We analyze minimal supersymmetric models in order to determine in what parameter regions with what amount of fine-tuning they are capable of accommodating the LHC-allowed top-stop degeneracy window. The stops must be light enough to enable Higgs naturalness yet heavy enough to induce a 125 GeV Higgs boson mass. These two constraints imply a large mass splitting. By an elaborate scan of the parameter space, we show that the stop-on-top scenario requires at least ${\mathrm{\Delta }}_{\mathrm{CMSSM}}\simeq \mathcal{O}({10}^4)$ fine-tuning in the constrained minimal supersymmetric Standard Model (CMSSM). By relaxing the CMSSM parameter space with nonuniversal Higgs masses, we find that ${\mathrm{\Delta }}_{\mathrm{NUHM}1}\simeq \mathcal{O}({10}^4)$. The CMSSM with a gravitino lightest supersymmetric particle works slightly better than the nonuniversal Higgs mass model. Compared to all these, the CMSSM with $\mu <0$ and nonuniversal gauginos yields a much smaller fine-tuning ${\mathrm{\Delta }}_{\mu ,g}\simeq \mathcal{O}(100)$. Our results show that the gaugino sector can pave the road toward a more natural stop-on-top scenario.

A new qualitative stringlike picture for mesons is proposed which leads to a simple and intuitively clear generalization of linear radial Regge trajectories to the case of massive quarks. The obtained universal relation is successfully tested in the sector of unflavored vector mesons, where many radial excitations are known. Some new predictions are given. Our results suggest that the quark masses can be easily estimated from the spectra of radially excited mesons.

We investigate the $CP$-averaged branching ratios, the polarization fractions, the relative phases, and the $CP$-violating asymmetries of the penguin-dominated $B\to \varphi K_1(1270)$ and $\varphi K_1(1400)$ decays in the perturbative QCD (pQCD) approach, where $K_1(1270)$ and $K_1(1400)$ are believed to be the mixtures of two distinct types of axial-vector $K_{1A}({}^3{P}_1)$ and $K_{1B}({}^1{P}_1)$ states with different behavior, however, their mixing angle ${\theta }_{K_1}$ is still a hot and controversial topic presently. By numerical evaluations with two different mixing angles ${\theta }_{K_1}\sim 33^{\circ }$ and 58° and phenomenological analysis, we find that: (i) the pQCD predictions for the branching ratio, the longitudinal polarization fraction and the direct $CP$ violation of $B^{\pm }\to \varphi K_1(1270{)}^{\pm }$ decay with the smaller angle 33° are in good agreement with the currently available data; (ii) though the central values significantly exceed the available upper limit, both pQCD predictions of $\mathrm{Br}(B^{\pm }\to \varphi K_1(1400{)}^{\pm })$ with two different mixing angles are consistent with that obtained in QCD factorization and with the preliminary data in $2\sigma$ errors. These results and other relevant predictions for the considered decays will be further tested by the LHCb and the forthcoming Super-B experiments; (iii) the weak annihilation contributions can play an important role in $B\to \varphi K_1(1270)$ and $\varphi K_1(1400)$ decays; (d) these pQCD predictions combined with the future precision measurements can examine the reliability of the factorization approach employed here, but also explore the complicated QCD dynamics and mixing angle ${\theta }_{K_1}$ of the axial-vector $K_1(1270)$ and $K_1(1400)$ system.

A more reliable treatment of transverse momentum-dependent physics and in particular transverse single-spin asymmetries is urgently required, e.g. for polarized $pA$ physics including novel effects like color entanglement. We argue that the measurement of azimuthal angular correlations of photons and jets produced in $pA$ collisions provides a direct access to the novel gluon distribution $G_4$ that enters into many such processes, though practically it will be very challenging to probe this distribution experimentally as it is a $1/N_c^2$-suppressed effect.

The variational method for the Sturm-Liouville eigenvalue problem is employed to study analytically properties of the holographic superconductor with a dark matter sector, in which a coupling between the Maxwell field and another $U(1)$-gauge field is considered. The backreaction of the dark matter sector on the gravitational background in question is also examined.

