An addition to the Standard Model of a real, gauge-singlet scalar field, coupled via a Higgs portal interaction, can reopen the possibility of a strongly first-order electroweak phase transition (EWPT) and successful electroweak baryogenesis (EWBG). If a discrete symmetry that forbids doublet-singlet mixing is present, this model is notoriously difficult to test at the Large Hadron Collider. As a result, it emerged as a useful benchmark for evaluating the capabilities of proposed future colliders to conclusively test EWPT and EWBG. In this paper, we evaluate the bubble nucleation temperature throughout the parameter space of this model where a first-order transition is expected. We find that in large parts of this parameter space, bubbles in fact do not nucleate at any finite temperature, eliminating these models as viable EWBG scenarios. This constraint eliminates most of the region where a “two-step” phase transition is naively predicted, while the “one-step” transition region is largely unaffected. In addition, expanding bubble walls must not reach relativistic speeds during the transition for baryon asymmetry to be generated. We show that this condition further reduces the parameter space with viable EWBG.

The leptonic widths of high $\psi$-resonances are calculated in a coupled-channel model with unitary inelasticity, where analytical expressions for the mixing angles between $(n+1){{}^{3}S}_1$ and $n{{}^{3}D}_1$ states and probabilities $Z_i$ of the $c\overline{c}$ component are derived. These factors depend on energy (mass) and can be different for $\psi (4040)$ and $\psi (4160)$. However, our calculations give a small difference between the mixing angles, $\theta (\psi (4040))=(28_{-2}^{+1})°$ and $\theta (\psi (4160))=(29_{-3}^{+2})°$, and $\sim 10\%$ difference between the probabilities $Z_1(\psi (4040))=0.85_{-0.02}^{+0.05}$ and $Z_2(\psi (4160))=0.79\pm 0.01$. It provides the leptonic widths ${\mathrm{\Gamma }}_{ee}(\psi (4040))=(1.0\pm 0.1)\mathrm{keV}$ and ${\mathrm{\Gamma }}_{ee}(\psi (4160))=(0.62\pm \mathrm{0.0.07})\mathrm{keV}$ in agreement with experiment; for $\psi (4415)$ the value ${\mathrm{\Gamma }}_{ee}(\psi (4415))=(0.66\pm 0.06)\mathrm{keV}$ is obtained, while for the missing resonance $\psi (4510)$, we predict its mass, $M(\psi (4500))=(4512\pm 2)\mathrm{MeV}$, and ${\mathrm{\Gamma }}_{ee}(\psi (4510))=(0.68\pm 0.14)\mathrm{keV}$.

We determine the non-Abelian version of the four nontransverse form factors of the quark-gluon vertex, using exact expressions derived from the Slavnov-Taylor identity that this vertex satisfies. In addition to the quark and ghost propagators, a key ingredient of the present approach is the quark-ghost scattering kernel, which is computed within the one-loop dressed approximation. The vertex form factors obtained from this procedure are evaluated for arbitrary Euclidean momenta, and display features not captured by the well-known Ball-Chiu vertex, deduced from the Abelian (ghost-free) Ward identity. Particularly interesting in this analysis is the so-called soft-gluon limit, which, unlike other kinematic configurations considered, is especially sensitive to the approximations employed for the vertex entering in the quark-ghost scattering kernel, and may even be affected by a subtle numerical instability. As an elementary application of the results obtained, we evaluate and compare certain renormalization-point-independent combinations, which contribute to the interaction kernels appearing in the standard quark gap and Bethe-Salpeter equations. In doing so, even though all form factors of the quark-gluon vertex, and in particular the transverse ones which are unconstrained by our procedure, enter nontrivially in the aforementioned kernels, only the contribution of a single form factor, corresponding to the classical (tree-level) tensor, will be considered.

This paper presents the extended results of measurements of $W^{\pm }{W}^{\pm }jj$ production and limits on anomalous quartic gauge couplings using $20.3{\mathrm{fb}}^{-1}$ of proton–proton collision data at $\sqrt{s}=8\mathrm{TeV}$ recorded by the ATLAS detector at the Large Hadron Collider. Events with two leptons ($e$ or $\mu$) with the same electric charge and at least two jets are analyzed. Production cross sections are determined in two fiducial regions, with different sensitivities to the electroweak and strong production mechanisms. An additional fiducial region, particularly sensitive to anomalous quartic gauge coupling parameters ${\alpha }_4$ and ${\alpha }_5$, is introduced, which allows more stringent limits on these parameters compared to the previous ATLAS measurement.

