CBChristopher Brust

Christopher Brust

*This is an algorithmically generated author record based on publicly available information.

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Christopher Brust has a total of 8 co-authors. Here are the top co-authors by number of shared publications:


Latest Publications

  • Open Access

    Partially Massless Higher-Spin Theory II: One-Loop Effective Actions

    by Christopher Brust, Kurt Hinterbichler

    We continue our study of a generalization of the D-dimensional linearized Vasiliev higher-spin equations to include a tower of partially massless (PM) fields. We compute one-loop effective actions by evaluating zeta functions for both the "minimal" and "non-minimal" parity-even versions of the theory. Specifically, we compute the log-divergent part of the effective action in odd-dimensional Euclidean AdS spaces for D=7 through 19 (dual to the a-type conformal anomaly of the dual boundary theory), and the finite part of the effective action in even-dimensional Euclidean AdS spaces for D=4 through 8 (dual to the free energy on a sphere of the dual boundary theory). We pay special attention to the case D=4, where module mixings occur in the dual field theory and subtlety arises in the one-loop computation. The results provide evidence that the theory is UV complete and one-loop exact, and we conjecture and provide evidence for a map between the inverse Newton's constant of the partially massless higher-spin theory and the number of colors in the dual CFT.

  • Open Access

    Partially Massless Higher-Spin Theory

    by Christopher Brust, Kurt Hinterbichler

    We study a generalization of the D-dimensional Vasiliev theory to include a tower of partially massless fields. This theory is obtained by replacing the usual higher-spin algebra of Killing tensors on (A)dS with a generalization that includes "third-order" Killing tensors. Gauging this algebra with the Vasiliev formalism leads to a fully non-linear theory which is expected to be UV complete, includes gravity, and can live on dS as well as AdS. The linearized spectrum includes three massive particles and an infinite tower of partially massless particles, in addition to the usual spectrum of particles present in the Vasiliev theory, in agreement with predictions from a putative dual CFT with the same symmetry algebra. We compute the masses of the particles which are not fixed by the massless or partially massless gauge symmetry, finding precise agreement with the CFT predictions. This involves computing several dozen of the lowest-lying terms in the expansion of the trilinear form of the enlarged higher-spin algebra. We also discuss nuances in the theory that occur in specific dimensions; in particular, the theory dramatically truncates in bulk dimensions D=3,5 and has non-diagonalizable mixings which occur in D=4,7.

  • Open Access

    Free box^k Scalar Conformal Field Theory

    by Christopher Brust, Kurt Hinterbichler

    We consider the generalizations of the free U(N) and O(N) scalar conformal field theories to actions with higher powers of the Laplacian box^k, in general dimension d. We study the spectra, Verma modules, anomalies and OPE of these theories. We argue that in certain d and k, the spectrum contains zero norm operators which are both primary and descendant, as well as extension operators which are neither primary nor descendant. In addition, we argue that in even dimensions d <= 2k, there are well-defined operator algebras which are related to the box^k theories and are novel in that they have a finite number of single-trace states.

  • Open Access

    Cosmological Constraints on Interacting Light Particles

    by Christopher Brust, Yanou Cui, Kris Sigurdson

    Cosmological observations are becoming increasingly sensitive to the effects of light particles in the form of dark radiation (DR) at the time of recombination. The conventional observable of effective neutrino number, $N_{\rm eff}$, is insufficient for probing generic, interacting models of DR. In this work, we perform likelihood analyses which allow both free-streaming effective neutrinos (parametrized by $N_{\rm eff}$) and interacting effective neutrinos (parametrized by $N_{\rm fld}$). We motivate an alternative parametrization of DR in terms of $N_{\rm tot}$ (total effective number of neutrinos) and $f_{\rm fs}$ (the fraction of effective neutrinos which are free-streaming), which is less degenerate than using $N_{\rm eff}$ and $N_{\rm fld}$. Using the Planck 2015 likelihoods in conjunction with measurements of baryon acoustic oscillations (BAO), we find constraints on the total amount of beyond the Standard Model effective neutrinos (both free-streaming and interacting) of $\Delta N_{\rm tot} < 0.39$ at 2$\sigma$. In addition, we consider the possibility that this scenario alleviates the tensions between early-time and late-time cosmological observations, in particular the measurements of $\sigma_8$ (the amplitude of matter power fluctuations at 8$h^{-1}$ Mpc), finding a mild preference for interactions among light species. We further forecast the sensitivities of a variety of future experiments, including Advanced ACTPol (a representative CMB Stage-III experiment), CMB Stage-IV, and the Euclid satellite. This study is relevant for probing non-standard neutrino physics as well as a wide variety of new particle physics models beyond the Standard Model that involve dark radiation.

  • Open Access

    Partially massless higher-spin theory

    by Christopher Brust, Kurt Hinterbichler


  • Top Cited Papers
    Open Access

    Free □ k scalar conformal field theory

    by Christopher Brust, Kurt Hinterbichler


  • Open Access

    Partially massless higher-spin theory II: one-loop effective actions

    by Christopher Brust, Kurt Hinterbichler


  • Open Access

    Resurgent Supersymmetry and String Theory

    by Christopher Brust

    We study a realization of accidental supersymmetry in type IIB string theory as a proof-of-principle of the mechanism and as a prototype of the strong sector present in resurgent supersymmetry, a warped UV-completion of natural supersymmetry. We first introduce the mechanism of accidental supersymmetry as a way of producing a supersymmetric spectrum in the IR of a quasi-conformal field theory, and then go on to discuss the utility of the mechanism in the specific BSM model of resurgent supersymmetry. The realization of accidental SUSY that we study is IIB string theory on an orbifold of the Klebanov-Strassler solution.