International Journal of Modern Physics A

In this paper, we present some general features of gamma-ray spectra from dark matter (DM). We find that the spectrum with sharp features could appear in a wide class of DM models and mimic the gamma line signals. If all other physical degrees of freedom are heavy or effectively decoupled, the resulting gamma ray from DM decay or annihilation would generally have polynomial-type spectra or power-law with positive index. We illustrate our findings in a model-independent framework with generic kinematic analysis. Similar results can also apply for cosmic ray or neutrino cases.

In this paper, we extend the Minimal Supersymmetric Standard Model (MSSM) with additional vector-like particles (VLPs) and compared the differences of mass spectrum and Feynman rules between the MSSM and MSSMV. We analytically calculate the one loop contributions to the Higgs boson mass from the fermions and sfermions in the on shell renormalization scheme. After discussing and numerically analyzing cases without bilinear terms and a case with a (partial) decoupling limit, we find: (i) the corrections depend on the mass splittings between quarks and squarks and between vector-like fermions and their sfermions; (ii) there exists the (partial) decoupling limit, where the VLPs decouple from the electroweak (EW) energy scale, even when one of the VLPs is light around the EW scale. The reason is that the contributions to Higgs mass can be suppressed by the (or partial) decoupling effects, which can make the EW phenomenology different from the MSSM. Moreover, we present some numerical analysis to understand these unique features.

Motivated by the naturalness, we study a simplified Minimal Supersymmetric Standard Model (MSSM) scenario where only the bino-like lightest supersymmetric particle (LSP) and higgsino-like next-lightest supersymmetric particle (NLSP) are light. We first scan the parameter space of this scenario, considering the constraints from the Higgs mass, flavor physics, electroweak precision measurements and dark matter experiments. Then in the allowed parameter space, we perform a Monte Carlo simulation for the ${\tilde{\chi }}_1^{\pm }{\tilde{\chi }}_{2,3}^0$ production followed by ${\tilde{\chi }}_1^{\pm }\to W^{\pm }{\tilde{\chi }}_1^0$ and ${\tilde{\chi }}_{2,3}^0\to Z{\tilde{\chi }}_1^0$. By examining the presently available trilepton bounds on the wino-like chargino/neutralino, we find that only a narrow region $40\mathrm{\text{GeV}}\lesssim m_{{\tilde{\chi }}_1^0}\lesssim 50\mathrm{\text{GeV}}$ and $160\mathrm{\text{GeV}}\lesssim m_{{\tilde{\chi }}_{2,3}^0}\lesssim 170\mathrm{\text{GeV}}$ on the plane of $m_{{\tilde{\chi }}_1^0}-m_{{\tilde{\chi }}_{2,3}^0}$ can be excluded. Finally, we explore the potential of trilepton signature in probing such a scenario at 14 TeV Large Hadron Collider (LHC) and find that the region with $40\mathrm{\text{GeV}}\lesssim m_{{\tilde{\chi }}_1^0}\lesssim 60\mathrm{\text{GeV}}$ and $160\mathrm{\text{GeV}}\lesssim m_{{\tilde{\chi }}_{2,3}^0}\lesssim 300\mathrm{\text{GeV}}$ can be covered at $3\sigma$ level with luminosity ${ℒ}=300{\mathrm{\text{fb}}}^{-1}$.

In this paper, we realize nonuniversal couplings between Kaluza–Klein (KK) gravitons and bulk Standard Model (SM) vectors in the Randall–Sundrum (RS) model by including both UV and IR brane-localized gauge kinetic terms. We find that such kinetic terms can reduce the couplings of KK gravitons to SM gauge bosons and also ensure the KK vector masses are consistent with electroweak precision constraints.

In this work, we investigate the degenerate heavy Higgs bosons in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) by introducing vector-like particles. Such an extension is well motivated from the top-down view since some grand unified theories usually predict the existence of singlet scalars and vector-like particles at weak scale. Under the constraints from the Large Hadron Collider (LHC) and dark matter experiments, we find that (1) the null results of searching for high mass resonances have tightly constrained the parameter space; (2) two degenerate heavy singlet Higgs bosons $h_2$ and $a_1$ can sizably decay to ${\chi }_1^0{\chi }_1^0$ invisibly. Therefore, search for the monojet events through the process $gg\to h_2/a_1(\to {\chi }_1^0{\chi }_1^0)j$ may further test our scenario at the future LHC.

