We construct a string-inspired model for the central production of $\eta$ and ${\eta }^{\prime }$ mesons in proton-proton collisions via double Pomeron exchange. Using general symmetry considerations, we construct a low-energy differential cross section for double glueball exchange in terms of some undetermined coupling constants and form factors. We extend this model to the Regge regime, replacing the glueball propagators with Pomeron trajectories and modifying the interaction term by a factor derived from the five-string scattering amplitude in flat space. We then fix the couplings which remain undetermined, using the Sakai–Sugimoto framework to model low-energy QCD. Finally, we generate a simulation of the scattering process at $\sqrt{s}=29.1\mathrm{GeV}$, where double Pomeron exchange should play a role (secondary to double Reggeon exchange). We focus on the dependence of the scattering cross section on ${\theta }_{34}$, the angle between the scattered protons in the transverse plane. The results exhibit a definite deviation from the pure ${\sin }^2{\theta }_{34}$ dependence that arises as a consequence of natural parity violation alone. The amount of deviation is primarily determined by couplings that come from the Chern–Simons action of the anti-de Sitter/QCD supergravity dual, which is directly related to the QCD gravitational anomaly, and thus constitutes a universal part of any five-dimensional string/gravity dual theory of QCD. We argue that this makes the high-energy central production of pseudoscalar mesons an interesting probe of anti-de Sitter/QCD models.

In this short paper we investigate the ultrarelativistic collisions of small amplitude oscillons in $1+1$ dimensions. Using the amplitude of the oscillons and the inverse relativistic boost factor ${\gamma }^{-1}$ as the perturbation variables, we analytically calculate the leading order spatial and temporal phase shifts, and the change in the amplitude of the oscillons after the collisions. At leading order, we find that only the temporal phase shift receives a nonzero contribution, and that the collision is elastic. This work is also the first application of the general kinematic framework for understanding ultrarelativistic collisions [1] to intrinsically time-dependent solitons.

Within the framework of $\mathcal{N}=1$ gauged supergravity, using a phenomenological model that can be obtained locally as a Swiss-cheese Calabi-Yau string-theoretic compactification with a mobile $D3$-brane localized on a nearly special Lagrangian three cycle in the Calabi-Yau and fluxed stacks of wrapped $D7$-branes, and which provides a natural realization of $\mu$-split supersymmetry (SUSY), we show that in addition to getting a significant value of an [electron/neutron (e/n)] electron dipole moment (EDM) at two-loop level, one can obtain a sizable contribution of (e/n) EDM even at one-loop level due to the presence of heavy supersymmetric fermions nearly isospectral with heavy sfermions. Unlike traditional split SUSY models in which the one-loop diagrams do not give significant contribution to the EDM of the electron/neutron because of very heavy sfermions existing as propagators in the loop, we show that one obtains a “healthy” value of the EDM in our model because of the presence of a heavy Higgsino, neutralino/chargino, and gaugino as fermionic propagators in the loops. The independent $CP$-violating phases are generated from nontrivial distinct phase factors associated with four Wilson line moduli [identified with first-generation leptons and quarks and their $SU(2{)}_L$-singlet cousins] as well as the $D3$-brane position moduli (identified with two Higgses), and the same are sufficient to produce overall distinct phase factors corresponding to all possible effective Yukawas as well as effective gauge couplings that we discuss in the context of $\mathcal{N}=1$ gauged supergravity action. However, the complex phases responsible to generate a nonzero EDM at one-loop level mainly appear from an off-diagonal contribution of sfermion as well as Higgs mass matrices at the electroweak scale (EW). In our analysis, we obtain a dominant contribution of the electron/neutron EDM around $d_e/e\equiv \mathcal{O}(10^{-29})\mathrm{cm}$ from two-loop diagrams involving heavy sfermions and a light Higgs, and $d_e/e\equiv \mathcal{O}(10^{-32})\mathrm{cm}$ from a one-loop diagram involving a heavy chargino and a light Higgs as propagators in the loop. The neutron EDM gets a dominant contribution of the order $d_n/e\equiv \mathcal{O}(10^{-33})\mathrm{cm}$ from the one-loop diagram involving SM-like quarks and Higgs. To justify the possibility of obtaining a large EDM value in the case of a Barr-Zee diagram which involves $W^{\pm }$ and the Higgs (responsible to generate the nontrivial $CP$-violating phase) in the two-loop diagrams as discussed by Leigh et al. [Nucl. Phys. B267, 509 (1986)], we provide an analysis of the same in the context of our $D3/D7$ $\mu$-split SUSY model at the EW scale. By conjecturing that the $CP$-violating phase can appear from the diagonalization of the Higgs mass matrix obtained in the context of $\mu$-split SUSY, we also get an EDM of the electron/neutron around $\mathcal{O}(10^{-27})e\mathrm{cm}$ in the case of the two-loop diagram involving $W^{\pm }$ bosons.

