We study a minimal one-loop radiative mechanism for generating small Majorana neutrino masses in inverse seesaw extensions of the Standard Model with two singlet fermions per family. The new feature of this radiative mechanism is that the one-loop induced left-handed neutrino mass matrix is directly proportional to the Majorana mass matrix of the right-handed neutrinos. This is a very economical scenario without necessitating the existence of nonstandard scalar or gauge fields.

A new set of projection operators for three-dimensional models are constructed. Using these operators, an uncomplicated and easy handling algorithm for analyzing the unitarity of the aforementioned systems is built up. Interestingly enough, this method converts the task of probing the unitarity of a given three-dimensional system, which is in general a time-consuming work, into a straightforward algebraic exercise; besides, it also greatly clarifies the physical interpretation of the propagating modes. To test the efficacy and quickness of the algorithm at hand, the unitarity of some important and timely higher-order electromagnetic (gravitational) systems augmented by both Chern-Simons and higher order Chern-Simons terms are investigated.

We consider the problem of quantum field theory on the Bertotti-Robinson space-time, which arises naturally as the near-horizon geometry of an extremal Reissner-Nordström black hole, but can also arise in certain near-horizon limits of nonextremal Reissner-Nordström space-time. The various vacuum states have been considered in the context of ${\mathrm{AdS}}_2$ black holes [M. Spradlin and A. Strominger, J. High Energy Phys. 11 (1999) 021] where it was shown that the Poincaré vacuum, the global vacuum and the Hartle-Hawking vacuum are all equivalent, while the Boulware vacuum and the Schwarzschild vacuum are equivalent. We verify this by explicitly computing the Green’s functions in closed form for a massless scalar field corresponding to each of these vacua. Obtaining a closed form for the Green’s function corresponding to the Boulware vacuum is nontrivial, and the novel computational technique employed may well be useful in deriving closed form Green’s functions in other space-times. Having obtained the propagator for the Boulware vacuum, which is a zero-temperature Green’s function, we can then consider the case of a scalar field at an arbitrary temperature by an infinite image imaginary-time sum, which yields the Hartle-Hawking propagator upon setting the temperature to the Hawking temperature. Finally, we compute the renormalized stress-energy tensor for a massless scalar field in the various quantum vacua.

Slowroll after tunneling is a crucial step in one popular framework of the multiverse—false vacuum eternal inflation. In a landscape with a large number of fields, we provide a heuristic estimation for its probability. We find that the chance to slowroll is exponentially suppressed, where the exponent comes from the number of fields. However, the relative probability to have more e-foldings is only mildly suppressed as $N_e^{-\alpha }$ with $\alpha \sim 3$. Based on these two properties, we show that the false vacuum eternal inflation picture is still self-consistent and may have a strong preference between different slowroll models.

We study saturation effects in the production of dijets in $p\mathrm{\text{−}}p$ and $p$-Pb collisions using the framework of high energy factorization. We focus on central-forward jet configurations, which allow for probing gluon density at low longitudinal momentum fraction. We find significant suppression of the central-forward jet decorrelations in $p$-Pb compared to $p\mathrm{\text{−}}p$, which we attribute to saturation of gluon density in nuclei.

The experimental determination of the properties of the newly discovered boson at the Large Hadron Collider is currently the most crucial task in high-energy physics. We show how information about the spin, parity, and, more generally, the tensor structure of the boson couplings can be obtained by studying angular and mass distributions of events in which the resonance decays to pairs of gauge bosons, $ZZ$, $WW$, and $\gamma \gamma$. A complete Monte Carlo simulation of the process $pp\to X\to VV\to 4f$ is performed and verified by comparing it to an analytic calculation of the decay amplitudes $X\to VV\to 4f$. Our studies account for all spin correlations and include general couplings of a spin $J=0$, 1, 2 resonance to Standard Model particles. We also discuss how to use angular and mass distributions of the resonance decay products for optimal background rejection. It is shown that by the end of the 8 TeV run of the LHC, it might be possible to separate extreme hypotheses of the spin and parity of the new boson with a confidence level of 99% or better for a wide range of models. We briefly discuss the feasibility of testing scenarios where the resonance is not a parity eigenstate.

