In this paper we present a new search technique for electroweakinos, the superpartners of electroweak gauge and Higgs bosons, based on final states with missing transverse energy, a photon, and a dilepton pair, ${\ell }^{+}{\ell }^{-}+\gamma +{\cancel{E}}_T$. Unlike traditional electroweakino searches, which perform best when $m_{{\tilde{\chi }}_{2,3}^0}-m_{{\tilde{\chi }}_1^0},m_{{\tilde{\chi }}^{\pm }}-m_{{\tilde{\chi }}_1^0}>m_Z$, our search favors nearly degenerate spectra; degenerate electroweakinos typically have a larger branching ratio to photons, and the cut $m_{\ell \ell }\ll m_Z$ effectively removes on shell Z boson backgrounds while retaining the signal. This feature makes our technique optimal for “well-tempered” scenarios, where the dark matter relic abundance is achieved with interelectroweakino splittings of $\sim 20–70\mathrm{GeV}$. Additionally, our strategy applies to a wider range of scenarios where the lightest neutralinos are almost degenerate, but only make up a subdominant component of the dark matter—a spectrum we dub well forged. Focusing on bino-Higgsino admixtures, we present optimal cuts and expected efficiencies for several benchmark scenarios. We find bino-Higgsino mixtures with $m_{{\tilde{\chi }}_{2,3}^0}\lesssim 190\mathrm{GeV}$ and $m_{{\tilde{\chi }}_{2,3}^0}-m_{{\tilde{\chi }}_1^0}\cong 30\mathrm{GeV}$ can be uncovered after roughly $600{\mathrm{fb}}^{-1}$ of luminosity at the 14 TeV LHC. Scenarios with lighter states require less data for discovery, while scenarios with heavier states or larger mass splittings are harder to discriminate from the background and require more data. Unlike many searches for supersymmetry, electroweakino searches are one area where the high luminosity of the next LHC run, rather than the increased energy, is crucial for discovery.

In the lattice QCD formalism, we investigate the relation between confinement and chiral symmetry breaking. A gauge-invariant analytical relation connecting the Polyakov loop and the Dirac modes is derived on a temporally odd-number lattice, where the temporal lattice size is odd, with the normal (nontwisted) periodic boundary condition for link variables. This analytical relation indicates that low-lying Dirac modes have little contribution to the Polyakov loop, and it is numerically confirmed at the quenched level in both confinement and deconfinement phases. This fact indicates no direct one-to-one correspondence between confinement and chiral symmetry breaking in QCD. Using the relation, we also investigate the contribution from each Dirac mode to the Polyakov loop. In the confinement phase, we find a new “positive/negative symmetry” of the Dirac-mode matrix element of the link-variable operator, and this symmetry leads to the zero value of the Polyakov loop. In the deconfinement phase, there is no such symmetry and the Polyakov loop is nonzero. Also, we develop a new method for spin-diagonalizing the Dirac operator on the temporally odd-number lattice modifying the Kogut-Susskind formalism.

We study the dependence on the charm quark mass of the leading-order low-energy constants of the $\mathrm{\Delta }S=1$ effective Hamiltonian, with the aim of elucidating the role of the charm mass scale in the $\mathrm{\Delta }I=1/2$ rule for $K\to \pi \pi$ decay. To that purpose, finite-volume chiral perturbation theory predictions are matched to QCD simulations, performed in the quenched approximation with overlap fermions and $m_u=m_d=m_s$. Light quark masses range between a few MeV up to around one third of the physical strange mass, while charm masses range between $m_u$ and a few hundred MeV. Novel variance reduction techniques are used to obtain a signal for penguin contractions in correlation functions involving four-fermion operators. The important role played by the subtractions required to construct renormalized amplitudes for $m_c\ne m_u$ is discussed in detail. We find evidence that the moderate enhancement of the $\mathrm{\Delta }I=1/2$ amplitude previously found in the GIM limit $m_c=m_u$ increases only slightly as $m_c$ abandons the light quark regime. Hints of a stronger enhancement for even higher values of $m_c$ are also found, but their confirmation requires a better understanding of the subtraction terms.

