Twenty years ago, construction began on the Laser Interferometer Gravitational-wave Observatory (LIGO). Advanced LIGO, with a factor of 10 better design sensitivity than Initial LIGO, will begin taking data this year, and should soon make detections a monthly occurrence. While Advanced LIGO promises to make first detections of gravitational waves from the nearby universe, an additional factor of 10 increase in sensitivity would put exciting science targets within reach by providing observations of binary black hole inspirals throughout most of the history of star formation, and high signal to noise observations of nearby events. Design studies for future detectors to date rely on significant technological advances that are futuristic and risky. In this paper we propose a different direction. We resurrect the idea of using longer arm lengths coupled with largely proven technologies. Since the major noise sources that limit gravitational wave detectors do not scale trivially with the length of the detector, we study their impact and find that 40 km arm lengths are nearly optimal, and can incorporate currently available technologies to detect gravitational wave sources at cosmological distances $(z\gtrsim 7)$.

By using quark Yukawa matrices only, we can construct renormalization invariants that are exact at the one-loop level in the standard model. One of them, $I^q$, is accidentally consistent with unity, even though quark masses are strongly hierarchical. We calculate a lepton version of the invariant $I^l$ for Dirac and Majorana neutrino cases and find that $I^l$ can also be close to unity. For the Dirac neutrino and inverted hierarchy case, if the lightest neutrino mass is 3.0 meV to 8.8 meV, an equality $I^q=I^l$ can be satisfied. These invariants are not changed even if new particles couple to the standard model particles, as long as those couplings are generation independent.

We study the production of heavy neutrinos at the Large Hadron Collider through the dominant $s$-channel production mode as well as the vector boson fusion process. We consider the TeV scale minimal linear seesaw model containing two heavy singlets with the opposite lepton number. This model is fully reconstructible from oscillation data apart from an overall normalization constant which can be constrained from the metastability of the electroweak vacuum and bounds coming from lepton flavor violation searches. The Dirac nature of heavy neutrinos in this model implies suppression of the conventional same-sign-dilepton signal at the Large Hadron Collider. We analyze the collider signatures with the trilepton final state and missing transverse energy as well as vector boson fusion type signals which are characterized by two additional forward tagged jets. Our investigation reveals that due to stringent constraints on light-heavy mixing coming from lepton flavor violation and metastability bounds, the model can be explored only for a light to moderate mass range of heavy neutrinos. We also note that in case of a positive signal, flavor counting of the final trilepton channel can give information about the mass hierarchy of the light neutrinos.

We study the impact of an additional $U(1{)}^{\prime }$ gauge symmetry with flavor-dependent charges for quarks and leptons on the LHC flavor anomalies observed in $B\to K^{*}{\mu }^{+}{\mu }^{-}$, $R(K)=B\to K{\mu }^{+}{\mu }^{-}/B\to K{e}^{+}{e}^{-}$, and $h\to \mu \tau$. In its minimal version with two scalar doublets, the resulting model naturally explains the deviations from the Standard Model observed in $B\to K^{*}{\mu }^{+}{\mu }^{-}$ and $R(K)$. The CMS access in $h\to \mu \tau$ can be explained by introducing a third scalar doublet, which gives rise to a prediction for $\tau \to 3\mu$. We investigate constraints from flavor observables and direct LHC searches for $pp\to Z^{\prime }\to {\mu }^{+}{\mu }^{-}$. Our model successfully generates the measured fermion-mixing matrices and does not require vectorlike fermions, unlike previous attempts to explain these anomalies.

We derive the relations necessary for the extraction of matrix elements of multihadron systems from finite-volume lattice QCD calculations. We focus on systems of $n\ge 2$ weakly interacting identical particles without spin. These results will be useful in extracting physical quantities from lattice QCD measurements of such matrix elements in many-pion and many-kaon systems.

We adopt a fully gauge-invariant effective-field-theory approach for parametrizing top-quark flavor-changing-neutral-current interactions. It allows for a global interpretation of experimental constraints (or measurements) and the systematic treatment of higher-order quantum corrections. We discuss some recent results obtained at next-to-leading-order accuracy in QCD and perform, at that order, a first global analysis of a subset of the available experimental limits in terms of effective operator coefficients. We encourage experimental collaborations to adopt this approach and extend the analysis by using all information they have prime access to.

In contrast to other atomic systems, in true muonium (${\mu }^{+}{\mu }^{-}$) the leading-order $Z$ boson corrections to the hyperfine splitting are shown to be experimentally accessible in the near future. This contribution ($-109\mathrm{MHz}$) constitutes a necessary contribution to a full $\mathcal{O}(m{\alpha }^7)$ calculation of the true muonium hyperfine splitting. This calculation would enable a number of possible solutions to the muon problem to be constrained. Additionally, we compute the general expression for a pseudovector coupling to particle-antiparticle bound states at leading order, including the annihilation channel.

