Lance Labun

Lance Labun
University of Texas at Austin | UT · Department of Physics

PhD

About

41
Publications
2,889
Reads
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443
Citations
Additional affiliations
October 2012 - September 2014
National Taiwan University
Position
  • Distinguished Junior Fellow
January 2012 - September 2012
The University of Arizona
Position
  • Research Associate
May 2011 - August 2011
CERN
Position
  • Visiting researcher
Education
September 2003 - June 2007
Dartmouth College
Field of study
  • Physics and mathematics

Publications

Publications (41)
Preprint
The classical theory of single-electron dynamics in focused laser pulses is the foundation of both the relativistic ponderomotive force (RPF), which in turn underlies models of laser-collective-plasma dynamics, and the discovery of novel strong-field radiation dynamics. Despite this bedrock importance, consensus eludes the community as to whether a...
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The long-standing challenge to describing charged particle dynamics in strong classical electromagnetic fields is how to incorporate classical radiation, classical radiation reaction and quantized photon emission into a consistent unified framework. The current, semiclassical methods to describe dynamics of quantum particles in strong classical fie...
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We discuss the inverse \(\beta\)-decay of accelerated protons in the context of neutrino flavor superpositions (mixings) in mass eigenstates. The process \( p\rightarrow n \ell^{+} \nu_{\ell}\) is kinematically allowed because the accelerating field provides the rest energy difference between initial and final states. The rate of \( p\rightarrow n\...
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We show that universality near a critical end point implies a characteristic relation between third- and fourth-order baryon susceptibilities $\chi_3$ and $\chi_4$, resulting in a banana-shaped loop when $\chi_4$ is plotted as a function of $\chi_3$ along a freeze-out line. Including the individual enhancements of $\chi_3$ and $\chi_4$ near a criti...
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We evaluate the third- and fourth-order baryon, charge and strangeness susceptibilities near a chiral critical point using the Nambu-Jona-Lasinio model. We identify robust qualitative behaviours of the susceptibilities along hypothetical freeze-out lines that agree with previous model studies. Quantitatively, baryon number fluctuations are the larg...
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We discuss the inverse $\beta$-decay of accelerated protons in the context of neutrino oscillations. The process $p\rightarrow n \ell^+ \nu_\ell$ is kinematically allowed because the accelerating field provides the rest energy difference between initial and final states. The rate of $p\to n$ conversions can be evaluated in either the laboratory fra...
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We point out that neutrino oscillations imply an ambiguity in the definition of the vacuum and the coupling to gravity, with experimentally observable consequences due to the Unruh effect. In an accelerating frame, the detector should see a bath of mass Eigenstates neutrinos. In inertial processes, neutrinos are produced and absorbed as charge Eige...
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We study the low energy effective theory describing gravity with broken spatial diffeomorphism invariance. In the unitary gauge, the Goldstone bosons associated with broken diffeomorphisms are eaten and the graviton becomes a massive spin-2 particle with 5 well-behaved degrees of freedom. In this gauge, the most general theory is built with the low...
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We study the impact of gravitational slingshot on the distribution of cold dark matter in early and modern era galaxies. Multiple gravitational encounters of a lower mass dark matter particle with massive baryonic astrophysical bodies would lead to an average energy gain for the dark matter, similar to second order Fermi acceleration. We calculate...
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We calculate model-independently the impact of the critical point on higher order baryon susceptibilities $\chi_n$, showing how they depend on fluctuations of the order parameter. Including all tree level diagrams, we find new contributions to $\chi_4$ equally important to the kurtosis of the order parameter fluctuations, and we characterize the ku...
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We show a new scheme of nonperturbative pair production by high energy photons ($\omega\gtrsim m$) in a strong external field is achievable at the next high intensity laser experiments. The pair momentum is boosted and for $\omega\gtrsim 1.2m$ the pair yield is increased when the external field is formed by two laser pulses converging at a small an...
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Mergers of binary neutron stars create conditions of supranuclear density $n\gtrsim n_{\rm nuc}\simeq 0.17 {\rm fm}^{-3}$ and moderate temperature $50\lesssim T \lesssim 90 {\rm MeV}$. These events thus probe a sensitive region of the density-temperature phase diagram of QCD matter. We study photon production by the QCD conformal anomaly for a sign...
