The light-front quark model has been applied to calculate the transition matrix elements of heavy hadron decays. However, it is noted that using the traditional wave functions of the light-front quark model given in the literature, the theoretically determined decay constants of the ${\rm Y}(nS)$ obviously contradict the data. This implies that the wave functions must be modified. Keeping the orthogonality among the $nS$ states and fitting their decay constants, we obtain a series of the wave functions for ${\rm Y}(nS)$. Based on these wave functions and by analogy with the hydrogen atom, we suggest a modified analytical form for the ${\rm Y}(nS)$ wave functions. Using the modified wave functions, the obtained decay constants are close to the experimental data. Then we calculate the rates of radiative decays of ${\rm Y}(nS)\to {\eta }_b+\gamma$. Our predictions are consistent with the experimental data on decays ${\rm Y}(3S)\to {\eta }_b+\gamma$ within the theoretical and experimental errors.

We consider the supernova shock effects, the Mikheyev-Smirnov-Wolfenstein effects, the collective effects, and the Earth matter effects in the detection of type II supernova neutrinos on the Earth. It is found that the event number of supernova neutrinos depends on the neutrino mass hierarchy, the neutrino mixing angle ${\theta }_{13}$, and neutrino masses. Therefore, we propose possible methods to identify the mass hierarchy and acquire information about ${\theta }_{13}$ and neutrino masses by detecting supernova neutrinos. We apply these methods to some current neutrino experiments.

Tau neutrino and antineutrino interactions with nucleons in large underground or under-ice detectors will be important signals of astrophysical and atmospheric sources of neutrinos. We present here a theoretical update of the deep inelastic scattering contribution to the tau neutrino and antineutrino charged current cross sections with isoscalar nucleon targets and proton targets for incident neutrinos and antineutrinos in the energy range from 10 GeV to 10 TeV. Next-to-leading order quantum chromodynamic corrections, target mass corrections, and heavy quark effects are included. Uncertainties in the cross section associated with the structure functions and low momentum transfers, the input parton distribution functions, scale dependence, and flavor number scheme are discussed.

We propose a specific ansatz for the structure of Yukawa matrices in $SO(10)$ models that lead to quasidegenerate neutrinos through the type-I seesaw mechanism. Consistency of this ansatz is demonstrated through detailed fits to fermion masses and mixing angles, all of which can be explained with reasonable accuracy in a model that uses the Higgs fields transforming as 10, 120, and $\overline{126}$ representations of $SO(10)$. The proposed ansatz is shown to follow from an extended model based on the three generations of the vectorlike fermions and an $O(3)$ flavor symmetry. Successful numerical fits are also discussed in earlier proposed models, which used a combination of the type-I and type-II seesaw mechanisms for obtaining quasidegenerate neutrinos. Large neutrino mixing angles emerge as a consequence of neutrino mass degeneracy in both these cases.

We perform an all-order calculation of the $\rho$ parameter in a simplified framework, where the top propagator can be calculated exactly. Special emphasis is placed on the question of gauge invariance and the treatment of nonperturbative cutoff effects.

The minimal bimetric theory employing a disformal transformation between matter and gravity metrics is known to produce exactly scale-invariant fluctuations. It has a purely equilateral non-Gaussian signal, with an amplitude smaller than that of Dirac Born Infeld inflation (with opposite sign) but larger than standard inflation. We consider nonminimal bimetric models, where the coupling $B$ appearing in the disformal transformation ${\widehat{g}}_{\mu \nu }=g_{\mu \nu }-B{\partial }_{\mu }\varphi {\partial }_{\nu }\varphi$ can run with $\varphi$. For power-law $B(\varphi )$ these models predict tilted spectra. For each value of the spectral index, a distinctive distortion to the equilateral property can be found. The constraint between this distortion and the spectral index can be seen as a “consistency relation” for nonminimal bimetric models.