This article summarizes the status of the global fit of the Cabibbo-Kobayashi-Maskawa (CKM) parameters within the Standard Model performed by the CKMfitter group. Special attention is paid to the inputs for the CKM angles $\alpha$ and $\gamma$ and the status of $B_s\to \mu \mu$ and $B_d\to \mu \mu$ decays. We illustrate the current situation for other unitarity triangles. We also discuss the constraints on generic $\mathrm{\Delta }F=2$ new physics. All results have been obtained with the CKMfitter analysis package, featuring the frequentist statistical approach and using Rfit to handle theoretical uncertainties.

We define and test $CP$-even and $CP$-odd partial differential widths for the process $\tau \to K\pi \pi {\nu }_{\tau }$ assuming that an intermediate heavy charged scalar contributes to the decay amplitude. Adopting a model-independent approach, we use a Monte Carlo simulation in order to study the number of events needed to recover information on the new physics from these observables. Our analysis of the $CP$-odd observables indicates that the magnitude of $f_H{\eta }_P$, which is related to the new-physics contribution, can be recovered with an uncertainty smaller than 3% for $3\times 10^6$ events. This number of events would also allow one to retrieve certain parameters appearing in the Standard Model amplitude at the percent level. In addition, we discuss the possibility of using the proposed observables to study specific models involving two Higgs doublets, such as the aligned two-Higgs-doublet model. This analysis is undertaken within the context of the upcoming super B-factories, which are expected to provide a considerably larger number of events than that which was supplied by the B-factories. Moreover, a similar set of observables could be employed to study other decay modes such as $\tau \to \pi \pi \pi {\nu }_{\tau }$, $\tau \to KK\pi {\nu }_{\tau }$ and $\tau \to KKK{\nu }_{\tau }$.

We report a search for the rare charmless decay $B^{+}\to {\overline{K}}^{*0}{K}^{*+}$ using a data sample of $772\times 10^6$ $B\overline{B}$ pairs collected at the $\mathrm{\Upsilon }(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. No statistically significant signal is found and a 90% confidence-level upper limit is set on the decay branching fraction of $\mathcal{B}(B^{+}\to {\overline{K}}^{*0}{K}^{*+})<1.31\times 10^{-6}$.

We present a holographic perspective on magnetic oscillations in strongly correlated electron systems via a fluid of charged spin $1/2$ particles outside a black brane in an asymptotically anti-de-Sitter spacetime. The resulting backreaction on the spacetime geometry and bulk gauge field gives rise to magnetic oscillations in the dual field theory, which can be directly studied without introducing probe fermions, and which differ from those predicted by Fermi liquid theory.

In this work we study the duality between $F$-theory and the heterotic string beyond the stable degeneration limit in $F$-theory and large fiber limit in the heterotic theory. Building upon a recent proposal by Clingher and Doran and by Malmendier and Morrison—which phrases the duality on the heterotic side for a particular class of models in terms of (fibered) genus-two curves as nongeometric heterotic compactifications—we establish the precise limit to the semiclassical heterotic string in both eight and lower space-time dimensions. In particular for six-dimensional theories, we argue that this class of nongeometric heterotic compactifications capture ${\alpha }^{\prime }$ quantum corrections to the semiclassical heterotic supergravity compactifications on elliptically fibered $K3$ surfaces. From the nongeometric heterotic theory, the semiclassical phase on the $K3$ surface is recovered from a remarkable limit of genus-two Siegel modular forms combined with a geometric surgery operation. Finally, in four dimensions we analyze another limit deep in the quantum regime of the nongeometric heterotic string, which we refer to as the heterotic Sen limit. In this limit we can explicitly argue that the semiclassical two-staged fibrational structure of the heterotic hypermultiplet moduli space—recently established by Alexandrov, Louis, Pioline, and Valandro—gets corrected by quantum effects.

We defend the Fock-space Hamiltonian truncation method, which allows us to calculate numerically the spectrum of strongly coupled quantum field theories, by putting them in a finite volume and imposing a UV cutoff. The accuracy of the method is improved via an analytic renormalization procedure inspired by the usual effective field theory. As an application, we study the two-dimensional ${\varphi }^4$ theory for a wide range of couplings. The theory exhibits a quantum phase transition between the symmetry-preserving and symmetry-breaking phases. We extract quantitative predictions for the spectrum and the critical coupling and make contact with previous results from the literature. Future directions to further improve the accuracy of the method and enlarge its scope of applications are outlined.

An algorithmic approach towards the formulation of nonrelativistic diffeomorphism invariance has been developed which involves both matter and gauge fields. A step-by-step procedure has been provided which can accommodate all types of (Abelian) gauge interaction. The algorithm is applied to the problem of a two-dimensional electron moving under an external field and also under the Chern-Simons dynamics.