Ooguri and Vafa [arXiv:1610.01533] have recently proposed a stronger version of the weak gravity conjecture (WGC), based on which they concluded that all those nonsupersymmetric AdS vacua that can be embedded within a consistent theory of quantum gravity necessarily develop instabilities. In this paper we further elaborate on this proposal by arguing that the aforementioned instabilities have a perturbative nature and arise from the crucial interplay between the closed and the open string sectors of the theory.

We show that, contrary to what is usually claimed in the literature, the zero mass limit of Kerr spacetime is not flat Minkowski space but a spacetime whose geometry is only locally flat. This limiting spacetime, as the Kerr spacetime itself, contains two asymptotic regions and hence cannot be topologically trivial. It also contains a curvature singularity, because the power-law singularity of the Weyl tensor vanishes in the limit but there remains a distributional contribution of the Ricci tensor. This spacetime can be interpreted as a wormhole sourced by a negative tension ring. We also extend the discussion to similarly interpret the zero mass limit of the Kerr–(anti–)de Sitter spacetime.

We demonstrate the existence of $P-V$ criticality of the topological Hořava-Lifshitz (HL) black holes with a spherical horizon ($k=1$) in the extended phase space. With the electric charge, we find that the critical behaviors of the HL black hole are nearly the same as those of a van der Waals (VdW) system. For the uncharged case, the HL black hole has a peculiar $P-V$ criticality. The critical behavior is completely controlled by a parameter $\epsilon$, but not the temperature $T$. When $\epsilon$ is larger than a critical value ${\epsilon }_c$, no matter what the temperature is, there will be the first-order phase transition. Moreover, we find that there is an infinite number of critical points which form a “critical curve.” As far as we know, this is the first time to find this kind of peculiar $P-V$ criticality.

Recent work has established the existence of stable quantum phases of matter described by symmetric tensor gauge fields, which naturally couple to particles of restricted mobility, such as fractons. We focus on a minimal toy model of a rank 2 tensor gauge field, consisting of fractons coupled to an emergent graviton (massless spin-2 excitation). We show how to reconcile the immobility of fractons with the expected gravitational behavior of the model. First, we reformulate the fracton phenomenon in terms of an emergent center of mass quantum number, and we show how an effective attraction arises from the principles of locality and conservation of center of mass. This interaction between fractons is always attractive and can be recast in geometric language, with a geodesiclike formulation, thereby satisfying the expected properties of a gravitational force. This force will generically be short-ranged, but we discuss how the power-law behavior of Newtonian gravity can arise under certain conditions. We then show that, while an isolated fracton is immobile, fractons are endowed with finite inertia by the presence of a large-scale distribution of other fractons, in a concrete manifestation of Mach’s principle. Our formalism provides suggestive hints that matter plays a fundamental role, not only in perturbing, but in creating the background space in which it propagates.

In this work, expanded solutions of force-free magnetospheres on general Kerr black holes are derived through a radial distance expansion method. From the regular conditions both at the horizon and at spatial infinity, two previously known asymptotical solutions (one of them is actually an exact solution) are identified as the only solutions that satisfy the same conditions at the two boundaries. Taking them as initial conditions at the boundaries, expanded solutions up to the first few orders are derived by solving the stream equation order by order. It is shown that our extension of the exact solution can (partially) cure the problems of the solution: it leads to magnetic domination and a mostly timelike current for restricted parameters.

Axion-like particles (ALPs) might constitute the totality of the cold dark matter (CDM) observed. The parameter space of ALPs depends on the mass of the particle $m$ and on the energy scale of inflation $H_I$, the latter being bound by the nondetection of primordial gravitational waves. We show that the bound on $H_I$ implies the existence of a mass scale ${\overline{m}}_{\chi }=10n\mathrm{eV}–0.5\mathrm{peV}$, depending on the ALP susceptibility $\chi$, such that the energy density of ALPs of mass smaller than ${\overline{m}}_{\chi }$ is too low to explain the present CDM budget, if the ALP field has originated after the end of inflation. This bound affects ultra-light axions (ULAs), which have recently regained popularity as CDM candidates. Light ($m<m_{\chi }$) ALPs can then be CDM candidates only if the ALP field has already originated during the inflationary period, in which case the parameter space is constrained by the nondetection of axion isocurvature fluctuations. We comment on the effects on these bounds from additional physics beyond the standard model, besides ALPs.