We consider the Kaluza–Klein (KK) graviton and its decays in the presence of the light radion, the modulus of extra dimension, appearing naturally light due to classical scale invariance in warped gravity. Due to the presence of a sizable wave function overlap in the extra dimension between the KK graviton and the radion, the KK graviton can decay largely into a pair of radions, each of which decays into a pair of collimated photons or photon-jets. Focusing on the setup where the KK graviton has suppressed couplings to the Higgs boson and fermions, we discuss the bounds on the light radion in the parameter space where the photon-jets are relevant. Moreover, we pursue the possibility of distinguishing the scenario from the case with direct photon contributions by the angular distributions of photons in the LHC Run 2. Roles of KK graviton and radion as mediators of dark matter interactions, extensions with brane kinetic terms and the model with a holographic composite Higgs are also addressed.

A brief review of the physics of systems including higher derivatives in the Lagrangian is given. All such systems involve ghosts, i.e. the spectrum of the Hamiltonian is not bounded from below and the vacuum ground state is absent. Usually, this leads to collapse and loss of unitarity. In certain special cases, this does not happen, however, ghosts are benign.

We speculate that the Theory of Everything is a higher-derivative field theory, characterized by the presence of such benign ghosts and defined in a higher-dimensional bulk. Our Universe then represents a classical solution in this theory, having the form of a 3-brane embedded in the bulk.

The noncommutative (NC) framework elaborated by Doplicher, Fredenhagen and Roberts (DFR) has a Lorentz invariant space–time structure in order to be considered as a candidate to understand the physics of the early Universe. In DFR formalism, the NC parameter $({𝜃}^{\mu \nu })$ is a coordinate operator in an extended Hilbert space and it has a conjugate momentum. Since $x$ and ${𝜃}^{\mu \nu }$ are independent coordinates, the Moyal–Weyl (MW) product can be used in this framework. With these elements, in this work, we have constructed the standard electroweak model. To accomplish this task, we have begun with the MW-product basis group of symmetry. After that we have introduced the spontaneous symmetry breaking and the hypercharge in DFR framework. The electroweak symmetry breaking was analyzed and the masses of the new bosons were computed. Finally, the gauge symmetry and gauge transformations were discussed.

We derive the off-shell nilpotent symmetries of the two $(1+1)$-dimensional (2D) non-Abelian 1-form gauge theory by using the theoretical techniques of the geometrical superfield approach to Becchi–Rouet–Stora–Tyutin (BRST) formalism. For this purpose, we exploit the augmented version of superfield approach (AVSA) and derive theoretically useful nilpotent (anti-)BRST, (anti-)co-BRST symmetries and Curci–Ferrari (CF)-type restrictions for the self-interacting 2D non-Abelian 1-form gauge theory (where there is no interaction with matter fields). The derivation of the (anti-)co-BRST symmetries and all possible CF-type restrictions are completely novel results within the framework of AVSA to BRST formalism where the ordinary 2D non-Abelian theory is generalized onto an appropriately chosen $(2,2)$-dimensional supermanifold. The latter is parametrized by the superspace coordinates $Z^M=(x^{\mu },𝜃,\overline{𝜃})$ where $x^{\mu }$ (with $\mu =0,1$) are the bosonic coordinates and a pair of Grassmannian variables $(𝜃,\overline{𝜃})$ obey the relationships: ${𝜃}^2={\overline{𝜃}}^2=0$, $𝜃\overline{𝜃}+\overline{𝜃}𝜃=0$. The topological nature of our 2D theory allows the existence of a tower of CF-type restrictions.

Using the massive helicity formalism, we calculate the five-body average square amplitude of the decays ${\tau }^{-}\to {\ell }_i^{-}{\ell }_i^{+}{\ell }_j^{-}{\bar{\nu }}_j{\nu }_{\tau }$ $(\ell =e,\mu )$ within the Standard Model (SM), we then introduce a dimension-five effective vertex ${\mathrm{\Gamma }}^{\tau \tau \gamma }$ in order to determine the feasibility of imposing limits on the tau anomalous magnetic dipole moment $(a_{\tau })$ via the current or future experimental measurements of the branching ratio for the decay ${\tau }^{-}\to e^{-}{e}^{+}{e}^{-}{\bar{\nu }}_e{\nu }_{\tau }$.

