In this paper, we study the properties of media with chiral imbalance parametrized by chiral chemical potential. It is shown that depending on the strength of interaction between constituents in the media the chiral chemical potential either creates or enhances dynamical chiral symmetry breaking. Thus, the chiral chemical potential plays the role of the catalyst of dynamical chiral symmetry breaking. Physically, this effect results from the appearance of the Fermi surface and additional fermion states on this surface, which take part in dynamical chiral symmetry breaking. An interesting conclusion which can be drawn is that at sufficiently small temperature chiral plasma is unstable with respect to condensation of Cooper pairs and dynamical chiral symmetry breaking even for vanishingly small interactions between constituents.

We present detailed calculations for quantum-gravitational corrections to the power spectra of gauge-invariant scalar and tensor perturbations during inflation. This is done by performing a semiclassical Born-Oppenheimer type of approximation to the Wheeler-DeWitt equation, from which we obtain a Schrödinger equation with quantum-gravitational correction terms. As a first step, we perform our calculation for a de Sitter universe and find that the correction terms lead to an enhancement of power on the largest scales.

We investigate the four solar system tests of gravity—perihelion precession, light bending, Shapiro time delay, gravitational redshift—in $f(T)$ gravity. In particular, we investigate the solution derived by Ruggiero and Radicella, Phys. Rev. D 91, 104014 (2015). for a nondiagonal vierbein field for a polynomial $f(T)=T+\alpha T^n$, where $\alpha$ is a constant and $|n|\ne 1$. In this paper, we derive the solutions for each test, in which Weinberg’s, Bodenner and Will’s, Cattani et al., and Rindler and Ishak’s methods are applied, Gravitation and Cosmology: Principles and Applications of the General Theory of Relativity (Wiley, New York, 1972); Am. J. Phys. 71 (2003); Phys. Rev. D 87, 047503 (2013); Phys. Rev. D 76, 043006 (2007). We set a constraint on $\alpha$ for $n=2$, 3 by using data available from literature.

In this work, we consider a noncommutative (NC) massless scalar field coupled to the classical nonrotational BTZ geometry. In a manner of the theories where the gravity emerges from the underlying scalar field theory, we study the effective action and the entropy derived from this noncommutative model. In particular, the entropy is calculated by making use of the two different approaches, the brick-wall method and the heat kernel method designed for spaces with conical singularity. We show that the UV divergent structures of the entropy obtained through these two different methods agree with each other. It is also shown that the same renormalization condition that removes the infinities from the effective action can also be used to renormalize the entanglement entropy for the same system. Besides, the interesting feature of the NC model considered here is that it allows an interpretation in terms of an equivalent system comprising a commutative massive scalar field but in a modified geometry: that of the rotational BTZ black hole, the result that hints at a duality between the commutative and noncommutative systems in the background of a BTZ black hole.

We search for a continuum limit in the causal dynamical triangulation approach to quantum gravity by determining the change in lattice spacing using two independent methods. The two methods yield similar results that may indicate how to tune the relevant couplings in the theory in order to take a continuum limit.

We provide the latest constraints on the power spectra of both scalar and tensor perturbations from the cosmic microwave background data (including Planck 2015, BICEP2, and Keck Array experiments) and the new baryon acoustic oscillation scales from SDSS-III BOSS observations. We find that the inflation model with a convex potential is not favored and both the inflation model with a monomial potential and the natural inflation model are marginally disfavored at around 95% confidence level. But both the brane inflation model and the Starobinsky inflation model fit the data quite well.

We study the collider phenomenology of the electroweak phase transition and electroweak baryogenesis in the framework of the effective field theory. Our study shows that the effective theory using the dimension-6 operators can enforce strong first order phase transition and provide sizable $CP$ violation to realize a successful electroweak baryogenesis. Such dimension-6 operators can induce interesting Higgs phenomenology that can be verified at colliders such as the LHC and the planning CEPC. We then demonstrate that this effective theory can originate from vectorlike quarks and the triplet Higgs.

The Starobinsky model is one of the inflation models consistent with the result of CMB observation by the Planck satellite. We consider the dynamics of the Starobinsky inflation in the presence of another scalar field with a large expectation value during inflation due to a negative Hubble-induced mass. We find that it would be affected if the other field has an amplitude close to the Planck scale. In this case, we may observe such effects on the Starobinsky model by future CMB experiments.

We perform a complete decoupling of the degrees of freedom of quadratic gravity and the generic $f(R_{\mu \nu \sigma \rho })$ theory about any one of their possible vacua, i.e. maximally symmetric solutions, and find the masses of the spin-2 and spin-0 modes in explicit forms.