We consider the model based on the $SU(2{)}_R\times SU(2{)}_L\times U(1{)}_{B-L}$ gauge group with Majorana neutrinos. In this model the transit dipole magnetic moment $({\mu }^{\nu N}{)}_{if}$ which is associated with the $N_i\to {\nu }_f\gamma$ transition may be as large as a $\text{few}\times 10^{-8}{\mu }_B$. The possible manifestations of the $({\mu }^{\nu N}{)}_{if}$ at hadron colliders are investigated. In doing so, we assume that one of the three heavy right-handed neutrinos $N_{eR}$ is on the electroweak scale. The process of $N_{eR}$ production $p+p\to W_R^{-}\to e^{-}{N}_{eR}$, with the subsequent $N_{eR}$ decay through the channel $N_{eR}\to {\nu }_{eL}+\gamma$, is investigated. Problems caused by selecting the signal from background is examined. It is shown that the process in question is the most perspective one for detecting the $({\mu }^{\nu N}{)}_{if}$, provided the condition $m_{W_R}<6\mathrm{TeV}$ is realized. The cross section of $N_{\mu R}$ production under the collision of a high-energy light neutrino beam with the proton target ${\nu }_{\mu L}+p\to \gamma \to N_{\mu R}+p+X$ is investigated. The produced $N_{\mu R}$ neutrino is identified through the decay channel $N_{\mu R}\to {\mu }^{\pm }+2j$. Detection of both the positive and negative charged muons will point to the Majorana nature of the neutrino. On the other hand, detection of the right-handed polarized muons will be unambiguously indicative of a nonzero value of $({\mu }^{\nu N}{)}_{if}$.

We argue that the deconfinement transition of large-$N$ Yang-Mills theory is the condensation of very long and self-intersecting chromo-electric flux strings (QCD string), which is analogous to the formation of a black hole in string theory. We do this by using lattice gauge theory and matrix models. As evidence, we derive an analytic formula for the deconfinement temperature in the strong coupling limit and confirm it numerically. Dual gravity descriptions interpreted in this manner should make it possible to understand the details of the formation of black holes in terms of fundamental strings. We argue that very simple matrix models capture the essence of the formation of black holes.

We construct a quasilocal formalism for conserved charges in a theory of gravity in the presence of matter fields that may have slow falloff behaviors at the asymptotic infinity. This construction depends only on equations of motion, and so it is irrespective of ambiguities in the total derivatives of the Lagrangian. By using identically conserved currents, we show that this formalism leads to the same expressions of conserved charges as those in the covariant phase space approach. At the boundary of the asymptotic anti-de Sitter space, we also introduce an identically conserved boundary current that has the same structure as the bulk current and then show that this boundary current gives us the holographic conserved charges identical with those from the boundary stress tensor method. In our quasilocal formalism, we present a general proof that conserved charges from the bulk potential are identical with those from the boundary current. Our results can be regarded as the extension of the existing results on the equivalence of conserved charges by the covariant phase space approach and by the boundary stress tensor method.

Analogue models of gravity have played a pivotal role in the past years by providing a test bench for many open issues in quantum field theory in curved spacetime such as the robustness of Hawking radiation and cosmological particle production. More recently, the same models have offered a valuable framework within which current ideas about the emergence of spacetime and its dynamics could be discussed via convenient toy models. In this context, we study here an analogue gravity system based on a relativistic Bose-Einstein condensate. We show that in a suitable limit this system provides not only an example of an emergent spacetime (with a massive and a massless relativistic fields propagating on it) but also that such spacetime is governed by an equation with geometric meaning that takes the familiar form of Nordström theory of gravitation. In this equation the gravitational field is sourced by the expectation value of the trace of the effective stress-energy tensor of the quasiparticles while the Newton and cosmological constants are functions of the fundamental scales of the microscopic system. This is the first example of analogue gravity in which a Lorentz invariant, geometric theory of semiclassical gravity emerges from an underlying quantum theory of matter in flat spacetime.

We consider the ghost-free higher-order corrections to the Starobinsky model in the old-minimal supergravity, focusing on a sector among several scalar fields in the model that reproduces the scalaron potential in the original Starobinsky model. In general, higher-order corrections cannot be forbidden by symmetries, which likely violate the flatness of the scalaron potential and make inflation difficult in explaining the present Universe. We find a severe constraint on the dimensionless coupling of the $R^4$ correction as $-5.5\times {10}^{-8}<s<9.1\times {10}^{-8}$ from the recent results of the Planck observation. If we start from the chaotic initial condition, the constraint becomes much more severe. However, in the case in which the coupling of the $R^4$ correction is positive, the scalaron potential has a local maximum with two local minima at the origin and infinity, which admits topological inflation. In this case, inflation can take place naturally if the coupling satisfies the observational constraints.