We calculate the $q\gamma q$ correlation function associated to transverse target lepton-nucleon inclusive deep-inelastic scattering by direct evaluation of the corresponding matrix element utilizing the electromagnetic impact parameter fields for a transversely polarized nucleon. The results are compared with the two existing models for the $q\gamma q$ correlator. Using the calculated $q\gamma q$ correlation function, we estimate the transverse target single-spin asymmetry in an inclusive DIS process.

A phenomenological pion-nucleon interaction is used to obtain pionic mass modification in presence of constant homogeneous magnetic field background at finite temperature and chemical potential in the real time formalism of thermal field theory. The magnetically modified propagator in its complete form is used to obtain the one loop self-energy for pions. For charged pions we find that the effective mass increases with the magnetic field at given temperature and chemical potential. Since the transverse momentum of charged pion is quantized and its contribution to Dyson-Schwinger equation is large compared to the loop correction, the charged pion mass remains constant with both temperature and chemical potential for a given landau level. In order to unveil the role of the real part of the self-energy, we also calculate the effective mass neglecting the trivial shift. The effective mass for charged pions shows an oscillatory behavior which is attributed to the thermal contribution of the self-energy. It is argued that the magnetic field dependent vacuum contribution to the self-energy influences the behavior of the effective mass both qualitatively and quantitatively. We also find that very large field is necessary for neutral pions to condense.

We discuss a novel worldline framework for computations of the chiral magnetic effect (CME) in ultrarelativistic heavy-ion collisions. Starting from the fermion determinant in the QCD effective action, we show explicitly how its real part can be expressed as a supersymmetric worldline action of spinning, colored, Grassmannian particles in background fields. Restricting ourselves for simplicity to spinning particles, we demonstrate how their constrained Hamiltonian dynamics arises for both massless and massive particles. In a semiclassical limit, this gives rise to the covariant generalization of the Bargmann-Michel-Telegdi equation; the derivation of the corresponding Wong equations for colored particles is straightforward. In a previous paper [N. Mueller and R. Venugopalan, arXiv:1701.03331.], we outlined how Berry’s phase arises in a nonrelativistic adiabatic limit for massive particles. We extend the discussion here to systems with a finite chemical potential. We discuss a path integral formulation of the relative phase in the fermion determinant that places it on the same footing as the real part. We construct the corresponding anomalous worldline axial-vector current and show in detail how the chiral anomaly appears. Our work provides a systematic framework for a relativistic kinetic theory of chiral fermions in the fluctuating topological backgrounds that generate the CME in a deconfined quark-gluon plasma. We outline some further applications of this framework in many-body systems.

In light of the 125 GeV Higgs ($h$) discovery at the Large Hadron Collider (LHC), one of the primary goals of the LHC and possible future colliders is to understand its interactions more precisely. Here we have studied the $h\text{−}b\text{−}\overline{b}\text{−}\gamma$ effective interaction terms arising out of gauge-invariant dimension-6 operators in a model-independent setting, as a potential source of new physics. Their role in some detectable final states has been compared with those coming from anomalous $h\text{−}b\text{−}\overline{b}$ interactions. We have considered the bounds coming from the existing collider and other low-energy experimental data in order to derive constraints on the potential new physics couplings and predict possible collider signals for the two different new physics scenarios in the context of 14 TeV LHC and a future $e^{+}{e}^{-}$ machine. We conclude that the anomalous $h\text{−}b\text{−}\overline{b}\text{−}\gamma$ coupling can be probed at the LHC at 14 TeV at the $3\sigma$ level with an integrated luminosity of $\sim 2000{\mathrm{fb}}^{-1}$, which an $e^{+}{e}^{-}$ collider can probe at the $3\sigma$ level with $\sim 12(7){\mathrm{fb}}^{-1}$ at $\sqrt{s}=250(500)\mathrm{GeV}$. It is also found that anomalous $h\text{−}b\text{−}\overline{b}$ interactions, subject to the existing LHC constraints, cannot compete with the rates driven by $h\text{−}b\text{−}\overline{b}\text{−}\gamma$ effective interactions.

We provide an analysis of the $x$ dependence of the bare unpolarized, helicity, and transversity isovector parton distribution functions (PDFs) from lattice calculations employing (maximally) twisted mass fermions. The $x$ dependence of the calculated PDFs resembles the one of the phenomenological parameterizations, a feature that makes this approach very promising. Furthermore, we apply momentum smearing for the relevant matrix elements to compute the lattice PDFs and find a large improvement factor when compared to conventional Gaussian smearing. This allows us to extend the lattice computation of the distributions to higher values of the nucleon momentum, which is essential for the prospects of a reliable extraction of the PDFs in the future.