We present Hilbert space representation for a relatively broad class of minimum-length deformed quantum mechanical models obtained by incorporating a space-time uncertainty relation into quantum mechanics. The correspondingly modified field theory is used for estimating the deviation of the light incoherence rate from distant astrophysical sources from the standard case.

We investigate a mono-$Z$ process as a potential dark matter search strategy at the LHC. In this channel a single $Z$ boson recoils against missing transverse momentum, attributed to dark matter particles, $\chi$, which escape the detector. This search strategy is related and complementary to monojet and monophoton searches. For illustrative purposes we consider the process $q\overline{q}\to \chi \chi Z$ in a toy dark matter model, where the $Z$ boson is emitted from either the initial state quarks or from the internal propagator. Among the signatures of this process will be a pair of muons with high $p_T$ that reconstruct to the invariant mass the $Z$, and large amounts of missing transverse energy. Being a purely electroweak signal, QCD and other Standard Model backgrounds are relatively easily removed with modest selection cuts. We compare the signal to Standard Model backgrounds and demonstrate that even for conservative cuts, there exist regions of parameter space where the signal may be clearly visible above background in future LHC data, allowing either new discovery potential or the possibility of supplementing information about the dark sector beyond that available from other observable channels.

$N$-Higgs-doublet models (NHDM) are among the most popular examples of electroweak symmetry breaking mechanisms beyond the Standard Model. Discrete symmetries imposed on the NHDM scalar potential play a pivotal role in shaping the phenomenology of the model, and various symmetry groups have been studied so far. However, in spite of all efforts, the classification of finite Higgs-family symmetry groups realizable in NHDM for any $N>2$ is still missing. Here, we solve this problem for the three-Higgs-doublet model by making use of Burnside’s theorem and other results from pure finite group theory which are rarely exploited in physics. Our method and results can also be used beyond high-energy physics, for example, in the study of possible symmetries in three-band superconductors.

We quantify uncertainties in the Monte Carlo simulation of inclusive and dijet final states, which arise from using the MC@NLO technique for matching next-to-leading order parton-level calculations and parton showers. We analyse a large variety of data from early measurements at the LHC. In regions of phase space where Sudakov logarithms dominate over high-energy effects, we observe that the main uncertainty can be ascribed to the free parameters of the parton shower. In complementary regions, the main uncertainty stems from the considerable freedom in the simulation of underlying events.

We present a new solution in 5D Einstein-Maxwell-dilaton gravity describing an equilibrium configuration of extremal rotating black holes with lens space horizon topologies. The basic properties of the solution are investigated and the basic physical quantities are calculated. It is shown that the black-hole horizons are superconducting in the sense that they expel the magnetic flux lines.

Noncommutative geometry, an offshoot of string theory, replaces pointlike structures with smeared objects and has recently been extended to higher dimensions. The purpose of this paper is to obtain wormhole solutions with this extended noncommutative geometry as a background. It is found through this investigation that wormhole solutions exist in the usual four, as well as in five dimensions, but they do not exist in higher-dimensional spacetimes.

In this paper, based on an analytic technique, several properties of holographic $s$-wave superconductors have been investigated in the presence of various higher derivative (nonlinear) corrections to the usual Maxwell action. Explicit expressions for the critical temperature and the condensation values have been obtained in the probe limit. Finally, the nature of condensate solutions has been investigated by immersing the superconductor in an external magnetic field. It is found that below certain critical magnetic field strength ($B_c$) there exists a superconducting phase. Most importantly, it has been observed that the value of this critical field strength ($B_c$) indeed gets affected due to the presence of higher derivative corrections to the usual Maxwell action.

Starting from the effective action of high energy QCD we derive Ward identities for Green’s functions of Reggeized gluons. They follow from the gauge invariance of the effective action, and allow us to derive new representations of amplitudes containing physical particles as well as Reggeized gluons. We explicitly demonstrate their validity for the Balitsky-Fadin-Kuraev-Lipatov kernel, and we present a new derivation of the kernel.