The joint probability distribution function (PDF) of the density within multiple concentric spherical cells is considered. It is shown how its cumulant generating function can be obtained at tree order in perturbation theory as the Legendre transform of a function directly built in terms of the initial moments. In the context of the upcoming generation of large-scale structure surveys, it is conjectured that this result correctly models such a function for finite values of the variance. Detailed consequences of this assumption are explored. In particular the corresponding one-cell density probability distribution at finite variance is computed for realistic power spectra, taking into account its scale variation. It is found to be in agreement with $\mathrm{\Lambda }$-cold dark matter simulations at the few percent level for a wide range of density values and parameters. Related explicit analytic expansions at the low and high density tails are given. The conditional (at fixed density) and marginal probability of the slope—the density difference between adjacent cells—and its fluctuations is also computed from the two-cell joint PDF; it also compares very well to simulations. It is emphasized that this could prove useful when studying the statistical properties of voids as it can serve as a statistical indicator to test gravity models and/or probe key cosmological parameters.

Fast-spinning newborn pulsars are intriguing candidate sources of ultrahigh-energy cosmic rays (UHECRs). The acceleration of particles with a given composition in a fraction of the extragalactic pulsar population can give a consistent explanation for the measurements of the Auger Observatory. We calculate the associated diffuse neutrino flux produced while particles cross the supernova ejecta surrounding the stars. We show that in the minimal pulsar scenarios that are compatible with the UHECR data, the effective optical depth to hadronuclear interactions is larger than unity at ultrahigh energies. Thus, even in the most pessimistic case, one expects energy fluxes of $\sim 0.1–1\mathrm{EeV}$ neutrinos that should be detectable with IceCube or the Askaryan Radio Array within a decade.

In this article, we study a particular method of detection of chirp signals from coalescing compact binary stars—the so-called dynamical tuning, i.e., amplification of the signal via tracking of its instantaneous frequency by the tuning of a signal-recycled detector. The motion of the signal-recycling mirror, the position of which defines the tuning of the detector, causes nonstationarity of the detector. The dynamically tuned detector can be simulated in a quasistationary approximation if the mirror position, amplitude, and frequency of a chirp signal are changing slowly. A time-domain consideration developed for signal-recycled interferometers, in particular GEO 600, describes the signal and noise evolution in the more general case of a purely nonstationary detector. We prove that the shot noise from the dark port and optical losses remains white in this case. The analysis of the transient effects shows that during the perfect tracking of the chirp frequency only transients from fast amplitude changes arise because the transients from changes of the detector tuning and signal frequency completely cancel each other. The slow change of the amplitude in this case establishes a so-called virtually stationary detection, meaning the signal fields at the detector hold their stationary values at each instance of time, corresponding to the instantaneous parameters of the gravitational wave and of the detector. The signal-to-noise-ratio gain from the implementation of dynamical tuning, calculated in this paper, is $\sim 17$ for a shot noise-limited GEO 600-like detector and $\sim 7$ for a detector with both shot and displacement noise.

We study the possibility of the existence of negative mass bubbles within a de Sitter spacetime background with matter content corresponding to a perfect fluid. It is shown that there exist configurations of the perfect fluid that satisfy everywhere the dominant energy condition, the Einstein equations and the equations of hydrostatic equilibrium which asymptotically approach the exact solution of Schwarzschild—de Sitter spacetime with a negative mass.

The $\pi$-$\pi$ scattering amplitude calculated with a model for the quark-antiquark interaction in the framework of the covariant spectator theory (CST) is shown to satisfy the Adler zero constraint imposed by chiral symmetry. The CST formalism is established in Minkowski space and our calculations are performed in momentum space. We prove that the axial-vector Ward-Takahashi identity is satisfied by our model. Then we show that, similar to what happens within the Bethe-Salpeter formalism, application of the axial-vector Ward-Takahashi identity to the CST $\pi$-$\pi$ scattering amplitude allows us to sum the intermediate quark-quark interactions to all orders. The Adler self-consistency zero for $\pi$-$\pi$ scattering in the chiral limit emerges as the result for this sum.