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We describe properties and gravitational interactions of meteor-mass and greater compact ultra dense objects with nuclear density or greater (CUDO s). We discuss possible enclosure of CUDO s in comets, stability of these objects on impact with the Earth and Sun and show that the hypothesis of a CUDO core helps resolve issues challenging the underst...
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The properties of the quark and hadron Universe are explored. Kinetic theory considerations are presented proving that hadron abundances after phase transformation from quarks to hadrons remain intact till abundances of hadrons become irrelevant. The hadronization process and the evolution of hadron yields is described in detail.
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We obtain the effective interaction ${\cal L}_{hgg}$, which is driven by the fluctuations of the top quark, as a function of the top quark chromomagnetic factor $\kappa_t$. We show that for $\kappa_t\ne 2$ the Higgs-to-two gluon, $h\to gg$, decay rate is always significantly suppressed as compared to the standard case $\kappa_t= 2$, which would be...
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We compute the dependence of the Higgs to two-photon decay rate $\Gamma_{h\to \gamma \gamma}$ on the top quark gyromagnetic factor $g_t$ in the heavy top limit and evaluate the expected change for one-loop SM correction to $g_t$. Our results are general and allow consideration of further modifications of $g_t$ and we predict the resultant $\Gamma_{...
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We explore the first order in \alpha properties of the QED effective action Veff as a function of the gyromagnetic factor g for arbitrarily strong constant and homogeneous fields. We find a cusp in both the b_0 -renormalization group coefficient and the weak field, infrared limit expansion of the light-light scattering coefficients.
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Little is known about the physics frontier of strong acceleration; both classical and quantum physics need further development in order to be able to address this newly accessible area of physics. In this lecture we discuss what strong acceleration means and possible experiments using electron-laser collisions and, data available from ultra-relativ...
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The electron vacuum fluctuations measured by $\cond$ do not vanish in an externally applied electric field $\calE$. For an exactly constant field, that is for vacuum fluctuations in presence of a constant accelerating force, we show that $\cond$ has a Boson-like structure with spectral state density $\tanh^{-1}(E/m)$ and temperature $\TEH = e\calE/...
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The quantum fluctuations of an "accelerated" vacuum state, that is vacuum fluctuations in the presence of a constant electromagnetic field, can be described by the temperature $\TEH$. Considering $\TEH$ for the gyromagnetic factor $g=1$ we show that $\TEH(g=1)=\THU$, where $\THU$ is the Unruh temperature experienced by an accelerated observer. We c...
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We propose a model of clustered u-d-s quark matter that leads to stable bulk strange quark matter. We discuss qualitatively consequences of impacts by sub-planetary mass strangelets on rocky solar system bodies.
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We consider compact astrophysical objects formed from dark matter fermions of mass 250 GeV to 100 TeV or from massless fermions hidden by vacuum structure of similar energy scale. These macroscopic objects have maximum stable masses of sub-planetary scale (asteroids) and radii of micron to centimeter scale. We describe the surface gravity and tidal...
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We evaluate particle production in highly asymmetric head-on collisions of lasers pulses due to non-perturbative coherent action of many photons. We obtain the yield of electron-positron pairs, which is controlled by the photon content of the weaker pulse, and show that the wavelength of the weaker pulse and the momentum asymmetry determine laborat...
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We study interactions of meteor-like compact ultra dense objects with nuclear density or greater (CUDOs) with the Earth and other rocky bodies in the solar system as a possible source of information about novel forms of matter. We study the energy loss in CUDO puncture of the body and describe differences between regular matter and CUDO impacts.
Article
Quantum electrodynamics generates a nonlinear theory of electromagnetism from fluctuations of electron-positron pairs. The nonlinear interactions are suppressed by the field scale Bc= me^2/e = 4.1x10^9:T. Fields approaching this magnitude are thought to be found only in the neighbourhood of strongly-magnetized compact stars, and in these environs t...
