Kris Sigurdson

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We compute the probability distribution for bubble collisions in an inflating false vacuum which decays by bubble nucleation. Our analysis generalizes previous work of Guth, Garriga, and Vilenkin to the case of general cosmological evolution inside the bubble, and takes into account the dynamics of the domain walls that form between the colliding bubbles.(More)
We present a novel mechanism for generating both the baryon and dark matter densities of the Universe. A new Dirac fermion X carrying a conserved baryon number charge couples to the standard model quarks as well as a GeV-scale hidden sector. CP-violating decays of X, produced nonthermally in low-temperature reheating, sequester antibaryon number in the(More)
We study the effects on cosmic microwave background ~CMB! temperature and polarization anisotropies of spatial fluctuations of the fine-structure parameter between causally disconnected regions of the Universe at the time of recombination. Analogous to weak gravitational lensing, in addition to modifying the mean power spectra and inducing a curl component(More)
We present the first simulations within an effective theory of structure formation (ETHOS), which includes the effect of interactions between dark matter and dark radiation on the linear initial power spectrum and dark matter self-interactions during non-linear structure formation. We simulate a Milky Way-like halo in four different dark matter models and(More)
Francis-Yan Cyr-Racine, 2, ∗ Kris Sigurdson, 4 Jesús Zavala, Torsten Bringmann, Mark Vogelsberger, and Christoph Pfrommer Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA California Institute of Technology, Pasadena, California 91125, USA School of Natural Sciences, Institute for Advanced Study, Princeton, New Jersey 08540, USA(More)
We propose that "standard pings," brief broadband radio impulses, can be used to study the three-dimensional clustering of matter in the Universe even in the absence of redshift information. The dispersion of radio waves as they travel through the intervening plasma can, like redshift, be used as a cosmological distance measure. Because of inhomogeneities(More)
We consider the consequences of a neutral dark-matter particle with a nonzero electric and/or magnetic dipole moment. Theoretical constraints, as well as constraints from direct searches, precision tests of the standard model, the cosmic microwave background and matter power spectra, and cosmic gamma rays, are included. We find that a relatively light(More)
Recently, the PVLAS Collaboration reported an anomalously large rotation of the polarization of light in the presence of a magnetic field in vacuum. As a possible explanation, they consider the existence of a light spin-zero particle coupled to two photons. We propose here a method of independently testing this result using a high-energy photon regeneration(More)