The inclusive hadronic production of ${\eta }_Q$ (${\eta }_c$ or ${\eta }_b$) pair is proposed to extract the transverse momentum-dependent (TMD) gluon distribution functions. We use nonrelativistic QCD (NRQCD) for the production of ${\eta }_Q$. Under the nonrelativistic limit, the TMD factorization for this process is assumed to make a lowest-order calculation. For unpolarized initial hadrons, unpolarized and linearly polarized gluon distributions can be extracted by studying different angular distributions.

We study the factorization and resummation of the $t\overline{t}{W}^{\pm }$ production at hadron colliders. The cross section in the threshold limit can be factorized into a convolution of hard and soft functions and parton distribution functions with the soft-collinear effective theory. We calculate the next-to-leading order soft function for the associated production of the heavy quark pair and colorless particle, and we perform the resummation calculation with the next-to-next-to-leading logarithm accuracy. Our results show that the resummation effects reduce the dependence of the cross section on the scales significantly and increase the total cross section by 7%–13% compared with NLO QCD results.

In light of recent experimental results, we carefully analyze the effects of interference in neutrinoless double beta decay, when more than one mechanism is operative. If a complete cancellation is at work, the half-life of the corresponding isotope is infinite, and any constraint on it will automatically be satisfied. We analyze this possibility in detail assuming a cancellation in ${}^{136}\mathrm{Xe}$, and find its implications on the half-life of other isotopes, such as ${}^{76}\mathrm{Ge}$. For definiteness, we consider the role of light and heavy sterile neutrinos. In this case, the effective Majorana mass parameter can be redefined to take into account all contributions, and its value gets suppressed. Hence, larger values of neutrino masses are required for the same half-life. The canonical light neutrino contribution cannot saturate the present limits of half-lives or the positive claim of observation of neutrinoless double beta decay, once the stringent bounds from cosmology are taken into account. For the case of cancellation, where all the sterile neutrinos are heavy, the tension between the results from neutrinoless double beta decay and cosmology becomes more severe. We show that the inclusion of light sterile neutrinos in this setup can resolve this issue. Using the recent results from GERDA, we derive upper limits on the active-sterile mixing angles and compare them with the case of no cancellation. The required values of the mixing angles become larger, if a cancellation is at work. A direct test of destructive interference in ${}^{136}\mathrm{Xe}$ is provided by the observation of this process in other isotopes, and we study in detail the correlation between their half-lives. Finally, we discuss the model realizations which can accommodate light and heavy sterile neutrinos and the cancellation. We show that sterile neutrinos of few hundred MeV or GeV mass range, coming from an Extended seesaw framework or a further extension, can satisfy the required cancellation.

We discuss how the $CP$-violating phase $\delta$ and the mixing angle ${\theta }_{23}$ can be measured precisely in an environment where there are strong correlations between them. This is achieved by paying special attention to the mutual roles and the interplay between the appearance and the disappearance channels in long-baseline neutrino oscillation experiments. We analyze and clarify the general structure of the ${\theta }_{23}-{\theta }_{13}-\delta$ degeneracy for both the appearance and disappearance channels in a more complete fashion than what has previously been discussed in the literature. A full understanding of this degeneracy is of vital importance if ${\theta }_{23}$ is close to maximal mixing. The relative importance between the appearance and disappearance channels depends upon the particular setup and how close to maximal mixing nature has chosen the value for ${\theta }_{23}$. For facilities that operate with a narrow band beam or a wideband beam centered on the first oscillation extremum, the contribution of the disappearance channel depends critically on the systematic uncertainties assumed for this channel, whereas for facilities that operate at energies above the first oscillation extremum or at the second oscillation extremum, the appearance channels dominate. On the other hand, for $\delta$ we find that the disappearance channel usually improves the sensitivity, modestly for facilities around the first oscillation extremum and more significantly for facilities operating at an energy above the first oscillation extremum, especially near $\delta \sim \pm \pi /2$.