We study the LHC searches for the heavy $CP$-odd Higgs boson $A$ and $CP$-even Higgs boson $H$ in the context of a general two-Higgs-doublet model. Specifically, we consider the decay mode of $A/H\to t\overline{t}$ through the $t\overline{t}$ associated production channels. In the so-called “alignment limit” of the two-Higgs-doublet model, this decay mode can be the most dominant one. By employing the HEPTopTagger and the multivariate analysis method, we present the search sensitivities for both $CP$-odd Higgs boson $A$ and $CP$-even Higgs boson $H$ via this channel with multiple top quarks at the high-luminosity LHC runs.

We investigate the elastic and inelastic scattering of lightest supersymmetric particle (LSP) dark matter off two possible target nuclei, ${}^{83}\mathrm{Kr}$ and ${}^{125}\mathrm{Te}$. For the nuclear-structure calculations, we employ the nuclear shell model using recently generated realistic interactions. We have condensed the nuclear-physics contribution to a set of nuclear-structure factors that are independent of the adopted supersymmetric (SUSY) model. Total event rates are then easily calculated by combining the nuclear-structure factors with SUSY parameters of choice. In particular, ${}^{125}\mathrm{Te}$ shows promise as a detector material with both the elastic and inelastic channels yielding an appreciable nuclear response.

We explain the recent diphoton excesses around 750 GeV by both ATLAS and CMS as a singlet scalar $\mathrm{\Phi }$ which couples to SM gluon and neutral gauge bosons only through higher-dimensional operators. A natural explanation is that $\mathrm{\Phi }$ is a pseudo-Nambu-Goldstone boson (pNGB) which receives parity violation through anomaly if there exists a hidden strong dynamics. The singlet and other light pNGBs will decay into two SM gauge bosons and even serves as the metastable colored states which can be probed in the future. By accurately measuring their relative decay and the total production rate in the future, we will learn the underlying strong dynamics parameter. The lightest baryon in this confining theory could serve as a viable dark matter candidate.

The production of weak gauge bosons in association with heavy flavored mesons at the LHCb conditions is considered, and a detailed study of the different contributing processes is presented including single and double parton scattering (DPS) mechanisms. We find that the usual DPS factorization formula needs to be corrected for the limited partonic phase space, and that including the relevant corrections reduces discrepancies in the associated $ZD$ production. We conclude finally that double parton scattering dominates the production of same-sign $W^{\pm }{D}^{\pm }$ states, as well as the production of $W^{-}$ bosons associated with $B$ mesons. The latter processes can thus be regarded as new useful DPS indicators.

In the framework of the $k_T$-factorization approach, the production of prompt $\psi (2S)$ mesons in $pp$ collisions at the LHC energies is studied. Our consideration is based on the off-shell amplitudes for hard partonic subprocesses $g^{*}{g}^{*}\to {\chi }_{cJ}$ and nonrelativistic QCD formalism for bound states. The transverse-momentum-dependent (unintegrated) gluon densities in a proton were derived from the Ciafaloni-Catani-Fiorani-Marchesini evolution equation or, alternatively, were chosen in accordance with the Kimber-Martin-Ryskin prescription. Taking into account both color-singlet and color-octet contributions, we deduce the corresponding nonperturbative long-distance matrix elements from the fits to the latest ATLAS data on ${\chi }_{c1}$ and ${\chi }_{c2}$ transverse-momentum distributions at $\sqrt{s}=7\mathrm{TeV}$. We find that these distributions at small and moderate $p_T$ are formed mainly by the color-singlet components. We successfully described the data on the relative production rates $\sigma ({\chi }_{c2})/\sigma ({\chi }_{c1})$ presented by the ATLAS, CMS, and LHCb Collaborations. We find that the fit points to unequal wave functions of ${\chi }_{c1}$ and ${\chi }_{c2}$ states.

A search for the standard model Higgs boson produced in association with a vector boson with the decay $H\to \tau \tau$ is presented. The data correspond to $20.3{\mathrm{fb}}^{-1}$ of integrated luminosity from proton-proton collisions at $\sqrt{s}=8\mathrm{TeV}$ recorded by the ATLAS experiment at the LHC during 2012. The data agree with the background expectation, and 95% confidence-level upper limits are placed on the cross section of this process. The observed (expected) limit, expressed in terms of the signal strength $\mu =\sigma /{\sigma }_{\mathrm{SM}}$ for $m_{\mathrm{H}}=125\mathrm{GeV}$, is $\mu <5.6$ (3.7). The measured value of the signal strength is $\mu =2.3\pm 1.6$.