The energy of a particle moving on a space–time, in principle, can affect the background metric. The modifications to it depend on the ratio of energy of the particle and the Planck energy, known as rainbow gravity. Here, we find the explicit expressions for the coordinate transformations from rainbow Minkowski space–time to accelerated frame. The corresponding metric is also obtained which we call as rainbow Rindler metric. So far we are aware of that no body has done it in a concrete manner. Here, this is found from the first principle and hence all the parameters are properly identified. The advantage of this is that the calculated Unruh temperature is compatible with the Hawking temperature of the rainbow black hole horizon, obtained earlier. Since the accelerated frame has several importance in revealing various properties of gravity, we believe that the present result will not only fill that gap, but also help to explore different aspects of rainbow gravity paradigm.

The nucleon and nuclear longitudinal structure functions are determined by the Kharzeev–Levin–Nardin (KLN) model of the low-$x$ gluon distribution. The behavior of the gluon distribution ratio $R_g$ and the ratio $R_L^{\mathrm{\text{total}}}$ in $eA$ processes are shown in this paper. The heavy longitudinal structure function ratios in $eA$ processes at the LHeC region are discussed. Heavy contributions to the ratio of the total longitudinal structure function are considerable and should not be neglected especially at smaller $x$ of the LHeC project. In the KLN model, the new geometrical scaling for transition from the linear to nonlinear regions in accordance with the LHeC processes is used, whose results intensively depended on the heavy quark mass effect.

The black hole information paradox presumes that quantum field theory in curved space–time can provide unitary propagation from a near-horizon mode to an asymptotic Hawking quantum. Instead of invoking conjectural quantum-gravity effects to modify such an assumption, we propose a self-consistency check. We establish an analogy to Feynman’s analysis of a double-slit experiment. Feynman showed that unitary propagation of the interfering particles, namely ignoring the entanglement with the double-slit, becomes an arbitrarily reliable assumption when the screen upon which the interference pattern is projected is infinitely far away. We argue for an analogous self-consistency check for quantum field theory in curved space–time. We apply it to the propagation of Hawking quanta and test whether ignoring the entanglement with the geometry also becomes arbitrarily reliable in the limit of a large black hole. We present curious results to suggest a negative answer, and we discuss how this loss of naive unitarity in QFT might be related to a solution of the paradox based on the soft-hair-memory effect.

A combined analysis of both $e^{+}{e}^{-}$ (LEP, SLD) and $pp$ (RHIC-PHENIX and LHC-ALICE) hadroproduction processes are done for the first time for the vector meson nonet at the next-to-leading order (NLO) using a model with broken SU(3) symmetry. The transverse momentum ($p_T$) and rapidity ($y$) dependence of the differential cross-section for $\omega$ and $\varphi$ mesons of the $pp$ data are also discussed. The input universal quark (valence and singlet) fragmentation functions at a starting scale of $Q_0^2=1.5{\mathrm{\text{GeV}}}^2$, after evolution, have values that are consistent with the earlier analysis for $e^{+}{e}^{-}$ at NLO. However, the universal gluon fragmentation function is now well determined from this study with significantly smaller error bars, as the $pp$ hadroproduction cross-section is particularly sensitive to the gluon fragmentation since it occurs at the same order as the quark fragmentation, in contrast to the $e^{+}{e}^{-}$ hadroproduction process. Additional parameters involved in describing the strangeness and sea suppression and octet–singlet mixing are found to be close to the earlier analysis; in addition, a new relation between the gluon and sea suppression in $K^{\ast }$ and $\varphi$ hadroproduction has been observed.

Knotted solutions to electromagnetism and fluid dynamics are investigated, based on relations we find between the two subjects. We can write fluid dynamics in electromagnetism language, but only on an initial surface, or for linear perturbations, and we use this map to find knotted fluid solutions, as well as new electromagnetic solutions. We find that knotted solutions of Maxwell electromagnetism are also solutions of more general nonlinear theories, like Born–Infeld, and including ones which contain quantum corrections from couplings with other modes, like Euler–Heisenberg and string theory DBI. Null configurations in electromagnetism can be described as a null pressureless fluid, and from this map we can find null fluid knotted solutions. A type of nonrelativistic reduction of the relativistic fluid equations is described, which allows us to find also solutions of the (nonrelativistic) Euler’s equations.

In this paper we discuss the boson/vortex duality by mapping the (3+1)D Gross–Pitaevskii theory into an effective string theory in the presence of boundaries. Via the effective string theory, we find the Seiberg–Witten map between the commutative and the noncommutative tachyon field theories, and consequently identify their soliton solutions with D-branes in the effective string theory. We perform various checks of the duality map and the identification of soliton solutions. This new insight between the Gross–Pitaevskii theory and the effective string theory explains the similarity of these two systems at quantitative level.