We take string theory in a box of volume $V$, and ask for the entropy $S(E,V)$. We let $E$ exceed the value $E_{bh}$ corresponding to the largest black hole that can fit in the box. Several approaches in the past have suggested the expression $S\sim \sqrt{EV/G}$. We recall these arguments, and in particular expand on an argument that uses dualities of string theory. We require that the expression for $S(E,V)$ be invariant under the $T$ and $S$ when $E\sim E_{bh}$. These criteria lead to the above expression for $S$. We note that this expression has been obtained also by a imposing a quite different requirement—that the entropy within a cosmological horizon be of the order of the Bekenstein entropy for a black hole the size of the cosmological horizon. We recall the earlier proposed model of a “dense gas of black holes” to model this entropy, and discuss its realization as a set of intersecting brane states. Finally we speculate that the cosmological evolution of such a phase may depart from the evolution expected from the classical Einstein equations, since the very large value of the entropy can lead to novel effects similar to the fuzzball dynamics found in black holes.

Employing higher order perturbation theory, we obtain five-dimensional rotating black holes in the Einstein gravity with nonlinear electrodynamics. We consider asymptotically flat charged rotating black hole solutions with two equal angular momenta and introduce the electric charge, $q$, as the perturbative parameter. We construct the extremal rapidly rotating black holes in the Einstein-nonlinear Maxwell theory in five dimensions, where we solve the equations of motion up to fourth order in $q$. We show that the perturbative parameters $q$ and the nonlinearity parameter $\beta$ may modify the values of the physical quantities of the black holes. In particular, we find that $\beta$ may change the sign of the magnetic moment and the gyromagnetic ratio of the black hole spacetime when this parameter starts to depart strongly from the Maxwell limit. Finally, we obtain a generalized Smarr formula for the rotating black hole solutions.

We investigate the vacuum energy of a scalar massless field confined in a Casimir cavity moving in a circular equatorial orbit in the exact Kerr space-time geometry. We find that both the orbital motion of the cavity and the underlying space-time geometry conspire in lowering the absolute value of the (renormalized) Casimir energy $⟨{\epsilon }_{\text{vac}}{⟩}_{\text{ren}}$, as measured by a comoving observer, with respect to whom the cavity is at rest. This, in turn, causes a weakening in the attractive force between the Casimir plates. In particular, we show that the vacuum energy density $⟨{\epsilon }_{\text{vac}}{⟩}_{\text{ren}}\to 0$ when the orbital path of the Casimir cavity comes close to the corotating or counter-rotating circular null orbits (possibly geodesic) allowed by the Kerr geometry. Such an effect could be of some astrophysical interest on relevant orbits, such as the Kerr innermost stable circular orbits, being potentially related to particle confinement (as in some interquark models). The present work generalizes previous results obtained by several authors in the weak field approximation.