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The spectrum of electrons and positrons originating from vacuum decay occurring in the collision of two non-colinear laser pulses is obtained. It displays high energy, highly-collimated particle bunches traveling in a direction separate from the laser beams. This result provides an unmistakable signature of the vacuum decay phenomenon and could sug...
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As a means of detecting compact ultra dense objects (CUDOs) with nuclear density or greater, and a mass $10^{-10}
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This thesis is a guide to a selection of the author's published work that connect and contribute to understanding the vacuum of quantum electrodynamics in strong, prescribed electromagnetic fields. This theme is elaborated over the course of two chapters: The first chapter sets the context, defining the relevant objects and conditions of the study...
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We consider that the universe is trapped in an excited vacuum state and the resulting excitation energy provides the observed dark energy. We explore the conditions under which this situation can arise from physics already known. Considering the example of how macroscopic QED fields alter the vacuum structure, we find that the energy scale 1 meV --...
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Understanding physics in domains of critical (quantum unstable) fields requires investigating the classical and quantum particle dynamics at the critical acceleration, $\dot u \to 1$ [natural units]. This regime of physics remains today experimentally practically untested. Particle and light collision experiments reaching critical acceleration are...
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The goal of this paper is twofold: to explore the response of classical charges to electromagnetic force at the level of unity in natural units and to establish a criterion that determines physical parameters for which the related radiation-reaction effects are detectable. In pursuit of this goal, the Landau-Lifshitz equation is solved analytically...
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We study the properties of the trace T of the QED energy–momentum tensor in the presence of quasi-constant external electromagnetic fields. We exhibit the origin of T in the quantum nonlinearity of the electromagnetic theory. We obtain the quantum vacuum fluctuation-induced interaction of a particle with the field of a strongly magnetized compact s...
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Quasiconstant external fields in nonlinear electromagnetism generate a global contribution proportional to gμν in the energy-momentum tensor, thus a simulacrum of dark energy. To provide a thorough understanding of the origin and strength of its effects, we undertake a complete theoretical and numerical study of the energy-momentum tensor Tμν for n...
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Discussing the limitations on the validity of classical electrodynamics, we show that present day laser pulse technology applied to head-on-collisions with relativistic electrons generates fields strong enough to permit experimentation at the limits of validity of the Lorentz force, and the development of experimental tests of Mach's principle. We...
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Contemporary physics faces three great riddles that lie at the intersection of quantum theory, particle physics and cosmology. They are 1. The expansion of the universe is accelerating – an extra factor of two appears in the size. 2. Zero-point fluctuations do not gravitate – a matter of 120 orders of magnitude 3. The “True ” quantum vacuum state d...
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Violation of the superposition principle in the Maxwell field could arise from intrinsic nonlinearity in the fundamental theory of the photon, such as seen in Born-Infeld (BI) electrodynamics, but certainly occurs due to charged particle vacuum fluctuations, i.e. one-loop quantum electrodynamics (QED). The necessary presence of a dimensioned scale...
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We consider dynamics of vacuum decay and particle production in the context of short pulse laser experiments. We identify and evaluate the invariant "materialization time," $\tau$, the timescale for the conversion of an electromagnetic field energy into particles, and we compare to the laser related time scales.
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We investigate the stochastic dynamics of a particle in the presence of a modulated sinusoidal potential. Using the time derivative of the winding number, we quantify the particle's motion according to its running time, the time it runs monotonically to the left or right. For a range of model parameters, we show that, in the overdamped regime, the...
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The structure of the global heliosphere is driven not only by the properties of the respective interstellar plasma and neutral populations but also by the temporal and spatial variation of the solar wind plasma itself. Often assumptions of symmetry or stationarity are made for modeling the global heliosphere that greatly reduce the problem space. H...

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