In this article we present exact calculations that substantiate a clear picture relating the confining force of QCD to the zero-modes of the Faddeev-Popov (FP) operator $\mathcal{M}(gA)=-\partial ·D(gA)$. This is done in two steps. First we calculate the spectral decomposition of the FP operator and show that the ghost propagator $\mathcal{G}(k;gA)=⟨\overrightarrow{k}|{\mathcal{M}}^{-1}(gA)|\overrightarrow{k}⟩$ in an external gauge potential $A$ is enhanced at low $k$ in Fourier space for configurations $A$ on the Gribov horizon. This results from the new formula in the low-$k$ regime ${\mathcal{G}}^{ab}(k,gA)={\delta }^{ab}{\lambda }_{|\overrightarrow{k}|}^{-1}(gA)$, where ${\lambda }_{|\overrightarrow{k}|}(gA)$ is the eigenvalue of the FP operator that emerges from ${\lambda }_{|\overrightarrow{k}|}(0)={\overrightarrow{k}}^2$ at $A=0$. Next we derive a strict inequality signaling the divergence of the color-Coulomb potential at low momentum $k$ namely, $\tilde{\mathcal{V}}(k)\ge k^2{\mathcal{G}}^2(k)$ for $k\to 0$, where $\tilde{\mathcal{V}}(k)$ is the Fourier transform of the color-Coulomb potential $\mathcal{V}(r)$ and $\mathcal{G}(k)$ is the ghost propagator in momentum space. Although the color-Coulomb potential is a gauge-dependent quantity, we recall that it is bounded below by the gauge-invariant Wilson potential, and thus its long range provides a necessary condition for confinement. The first result holds in the Landau and Coulomb gauges, whereas the second holds in the Coulomb gauge only.

The ordering problem in quantum systems with position-dependent mass (PDM) is treated by inclusion of the classically fictitious similarity transformation into the kinetic term. This provides a generation of supersymmetry with the first-order supercharges from the kinetic term alone, while inclusion of the potential term allows us also to generate nonlinear supersymmetry with higher-order supercharges. A broad class of finite-gap systems with PDM is obtained by different reduction procedures, and general results on supersymmetry generation are applied to them. We show that elliptic finite-gap systems of Lamé and Darboux-Treibich-Verdier types can be obtained by reduction to Seiffert’s spherical spiral and Bernoulli lemniscate in the presence of Calogero-like or harmonic oscillator potentials, or by angular momentum reduction of a free motion on some ${\mathrm{AdS}}_2$-related surfaces in the presence of Aharonov-Bohm flux. The limiting cases include the Higgs and Mathews-Lakshmanan oscillator models as well as a reflectionless model with PDM exploited recently in the discussion of cosmological inflationary scenarios.

In this paper the duality correspondence between fermion-antifermion and difermion interaction channels is established in two ($2+1$)-dimensional Gross-Neveu–type models with a fermion number chemical potential $\mu$ and a chiral chemical potential ${\mu }_5$. The role and influence of this property on the phase structure of the models are investigated. In particular, it is shown that the chemical potential ${\mu }_5$ promotes the appearance of dynamical chiral symmetry breaking, whereas the chemical potential $\mu$ contributes to the emergence of superconductivity.

In this work, we study the motion of charged test particles in Kerr-Newman-Taub-NUT spacetime. We analyze the angular and the radial parts of the orbit equations and examine the possible orbit types. We also investigate the spherical orbits and their stabilities. Furthermore, we obtain the analytical solutions of the equations of motion and express them in terms of Jacobian and Weierstrass elliptic functions. Finally, we discuss the observables of the bound motion and calculate the perihelion shift and Lense-Thirring effect for the bound orbits.

One of the most frustrating issues in early universe cosmology centers on how to reconcile the vast choice of universes in string theory and in its most plausible high energy sibling, eternal inflation, which jointly generate the string landscape with the fine-tuned and hence relatively small number of universes that have undergone a large expansion and can accommodate observers and, in particular, galaxies. We show that such observations are highly favored for any system whereby physical parameters are distributed at a high energy scale, due to the conservation of the Liouville measure and the gauge nature of volume, asymptotically approaching a period of large isotropic expansion characterized by $w=-1$. Our interpretation predicts that all observational probes for deviations from $w=-1$ in the foreseeable future are doomed to failure. The purpose of this paper is not to introduce a new measure for the multiverse, but rather to show how what is perhaps the most natural and well-known measure, volume weighting, arises as a consequence of the conservation of the Liouville measure on phase space during the classical slow-roll expansion.