The coupling between dark sectors provides a possible approach to mitigate the coincidence problem of the cosmological standard model. In this paper, dark energy is treated as a fluid with a constant equation of state, whose coupling with dark matter is proportional the Hubble parameter and energy density of dark energy, that is, $\overline{Q}=3{\xi }_x\overline{H}{\overline{\rho }}_x$. In particular, we consider the Hubble expansion rate to be perturbed in the perturbation evolutions of dark sectors. Using joint data sets which include cosmic microwave background radiation, baryon acoustic oscillation, type Ia supernovae, and redshift-space distortions, we perform a full Markov chain Monte Carlo likelihood analysis for the coupled model. The results show that the mean value with errors of the interaction rate is ${\xi }_x=0.00305_{-0.00305-0.00305-0.00305}^{+0.000645+0.00511+0.00854}$ for $Q_A^{\mu }\parallel u_c^{\mu }$ and ${\xi }_x=0.00317_{-0.00317-0.00317-0.00317}^{+0.000628+0.00547+0.00929}$ for $Q_A^{\mu }\parallel u_x^{\mu }$, which means that the recent cosmic observations favor a small interaction rate which is up to the order of ${10}^{-3}$. Moreover, in contrast to the coupled model with an unperturbed expansion rate, we find the perturbed Hubble expansion rate can bring about a negligible impact on the model parameter space.

We compute the leptonic decay constants $f_{D^{+}}$, $f_{D_s}$, and $f_{K^{+}}$ and the quark-mass ratios $m_c/m_s$ and $m_s/m_l$ in unquenched lattice QCD using the experimentally determined value of $f_{{\pi }^{+}}$ for normalization. We use the MILC highly improved staggered quark ensembles with four dynamical quark flavors—up, down, strange, and charm—and with both physical and unphysical values of the light sea-quark masses. The use of physical pions removes the need for a chiral extrapolation, thereby eliminating a significant source of uncertainty in previous calculations. Four different lattice spacings ranging from $a\approx 0.06$ to 0.15 fm are included in the analysis to control the extrapolation to the continuum limit. Our primary results are $f_{D^{+}}=212.6(0.4)(\genfrac{}{}{0ex}{}{+1.0}{-1.2})\mathrm{MeV}$, $f_{D_s}=249.0(0.3)(\genfrac{}{}{0ex}{}{+1.1}{-1.5})\mathrm{MeV}$, and $f_{D_s}/f_{D^{+}}=1.1712(10)(\genfrac{}{}{0ex}{}{+29}{-32})$, where the errors are statistical and total systematic, respectively. The errors on our results for the charm decay constants and their ratio are approximately 2–4 times smaller than those of the most precise previous lattice calculations. We also obtain $f_{K^{+}}/f_{{\pi }^{+}}=1.1956(10)(\genfrac{}{}{0ex}{}{+26}{-18})$, updating our previous result, and determine the quark-mass ratios $m_s/m_l=27.35(5)(\genfrac{}{}{0ex}{}{+10}{-7})$ and $m_c/m_s=11.747(19)(\genfrac{}{}{0ex}{}{+59}{-43})$. When combined with experimental measurements of the decay rates, our results lead to precise determinations of the Cabibbo-Kobayashi-Maskawa matrix elements $|V_{us}|=0.22487(51)(29)(20)(5)$, $|V_{cd}|=0.217(1)(5)(1)$ and $|V_{cs}|=1.010(5)(18)(6)$, where the errors are from this calculation of the decay constants, the uncertainty in the experimental decay rates, structure-dependent electromagnetic corrections, and, in the case of $|V_{us}|$, the uncertainty in $|V_{ud}|$, respectively.

We write down explicit expressions for the $x$ evolution (equivalent to energy or rapidity evolution) of $2n$ ($n=1,2,\cdots$) Wilson lines using the JIMWLK equation and the color glass condensate formalism. We investigate the equation in the weak gluon field limit (linear regime) by expanding the Wilson lines in powers of the gluon field and show that it reduces to the BJKP equation describing the evolution of a state of $2n$ Reggeized gluons with energy. We also make available for download a Mathematica program which provides this expression for any value of $n$.

