Using nonlinear evolution equations of QCD, we compute the von Neumann entropy of the system of partons resolved by deep inelastic scattering at a given Bjorken $x$ and momentum transfer $q^2=-Q^2$. We interpret the result as the entropy of entanglement between the spatial region probed by deep inelastic scattering and the rest of the proton. At small $x$ the relation between the entanglement entropy $S(x)$ and the parton distribution $xG(x)$ becomes very simple: $S(x)=\ln [xG(x)]$. In this small $x$, large rapidity $Y$ regime, all partonic microstates have equal probabilities—the proton is composed by an exponentially large number $\exp (\mathrm{\Delta }Y)$ of microstates that occur with equal and exponentially small probabilities $\exp (-\mathrm{\Delta }Y)$, where $\mathrm{\Delta }$ is defined by $xG(x)\sim 1/x^{\mathrm{\Delta }}$. For this equipartitioned state, the entanglement entropy is maximal—so at small $x$, deep inelastic scattering probes a maximally entangled state. We propose the entanglement entropy as an observable that can be studied in deep inelastic scattering. This will require event-by-event measurements of hadronic final states, and would allow to study the transformation of entanglement entropy into the Boltzmann one. We estimate that the proton is represented by the maximally entangled state at $x\le {10}^{-3}$; this kinematic region will be amenable to studies at the Electron Ion Collider.

Non-Abelian flux tubes (strings) are well studied in $\mathcal{N}=2$ supersymmetric QCD in ($3+1$) dimensions. In addition to translational zero modes they have also orientational moduli associated with rotations of their fluxes inside a non-Abelian group. The dynamics of the orientational moduli is described by the two-dimensional $CP(N-1)$ model living on the world sheet of the non-Abelian string. In this paper we consider a deformation of $\mathcal{N}=2$ supersymmetric QCD with the $\mathrm{U}(N)$ gauge group and $N_f=N$ quark flavors with a mass term $\mu$ of the adjoint matter. In the limit of large $\mu$ the theory flows to an $\mathcal{N}=1$ supersymmetric QCD. We study the solution for the non-Abelian string in this limit and derive an effective theory on the string world sheet. The bosonic sector of this theory is still given by the $CP(N-1)$ model but its scale is exponentially small as compared to the scale of the four-dimensional bulk theory in contrast to the $\mathcal{N}=2$ case where these scales are equal. We study also the fermionic sector of the world sheet theory. Upon the deformation, the non-Abelian string is no longer Bogomol’nyi-Prasad-Sommerfield (BPS) state and we show that the fermionic superorientational zero modes are all lifted. This leaves us with the pure bosonic $CP(N-1)$ model on the string world sheet in the limit of $\mathcal{N}=1$ QCD. We also discuss what happens to confined monopoles at large $\mu$.

We propose the use of a waveguidelike transmission line based on direct-current superconducting quantum interference devices (dc-SQUID) and demonstrate that the node flux in this transmission line behaves in the same way as quantum fields in an expanding (or contracting) universe. We show how to detect the analog cosmological particle generation and analyze its feasibility with current circuit quantum electrodynamics (cQED) technology. Our setup in principle paves a new way for the exploration of analog quantum gravitational effects.

We consider a real scalar singlet field which provides a strong first-order electroweak phase transition via its coupling to the Higgs boson, and gives a $CP$ violating contribution on the top quark mass via a dimension-6 operator. We study the correlation between the baryon-to-entropy ratio produced by electroweak baryogenesis, and the gravitational wave signal from the electroweak phase transition. We show that future gravitational wave experiments can test, in particular, the region of the model parameter space where the observed baryon-to-entropy ratio can be obtained even if the new physics scale, which is explicit in the dimension-6 operator, is high.

