Browsing by Author "Turner, Jessica"

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    Phase of confined electroweak force in the early Universe
    (American Physical Society, 2019) Berger, Joshua; Long, Andrew J.; Turner, Jessica
    We consider a modified cosmological history in which the presence of beyond-the-Standard-Model physics causes the weak gauge sector, SU(2)L, to confine before it is Higgsed. Under the assumption of chiral symmetry breaking, quark and lepton weak doublets form condensates that break the global symmetries of the Standard Model, including baryon and lepton number, down to a U(1) subgroup under which only the weak singlet fermions and Higgs boson transform. The weakly coupled gauge group SU(3)c×U(1)Y is also broken to an SU(2)c×U(1)Q gauge group. The light states include (pseudo-)Goldstone bosons of the global symmetry breaking, mostly elementary fermions primarily composed of the weak singlet quarks and leptons, and the gauge bosons of the weakly coupled gauge group. We discuss possible signatures from early Universe cosmology including gravitational wave radiation, topological defects, and baryogenesis.
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    Thermal pressure on ultrarelativistic bubbles from a semiclassical formalism
    (IOP Publishing, 2024) Long, Andrew J.; Turner, Jessica
    We study a planar bubble wall that is traveling at an ultrarelativistic speed through a thermal plasma. This situation may arise during a first-order electroweak phase transition in the early universe. As particles cross the wall, it is assumed that their mass grows from m a to m b , and they are decelerated causing them to emit massless radiation (m c = 0). We are interested in the momentum transfer to the wall, the thermal pressure felt by the wall, and the resultant terminal velocity of the wall. We employ the semiclassical current radiation (SCR) formalism to perform these calculations. An incident-charged particle is treated as a point-like classical electromagnetic current, and the spectrum of quantum electromagnetic radiation (photons) is derived by calculating appropriate matrix elements. To understand how the spectrum depends on the thickness of the wall, we explore simplified models for the current corresponding to an abrupt and a gradual deceleration. For the model of abrupt deceleration, we find that the SCR formalism can reproduce the P therm ∝ γ 0 w scaling found in earlier work by assuming that the emission is soft, but if the emission is not soft the SCR formalism can be used to obtain P therm ∝ γ 2 w instead. For the model of gradual deceleration, we find that the wall thickness L w enters to cutoff the otherwise log-flat radiation spectrum above a momentum of ∼ γ 2 w / L w , and we discuss the connections with classical electromagnetic bremsstrahlung.