The AdS/CFT correspondence may offer new and useful insights into the nonperturbative regime of strongly coupled gauge theories such as QCD. We present an AdS/CFT-inspired model that describes the spectra of light mesons. The conformal symmetry is broken by a background dilaton field, and chiral symmetry breaking and linear confinement are described by a chiral condensate field. These background fields, along with a background glueball condensate field, are derived from a potential. We describe the construction of the potential, and the calculation of the meson spectra, which match experimental data well. We argue that the presence of the third background field is necessary to properly describe the meson spectra.

Jet radiation patterns are indispensable for the purpose of discriminating partons with different quantum numbers. However, they are also vulnerable to various contaminations from the underlying event, pileup, and radiation of adjacent jets. In order to maximize the discrimination power, it is essential to optimize the jet radius used when analyzing the radiation patterns. We introduce the concept of jet radiation radius, which quantifies how the jet radiation is distributed around the jet axis. We study the color and momentum dependence of the jet radiation radius and discuss two applications: quark-gluon discrimination and $W$-jet tagging. In both cases, smaller (sub)jet radii are preferred for jets with higher $p_T$’s, albeit due to different mechanisms: the running of the QCD coupling constant and the boost to a color-singlet system. A shrinking cone $W$-jet tagging algorithm is proposed to achieve better discrimination than previous methods.

In this paper, we study residual symmetries in the lepton sector. Our first concern is the symmetry of the charged lepton mass matrix in the basis where the Majorana neutrino mass matrix is diagonal, which is strongly constrained by the requirement that the symmetry group generated by residual symmetries is finite. In a recent work, R. M. Fonseca and W. Grimus found that there exists a set of constraint equations that can be completely solved, which is essential in their approach to the classification of lepton mixing matrices that are fully determined by residual symmetries. In this paper, a method to handle trigonometric Diophantine equations is introduced. We will show that the constraint equations found by Fonseca and Grimus can also be solved by this method. Detailed derivation and discussion will be presented in a self-contained way. In addition, we will also show that, in the case where residual symmetries satisfy a reality condition, this method can be used to solve the equation constraining parameters in the symmetry assignment that controls the group structure generated by residual symmetries and is directly related to mixing matrix elements.

We perform for the first time a detailed fit to the ${\overline{\nu }}_e\to {\overline{\nu }}_e$ disappearance data of the Daya Bay experiment in order to constrain the parameter space of models where sterile neutrinos can propagate in a large compactified extra dimension (LED) and models where nonstandard interactions (NSI) affect the neutrino production and detection. We find that the compactification radius $R$ in LED scenarios can be constrained at the level of $0.51\mu \mathrm{m}$ for normal ordering and of $0.17\mu \mathrm{m}$ for inverted ordering, at a confidence level of $2\sigma$. For the NSI model, reactor data put a strong upper bound on the parameter ${ϵ}_{ee}$ at the level of $\sim 10^{-2}$, whereas the main effect of ${ϵ}_{e\mu }$ and ${ϵ}_{e\tau }$ is a worsening of the determination of ${\theta }_{13}$.

In the current paper the properties of a quantum field theory based on certain sets of Lorentz-violating coefficients in the nonminimal fermion sector of the Standard Model extension are analyzed. In particular, three families of coefficients are considered, where two of them are $CPT$ even and the third is $CPT$ odd. As a first step the modified fermion dispersion relations are obtained. Then the positive- and negative-energy solutions of the modified Dirac equation and the fermion propagator are derived. These are used to demonstrate the validity of the optical theorem at tree level, which provides a cross-check for the results obtained. Furthermore unitarity is examined and seems to be valid for the first set of $CPT$-even coefficients. However for the remaining sets certain issues with unitarity are found. The article demonstrates that the adapted quantum field theoretical methods at tree level work for the nonminimal, Lorentz-violating framework considered. Besides, the quantum field theory based on the first family of $CPT$-even coefficients is most likely well behaved at lowest order perturbation theory. The results are important for future phenomenological investigations carried out in the context of field theory, e.g., the computation of decay rates and cross sections at tree level.