In the standard model with a fourth generation of quarks, we study the relation between the Jarlskog invariants and the triangle areas in the $4\times 4$ Cabibbo-Kobayashi-Maskawa matrix. To identify the leading effects that may probe the $CP$ violation in processes involving quarks, we invoke small mass and small angle expansions, and show that these leading effects are enhanced considerably compared to the three-generation case by the large masses of fourth-generation quarks. We discuss the leading effect in several cases, in particular, the possibility of large $CP$ violation in $b\to s$ processes, which echoes the heightened recent interest because of experimental hints.

We construct a full left-right model for the electroweak interactions based on the $\mathrm{SU}(3{)}_L\otimes \mathrm{SU}(3{)}_R\otimes \mathrm{U}(1{)}_X$ gauge symmetry. The fermion content of the model is such that anomaly cancellation restricts the number of families to be a multiple of three. One of the most important features of the model is the joint presence of three light active neutrinos, three additional neutrinos at keV mass scale, and six heavy ones with masses around ${10}^{11}\mathrm{GeV}$. They form a well-motivated part of the spectrum in the sense that they address challenging problems related to neutrino oscillation, warm dark matter, and baryogenesis through leptogenesis.

New physics models that increase the decay rate of $B_s\to {\tau }^{+}{\tau }^{-}$ contribute to the absorptive part of $B_s–{\overline{B}}_s$ mixing, and may enhance $\Delta {\Gamma }_s$ all the way up to its current experimental bound. In particular, the model with a scalar leptoquark can lead to a significant violation of the expectation $\Delta {\Gamma }_s\le \Delta {\Gamma }_s(\mathrm{SM})$. It can even allow regions in the $\Delta {\Gamma }_s–{\beta }_s$ parameter space that are close to the best fit obtained by CDF and D0 through $B_s\to J/\psi \varphi$. In addition, it can help explain the anomalous like-sign dimuon charge asymmetry observed recently by D0. A measurement of $\mathrm{BR}(B_s\to {\tau }^{+}{\tau }^{-})$ is thus crucial for a better understanding of new physics involved in $B_s–{\overline{B}}_s$ mixing.

It has recently been shown in high resolution numerical simulations that relativistic collisions of bubbles in the context of a multivacua potential may lead to the creation of bubbles in a new vacuum. In this paper, we show that scalar fields with only potential interactions behave like free fields during high-speed collisions; the kick received by them in a collision can be deduced simply by a linear superposition of the bubble wall profiles. This process is equivalent to the scattering of solitons in $1+1$ dimensions. We deduce an expression for the field excursion (shortly after a collision), which is related simply to the field difference between the parent and bubble vacua, i.e. contrary to expectations, the excursion cannot be made arbitrarily large by raising the collision energy. There is however a minimum energy threshold for this excursion to be realized. We verify these predictions using a number of $3+1$ and $1+1$ numerical simulations. A rich phenomenology follows from these collision-induced excursions—they provide a new mechanism for scanning the landscape, they might end/begin inflation, and they might constitute our very own big bang, leaving behind a potentially observable anisotropy.

We review the similarities between the effective chiral Lagrangrian, relevant for low-energy strong interactions, and the Einstein-Hilbert action. We use these analogies to suggest a specific mechanism whereby gravitons would emerge as Goldstone bosons of a global $SO(D)\times GL(D)$ symmetry broken down to $SO(D)$ by fermion condensation. We propose a two-dimensional toy model where a dynamical zweibein is generated from a topological theory without any preexisting metric structure, the space being endowed only with an affine connection. A metric appears only after the symmetry breaking; thus the notion of distance is an induced effective one. In spite of several nonstandard features this simple toy model appears to be renormalizable and at long distances is described by an effective Lagrangian that corresponds to that of two-dimensional gravity (Liouville theory). The induced cosmological constant is related to the dynamical mass $M$ acquired by the fermion fields in the breaking, which also acts as an infrared regulator. The low-energy expansion is valid for momenta $k>M$, i.e. for supra-horizon scales. We briefly discuss a possible implementation of a similar mechanism in four dimensions.

