We test a model of inflation with a fast-rolling kinetic-dominated initial condition against data from Planck using Markov chain Monte Carlo parameter estimation. We test both an $m^2{\varphi }^2$ potential and the $R+R^2$ gravity model and perform a full numerical calculation of both the scalar and tensor primordial power spectra. We find a slight (though not significant) improvement in fit for this model over the standard eternal slow-roll case.

Previously, we had proposed a gravitational wave detector that incorporates the white-light-cavity (WLC) effect using a compound cavity for signal recycling (CC-SR). Here, we first use an idealized model for the negative dispersion medium (NDM) and use the so-called Caves model for a phase-insensitive linear amplifier to account for the quantum noise (QN) contributed by the NDM, in order to determine the upper bound of the enhancement in the sensitivity-bandwidth product. We calculate the quantum noise limited sensitivity curves for the CC-SR design, and find that the broadening of sensitivity predicted by the classical analysis is also present in these curves, but is somewhat reduced. Furthermore, we find that the curves always stay above the standard quantum limit. To circumvent this limitation, we modify the dispersion to compensate the nonlinear phase variation produced by the optomechanical resonance effects. We find that the upper bound of the factor by which the sensitivity-bandwidth product is increased, compared to the highest-sensitivity result predicted by Bunanno and Chen [Phys. Rev. D 64, 042006 (2001)], is $\sim 14$. We also present a simpler scheme (WLC-SR), where a dispersion medium is inserted into the SR cavity. For this scheme, we found the upper bound of the enhancement factor to be $\sim 18$. We then consider an explicit system for realizing the NDM, which makes use of five energy levels in M configuration to produce gain, accompanied by electromagnetically induced transparency (the GEIT system). For this explicit system, we employ the rigorous approach based on Master Equation to compute the QN contributed by the NDM, thus enabling us to determine the enhancement in the sensitivity-bandwidth product definitively rather than the upper bound thereof. Specifically, we identify a set of parameters for which the sensitivity-bandwidth product is enhanced by a factor of 17.66.

Based on a recent proposal for the volume inside a black hole, we calculate the entropy associated with this volume and show that such entropy is proportional to the surface area of the black hole. Together with the consideration of black hole radiation, we find that the thermodynamics associated with the entropy is likely to be caused by the vacuum polarization near the horizon.

We investigate the transition from unitary to dissipative dynamics in the relativistic $O(N)$ vector model with the $\lambda {({\phi }^2)}^2$ interaction using the nonperturbative functional renormalization group in the real-time formalism. In thermal equilibrium, the theory is characterized by two scales, the interaction range for coherent scattering of particles and the mean free path determined by the rate of incoherent collisions with excitations in the thermal medium. Their competition determines the renormalization group flow and the effective dynamics of the model. Here we quantify the dynamic properties of the model in terms of the scale-dependent dynamic critical exponent $z$ in the limit of large temperatures and in $2\le d\le 4$ spatial dimensions. We contrast our results to the behavior expected at vanishing temperature and address the question of the appropriate dynamic universality class for the given microscopic theory.

We consider a composite Higgs model embedded into a grand unified theory (GUT) based on the $E_6$ gauge group. The phenomenological viability of this $E_6\text{inspired}$ composite Higgs model (${\mathrm{E}}_6\mathrm{CHM}$) implies that standard model (SM) elementary fermions with different baryon or lepton number should stem from 27 different representations of $E_6$. We present a six-dimensional orbifold GUT model in which the $E_6$ gauge symmetry is broken to the SM gauge group so that the appropriate splitting of the bulk 27-plets takes place. In this model the strongly coupled sector is localized on one of the branes and possesses an $SU(6)$ global symmetry that contains the $SU(3{)}_C\times SU(2{)}_W\times U(1{)}_Y$ subgroup. In this case the approximate gauge coupling unification can be attained if the right-handed top quark is a composite state and the elementary sector involves extra exotic matter beyond the SM which ensures anomaly cancellation. The breakdown of the approximate $SU(6)$ symmetry at low energies in this model results in a set of the pseudo-Nambu-Goldstone states which include a Higgs doublet and scalar color triplet. We discuss the generation of the masses of the SM fermions in the ${\mathrm{E}}_6\mathrm{CHM}$. The presence of the TeV scale vectorlike exotic quarks and scalar color triplet may provide spectacular new physics signals that can be observed at the LHC.

