New directions EXploring the Unknown beyond the Standard Model (NEXUS 2026)

Session

Parallel talks (2B)

12 Sept 2026, 16:20

Tsung-Dao Lee Institute/S5F-S500 - Lecture Room (Tsung-Dao Lee Institute)

6. WIMP Meets ALP: Coherent Freeze-Out of Dark Matter

Dr Bingrong Yu (Cornell University)

12/09/2026, 16:20

Oral Presentation

The microscopic nature of dark matter is the major open question in science. Weakly-Interacting Massive Particles (WIMPs) and Axion-Like Particles (ALPs) are the two most theoretically motivated dark matter candidates. Thousands of papers consider them separately. We point out that if both species are present in the theory, even a tiny (Planck-suppressed) interaction between them could lead to...

68. Late-time Quantum Vacuum Decay and its Cosmological Implications

Sida Lu (Sun Yat-sen University)

12/09/2026, 16:40

The existence of a landscape of metastable vacua raises the possibility that our Universe may have undergone quantum vacuum decay at late times. This work explores how such a transition can be tested with cosmological observables, focusing on precision distance measurements and cosmic microwave background (CMB) anisotropies. A set of phenomenological models is constructed in which late-time...

27. Defect-Mediated Conversion: Dark Matter from Cosmological Domain-Wall Scattering

Mohamed Younes Sassi (Tsung-Dao Lee Institute, Shanghai Jiao Tong University)

12/09/2026, 17:00

Oral Presentation

We propose a new mechanism for dark matter genesis, Defect-Mediated Conversion (DMC). Cosmological domain walls–generic remnants of spontaneously broken discrete symmetries–can host a scalar condensate in their core that acts as a portal between the Standard Model and a dark sector: thermal-bath fermions crossing the wall are partially and non-thermally converted into dark particles. The...

35. Direct detection and cosmological constraints of dark matter with dark dipoles

Takumi Kuwahara (Jilin U)

12/09/2026, 17:20

We study a fermionic dark matter candidate that couples to the standard model particles exclusively through electric and magnetic dipole operators mediated by a massive dark photon. Such dipole portals naturally arise in dark sectors where the dark matter is neutral under a hidden U(1)D, and they lead to phenomenology distinct from conventional vector-current interactions. We consider the...

20. Formation and Dynamics of Multi-Vacuum Domains from Axion Fragmentation

Yun Jiang

Oral Presentation

Axion-like fields with tilted periodic potentials can contain multiple metastable minima. I will discuss how resonant amplification of axion fluctuations can fragment an initially homogeneous field, causing different regions to settle into different vacua without tunneling. Using 3D lattice simulations in an expanding universe, we study the formation, expansion, and collision of these vacuum...