The most promising method for measuring primordial non-Gaussianity in the post-Planck era is to detect large-scale, scale-dependent galaxy bias. Considering the information in the galaxy power spectrum, we here derive the properties of a galaxy clustering survey that would optimize constraints on primordial non-Gaussianity using this technique. Specifically, we ask the question of what survey design is needed to reach a precision $\sigma (f_{\mathrm{NL}}^{\mathrm{loc}})\approx 1$. To answer this question, we calculate the sensitivity to $f_{\mathrm{NL}}^{\mathrm{loc}}$ as a function of galaxy number density, redshift accuracy and sky coverage. We include the multitracer technique, which helps minimize cosmic variance noise, by considering the possibility of dividing the galaxy sample into stellar mass bins. We show that the ideal survey for $f_{\mathrm{NL}}^{\mathrm{loc}}$ looks very different than most galaxy redshift surveys scheduled for the near future. Since those are more or less optimized for measuring the baryon acoustic oscillation scale, they typically require spectroscopic redshifts. On the contrary, to optimize the $f_{\mathrm{NL}}^{\mathrm{loc}}$ measurement, a deep, wide, multiband imaging survey is preferred. An uncertainty $\sigma (f_{\mathrm{NL}}^{\mathrm{loc}})=1$ can be reached with a full-sky survey that is complete to an $i$-band AB magnitude $i\approx 23$ and has a number density $\sim 8{\mathrm{arcmin}}^{-2}$. Requirements on the multiband photometry are set by a modest photo-$z$ accuracy $\sigma (z)/(1+z)<0.1$ and the ability to measure stellar mass with a precision $\sim 0.2$ dex or better (or another proxy for halo mass with equivalent scatter). Finally, we estimate that for the idealized case of a survey measuring all halos down to a mass $10^{10}{h}^{-1}{M}_{\odot }$ on the full sky out to high redshift, in principle a precision of order $\sigma (f_{\mathrm{NL}})\sim 0.1$ can be achieved.

A new type of gauged BPS baby Skyrme model is presented, where the derivative term is just the Schroers current (i.e., gauge invariant and conserved version of the topological current) squared. This class of models has a topological bound saturated for solutions of the pertinent Bogomolnyi equations supplemented by a so-called superpotential equation. In contrast to the gauged BPS baby Skyrme models considered previously, the superpotential equation is linear and, hence, completely solvable. Furthermore, the magnetic flux is quantized in units of $2\pi$, which allows, in principle, to define this theory on a compact manifold without boundary, unlike all gauged baby Skyrme models considered so far.

We consider a five dimensional anti–de Sitter (AdS) warped spacetime in presence of a massive scalar field in the bulk. The scalar field potential fulfills the requirement of modulus stabilization even when the effect of backreaction of the stabilizing field is taken into account. In such a scenario, we explore the role of backreaction on the localization of bulk fermions which in turn determines the effective radion-fermion coupling on the brane. Our result reveals that both the chiral modes of the zeroth Kaluza-Klein (KK) fermions get localized near TeV brane as the backreaction of the scalar field increases. We also show that the profile of massive KK fermions shifts towards the Planck brane with an increasing backreaction parameter. Some implications in the context of LHC physics are discussed.

Single inclusive particle production cross sections in high energy hadron collisions at forward rapidity are an important benchmark process for the Color Glass Condensate picture of small $x$ QCD. Recent calculations of this process have not led to a stable perturbative expansion for this quantity at high transverse momenta. We consider the quark channel production cross section using the new rapidity factorization procedure proposed by Iancu et al. We show that for fixed coupling one does indeed obtain a physically meaningful cross section which is positive and reduces in a controlled way to previous leading order calculations. We also consider a running coupling that depends on the transverse momentum of the produced particle. This gives a stable result which, however, is not fully consistent with previous leading order calculations that use a coordinate space running coupling.

The decay mode $B\to K^{*}{\ell }^{+}{\ell }^{-}$ is one of the most promising modes to probe physics beyond the standard model (SM), since the angular distribution of the decay products enables measurement of several constraining observables. LHCb has recently measured these observables using $3{\mathrm{fb}}^{-1}$ of data as a binned function of $q^2$, the dilepton invariant mass squared. We find that LHCb data imply evidence for right-handed currents, which are absent in the SM. These conclusions are derived in the maximum $q^2$ limit and are free from hadronic corrections. Our approach differs from other approaches that probe new physics at low $q^2$ as it does not require estimates of hadronic parameters but relies instead on heavy quark symmetries that are reliable at the maximum $q^2$ kinematic end point.