In the alignment limit of a multidoublet Higgs sector, one of the Higgs mass eigenstates aligns with the direction of the scalar field vacuum expectation values, and its couplings approach those of the Standard Model (SM) Higgs boson. We consider $CP$-conserving two-Higgs-doublet models (2HDMs) of Type I and Type II near the alignment limit in which the lighter of the two $CP$-even Higgs bosons, $h$, is the SM-like state observed at 125 GeV. In particular, we focus on the 2HDM parameter regime where the coupling of $h$ to gauge bosons approaches that of the SM. We review the theoretical structure and analyze the phenomenological implications of the regime of the alignment limit without decoupling, in which the other Higgs scalar masses are not significantly larger than $m_h$ and thus do not decouple from the effective theory at the electroweak scale. For the numerical analysis, we perform scans of the 2HDM parameter space employing the software packages 2hdmc and lilith, taking into account all relevant pre-LHC constraints, the latest constraints from the measurements of the 125 GeV Higgs signal at the LHC, as well as the most recent limits coming from searches for heavy Higgs-like states. We contrast these results with the alignment limit achieved via the decoupling of heavier scalar states, where $h$ is the only light Higgs scalar. Implications for Run 2 at the LHC, including expectations for observing the other scalar states, are also discussed.

We study the topological charge distribution of the SU(3) Yang-Mills theory with high precision in order to be able to detect deviations from Gaussianity. The computation is carried out on the lattice with high statistics Monte Carlo simulations by implementing a naive discretization of the topological charge evolved with the Yang-Mills gradient flow. This definition is far less demanding than the one suggested from Neuberger’s fermions and, as shown in this paper, in the continuum limit its cumulants coincide with those of the universal definition appearing in the chiral Ward identities. Thanks to the range of lattice volumes and spacings considered, we can extrapolate the results for the second and fourth cumulant of the topological charge distribution to the continuum limit with confidence by keeping finite volume effects negligible with respect to the statistical errors. Our best results for the topological susceptibility is $t_0^2\chi =6.67(7)\times 10^{-4}$, where $t_0$ is a standard reference scale, while for the ratio of the fourth cumulant over the second, we obtain $R=0.233(45)$. The latter is compatible with the expectations from the large $N_c$ expansion, while it rules out the $\theta$ behavior of the vacuum energy predicted by the dilute instanton model. Its large distance from 1 implies that, in the ensemble of gauge configurations that dominate the path integral, the fluctuations of the topological charge are of quantum nonperturbative nature.

In a recent paper we used chiral perturbation theory to determine the phase diagram and pion spectrum for Wilson and twisted-mass fermions at nonzero lattice spacing with nondegenerate up and down quarks. Here we extend this work to include the effects of electromagnetism, so that it is applicable to recent simulations incorporating all sources of isospin breaking. For Wilson fermions, we find that the phase diagram is unaffected by the inclusion of electromagnetism—the only effect is to raise the charged pion masses. For maximally twisted fermions, we previously took the twist and isospin-breaking directions to be different, in order that the fermion determinant is real and positive. However, this is incompatible with electromagnetic gauge invariance, and so here we take the twist to be in the isospin-breaking direction, following the RM123 Collaboration. We map out the phase diagram in this case, which has not previously been studied. The results differ from those obtained with different twist and isospin directions. One practical issue when including electromagnetism is that the critical masses for up and down quarks differ. We show that one of the criteria suggested to determine these critical masses does not work, and propose an alternative.

We consider the general chiral effective action which parametrizes the nonlinear realization of the spontaneous breaking of the electroweak symmetry with a light Higgs boson and compute the one-loop ultraviolet divergences coming from Higgs and electroweak Goldstone fluctuations using the background field method. The renormalization of the divergences is carried out through operators of next-to-leading order in the chiral counting, i.e., of $\mathcal{O}(p^4)$. Being of the same order in power counting, the logarithmic corrections linked to these divergences can be as important as the tree-level contributions from the $\mathcal{O}(p^4)$ operators and must be accounted for in the phenomenological analysis of experimental data. Deviations in the $\mathcal{O}(p^2)$ (leading-order) couplings with respect to the Standard Model values, e.g., in the $h\to WW$ coupling, would generate contributions from the one-loop chiral logarithms computed in this work to a vast variety of observables, which do not have a counterpart in the conventional electroweak effective theory with a linearly transforming Higgs complex doublet.

