arXiv subjects

Nicholas Agia

Publications and source records attributed to Nicholas Agia.

6 recordsLinked to original sources

arXiv2025

On Nonlinear Inertial Transformations

It is often assumed that the most general transformation between two inertial reference frames is affine linear in their Cartesian coordinates, an assumption which is however not true. We provide a complete derivation of the most general inertial frame transformation, which is indeed nonlinear; along the way, we shall find that the conditions of preserving the Law of Inertia take the form of Schwarzian differential equations, providing perhaps the simplest possible physics setting in which the Schwarzian derivative appears. We then demonstrate that the most general such inertial transformation which further preserves the speed of light in all directions is, however, still affine linear. Physically, this paper may be viewed as a reduction of the number of postulates needed to uniquely specify special relativity by one, as well as a proof that inertial transformations automatically imbue spacetime with a vector space structure, albeit in one higher dimension than might be expected. Mathematically, this paper may be viewed as a derivation of the higher-dimensional analog of the Schwarzian differential equation and its most general solution.

physics.class-ph↗

arXiv2024

The 2d Free Boson Minkowski CFT with Asymptotic Charges

We explicitly construct the states of the 2d free boson on the infinite line with specified asymptotic charges. The Minkowski CFT states derive from (the analytic continuation of) the shrinking limit of Euclidean angular quantization, wherein the superselection sector for fixed asymptotic charges corresponds to specific endpoint operators for the angular quantization on the sphere. When applied to string theory, we obtain a new class of fundamental strings that are neither open nor closed and which we dub "stretched strings". We describe constant-time snapshots of the worldsheets of the different types of stretched strings, and as a special case we find a heuristic picture of Maldacena's "long strings" in the $c=1$ string theory.

hep-th↗

arXiv2023

AdS$_3$ String Stars at Pure NSNS Flux

We study Horowitz-Polchinski string stars in pure AdS$_3$ near the Hagedorn temperature using the technique of worldsheet conformal perturbation theory. Since the worldsheet CFT for pure AdS$_3$ is known exactly, our methodology provides a systematic way to construct Horowitz-Polchinski backgrounds to all orders in $\alpha'$. We explicitly construct the leading string star equations in a double expansion in temperature and WZW level $k$ which we then solve numerically.

hep-th↗

arXiv2023

Massive Type IIB Superstrings Part I: 3- and 4-Point Amplitudes

We present the 3- and 4-point tree-level scattering amplitudes involving first-massive states in closed Type IIB superstring theory, computed in the Minkowski vacuum. In particular, the 3-point amplitudes are computed for all possible combinations of first-massive and massless string states, and the 4-point amplitudes are computed for all such combinations involving at most two massive string states. We verify that unitarity is satisfied by checking the massless and first-massive poles of a 4-point amplitude. This paper is intended to serve as a reference providing all these amplitudes explicitly in consistent conventions as well as worldsheet correlators necessary to perform further computations beyond those listed here.

hep-th↗

arXiv2022

Angular Quantization in CFT

The most common quantization scheme in which to study a conformal field theory is radial quantization, wherein a Hilbert space of states is defined on a sphere, whose Hamiltonian when mapped to the plane is the dilatation generator and which boasts a state/operator correspondence. In this paper, we consider an alternative quantization scheme for 2d CFTs in which the plane is foliated by constant-angle slices, as opposed to concentric circles, whose Hamiltonian is the rotation generator. In this angular quantization, there is no state/operator correspondence but instead an "asymptotics/operator correspondence". A central feature is that the quantization slice ends on two operators, and a regulator must be chosen by excising holes around each operator and imposing suitable boundary conditions such that the holes shrink to the desired local operators. This angular quantization may be viewed as constructing CFTs in Minkowski space, or separately as studying non-conformal (but local) boundary conditions in CFTs. We provide explicit Fock space constructions for various free 2d CFTs. In addition to the motivation of applying angular quantization in string theory situations where traditional radial quantization is insufficient, we comment on its relation to modular Hamiltonian approaches to entanglement entropy.

hep-th↗

arXiv2015

Low-Lying Cosmic String Spectrum and Background Fields in Effective String Theory

We present a detailed analysis of the cosmic string spectrum. Explicit solutions are numerically found using Mathematica and presented here for the lowest-lying supported modes. Most of the emphasis is on the Nambu-Goldstone modes and the least massive excitation, the latter of which is shown to be the scalar breather mode. We address the possibility of pseudoscalar excitations by adding suitable interactions to the string and show that it is possible to have a least massive pseudoscalar bound state with only bosonic fields. We finally show how certain interactions in the bulk UV theory give rise to background field interactions in the effective string theory.

hep-th↗