Event Category: 4D Seminar

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

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Abstract: Primordial sources of gravitational waves (GWs) have traditionally been probed through their contribution to the stochastic GW background, detectable via pulsar timing arrays and ground-based laser interferometers. However, these same tensor perturbations can also leave an imprint on the cosmic microwave background (CMB) in the form of B-mode polarization. While a detection of primordial B-modes has long been regarded as … Read More

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Abstract: Experts have been debating whether the standard cosmology prediction for primordial deuterium agrees with observation, with some finding agreement and others finding a mild tension (~2 sigma).  I will show that this disagreement has its roots not in Big Bang Nucleosynthesis theory or nuclear physics experiment, but instead in simple statistics. I will also introduce a new method to … Read More

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Abstract: Energy correlators are a class of cleverly constructed collider observables that provides unique insights into the field theory structure and phenomenology of QCD. In this talk, I study the leading nonperturbative contribution to energy correlators using field theory methods and discuss the universality across event shape observables of such contributions. I show that correctly including the nonperturbative improves our … Read More

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Abstract: I will present two examples of how cosmological lattice simulations can be used to study the properties of QCD axion dark matter in the early Universe. First, the phenomenology of three variants of the Axion Misalignment mechanism (Standard, Kinetic, and Large Misalignment) will be discussed. It can be shown that non-linearities and the phenomenon of fragmentation depend not only … Read More

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Abstract: Massive Compact Halo Objects (MACHOs) remain a viable dark matter candidate that can be tested through their dynamical effects on stellar systems. In this talk, I will present how dynamical heating of stars in ultrafaint dwarf (UFD) galaxies provides powerful constraints on MACHOs across a broad mass range. I will demonstrate the robustness of these bounds by conducting a … Read More

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Abstract: Experimental searches for axion dark matter often treat the axion as a classical field, but the axion can evolve into a quantum state with no classical analogue. I will present a general argument that the intrinsically quantum effects of these states are always strongly suppressed, so that near-future experiments cannot distinguish a quantum axion from a classical ensemble. Conversely, … Read More

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Abstract: A magnetically levitated mass couples to gravity and can act as an effective gravitational wave detector. In this talk, we will discuss show how a superconducting sphere levitated in a quadrupolar magnetic field, when excited by a gravitational wave, can produce magnetic field fluctuations that can be read out using a flux tunable microwave resonator, thus serving as a … Read More

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Abstract: Our limited understanding of dark matter motivates exploring a wide range of masses and interaction strengths, independent of specific mediators or production mechanisms. Astrophysical systems, with their high energies and long lifetimes, provide unique laboratories for this pursuit.  I will discuss two mechanisms by which dark matter can leave measurable imprints on astrophysical systems, even without annihilations. In the first, … Read More

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I will briefly review the observations of UHECRs, emphasizing which aspects are robust and which remain uncertain. Among the robust aspects, a key feature of the data strongly suggests that UHECRs are produced in BNS mergers.  Taking advantage of the well-defined initial conditions, I will identify the likely acceleration mechanism and explain how the spectral cutoff is determined.  The resulting … Read More