Within the framework of QCD sum rules, we use the least-squares fitting method to investigate the first radial excitations of the nucleon and light mesons such as $\rho$, $K^{*}$, $\pi$, and $\phi$. The extracted masses of these radial excitations are consistent with the experimental data. In particular, we find that the decay constant of $\pi (1300)$, which is the first radial excitation of $\pi$, is tiny and is strongly suppressed as a consequence of chiral symmetry.

We analyze the production of a Higgs boson in association with a Z boson at hadron colliders in the Standard Model and some simple extensions. We show how multijet merging algorithms at leading and next-to-leading order for the loop-induced gluon fusion and the Drell-Yan-like quark-induced processes, respectively, improve the descriptions for various differential distributions, in particular those that involve the production of additional jets. The phenomenological studies focus on two relevant channels of Higgs boson decays, namely $H\to \text{invisible}$ and $H\to b\overline{b}$. We find sizable and phenomenologically relevant corrections to the transverse momentum and invariant mass distributions for the Higgs boson candidate. Thanks to the large destructive interference for the top Yukawa terms, this process is very sensitive to the magnitude and sign of a possible nonstandard top-Higgs coupling. We analyze the impact of this anomalous interaction on distributions and estimate constraints from LHC Run II.

We show that the standard model (SM)-like Higgs boson may decay into neutrinos with a sizable decay branching ratio in one well-known two Higgs doublet model, so-called neutrinophilic Higgs model. This could happen if the mass of the lighter extra neutral Higgs boson is smaller than one half of the SM-like Higgs boson mass. The definite prediction of this scenario is that the rate of the SM-like Higgs boson decay into diphoton normalized by the SM value is about 0.9. In the case that a neutrino is Majorana particle, a displaced vertex of right-handed neutrino decay would be additionally observed. This example indicates that a large invisible Higgs boson decay could be irrelevant to dark matter.

We derive expressions for the neutrino mixing parameters that result from complex perturbations on (1) the Majorana neutrino mass matrix (in the basis of charged lepton mass eigenstates) and on (2) the charged lepton mass matrix, for arbitrary initial (unperturbed) mixing matrices. In the first case, we find that the phases of the elements of the perturbation matrix, and the initial values of the Dirac and Majorana phases, strongly impact the leading-order corrections to the neutrino mixing parameters and phases. For experimentally compatible scenarios wherein the initial neutrino mass matrix has $\mu -\tau$ symmetry, we find that the Dirac phase can take any value under small perturbations. Similarly, in the second case, perturbations to the charged lepton mass matrix can generate large corrections to the mixing angles and phases of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix. As an illustration of our generalized procedure, we apply it to a situation in which nonstandard scalar and nonstandard vector interactions simultaneously affect neutrino oscillations.

We explore, mostly using data from solar neutrino experiments, the hypothesis that the neutrino mass eigenstates are unstable. We find that, by combining ${}^8\mathrm{B}$ solar neutrino data with those on ${}^7\mathrm{Be}$ and lower-energy solar neutrinos, one obtains a mostly model-independent bound on both the ${\nu }_1$ and ${\nu }_2$ lifetimes. We comment on whether a nonzero neutrino decay width can improve the compatibility of the solar neutrino data with the massive neutrino hypothesis.

A search is presented for photonic signatures motivated by generalized models of gauge-mediated supersymmetry breaking. This search makes use of $20.3{\mathrm{fb}}^{-1}$ of proton-proton collision data at $\sqrt{s}=8\mathrm{TeV}$ recorded by the ATLAS detector at the LHC, and explores models dominated by both strong and electroweak production of supersymmetric partner states. Four experimental signatures incorporating an isolated photon and significant missing transverse momentum are explored. These signatures include events with an additional photon, lepton, $b$-quark jet, or jet activity not associated with any specific underlying quark flavor. No significant excess of events is observed above the Standard Model prediction and model-dependent 95% confidence-level exclusion limits are set.

