MIT Center for Theoretical Physics – a Leinweber Institute

Fast radio bursts (FRBs) are an emerging precision probe of cosmological fluctuations. The amount and quality of observed FRB data will grow enormously over the next decade. FRB dispersion data directly probe the free electron distribution up to intergalactic scales. Precision models of the free electron distribution are necessary to exploit this exciting new probe of large-scale structure. We show that the free electron distribution almost exactly follows the total matter distribution. We confirm this fact by estimating the electron field-level bias parameters for the first time from the FLAMINGO simulations. With simulation-based knowledge of a handful of electron free parameters, the electron distribution largely acts as a second realization of the matter distribution. Working on large scales, we can leverage this fact to combine FRB correlations with those of Cosmic Microwave Background (CMB) weak lensing to constrain cosmological parameters. Assuming access to localized FRBs with redshifts, we perform cosmological forecasts using these two large-scale matter probes, which have no strong dependence on baryonic feedback models nor on parameters that encode galaxy formation. We show that the parameters $σ_8$ and $Ω_m$ are constrained at a level similar to or better than that obtained by combining FRB dispersion with weak lensing of galaxy shapes under conservative assumptions. These results motivate the use of FRB data as a complementary probe of cosmic structure and will be especially compelling as redshifts become available for localized FRB host galaxies.

We present the first combined phenomenological study of non-global and super-leading logarithms in vector-boson-fusion Higgs production and its QCD-induced Higgs-plus-dijet background. A veto on radiation between the widely separated tagging jets provides a natural setting to investigate correlated soft emission and Glauber-induced violations of color coherence. We resum the leading non-global logarithms with the leading-color parton shower framework Marzili and the super-leading series with Glauber exchanges at $N_c=3$. Combining the two resummed contributions, we study their impact on gap cross sections and on the relative suppression of signal and background.

The Gaia mission has greatly improved our understanding of the stellar binary population. Beyond providing an extensive catalog of binary systems with two luminous stars, Gaia has also discovered several systems that appear to be star--black hole (BH) binaries. One of the leading candidate formation channels for these systems is dynamical exchange, in which one component of a star--star binary is ejected from the system and replaced by a BH. Exchange processes are very sensitive to the velocity distribution of the incoming objects, and become very efficient in the limit that perturbers are slow, so the exchanged binary population is a sensitive probe of slow-moving objects. A population of slow-moving, nonluminous objects is naturally produced in dissipative dark matter (DDM) scenarios, where a subcomponent of dark matter can cool to form a dark disk and dark compact objects (DCOs), including but not limited to BHs, with a small velocity dispersion. In this work, we evaluate the rate at which DCOs formed by DDM exchange into star--star binaries to form star--DCO binaries. We find that in a wide range of parameter space, even under conservative assumptions, the rate of exchange interactions is sufficient to produce the objects that Gaia has observed to date. In some portions of parameter space, the predicted exchange rate is well in excess of the rate estimated from observations. We point out the potential for competitive constraints on the DDM parameter space with current and future data, making the Gaia mission an important testbed for dark sector cooling.

Boosted, hadronically decaying $W$ and $Z$ bosons are among the most abundant heavy objects at colliders, and their vector nature makes their substructure qualitatively richer than that of a scalar. We initiate precision studies of the hadronic decays of boosted polarized vector bosons with energy correlators. In the narrow-width limit, the laboratory-frame two-point energy correlator is a sum of longitudinal and transverse decay spectra, each weighted by its polarized production rate and obtained by a closed-form boost kernel acting on rest-frame correlators. Combining polarized production density matrices, computed at NNLO in QCD for $ppto V+X$ and at leading order for $e^+e^-to W^+W^-$, with decay correlators that combine NNLO fixed order with NNLL collinear and N$^4$LL back-to-back resummation, we find for high-$p_T$$W/Z$ production that polarization shifts the spectrum by $mathcal{O}(10%)$ relative to a naive unpolarized treatment. Even without any reconstruction, hadronic $W/Z$ decays stand out over the realistic QCD background of untagged jet samples as a localized angular bump. Our results open the door to using energy correlators for polarimetry of electroweak bosons through their hadronic decays, for standard-candle measurements of electroweak bosons inside jets, and in sharper searches for new resonances.