Professor Puckett's Research Homepage

Prof. Sang Wook Cheong,
Department of Physics and Astronomy, Rutgers University

Trompe L'oeil Ferromagnetism


The characteristics of ferro-(ferri)magnetism with non-zero magnetization include magnetic attraction, magnetic circular dichroism, and magneto-optical Kerr (MOKE), Faraday, and various anomalous Hall-type (Hall, Ettingshausen, Nernst, and thermal Hall) effects. Non-magnetic or antiferromagnetic materials in external electric fields or other environments (called specimen constituents) can share symmetry operational similarity (SOS) with magnetization in relation to broken symmetries. These specimen constituents can be associated with non-zero magnetization and/or show ferromagnetism-like behaviors, so we say that they exhibit Trompe L’oeil Ferromagnetism. Examples include linear magnetoelectric materials such as Cr₂O₃ under electric fields, Faraday effect in chiral materials such as tellurium with current flow, magnetic field induced by the motion of Neel- or Bloch-type ferroelectric walls, and magneto-optical Kerr (MOKE), Faraday effect, and/or anomalous Hall-type effects in certain antiferromagnets such as Cr₂O₃, MnPSe₃, Mn₄(Nb,Ta)₂O₉, and Mn₃(Sn,Ge,Ga). A large number of new specimen constitutes having SOS with Magnetization will be discussed, and require future experimental verification of their ferromagnetism-like behaviors, and also theoretical understanding of possible microscopic mechanisms.

Zoom Meeting:

https://kth-se.zoom.us/j/61226950287

Prof. H.Haggard, Bard College

Why do so many black holes measured in gravitational waves have zero spin?

Black hole entropy is a robust prediction of quantum gravity with no established phenomenological consequences to date. We use the Bekenstein-Hawking entropy formula and general-relativistic statistical mechanics to determine the probability distribution of random geometries uniformly sampled in phase space. We show that this statistics (in the limit \( \hbar \to 0\) ) is relevant to large curvature perturbations, resulting in a population of primordial black holes with zero natal spin. In principle, the identification of such a population at LIGO, Virgo, and future gravitational wave observatories could provide the first observational evidence for the statistical nature of black hole entropy.

Prof. Steven Longmore, Liverpool John Moores University

Ecosystems and Life

Abstract: I will cover two topics united under the theme of ecosystems shaping the potential for life. In the first half, I will present recent results showing that the architecture of planetary systems is shaped by their environmental ecosystems, in particular the degree of stellar clustering around their host star (Winter et al, 2020, Nature, 586, 528). We identify old, co-moving stellar groups around exoplanet host stars in the astrometric data from the Gaia satellite and demonstrate that the architecture of planetary systems exhibits a strong dependence on local stellar clustering in position-velocity phase space, implying a dependence on their formation or evolution environment. After controlling for host stellar age, mass, metallicity, and distance from the Sun, we obtain highly significant differences in planetary (system) properties between phase space overdensities and the field. The median semi-major axis and orbital period of planets in overdensities are 0.087 au and 9.6 days, respectively, compared to 0.81 au and 154 days for planets around field stars. 'Hot Jupiters' (massive, close-in planets) predominantly exist in stellar phase-space overdensities, strongly suggesting that their extreme orbits originate from environmental perturbations rather than internal migration or planet-planet scattering. Our findings suggest that stellar clustering is an important factor setting the architectures of planetary systems. In the second half of the talk, I will discuss how we are using astrophysics research techniques to help ecologists protect ecosystems, save critically endangered animal species, and stop peat forest fires that are a major contributor to climate change.


Webex link: https://uconn-cmr.webex.com/meet/cab16109