We discuss an extension of the dyon-antidyon liquid model that includes light quarks in the dense center symmetric phase. In this work, like in our previous one, we use the simplest color SU(2) group. We start with a single fermion flavor $N_f=1$ and explicitly map the model onto a three-dimensional quantum effective theory with a fermion that is only ${\mathrm{U}}_V(1)$ symmetric. We use it to show, in the mean-field approximation, that in the dense center, the symmetric regime leads to the nonzero chiral condensate. We estimate its value and the $\sigma ,\eta$ meson masses. We then extend our analysis to an arbitrary number of quark flavors $N_f>1$ and colors $N_c>2$ and show that in the dense plasma phase the spontaneous chiral symmetry breaking disappears when $N_f/N_c\ge 2$. A reorganization of the ensemble into a gas of dyon-antidyon molecules restores chiral symmetry but may still preserve center symmetry in the linearized approximation.

We revisit the dyon-antidyon liquid model for the Yang-Mills confining vacuum discussed by Diakonov and Petrov, by retaining the effects of the classical interactions mediated by the streamline between the dyons and antidyons. In the SU(2) case the model describes a 4-component strongly interacting Coulomb liquid in the center symmetric phase. We show that in the linearized screening approximation, the streamline interactions yield Debye-Huckel-type corrections to the bulk parameters, such as the pressure and densities, but do not alter significantly the large-distance behavior of the correlation functions in leading order. The static scalar and charged structure factors are consistent with a plasma of a dyon-antidyon liquid with a Coulomb parameter ${\mathrm{\Gamma }}_{D\overline{D}}\approx 1$ in the dyon-antidyon channel. Heavy quarks are still linearly confined and the large spatial Wilson loops still exhibit area laws in leading order. The ${\mathrm{t}}^{\prime }$ Hooft loop is shown to be one modulo Coulomb corrections.

In this paper three-dimensional higher spin theories in the Chern-Simons formulation with gauge algebra $\mathrm{sl}(N,\mathbb{R})$ are investigated which have Lifshitz symmetry with scaling exponent $z$. We show that an explicit map exists for all $z$ and $N$ relating the Lifshitz Chern-Simons theory to the $(n,m)$ element of the Korteweg–de Vries hierarchy. Furthermore we show that the map and hence the conserved charges are independent of $z$. We derive these result from the Drinfeld-Sokolov formalism of integrable systems.

We present a new formulation of curved projective superspace. The $4D$ $\mathcal{N}=2$ supermanifold ${\mathcal{M}}^{4|8}$ (four bosonic and eight Grassmann coordinates) is extended by an auxiliary SU(2) manifold, which involves introducing a vielbein and related connections on the full ${\mathcal{M}}^{7|8}={\mathcal{M}}^{4|8}\times \mathrm{SU}(2)$. Constraints are chosen so that it is always possible to return to the central basis where the auxiliary SU(2) manifold largely decouples from the curved manifold ${\mathcal{M}}^{4|8}$ describing $4D$ $\mathcal{N}=2$ conformal supergravity. We introduce the relevant projective superspace action principle in the analytic subspace of ${\mathcal{M}}^{7|8}$ and construct its component reduction in terms of a five-form $\mathcal{J}$ living on ${\mathcal{M}}^4\times \mathcal{C}$, with $\mathcal{C}$ a contour in SU(2). This approach is inspired by and generalizes the original approach, which can be identified with a complexified version of the central gauge of the formulation presented here.

I propose a quantum gravity model in which the fundamental degrees of freedom are information bits for both discrete space-time points and links connecting them. The Hamiltonian is a very simple network model consisting of a ferromagnetic Ising model for space-time vertices and an antiferromagnetic Ising model for the links. As a result of the frustration between these two terms, the ground state self-organizes as a new type of low-clustering graph with finite Hausdorff dimension 4. The spectral dimension is lower than the Hausdorff dimension: it coincides with the Hausdorff dimension 4 at a first quantum phase transition corresponding to an IR fixed point, while at a second quantum phase transition describing small scales space-time dissolves into disordered information bits. The large-scale dimension 4 of the universe is related to the upper critical dimension 4 of the Ising model. At finite temperatures the universe graph emerges without a big bang and without singularities from a ferromagnetic phase transition in which space-time itself forms out of a hot soup of information bits. When the temperature is lowered the universe graph unfolds and expands by lowering its connectivity, a mechanism I have called topological expansion. The model admits topological black hole excitations corresponding to graphs containing holes with no space-time inside and with “Schwarzschild-like” horizons with a lower spectral dimension.