We investigate the discovery prospects for Higgs bosons in the next-to-mininmal supersymmetric extension of the Standard Model (NMSSM) during the 13 TeV run of the LHC. While one of the neutral Higgs bosons is demanded to have a mass around 125 GeV and Standard Model-like properties, there can be substantially lighter, nearby or heavier Higgs bosons that have not been excluded yet by LEP, Tevatron or the 8 TeV run of the LHC. The challenge consists in discovering the whole NMSSM Higgs mass spectrum. We present the rates for production and subsequent decay of the neutral NMSSM Higgs bosons in the most promising final states and discuss their possible discovery. The prospects for pinning down the Higgs sector of the natural NMSSM will be analyzed taking into account alternative search channels. We give a series of benchmark scenarios compatible with the experimental constraints, that feature Higgs-to-Higgs decays and entail (exotic) signatures with multifermion and/or multiphoton final states. These decay chains furthermore give access to the trilinear Higgs self-couplings. We briefly discuss the possibility of exploiting coupling sum rules in case not all the NMSSM Higgs bosons are discovered.

We calculate masses of the technipions in the walking technicolor model with the anomalous dimension ${\gamma }_m=1$, based on a holographic model which has a naturally light technidilaton $\varphi$ as a composite Higgs with mass $m_{\varphi }\simeq 125\mathrm{GeV}$. The one-family model (with four weak doublets) is taken as a concrete example in such a framework, with the inputs being $F_{\pi }=v/2\simeq 123\mathrm{GeV}$ and $m_{\varphi }\simeq 125\mathrm{GeV}$ as well as ${\gamma }_m=1$. It is shown that technipion masses are enhanced by the large anomalous dimension to typically $O(1)\mathrm{TeV}$. We find a correlation between the technipion masses and $S^{(\mathrm{TC})}$, the $S$ parameter arising only from the technicolor sector. The current LHC data on the technipion mass limit thus constrains $S^{(\mathrm{TC})}$ to be not as large as $O(1)$, giving a direct constraint on the technicolor model building. This is a new constraint on the technicolor sector alone, quite independent of other sectors connected by the extended-technicolor-type interactions—in sharp contrast to the conventional $S$ parameter constraint from the precision electroweak measurements.

In this paper we study the semileptonic decays of $B_c^{+}\to D_{(s)}^{(*)}(l^{+}{\nu }_l,l^{+}{l}^{-},\nu \overline{\nu })$ (here $l$ stands for $e$, $\mu$, or $\tau$). After evaluating the $B_c^{+}\to (D_{(s)},D_{(s)}^{*})$ transition form factors $F_{0,+,T}(q^2)$ and $V(q^2)$, $A_{0,1,2}(q^2)$, $T_{1,2,3}(q^2)$ by employing the perturbative QCD factorization approach, we calculate the branching ratios for all these semileptonic decays. Our predictions for the values of the $B_c^{+}\to D_{(s)}$ and $B_c^{+}\to D_{(s)}^{*}$ transition form factors are consistent with those obtained by using other methods. The branching ratios of the decay modes with $\overline{\nu }\nu$ are almost an order of magnitude larger than the corresponding decays with $l^{+}{l}^{-}$ after the summation over the three neutrino generations. The branching ratios for the decays with $b\to d$ transitions are much smaller than those decays with the $b\to s$ transitions, due to the Cabibbo-Kobayashi-Maskawa suppression. We define ratios $R_D$ and $R_{D^{*}}$ for the branching ratios with the $\tau$ lepton versus $\mu$, $e$ lepton final states to cancel the uncertainties of the form factors, which could possibly be tested in the near future.

Inspired by the newly observed $D^{(*)}(3000)$ and $D_{sJ}(3040)$ states, in this work we study the production of $D^{(*)}(3000)$, $D_{sJ}(3040)$, and their partners through the semileptonic decays of $B_{(s)}$ mesons, where the light-front quark model is applied to the whole calculation. Our numerical results indicate that the $B_{(s)}$ semileptonic decays into the $2P$ states of the charmed or charmed-strange meson family have considerable branching ratios, which shows that these semileptonic decays can be accessible at future experiments, especially LHCb and the forthcoming Belle II.