSY mu-problem in the framework of modular flavor symmetry. Relevant modulus stabilization mechanism with SUSY breaking contributions from nilpotent constrained superfield will also be discussed. .
We examine the general nucleon decay interactions that involve only three light quarks without any derivatives acting on them. We identify eight generic operator structures that correspond to eight different chiral representations, {$\pmb{8}_{\tt L}\otimes \pmb{1}_{\tt R}$, $\bar{\pmb{3}}_{\tt L}\otimes \pmb{3}_{\tt R}$, $\pmb{6}_{\tt L}\otimes \pmb{3}_{\tt R}$, $\pmb{10}_{\tt L}\otimes...
In the first part we discuss exotic proton decay processes within grand unification that are characterized by non-minimal embeddings of the Standard Model matter fields within the irreducible representations of the grand unified group. We take $SU(7)$ as the grand unified group and allow for different options for the dominant proton decay processes, depending on the details of the $SU(7)$...
We are going to show within a scalar extended seesaw models, leptogenesis can successfully generate sufficient BAU as the CP asymmetry is enhanced by the scalar interactions in the loop. In the meantime, the same scalar is responsible for a first-order electroweak phase transition, which can lead to observable gravitational waves~(GWs) in the near future experiments such as eLISA and...
In the past few decades, leptogenesis has been widely studied as a solution to the matter–antimatter asymmetry problem. However, certain theoretical effects that could alter the predictions have not yet been fully considered. In this talk, I will discuss the impact of flavour coupling effects on the predictions of SO(10)-inspired leptogenesis for low-energy neutrino parameters. I will show...
Video Tour: https://www.bilibili.com/video/BV1oSdPYnETo/?vd_source=f49c3b8c30becae8270d8cec5555b83b
Domain wall is one of the topological defects that can be generated during phase transitions. When a non-abelian discrete symmetry is broken, different types of domain walls can be created. Starting from a real scalar model with $S_4$ symmetry, we study the properties of different types of domain walls and then extend the analysis to models with $A_4$ symmetry as well as complex scalar models.
In this article, for the first time, we explore the scenario that the dark-QCD sector has a large chemical potential μ (on the order of magnitude of temperature) of dark quarks. It leads to a complex-valued Polyakov loop and tilts the partial confinement effect, driving the dark-QCD phase transition to a first-order one in the early universe. We present a toy model via the Affleck-Dine...
We build upon the intriguing possibility that the recently reported nano-Hz gravitational wave signal by Pulsar Timing Array (PTA) experiments is sourced by a strong first-order phase transition from a nearly conformal dark sector. The phase transition has to be strongly supercooled to explain the signal amplitude, while the critical temperature has to be in the (GeV) range, as dictated by the...
The tiny neutrino masses are most naturally explained by the seesaw mechanism through singlet right-handed neutrinos, which can further explain the matter-antimatter asymmetry in the universe. In this work, we propose a new approach to study cosmological signatures of neutrino seesaw through the interaction between inflaton and right-handed neutrinos. After inflation the inflaton predominantly...
The early universe is a natural laboratory for high-energy physics, and gravitational waves, as direct probes of this epoch, inherently carry rich information related to high-energy physics. Silk damping, resulting from dissipation in the cosmic fluid, is a significant physical phenomenon in the early universe. In this talk, I will introduce our first study on Silk damping in induced...
As with the standard grand unification, we may have a similar structure in the dark sector. The dark-sector counterpart of baryons plays a role of the dark matter at the low-energy scale when the particle-antiparticle asymmetries are shared in the Standard Model and dark sectors. Through the portal interaction sharing asymmetry, dark matter particles can decay into antineutrinos and...
Minimal dark matter is an attractive candidate for dark matter because it is stabilized without the need to impose additional symmetries. It is known that the SU(2)L quintuplet fermion can serve as a minimal dark matter candidate, with its mass predicted to be around 14 TeV, based on the thermal production mechanism. In this work, we embed the quintuplet dark matter within non-supersymmetric...
A pseudo-Nambu-Goldstone boson (pNGB) is a compelling candidate for
dark matter (DM), as it naturally evades the stringent constraints
from current DM direct detection experiments. In this framework, the
pNGB DM model can be embedded within an SO(10) grand unified theory,
where SO(10) is first broken to the Pati-Salam gauge group at the
unification scale and subsequently to the Standard...
We discuss the phenomenological consequences of the decay of the meta-stable dark sector during the thermal expansion of the universe. We consider that the latent heat is much larger than the plasma energy density in the dark sector. In this case, the Lorentz factor of the bubble walls can be extremely large and the effect of bubble propagation after collisions can not be ignored. We use a...
In various new physics theories, the spontaneous breaking of symmetries can lead to the formation of topological defects, such as domain walls and cosmic strings, in the early universe. The motion and collapse of domain walls, as well as relativistic oscillations of cosmic string loops, can generate significant stochastic gravitational waves, offering a unique opportunity to probe new physics....
In this paper, we discuss the predicted proton lifetimes in minimal supersymmetric (SUSY) $SU(5)$ grand unified theory (GUT) with gauge mediated supersymmetry breaking (GMSB). We focus on the case of $\mathbf{5} + \mathbf{\bar{5}}$ messengers and determine the low-scale mass spectrum of the scalar particles and gauginos using the renormalization group equations. With the obtained mass...
Recent observations from pulsar timing arrays (PTAs) suggest the existence of a stochastic gravitational wave background (GWB) in the nanohertz frequency range. One of the most promising explanations is a GWB generated by metastable cosmic strings.
However, the standard formation scenario for (meta)stable cosmic strings—based on the Kibble-Zurek mechanism triggered by a thermal phase...
We discuss the whole procedure from GUT scale to nuclear probes through the effective field theories. The procedure includes the UV models from SO(10) GUT symmetry breaking and the matching between UV models and SMEFT operators. The nuclear probes of proton decay will be obtained through the matching from the SMEFT to the LEFT which would be matched into Chiral EFT.