We investigate the cosmological implications of the recently constructed five-dimensional braneworld cosmology with gravitating Nambu-Goto matching conditions. Inserting both matter and radiation sectors, we extract analytical cosmological solutions. Additionally, we use observational data from Type Ia supernovae and baryon acoustic oscillations, along with requirements of big bang nucleosynthesis and cosmic microwave background radiation, in order to impose constraints on the parameters of the model. We find that the scenario at hand is in good agreement with observations, and thus a small departure from the standard Randall-Sundrum scenario is allowed. However, the concordance $\mathrm{\Lambda }\mathrm{CDM}$ cosmology is still favored comparing to both the standard braneworld model and the present scenario.

On-shell, analytic $S$-matrix elements in massless theories are constructed from a finite set of primitive three-point amplitudes, which are fixed by Poincaré invariance up to an overall numerical constant. We classify all such three-point amplitudes in four dimensions. Imposing the simplest incarnation of locality and unitarity on four-particle amplitudes constructed from these three-particle amplitudes rules out all but an extremely small subset of interactions among higher-spin massless states. Notably, the equivalence principle and the Weinberg-Witten theorem are simple corollaries of this principle. Further, no massless states with helicity larger than two may consistently interact with massless gravitons. Chromodynamics, electrodynamics, Yukawa and ${\varphi }^3$ theories are the only marginal and relevant interactions between massless states. Finally, we show that supersymmetry naturally emerges as a consistency condition on four-particle amplitudes involving spin-$3/2$ states, which must always interact gravitationally.

We construct two classes of exact solutions to six- and higher-dimensional Einstein-Maxwell theory in which the metric functions can be written as convolution-like integrals of two special functions. The solutions are regular everywhere and show a bolt structure on a single point in any dimensionality. Moreover, we find the exact nonstationary solutions to the Einstein-Maxwell theory with positive cosmological constant. We show that the cosmological solutions are expanding patches in asymptotically de Sitter spacetime.

The recent cosmic microwave background data from the Planck satellite experiment, when combined with Hubble Space Telescope determinations of the Hubble constant, are compatible with a larger, nonstandard number of relativistic degrees of freedom at recombination, parametrized by the neutrino effective number $N_{\text{eff}}$. In the curvaton scenario, a larger value for $N_{\text{eff}}$ could arise from a nonzero neutrino chemical potential connected to residual neutrino isocurvature density (NID) perturbations after the decay of the curvaton field, the component of which is parametrized by the amplitude ${\alpha }^{\mathrm{NID}}$. Here we present new constraints on $N_{\text{eff}}$ and ${\alpha }^{\mathrm{NID}}$ from an analysis of recent cosmological data. We find that the $\text{Planck}+\mathrm{WMAP}$ polarization data set does not show any indication of a NID component (severely constraining its amplitude), and that current indications for a nonstandard $N_{\text{eff}}$ are further relaxed.

The large-scale distribution of cold dark matter halos is generally assumed to trace the large-scale distribution of matter. In a universe with multiple types of matter fluctuations, as is the case with massive neutrinos, the relation between the halo field and the matter fluctuations may be more complicated. We develop a method for calculating the linear bias factor relating fluctuations in the halo number density to fluctuations in the mass density in the presence of multiple fluctuating components of the energy density. In the presence of massive neutrinos we find a small but pronounced feature in the halo bias near the neutrino free-streaming scale. The neutrino feature is a small step with amplitude that increases with halo mass and neutrino mass density. The scale-dependent halo bias lessens the suppression of the small-scale halo power spectrum and should therefore weaken constraints on neutrino mass from the galaxy autopower spectrum and correlation function. On the other hand, the feature in the bias is itself a novel signature of massive neutrinos that can be studied independently.