Event Category: 4D Seminar

4D Seminar series:
Monday at 2:30 on campus

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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

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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

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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

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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

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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

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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

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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

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Abstract: Thermal dark matter scenarios are characterized by an exponential decrease in the comoving dark matter number density as the temperature drops below the dark matter mass in the early Universe. In this talk, we will discuss a novel thermal framework, bouncing dark matter, where the abundance instead undergoes a “bounce:” a transition from the exponential fall to an exponential … Read More

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Is the gravitational field a quantized degree of freedom? It would be very satisfying to do a direct experimental test to answer this question. Unfortunately, as emphasized by Dyson, it is probably impossible to build a detector sensitive enough to detect single gravitons. I’ll give an overview of a more circuitous, but potentially feasible, experimental path to probe the quantization of the gravitational … Read More