We study properties of $2+1$-flavor QCD in the imaginary chemical potential region by using two approaches. One is a theoretical approach based on the QCD partition function, and the other is a qualitative one based on the Polyakov-loop extended Nambu–Jona-Lasinio (PNJL) model. In the theoretical approach, we clarify conditions imposed on the imaginary chemical potentials ${\mu }_f=i{\theta }_{f}T$ to realize the Roberge-Weiss (RW) periodicity. Here, $T$ is the temperature, the index $f$ denotes the flavor, and ${\theta }_f$ are dimensionless chemical potentials. We also show that the RW periodicity is broken if any one of ${\theta }_f$ is fixed to a constant value. In order to visualize the condition, we use the PNJL model as a model possessing the RW periodicity and draw the phase diagram as a function of ${\theta }_u={\theta }_d\equiv {\theta }_l$ for two conditions of ${\theta }_s={\theta }_l$ and ${\theta }_s=0$. We also consider two cases, $({\mu }_u,{\mu }_d,{\mu }_s)=(i{\theta }_{u}T,i{C}_{1}T,0)$ and $({\mu }_u,{\mu }_d,{\mu }_s)=(i{C}_{2}T,i{C}_{2}T,i{\theta }_{s}T)$; here, $C_1$ and $C_2$ are dimensionless constants, whereas ${\theta }_u$ and ${\theta }_s$ are treated as variables. For some choice of $C_1$ ($C_2$), the number density of the up (strange) quark becomes smooth in the entire region of ${\theta }_u$ (${\theta }_s$) even in the high $T$ region. This property may be important for lattice QCD simulations in the imaginary chemical potential region, since it makes the analytic continuation more feasible.

Mixing transformations for a uniformly accelerated observer (Rindler observer) are analyzed within the quantum field theory framework as a basis for investigating gravitational effects on flavor oscillations. In particular, the case of two charged boson fields with different masses is discussed. In spite of such a minimal setting, the standard Unruh radiation is found to lose its characteristic thermal interpretation due to the interplay between the Bogoliubov transformation hiding in field mixing and the one arising from the Rindler spacetime structure. The modified spectrum detected by the Rindler observer is explicitly calculated in the limit of the small mass difference.

We construct several towers of scalar quantum field theories with an $O(N)$ symmetry which have higher derivative kinetic terms. The Lagrangians in each tower are connected by lying in the same universality class at the $d$-dimensional Wilson-Fisher fixed point. Moreover the universal theory is studied using the large $N$ expansion and we determine $d$-dimensional critical exponents to $O(1/N^2)$. We show that these new universality classes emerge naturally as solutions to the linear relation of the dimensions of the fields deduced from the underlying force-matter interaction of the universal critical theory. To substantiate the equivalence of the Lagrangians in each tower we renormalize each to several loop orders and show that the renormalization group functions are consistent with the large $N$ critical exponents. While we focus on the first two new towers of theories and renormalize the respective Lagrangians to 16 and 18 dimensions there are an infinite number of such towers. We also briefly discuss the conformal windows and the extension of the ideas to theories with spin-$\frac{1}{2}$ and spin-1 fields as well as the idea of lower dimension completeness.

Recently proposed Born-Infeld (BI) theories of gravity assume a constant BI parameter ($\kappa$). However, no clear consensus exists on the sign and value of $\kappa$. Recalling the Brans-Dicke (BD) approach, where a scalar field was used to generate the gravitational constant $G$, we suggest an extension of Born-Infeld gravity with a similar Brans-Dicke flavor. Thus, a new action, with $\kappa$ elevated to a spacetime dependent real scalar field, is proposed. We illustrate this new theory in a cosmological setting with pressureless dust and radiation as matter. Assuming a functional form of $\kappa (t)$, we numerically obtain the scale factor evolution and other details of the background cosmology. It is known that BI gravity differs from general relativity (GR) in the strong-field regime but reduces to GR for intermediate and weak fields. Our studies in cosmology demonstrate how, with this new, scalar-tensor BI gravity, deviations from GR, as well as usual BI gravity, may arise in the weak-field regime too. For example, we note a late-time acceleration without any dark energy contribution. Apart from such qualitative differences, we note that fixing the sign and value of $\kappa$ is no longer a necessity in this theory, though the origin of the BD scalar does remain an open question.