The cross section and transverse single-spin asymmetries of ${\mu }^{-}$ and ${\mu }^{+}$ from open heavy-flavor decays in polarized $p+p$ collisions at $\sqrt{s}=200\mathrm{GeV}$ were measured by the PHENIX experiment during 2012 at the Relativistic Heavy Ion Collider. Because heavy-flavor production is dominated by gluon-gluon interactions at $\sqrt{s}=200\mathrm{GeV}$, these measurements offer a unique opportunity to obtain information on the trigluon correlation functions. The measurements are performed at forward and backward rapidity ($1.4<|y|<2.0$) over the transverse momentum range of $1.25<p_T<7\mathrm{GeV}/c$ for the cross section and $1.25<p_T<5\mathrm{GeV}/c$ for the asymmetry measurements. The obtained cross section is compared to a fixed-order-plus-next-to-leading-log perturbative-quantum-chromodynamics calculation. The asymmetry results are consistent with zero within uncertainties, and a model calculation based on twist-3 three-gluon correlations agrees with the data.

We construct a candidate for the most general chiral higher spin theory with ${\mathrm{AdS}}_3$ boundary conditions. In the Chern-Simons language, on the left it has the Drinfeld-Sokolov reduced form, but on the right all charges and chemical potentials are turned on. Altogether (for the spin-3 case) these are 19 functions. Despite this, we show that the resulting metric has the form of the “most general” ${\mathrm{AdS}}_3$ boundary conditions discussed by Grumiller and Riegler. The asymptotic symmetry algebra is a product of a ${\mathcal{W}}_3$ algebra on the left and an affine $sl(3{)}_k$ current algebra on the right, as desired. The metric and higher spin fields depend on all the 19 functions. We compare our work with previous results in the literature.

Motivated by various systems in which quantum effects occur in classical backgrounds, we consider the dynamics of a classical particle as described by a coherent state that is coupled to a quantum bath via biquadratic interactions. We evaluate the resulting quantum dissipation of the motion of the classical particle. We also find classical initial conditions for the bath that effectively lead to the same dissipation as that due to quantum effects, possibly providing a way to approximately account for quantum backreaction within a classical analysis.

We consider a head-on collision of two massive particles that move in the equatorial plane of an extremal Kerr black hole, which results in the production of two massless particles. Focusing on a typical case, where both of the colliding particles have zero angular momenta, we show that a massless particle produced in such a collision can escape to infinity with arbitrarily large energy in the near-horizon limit of the collision point. Furthermore, if we assume that the emission of the produced massless particles is isotropic in the center-of-mass frame but confined to the equatorial plane, the escape probability of the produced massless particle approaches $5/12$, and almost all escaping massless particles have arbitrarily large energy at infinity and an impact parameter approaching $2GM/c^2$, where $M$ is the mass of the black hole.

In this work, we study various aspects of supersymmetric three-dimensional higher-derivative field theories. We classify all possible models without derivative terms of the auxiliary field in the fermionic sector and find that scalar field theories of the form $P(X,\varphi )$, where $X=-(\partial \varphi {)}^2/2$, belong to this kind of models. A ghost-free supersymmetric extension of Galileon models is found in three spacetime dimensions. Finally, the auxiliary field problem is discussed.

A generally covariant version of Erik Verlinde’s emergent gravity model is proposed. The Lagrangian constructed here allows an improved interpretation of the underlying mechanism. It suggests that de Sitter space is filled with a vector field that couples to baryonic matter and, by dragging on it, creates an effect similar to dark matter. We solve the covariant equation of motion in the background of a Schwarzschild space-time and obtain correction terms to the noncovariant expression. Furthermore, we demonstrate that the vector field can also mimic dark energy.

The glueball dark matter, in the pure $\mathrm{SU}(N)$ Yang-Mills theory, engenders dark $\mathrm{SU}(N)$ stars that comprise self-gravitating compact configurations of scalar glueball fields. Corrections to the highest frequency of gravitational wave radiation emitted by dark $\mathrm{SU}(N)$ star mergers on a fluid brane with variable tension, implemented by the minimal geometric deformation, are derived, and their consequences are analyzed. Hence, dark $\mathrm{SU}(N)$ star mergers on a fluid braneworld are shown to be better detectable by the LIGO and the eLISA experiments.

We solve for all Szekeres metrics that have a single Killing vector. For quasihyperboloidal ($\epsilon =-1$) metrics, we find that translational symmetries are possible, but only in metrics that have shell crossings somewhere, while metrics that can be made free of shell crossings only permit rotations. The quasiplanar metrics ($\epsilon =0$) either have no Killing vectors, or they admit full planar symmetry. Single symmetries in quasispherical metrics ($\epsilon =+1$) are all rotations. The rotations correspond to a known family of axially symmetric metrics, which for each $\epsilon$ value, are equivalent to each other. We consider Szekeres metrics in which the line of dipole extrema is required to be geodesic in the 3-space and show the same set of families emerges. We investigate when two Szekeres metrics are physically equivalent and complete a previous list of transformations of the arbitrary functions.

