Abstract: A generic low-energy prediction of string theory is the existence of a large collection of axions, commonly known as a string axiverse. In a realistic axiverse, string axions can be distributed densely over many orders of magnitude in mass, and are expected to interact with one another through their joint potential. In this talk, I will show how non-linearities … Read More
In this talk, I will discuss the vector-portal dark matter model, with a dark photon that is slightly heavier than the dark matter. In this regime, a sub-GeV dark matter particle leads naturally to the correct relic abundance, with freezeout controlled by forbidden and 3-to-2 processes. The thermal freezeout behavior of dark matter can be classified into several different phases … Read More
Abstract: In this talk, I will propose the use of the Earth as a transducer for ultralight dark-matter detection. In particular I will point out a novel signal of kinetically mixed dark-photon dark matter: a monochromatic oscillating magnetic field generated at the surface of the Earth. Similar to the signal in a laboratory experiment in a shielded box (or cavity), … Read More
Abstract: The parameter εK is an important measure of the imbalance between matter and antimatter in the neutral kaon system. In particular, εK provides a sensitive probe of new physics and plays a critical role in the global fit of the Cabibbo-Kobayashi-Maskawa matrix. As one of the first discovered sources of CP violation, it has been extensively measured in experiment to per-mil precision. The theoretical calculation … Read More
Abstract: Macroscopic dark matter is mostly unconstrained over a wide asteroid-mass range, where it could scatter on visible matter with geometric cross section. In this talk, I shall describe when such a ‘dark asteroid’ travels through a star, it produces shock waves which reach the stellar surface, and gives out distinctive transient optical, UV and X-ray emission. This signature can be … Read More
We establish a paradigm where the (QCD) axion’s novel cosmological evolution, a rotation in the field space, gives rise to the baryon asymmetry by axiogenesis and dark matter by the kinetic misalignment mechanism. The axion rotations also provide a natural origin for a kination era, where the total energy density is dominated by the kinetic term of the axion field, … Read More
Abstract: We look for and place observational constraints on the imprint of ultralight dark matter (ULDM) soliton cores in rotation-dominated galaxies. Extending previous analyses, we find a conservative, model-independent constraint which disfavours the soliton-host halo relation found in numerical simulations over a broad range in the ULDM particle mass m. Combining the observational constraints with theoretical arguments for the efficiency … Read More
Abstract: The QCD axion is a promising candidate of the dark matter. In this paper, we discuss elastic scattering processes between nucleons and the QCD axion dark matter. We point out that the cross section can be enhanced by more than O(1025) by the coherent effect, compared to classical processes. As a result, for example, we show that QCD axions … Read More
Some judiciously chosen 4D Yang-Mills theories with various degree of supersymmetry (including no SUSY) support “Non-Abelian string solitons”, i.e. vortex strings with extra moduli on the string world sheet. The emerging target space theories on the world sheet are non-trivial, implying a number of consequence and novel applications both in HEP and condensed matter. I discuss some of them. For … Read More