We investigate the vector-current correlation ${\Pi }_{\mu \nu }$ (VCC) in the presence of a strong external magnetic field ($\mathit{B}=B_0\widehat{z}$) at low temperature ($T\lesssim T_c^{\chi }$) with $P$ and $CP$ violations, indicated by the nonzero chiral-chemical potential (${\mu }_{\chi }\ne 0$), i.e. the chiral-magnetic effect (CME). For this purpose, we employ the instanton-vacuum configuration at finite $T$ with nonzero topological charge ($Q_t\ne 0$). We also consider a simple estimation for the nonzero-mode contributions to the quark propagator, in addition to the zero-mode approximation. From the numerical calculations, it turns out that the longitudinal component of the connected VCC is linear in $B_0$ and shows a bump, representing a corresponding vector meson at $|Q|=(300\sim 400)\mathrm{MeV}$ for $T=0$. The bump becomes enhanced as $T$ increases and the bump position shifts to a lager $|Q|$ value. In the limit of $|Q|\to 0$, the transverse component of the connected VCC disappears, whereas the longitudinal one remains finite and becomes insensitive to $B_0$ with respect to $T$, due to diluting instanton contributions. Considering the simple collision geometry of heavy-ion collision and some assumptions on the induced magnetic field and screening effect, we can estimate the charge separation as a function of centrality using the present results for the VCC. The numerical results show a qualitative agreement with experiments for the $\mathrm{Au}+\mathrm{Au}$ and $\mathrm{Cu}+\mathrm{Cu}$ collisions. These results are almost independent on the source of the CME, instanton, or sphaleron, as long as the CME current is linear in $B_0$.

The mounting evidence for anomalously large peculiar velocities in our Universe presents a challenge for the $\Lambda \mathrm{CDM}$ paradigm. The recent estimates of the large-scale bulk flow by Watkins et al. are inconsistent at the nearly $3\sigma$ level with $\Lambda \mathrm{CDM}$ predictions. Meanwhile, Lee and Komatsu have recently estimated that the occurrence of high-velocity merging systems such as the bullet cluster (1E0657-57) is unlikely at a $6.5–5.8\sigma$ level, with an estimated probability between $3.3\times {10}^{-11}$ and $3.6\times {10}^{-9}$ in $\Lambda \mathrm{CDM}$ cosmology. We show that these anomalies are alleviated in a broad class of infrared-modifed gravity theories, called brane-induced gravity, in which gravity becomes higher-dimensional at ultralarge distances. These theories include additional scalar forces that enhance gravitational attraction and therefore speed up structure formation at late times and on sufficiently large scales. The peculiar velocities are enhanced by 24–34% compared to standard gravity, with the maximal enhancement nearly consistent at the $2\sigma$ level with bulk flow observations. The occurrence of the bullet cluster in these theories is $\approx {10}^4$ times more probable than in $\Lambda \mathrm{CDM}$ cosmology.

One of the most pressing issues in cosmology is whether general relativity (GR) plus a dark sector is the underlying physical theory or whether a modified gravity model is needed. Upcoming dark energy experiments designed to probe dark energy with multiple methods can address this question by comparing the results of the different methods in constraining dark energy parameters. Disagreement would signal the breakdown of the assumed model (GR plus dark energy). We study the power of this consistency test by projecting constraints in the $w_0\mathrm{\text{−}}{w}_a$ plane from the four different techniques of the Dark Energy Survey in the event that the underlying true model is modified gravity. We find that the standard technique of looking for overlap has some shortcomings, and we propose an alternative, more powerful Multidimensional Consistency Test. We introduce the methodology for projecting whether a given experiment will be able to use this test to distinguish a modified gravity model from GR.