We consider noncommutative gravity on a space with canonical noncommutativity that is based on the commutative MacDowell-Mansouri action. Gravity is treated as gauge theory of the noncommutative $SO(1,3{)}_{\star }$ group, and the Seiberg-Witten map is used to express noncommutative fields in terms of the corresponding commutative fields. In the commutative limit the noncommutative action reduces to the Einstein-Hilbert action plus the cosmological term and the topological Gauss-Bonnet term. After the Seiberg-Witten expansion in the noncommutative parameter the first order correction to the action, as expected, vanishes. We calculate the second order correction and write it in a manifestly gauge covariant way.

Nonlinear electrodynamics, QED included, is considered against the Lorentz-noninvariant external field background, treated as an anisotropic medium. Hamiltonian formalism is applied to electromagnetic excitations over the background, and entities of electrodynamics of media, such as field inductions and intensities, are made sense of in terms of canonical variables. Both conserved and nonconserved generators of space-time translations and rotations are defined on the phase space, and their Hamiltonian equations of motion and Dirac bracket relations, different from the Poincaré algebra, are established. Nonsymmetric, but—in return—gauge-invariant, energy-momentum tensor suggests a canonical momentum density other than the Poynting vector. A photon magnetic moment is found to govern the evolution of the photon angular momentum. It is determined by the antisymmetric part of the energy-momentum tensor.

We study the supersymmetric Wilson loop as introduced by Caron-Huot, which attaches to lightlike polygons certain edge and vertex operators, whose shape is determined by supersymmetry constraints. We state explicit formulas for the vertex operators to all orders in the Graßmann expansion, thus filling a gap in the literature. This is achieved by deriving a recursion formula out of the supersymmetry constraints.

We consider axially symmetric solutions of $SU(2)$ Yang-Mills-Higgs theory in globally AdS spacetime and a fixed Schwarzschild-AdS black hole background. The solutions are characterized by two integers $(m,n)$ where $m$ is related to the polar angle and $n$ to the azimuthal angle. Two types of finite-energy, regular configurations are considered: solutions with net magnetic charge $n>1$, and monopole-antimonopole pairs and chains with zero net magnetic charge. The configurations are endowed with an electric charge and also carry a nonvanishing angular momentum density.

A scalar field theory with quartic self-interaction in de Sitter space is studied using the two-particle irreducible effective action formalism. This formalism partially resums infinite series of loop diagrams and enables us to circumvent the IR divergence problem for a massless minimally coupled scalar field in de Sitter space. However, due to its nonperturbative nature, the renormalization prescription is a nontrivial task. To calculate physical quantities, an appropriate renormalization prescription is required. In this paper, we will show that the minimal subtraction-like scheme is possible at the Hartree-Fock truncation of the two-particle irreducible effective action in a general curved space, and infinite series of divergent terms are needed as counterterms. The infrared effects on the physical mass and phase structure are calculated.

One of the greatest theoretical challenges in the buildup to the era of second-generation gravitational-wave detectors is the modeling of generic binary waveforms. We introduce an approximation that has the potential to significantly simplify this problem. We show that generic precessing-binary inspiral waveforms (covering a seven-dimensional space of intrinsic parameters) can be mapped to a two-dimensional space of nonprecessing binaries, characterized by the mass ratio and a single effective total spin. The mapping consists of a time-dependent rotation of the waveforms into the quadrupole-aligned frame and is extremely accurate (matches $>0.99$ with parameter biases in the total spin of $\Delta \chi \le 0.04$), even in the case of transitional precession. In addition, we demonstrate a simple method to construct hybrid post-Newtonian–numerical relativity precessing-binary waveforms in the quadrupole-aligned frame and provide evidence that our approximate mapping can be used all the way to the merger. Finally, based on these results, we outline a general proposal for the construction of generic waveform models, which will be the focus of future work.