On the basis of the quantum Boltzmann equation governing the time evolution of the density matrix of polarized cosmic microwave background (CMB) photons in the primordial scalar perturbations of metric, we calculate the $B$-mode spectrum of polarized CMB photons contributed from the scattering of CMB photons and cosmic neutrino background neutrinos. We show that such a contribution to the $B$-mode spectrum is negligible for small $\ell$; however, it is made significantly larger for $50<\ell <200$ by plotting our results together with the BICEP2 data. Our study and results imply that in order to theoretically better understand the origin of the observed $B$-mode spectrum of polarized CMB photons ($r$ parameter), it should be necessary to study the relevant and dominated processes in both tensor and scalar perturbations.

We attempt an answer to the question as to why the evolution of a four-dimensional universe is governed by spacetime curvature but not torsion. An answer is found if there is an additional compact spacelike dimension with a warped geometry, with torsion caused by a Kalb-Ramond (KR) antisymmetric tensor field in the bulk. Starting from a Randall-Sundrum type of warped extra dimension, and including the inevitable backreaction ensuing from the radius stabilization mechanism, we show that there is always an extra exponential suppression of the KR field on the four-dimensional projection that constitutes our visible Universe. The backreaction is found to facilitate the process of such suppression.

The averaged null energy conditions (ANEC) states that, along a complete null curve, the negative energy fluctuations of a quantum field must be balanced by positive energy fluctuations. We use the AdS/CFT correspondence to prove the ANEC for a class of strongly coupled conformal field theories in flat spacetime. A violation of the ANEC in the field theory would lead to acausal propagation of signals in the bulk.

We derive, in curved spacetime, the most general Lorentz-violating electromagnetic Lagrangian containing dimension-five operators with one more derivative than the Maxwell term in the hypothesis that Lorentz symmetry is broken by a background four-vector $n_{\mu }$. We then study, for the case of isotropic $n_{\mu }$, the generation of cosmic magnetic fields at inflation and cosmic birefringence. In the limiting case of Minkowski spacetime, we find that other than the $CPT$-odd Myers-Pospelov term, there exists another $CPT$-odd term that gives rise to nontrivial dispersion and constitutive relations.

We study entanglement entropy (EE) for a Maxwell field in $(2+1)$ dimensions. We do numerical calculations in two-dimensional lattices. This gives a concrete example of the general results of our recent work [1] on entropy for lattice gauge fields using an algebraic approach. To evaluate the entropies we extend the standard calculation methods for the entropy of Gaussian states in canonical commutation algebras to the more general case of algebras with center and arbitrary numerical commutators. We find that while the entropy depends on the details of the algebra choice, mutual information has a well defined continuum limit as predicted in [1]. We study several universal terms for the entropy of the Maxwell field and compare with the case of a massless scalar field. We find some interesting new phenomena: an “evanescent” logarithmically divergent term in the entropy with topological coefficient which does not have any correspondence with ultraviolet entanglement in the universal quantities, and a nonstandard way in which strong subadditivity is realized. Based on the results of our calculations we propose a generalization of strong subadditivity for the entropy on some algebras that are not in tensor product.

We show that the four-loop four-point amplitudes of $\mathcal{N}=5$ supergravity are ultraviolet finite in four dimensions, contrary to expectations based on supersymmetry and duality-symmetry arguments. We explain why the diagrams of any covariant local formalism cannot manifestly exhibit the necessary cancellations for finiteness but instead require a new type of ultraviolet cancellation that we call an “enhanced cancellation.” We also show that the three-loop four-point amplitudes in $\mathcal{N}=4$ and $\mathcal{N}=5$ supergravity theories display enhanced cancellations. To construct the loop integrand, we use the duality between color and kinematics. We apply standard methods for extracting ultraviolet divergences in conjunction with the FIRE5 integral reduction program to arrive at the four-loop results.

