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B. Altschul

Publications and source records attributed to B. Altschul.

27 records · Page 2Linked to original sources
arXiv2004

Compton Scattering in the Presence of Lorentz and CPT Violation

We examine the process of Compton scattering, in the presence of a Lorentz- and CPT-violating modification to the structure of the electron. We calculate the complete tree-level contribution to the cross section; our result is valid to all orders in the Lorentz-violating parameter. We find a cross section that differs qualitatively from the Klein-Nishina result at small frequencies, and we also encounter a previously undescribed complication that will arise in the calculation of many Lorentz-violation cross sections: The Lorentz violation breaks the spin degeneracy of the external states, so we cannot use a closure relation to calculate the unpolarized cross section.

hep-ph↗
arXiv2004

Nonpolynomial Normal Modes of the Renormalization Group in the Presence of a Constant Vector Potential Background

We examine the renormalization group flow in the vicinity of the free-field fixed point for effective field theories in the presence of a constant, nondynamical vector potential background. The interaction with this vector potential represents the simplest possible form of Lorentz violation. We search for any normal modes of the flow involving nonpolynomial interactions. For scalar fields, the inclusion of the vector potential modifies the known modes only through a change in the field strength renormalization. For fermionic theories, where an infinite number of particle species are required in order for nonpolynomial interactions to be possible, we find no evidence for any analogous relevant modes. These results are consistent with the idea that the vector potential interaction, which may be eliminated from the action by a gauge transformation, should have no physical effects.

hep-th↗
arXiv2004

Failure of Gauge Invariance in the Nonperturbative Formulation of Massless Lorentz-Violating QED

We consider a Lorentz-violating modification to the fermionic Lagrangian of QED that is known to produce a finite Chern-Simons term at leading order. We compute the second order correction to the one-loop photon self-energy in the massless case using an exact propagator and a nonperturbative formulation of the theory. This nonperturbative theory assigns a definite value to the coefficient of the induced Chern-Simons term; however, we find that the theory fails to preserve gauge invariance at higher orders. We conclude that the specific nonperturbative value of the Chern-Simons coefficient has no special significance.

hep-th↗
arXiv2003

Exact Normal Modes for a System with Three Luttinger Liquids Interacting in an Elongated Trap

We consider a system of spinless fermions in a nearly one-dimensional cylindrical trap, with the Fermi level such that only the lowest-lying states with angular momenta l = +hbar, 0, or -hbar about the axis of the trap are occupied. We treat the particles in these states as comprising three separate Luttinger liquids, with the possibility for forward and backward scattering between them. We determine the normal modes in the system in the presence of this scattering, finding two sets of linear harmonic fluid modes and one set of modes that are self-coupled through a sine-Gordon interaction.

cond-mat.mes-hall↗
arXiv2003

Perturbative Energy Shifts of the Luttinger Liquid Due to the Presence of Additional Dimensions

We consider a system of spinless fermions in a nearly one-dimensional cylindrical trap. We introduce four-fermion interaction terms through which particles in low-lying modes of the trap may interact with particles in radially or angularly excited states. Treating these interactions as perturbations about a purely one-dimensional Luttinger liquid, we calculate the zero-temperature energy shifts of the bosonic quanta of the Luttinger model. We perform this calculation is two ways. First we use the bosonized forms of the fermion operators. Then we introduce a simplified, physically-motivated model; in this model, the methods used immediately generalize, so that we may also calculate the energy shifts of the Tomonaga-Luttinger model. By equating the results from the two disparate models, we obtain the numerical value of the Luttinger liquid bandwidth for this system.

cond-mat↗
arXiv2003

Fermions in a Multi-Soliton Background in 1+1 Dimensions

We consider the fermionic bound states associated with a soliton-antisoliton pair in 1+1 dimensions which have zero energy when the solitons are infinitely far apart. We calculate the energies of these states when the solitons are separated by a finite distance. The energies decay exponentially with the distance between the soliton and antisoliton. When the fermion mass is much larger than the boson mass, the energy simplifies substantially. These energies may be interpreted as a contribution to the effective potential between the soliton and antisoliton. The character of this contribution depends upon which fermionic states are occupied. Performing the analogous calculation for the simplest (3+1)-dimensional soliton system, we find no fermionic energy shift.

hep-th↗
arXiv2002

Analysis of a Toy Model of Electron "Splitting"

We examine Maris' recent suggestion that the fission of electron-inhabited bubbles in liquid helium may give rise to a new form of electron fractionization. We introduce a one-dimensional toy-model--a simplified analogue of the helium system--which may be analyzed using the Born-Oppenheimer approximation. We find that none of the model's low-lying energy eigenstates have the form suggested by Maris' computations, in which the bubbles were treated completely classically. Instead, the eigenstates are quantum-mechanically entangled superposition states, which the classical treatment overlooks.

cond-mat.soft↗
arXiv2001

Photon Decay at the Schwarzschild Horizon

A recent proposal that gravity theory is an emergent phenomenon also entails the possibility of photon decay near the Schwarzschild event horizon. We present a possible mechanism for such decay, which utilizes a dimensional reduction near the horizon.

gr-qc↗