The next-generation weak lensing surveys (i.e., LSST, Euclid, and WFIRST) will require exquisite control over systematic effects. In this paper, we address shear calibration and present the most realistic forecast to date for LSST/Euclid/WFIRST and CMB lensing from a stage 4 CMB experiment (“CMB S4”). We use the cosmolike code to simulate a joint analysis of all the two-point functions of galaxy density, galaxy shear, and CMB lensing convergence. We include the full Gaussian and non-Gaussian covariances and explore the resulting joint likelihood with Monte Carlo Markov chains. We constrain shear calibration biases while simultaneously varying cosmological parameters, galaxy biases, and photometric redshift uncertainties. We find that CMB lensing from CMB S4 enables the calibration of the shear biases down to 0.2%–3% in ten tomographic bins for LSST (below the $\sim 0.5\%$ requirements in most tomographic bins), down to 0.4%–2.4% in ten bins for Euclid, and 0.6%–3.2% in ten bins for WFIRST. For a given lensing survey, the method works best at high redshift where shear calibration is otherwise most challenging. This self-calibration is robust to Gaussian photometric redshift uncertainties and to a reasonable level of intrinsic alignment. It is also robust to changes in the beam and the effectiveness of the component separation of the CMB experiment, and slowly dependent on its depth, making it possible with third-generation CMB experiments such as AdvACT and SPT-3G, as well as the Simons Observatory.

Measurements of cosmic microwave background (CMB) anisotropies provide strong evidence for the existence of dark matter and dark energy. They can also test its composition, probing the energy density and particle mass of different dark-matter and dark-energy components. CMB data have already shown that ultralight axions (ULAs) with mass in the range ${10}^{-32}\mathrm{eV}\to {10}^{-26}\mathrm{eV}$ compose a fraction $\lesssim 0.01$ of the cosmological critical density. The next Stage-IV CMB experiment (CMB-S4) (assuming a 1 arcmin beam and $\sim 1\mu \mathrm{K}\text{−}\mathrm{arcmin}$ noise levels over a sky fraction of 0.4) to the density of ULAs and other dark-sector components is assessed. CMB-S4 data should be $\sim 10$ times more sensitive to the ULA energy density than Planck data alone, across a wide range of ULA masses ${10}^{-32}\lesssim m_a\lesssim {10}^{-23}\mathrm{eV}$, and will probe axion decay constants of $f_a\approx 10^{16}\mathrm{GeV}$, at the grand unified scale. CMB-S4 could improve the CMB lower bound on the ULA mass from $\sim {10}^{-25}\mathrm{eV}$ to ${10}^{-23}\mathrm{eV}$, nearing the mass range probed by dwarf galaxy abundances and dark-matter halo density profiles. These improvements will allow for a multi-$\sigma$ detection of percent-level departures from CDM over a wide range of masses. Much of this improvement is driven by the effects of weak gravitational lensing on the CMB, which breaks degeneracies between ULAs and neutrinos. We also find that the addition of ULA parameters does not significantly degrade the sensitivity of the CMB to neutrino masses. These results were obtained using the axionCAMB code (a modification to the CAMB Boltzmann code), presented here for public use.

Primordial black holes (PBHs) are one of the candidates to explain the gravitational wave (GW) signals observed by the LIGO detectors. Among several phenomena in the early universe, cosmic inflation is a major example to generate PBHs from large primordial density perturbations. In this paper, we discuss the possibility to interpret the observed GW events as mergers of PBHs that are produced by cosmic inflation. The primordial curvature perturbation should be large enough to produce a sizable amount of PBHs, and thus we have several other probes to test this scenario. We point out that the current pulsar timing array (PTA) experiments already put severe constraints on GWs generated via the second-order effects, and that the observation of the cosmic microwave background puts severe restriction on its $\mu$ distortion. In particular, it is found that the scalar power spectrum should have a very sharp peak at $k\sim 10^6{\mathrm{Mpc}}^{-1}$ to fulfill the required abundance of PBHs while evading constraints from the PTA experiments together with the $\mu$ distortion. We propose a mechanism that can realize such a sharp peak. In the future, simple inflation models that generate PBHs via almost Gaussian fluctuations could be probed/excluded.