We consider the role of the zero-point energy of a quantum field in cosmology and show that the flow of trans-Planckian momenta due to redshift acts as a source for this energy, regularized with a cutoff $\Lambda$ in physical momenta. In order to fulfill Bianchi identity, we generalize Einstein equations and discuss the corresponding Friedmann homogeneous and isotropic models. In case of a de Sitter phase, such as during inflation, the solution shows a logarithmic behavior of the Hubble parameter and a primordial spectrum of scalar perturbations characterized by the spectral index $n_s=1-{\Lambda }^2/(3\pi m_P^2)$ with $m_P$ the Planck mass. We also discuss possible implications of the scenario on the late accelerating stage of the Universe at small redshifts and the emergence of a fluid characterized by an equation of state $w=P/\rho =-1+{\Lambda }^2/(9\pi m_P^2)$. Primordial perturbation spectrum and dark energy parameter $w$ are, thus, predicted to be connected by the simple relation $w=-(2+n_s)/3$.

We inspect the mass spectrum of heavy-light mesons in deformed $\mathcal{N}=2$ super Yang-Mills theory using the AdS/CFT correspondence. We demonstrate how some of the degeneracies of the supersymmetric meson spectrum can be removed upon breaking the supersymmetry, thus leading to the emergence of a hyperfine structure. The explicit SUSY breaking scenarios we consider involve on the one hand, tilting one of the two fundamental D7-branes inside the internal ${\mathbb{R}}^6$ space, and on the other hand, applying an external magnetic field on the (untilted) branes. The latter scenario leads to the well-known Zeeman effect, which we inspect for both weak and strong magnetic fields.

Inflation can occur near a point of inflection in the potential of flat directions of the minimal supersymmetric standard model (MSSM). In this paper we elaborate on the complementarity between the bounds from cosmic microwave background measurements, dark matter, and particle physics phenomenology in determining the underlying parameters of MSSM inflation by specializing to the minimal supergravity scenario. We show that the future measurements from the Large Hadron Collider in tandem with all these constraints will significantly restrict the allowed parameter space. We also suggest a new perspective on the fine tuning issue of MSSM inflation. With quantum corrections taken into account, the necessary condition between the soft supersymmetry breaking parameters in the inflaton potential can be satisfied at scales of interest without a fine tuning of their boundary values at a high scale. The requirement that this happens at the inflection point determines a dimensionless coupling, which is associated with a nonrenormalizable interaction term in the Lagrangian and has no bearing for phenomenology, to very high accuracy.

We investigate the tensor form factors of the baryon octet within the framework of the chiral quark-soliton model, emphasizing those of the nucleon, taking linear $1/N_c$ rotational as well as linear $m_s$ corrections into account, and applying the symmetry-conserving quantization. We explicitly calculate the tensor form factors $H_T^q(Q^2)$ corresponding to the generalized parton distributions $H_T(x,\xi ,t)$. The tensor form factors are obtained for the momentum transfer up to $Q^2\le 1{\mathrm{GeV}}^2$ and at a renormalization scale of $0.36{\mathrm{GeV}}^2$. We find for the tensor charges $\delta u=1.08$, $\delta d=-0.32$, and $\delta s=-0.01$ and discuss their physical consequences, comparing them with those from other models. Results for tensor charges for the baryon octet are also given.

In this paper, a study of two-photon and two-gluon decays in the context of $p$-wave heavy quarkonia is presented. Within the covariant light-front framework, the annihilation rates of scalar and tensor quarkonium states are derived. In the absence of free parameters in this case, the results for the charmonium decay widths are consistent with the experimental data. However, in comparison to other theoretical calculations, there are large discrepancies in our results regarding bottomonia.

We complete the coordinate space calculation of the three-parton correlation in the two-loop massive soft anomalous dimension matrix. The full answer agrees with the result found previously by a different approach. The coordinate space treatment of renormalized two-loop gluon exchange diagrams exhibits their color symmetries in a transparent fashion. We compare coordinate space calculations of the soft anomalous dimension matrix with massive and massless eikonal lines and examine its nonuniform limit at absolute threshold.