We review the Bogomol’nyi equations and investigate an alternative route in obtaining it. It can be shown that the known Bogomol’nyi-Prasad-Sommerfield equations can be derived directly from the corresponding Euler-Lagrange equations via the separation of variables, without having to appeal to the Hamiltonian. We apply this technique to the Dirac-Born-Infeld solitons and obtain the corresponding equations and the potentials. This method is suitable for obtaining the first-order equations and determining the allowed potentials for noncanonical defects.

We derive a topological action that describes the confining phase of (super-)Yang–Mills theories with gauge group $SU(N)$, similar to the work recently carried out by Seiberg and collaborators. It encodes all the Aharonov–Bohm phases of the possible nonlocal operators and phases generated by the intersection of flux tubes. Within this topological framework we show that the world volume theory of domain walls contains a Chern–Simons term at level $N$ also seen in string theory constructions. The discussion can also illuminate dynamical differences of domain walls in the supersymmetric and nonsupersymmetric framework. Two further analogies, to string theory and the fractional quantum Hall effect, might lead to additional possibilities to investigate the dynamics.

In dense stellar regions, highly eccentric binaries of black holes and neutron stars can form through various $n$-body interactions. Such a binary could emit a significant fraction of its binding energy in a sequence of largely isolated gravitational-wave bursts prior to merger. Given expected black hole and neutron star masses, many such systems will emit these repeated bursts at frequencies within the sensitive band of contemporary ground-based gravitational-wave detectors. Unfortunately, existing gravitational-wave searches are ill suited to detect these signals. In this work, we adapt a “power stacking” method to the detection of gravitational-wave signals from highly eccentric binaries. We implement this method as an extension of the $Q$ transform, a projection onto a multiresolution basis of windowed complex exponentials that has previously been used to analyze data from the network of LIGO/Virgo detectors. Our method searches for excess power over an ensemble of time-frequency tiles. We characterize the performance of our method using Monte Carlo experiments with signals injected in simulated detector noise. Our results indicate that the power stacking method achieves substantially better sensitivity to eccentric binary signals than existing localized burst searches.

Current emission models of GeV-PeV neutrinos from gamma-ray bursts (GRBs) predict a neutrino flux with $\ll 1$ detected neutrinos per GRB with kilometer-scale neutrino observatories. The detection of this flux will require the stacking of data from a large number of GRBs, leading to an increased background rate, decreasing the significance of a single neutrino detection. We show that utilizing the temporal correlation between the expected gamma-ray and neutrino fluxes, one can significantly improve the neutrino signal-to-noise ratio. We describe how this temporal correlation can be used. Using realistic GRB and atmospheric neutrino fluxes and incorporating temporal, spectral and directional information, we estimate the probability of a single detected GRB-neutrino being a $5\sigma$ discovery.

Recent experimental results from the LHC have placed strong constraints on the masses of colored superpartners. The MSSM parameter space is also constrained by the measurement of the Higgs boson mass, and the requirement that the relic density of lightest neutralinos be consistent with observations. Although large regions of the MSSM parameter space can be excluded by these combined bounds, leptophilic versions of the MSSM can survive these constraints. In this paper we consider a scenario in which the requirements of minimal flavor violation, vanishing $CP$-violation, and mass universality are relaxed, specifically focusing on scenarios with light sleptons. We find a large region of parameter space, analogous to the original bulk region, for which the lightest neutralino is a thermal relic with an abundance consistent with that of dark matter. We find that these leptophilic models are constrained by measurements of the magnetic and electric dipole moments of the electron and muon, and that these models have interesting signatures at a variety of indirect detection experiments.