We consider the structure of the magnetic fields inside the neutron stars in Eddington-inspired Born-Infeld (EiBI) gravity. In order to construct the magnetic fields, we derive the relativistic Grad-Shafranov equation in EiBI and numerically determine the magnetic distribution in such a way that the interior magnetic fields should be connected to the exterior distribution. Then, we find that the magnetic distribution inside the neutron stars in EiBI is qualitatively similar to that in general relativity, where the deviation of magnetic distribution in EiBI from that in general relativity is almost comparable to uncertainty due to the equation of state for the neutron star matter. However, we also find that the magnetic fields in the crust region are almost independent of the coupling constant in EiBI, which suggests a possibility of obtaining the information about the crust equation of state independent from the gravitational theory via the observations of the phenomena associated with the crust region. In any case, since the imprint of EiBI gravity on the magnetic fields is weak, the magnetic fields could be a poor probe of gravitational theories, considering the many magnetic uncertainties.

We prove that a homogeneous and isotropic universe containing a scalar field with a power-law potential, $V(\varphi )=A{\varphi }^n$, with $0<n<1$ and $\mathrm{A}>0$ always develops a finite-time singularity at which the Hubble rate and its first derivative are finite, but its second derivative diverges. These are the first examples of cosmological models with realistic matter sources that possess weak singularities of “sudden” type. We also show that a large class of models with even weaker singularities exists for noninteger $n>1$. More precisely, if $k<n<k+1$ where $k$ is a positive integer then the first divergence of the Hubble rate occurs with its ($k+2$)th derivative. At early times these models behave like standard large-field inflation models but they encounter a singular end state when inflation ends. We term this singular inflation.

We investigate the Affleck-Dine baryogenesis after $D$-term inflation with a positive Hubble-induced mass term for a $B-L$ flat direction. It stays at a large field value during $D$-term inflation, and just after inflation ends it starts to oscillate around the origin of the potential due to the positive Hubble-induced mass term. The phase direction is kicked by higher-dimensional Kähler potentials to generate the $B-L$ asymmetry. The scenario predicts nonzero baryonic isocurvature perturbations, which would be detected by future observations of CMB fluctuations. We also provide a $D$-term inflation model which naturally explains the coincidence of the energy density of baryon and dark matter.

In natural supersymmetry models, Higgsinos are always light because ${\mu }^2$ cannot be much larger than $M_Z^2$, while squarks and gluinos may be very heavy. Unless gluinos are discovered at LHC13, the commonly assumed unification of gaugino mass parameters will imply correspondingly heavy winos and binos, resulting in a Higgsino-like lightest supersymmetric particle (LSP) and small inter-Higgsino mass splittings. The small visible energy release in Higgsino decays makes their pair production difficult to detect at the LHC. Relaxing gaugino mass universality allows for relatively light winos and binos without violating LHC gluino mass bounds and without affecting naturalness. In the case where the bino mass $M_1\lesssim \mu$, then one obtains a mixed bino-Higgsino LSP with instead sizable ${\tilde{W}}_1-{\tilde{Z}}_1$ and ${\tilde{Z}}_2-{\tilde{Z}}_1$ mass gaps. The thermal neutralino abundance can match the measured dark matter density in contrast to models with a Higgsino-like LSP where weakly interacting massive particles are underproduced by factors of 10–15. If instead $M_2\lesssim \mu$, then one obtains a mixed wino-Higgsino LSP with large ${\tilde{Z}}_2-{\tilde{Z}}_1$ but small ${\tilde{W}}_1-{\tilde{Z}}_1$ mass gaps with still an underabundance of thermally produced weakly interacting massive particles. We discuss dark matter detection in other direct and indirect detection experiments and caution that the bounds from these must be interpreted with care. Finally, we show that LHC13 experiments should be able to probe these nonuniversal mass scenarios via a variety of channels including $\text{multilepton}+E_T^{\text{miss}}$ events, $WZ+E_T^{\text{miss}}$ events, $Wh+E_T^{\text{miss}}$ events, and $W^{\pm }{W}^{\pm }+E_T^{\text{miss}}$ events from electroweak chargino and neutralino production.

We present a mechanism that allows a large Higgsino mass without large fine-tuning. The Higgs is a pseudo-Nambu-Goldstone boson (PNGB) of the global symmetry breaking pattern $SO(5)\to SO(4)$. Because of the PNGB nature of the light Higgs, the $SO(5)$ invariant Higgsino mass does not directly contribute to the Higgs mass. Large couplings in the Higgs sector that spontaneously breaks $SO(5)$ minimize the tuning, and are also motivated by the requirements of generating a sufficiently large Higgs quartic coupling and of maintaining a natural approximate global $SO(5)$ symmetry. When these conditions are imposed, theories of this type predict heavy Higgsinos. This construction differs from composite Higgs models in that no new particles are introduced to form complete $SO(5)$ multiplets involving the top quark—the stop is the only top partner. Compatibility with Higgs coupling measurements requires cancellations among contributions to the Higgs mass-squared parameter at the 10% level. An important implication of this construction is that the compressed region of stop and sbottom searches can still be natural.

A lattice formulation of Lifshitz-type gauge theories is presented. While the Lorentz-invariant Yang-Mills theory is not renormalizable in five dimensions, non-Abelian Lifshitz-type gauge theories are renormalizable and asymptotically free. We construct a lattice gauge action and numerically examine the continuum limit and the bulk phase structure.