We present calculations in which an energetic light quark shoots through a finite slab of strongly coupled $\mathcal{N}=4$ supersymmetric Yang-Mills (SYM) plasma, with thickness $L$, focusing on what comes out on the other side. We find that even when the “jets” that emerge from the plasma have lost a substantial fraction of their energy they look in almost all respects like “jets” in vacuum with the same reduced energy. The one possible exception is that the opening angle of the “jet” is larger after passage through the slab of plasma than before. Along the way, we obtain a fully geometric characterization of energy loss in the strongly coupled plasma and show that $d{E}_{\text{out}}/dL\propto L^2/\sqrt{x_{\text{stop}}^2-L^2}$, where $E_{\text{out}}$ is the energy of the “jet” that emerges from the slab of plasma and $x_{\text{stop}}$ is the (previously known) stopping distance for the light quark in an infinite volume of plasma.

We investigate electron-positron pair creation from the vacuum in a pulsed electric background field. Employing the Sauter-type pulsed field $E(t)=E_0{\text{sech}}^2(t/\tau )$ with height $E_0$ and width $\tau$, we demonstrate explicitly the interplay between the nonperturbative and perturbative aspects of pair creation in the background field. We analytically compute the number of produced pairs from the vacuum in the Sauter-type field, and the result reproduces Schwinger’s nonperturbative formula in the long pulse limit (the constant field limit), while in the short pulse limit it coincides with the leading-order perturbative result. We show that two dimensionless parameters $\nu =|e{E}_0|{\tau }^2$ and $\gamma =|e{E}_0|\tau /m_e$ characterize the importance of multiple interactions with the fields and the transition from the perturbative to the nonperturbative regime. We also find that pair creation is enhanced compared to Schwinger’s formula when the field strength is relativity weak $|e{E}_0|/m_e^2\lesssim 1$ and the pulse duration is relatively short $m_e\tau \lesssim 1$, and reveal that the enhancement is predominantly described by the lowest order perturbation with a single photon.

We detail the construction of the most general asymptotically flat, stationary, rotating, nonextremal, dyonic black hole of the four-dimensional $\mathcal{N}=2$ supergravity coupled to 3 vector multiplets that describes the $STU$ model. It generates through U dualities the most general asymptotically flat, stationary black hole of $\mathcal{N}=8$ supergravity. We develop the solution generating technique based on $\mathrm{SO}(4,4)/\mathrm{SL}(2,\mathbb{R}{)}^4$ coset model symmetries, with an emphasis on the 4-fold permutation symmetry of the gauge fields. We indicate how previously known nonextremal and extremal solutions of the $STU$ model are recovered as limiting cases. Several properties of the general black hole solution are discussed, including its thermodynamics, the quadratic mass formula, the Bogomolny-Prasad-Sommerfield limit, the slow and fast extremal rotating limits, its properties in regards to the Kerr/conformal field theory correspondence, its Killing tensors and the separability of geodesic motion and probe scalars.

The 21 cm line provides a powerful probe of astrophysics and cosmology at high redshifts, but unlocking the potential of this probe requires the robust mitigation of foreground contaminants that are typically several orders of magnitude brighter than the cosmological signal. Recent simulations and observations have shown that the smooth spectral structure of foregrounds combines with instrument chromaticity to contaminate a “wedge”-shaped region in cylindrical Fourier space. While previous efforts have explored the suppression of foregrounds within this wedge, as well as the avoidance of this highly contaminated region, all such efforts have neglected a rigorous examination of the error statistics associated with the wedge. Using a quadratic estimator formalism applied to the interferometric measurement equation, we provide a framework for such a rigorous analysis (incorporating a fully covariant treatment of errors). Additionally, we find that there are strong error correlations at high spatial wave numbers that have so far been neglected in sensitivity derivations. These error correlations substantially degrade the sensitivity of arrays relying on contributions from long baselines, compared to what one would estimate assuming uncorrelated errors.

We introduce a new method to search for the lepton-flavor violating Higgs decays $h\to {\tau }^{\pm }{\mu }^{\mp }$ and $h\to {\tau }^{\pm }{e}^{\mp }$ in the leptonic $\tau$ decay channel. In particular, the Standard Model background is estimated in a fully data driven way. The method exploits the asymmetry between electrons and muons in the final state of signal events and is sensitive to differences in the rates of the two decays. Using this method, we investigate the LHC sensitivity to these processes. With $20{\mathrm{fb}}^{-1}$ of data at $\sqrt{s}=8\mathrm{TeV}$, we expect a $3\sigma$ sensitivity for observing branching ratios of order 0.9%. The method and the suggested statistical treatment are discussed in detail.

Recently, the one-loop free energy of higher spin (HS) theories in Euclidean ${\mathrm{AdS}}_{d+1}$ was calculated and matched with the order $N^0$ term in the free energy of the large $N$ “vectorial” scalar CFT on the $S^d$ boundary. Here we extend this matching to the boundary theory defined on $S^1\times S^{d-1}$, where the length of $S^1$ may be interpreted as the inverse temperature. It has been shown that the large $N$ limit of the partition function on $S^1\times S^2$ in the $U(N)$ singlet sector of the CFT of $N$ free complex scalars matches the one-loop thermal partition function of the Vasiliev theory in ${\mathrm{AdS}}_4$, while in the $O(N)$ singlet sector of the CFT of $N$ real scalars it matches the minimal theory containing even spins only. We extend this matching to all dimensions $d$. We also calculate partition functions for the singlet sectors of free fermion CFTs in various dimensions and match them with appropriately defined higher spin theories, which for $d>3$ contain massless gauge fields with mixed symmetry. In the zero-temperature case $R\times S^{d-1}$ we calculate the Casimir energy in the scalar or fermionic CFT and match it with the one-loop correction in the global ${\mathrm{AdS}}_{d+1}$. For any odd-dimensional CFT the Casimir energy must vanish on general grounds, and we show that the HS duals obey this. In the $U(N)$ symmetric case, we exhibit the vanishing of the regularized one-loop Casimir energy of the dual HS theory in ${\mathrm{AdS}}_{d+1}$. In the minimal HS theory the vacuum energy vanishes for odd $d$ while for even $d$ it is equal to the Casimir energy of a single conformal scalar in $R\times S^{d-1}$ which is again consistent with AdS/CFT, provided the minimal HS coupling constant is $\sim 1/(N-1)$. We demonstrate analogous results for singlet sectors of theories of $N$ Dirac or Majorana fermions. We also discuss extensions to CFTs containing $N_f$ flavors in the fundamental representation of $U(N)$ or $O(N)$.

We revisit the classic $O(N)$ symmetric scalar field theories in $d$ dimensions with interaction $({\varphi }^i{\varphi }^i{)}^2$. For $2<d<4$ these theories flow to the Wilson-Fisher fixed points for any $N$. A standard large $N$ Hubbard-Stratonovich approach also indicates that, for $4<d<6$, these theories possess unitary UV fixed points. We propose their alternate description in terms of a theory of $N+1$ massless scalars with the cubic interactions $\sigma {\varphi }^i{\varphi }^i$ and ${\sigma }^3$. Our one-loop calculation in $6-\epsilon$ dimensions shows that this theory has an IR stable fixed point at real values of the coupling constants for $N>1038$. We show that the $1/N$ expansions of various operator scaling dimensions match the known results for the critical $O(N)$ theory continued to $d=6-\epsilon$. These results suggest that, for sufficiently large $N$, there are 5-dimensional unitary $O(N)$ symmetric interacting conformal field theories (CFTs); they should be dual to the Vasiliev higher-spin theory in ${\mathrm{AdS}}_6$ with alternate boundary conditions for the bulk scalar. Using these CFTs we provide a new test of the 5-dimensional $F$ theorem, and also find a new counterexample for the $C_T$ theorem.

We propose a scenario for realizing super-Planckian axion decay constants in Calabi-Yau orientifolds of type IIB string theory, leading to large-field inflation. Our construction is a simple embedding in string theory of the mechanism of Kim, Nilles, and Peloso, in which a large effective decay constant arises from alignment of two smaller decay constants. The key ingredient is gaugino condensation on magnetized or multiply-wound D7-branes. We argue that, under very mild assumptions about the topology of the Calabi-Yau, there are controllable points in moduli space with large effective decay constants.

If the recent measurement of B-mode polarization by BICEP2 is due to primordial gravitational waves, it implies that inflation was driven by energy densities at the grand unified theory scale $M_{\mathrm{GUT}}\sim 2\times {10}^{16}\mathrm{GeV}$. This favors single-field chaotic inflation models. These models require trans-Planckian excursions of the inflaton, forcing one to address the UV completion of the theory. We use a benchmark 4d effective field theory of axion–four-form inflation to argue that inflation driven by a quadratic potential (with small corrections) is well motivated in the context of high-scale string theory models; that it presents an interesting incitement for string model building; and that the dynamics of the UV completion can have observable consequences.

If a new heavy particle $\varphi$ is produced in association with the top quark in a hadron collider, the production cross section exhibits a collinear singularity of the form $\log (m_{\varphi }/m_t)$, which can be resummed by introducing a top quark parton distribution function (PDF). We reassess the necessity of such resummation in the context of a high-energy $pp$ collider. We find that the introduction of a top PDF typically has a small effect at $\sqrt{S}\sim 100\mathrm{TeV}$ due to three factors: (1) ${\alpha }_s$ at the scale $\mu =m_{\varphi }$, which is quite small when $\log (m_{\varphi }/m_t)$ is large, (2) the Bjorken $x\ll 1$ for $m_{\varphi }\lesssim 10\mathrm{TeV}$, and (3) the kinematic region where $\log (m_{\varphi }/m_t)\gg 1$ is suppressed by phase space. We consider the example of $pp\to t{H}^{+}$ at next-to-leading logarithm (NLL) order and show that, in terms of the total cross section, the effect of a top PDF is generically smaller than that of a bottom PDF in the associated production of $b\varphi$. However, in the $p_T$ distribution of the charged Higgs, the NLL calculation using a top PDF is crucial to generate the $p_T$ distribution for $p_T\lesssim m_t$.