Starting from the generalized $pp$ waves that are exact vacuum solutions of general relativity with a cosmological constant, we construct a new family of exact vacuum solutions of Poincaré gauge theory, the generalized $pp$ waves with torsion. The ansatz for torsion is chosen in accordance with the wave nature of the solutions. For a subfamily of these solutions, the metric is dynamically determined by the torsion.

We argue that the Lorentzian path integral is a better starting point for quantum cosmology than its Euclidean counterpart. In particular, we revisit the minisuperspace calculation of the Feynman path integral for quantum gravity with a positive cosmological constant. Instead of rotating to Euclidean time, we deform the contour of integration over metrics into the complex plane, exploiting Picard-Lefschetz theory to transform the path integral from a conditionally convergent integral into an absolutely convergent one. We show that this procedure unambiguously determines which semiclassical saddle point solutions are relevant to the quantum mechanical amplitude. Imposing “no-boundary” initial conditions, i.e., restricting attention to regular, complex metrics with no initial boundary, we find that the dominant saddle contributes a semiclassical exponential factor which is precisely the inverse of the famous Hartle-Hawking result.

From the LHC runs we know that, with increasing collider energy, weak-boson-fusion Higgs production dominates as an environment for precision measurements. We show how a future hadron collider performs for three challenging benchmark signatures. Because all of these measurements rely on the tagging jet signature, we first give a comprehensive analysis of weak-boson-fusion kinematics and a proposed two-step jet veto at a 100 TeV hadron collider. We then find this machine to be sensitive to invisible Higgs branching ratios of 0.5%, a second-generation muon Yukawa coupling of 2%, and an enhanced total Higgs width of around 5%, the latter with essentially no model dependence. This kind of performance crucially relies on a sufficient detector coverage and a dedicated weak-boson-fusion trigger channel.

We propose a test based on direct detection data that allows us to determine if the dark matter particle is different from its antiparticle. The test requires the precise measurement of the dark matter spin-independent direct detection cross sections off three different nuclei and consists of interpreting such signals in terms of self-conjugate ($\text{particle}=\text{antiparticle}$) dark matter to see if such interpretation is consistent. If it is not, the dark matter must be different from its antiparticle. We illustrate this procedure for two sets of target nuclei, $\{\mathrm{Xe},\mathrm{Ar},\mathrm{Si}\}$ and $\{\mathrm{Xe},\mathrm{Ar},\mathrm{Ge}\}$, identifying the regions of the parameter space where it is particularly feasible. Our results indicate that future signals in direct detection experiments, if sufficiently accurate, might be used to establish that the dark matter particle is not its own antiparticle—a major step towards the determination of the fundamental nature of the dark matter.

We present a theoretical study of quantum simulations of ($1+1$)-dimensional U(1) lattice gauge-Higgs models, which contain a compact U(1) gauge field and a Higgs matter field, by using ultracold bosonic gases on a one-dimensional optical lattice. Starting from the extended Bose-Hubbard model with on-site and nearest-neighbor interactions, we derive the U(1) lattice gauge-Higgs model as a low-energy effective theory. The derived gauge-Higgs model exhibits nontrivial phase transitions between the confinement and Higgs phases, and we discuss the relation with the phase transition in the extended Bose-Hubbard model. Finally, we study the real-time dynamics of an electric flux by the Gross-Pitaevskii equations and the truncated Wigner approximation. The dynamics is governed by a bosonic analog of the Schwinger mechanism—i.e., the shielding of an electric flux by a condensation of Higgs fields, which occurs differently in the Higgs and the confinement phases. These results, together with the obtained phase diagrams, shall guide experimentalists in designing quantum simulations of the gauge-Higgs models by using cold gases.

We propose and test a new approach to computation of canonical partition functions in lattice QCD at finite density. We suggest a few steps procedure. We first compute numerically the quark number density for imaginary chemical potential $i{\mu }_{qI}$. Then we restore the grand canonical partition function for imaginary chemical potential using the fitting procedure for the quark number density. Finally we compute the canonical partition functions using high precision numerical Fourier transformation. Additionally we compute the canonical partition functions using the known method of the hopping parameter expansion and compare results obtained by two methods in the deconfining as well as in the confining phases. The agreement between two methods indicates the validity of the new method. Our numerical results are obtained in two flavor lattice QCD with clover improved Wilson fermions.

We consider configuration mixing for the nonstrange positive parity excited baryons in the $[{\mathbf{56}}^{\prime },0^{+}]$, $[\mathbf{56},2^{+}]$, $[\mathbf{70},0^{+}]$, and $[\mathbf{70},2^{+}]$ quark model $SU(6)\times O(3)$ multiplets contained in the $N=2$ band. Starting from the effective mass operator for these states, we show by an explicit calculation that in the large $N_c$ limit they fall into six towers of degenerate states labeled by $K=0,1,1^{\prime },2,2^{\prime },3$. We find that the mixing of the spin-flavor states is much simpler than what is naively expected in the quark model. To leading order in $N_c$, only states carrying the same $K$ label can mix, which implies that, for the spin-flavor states we started with, configuration mixing can be parameterized by just two constants: ${\mu }_{K=1}$ and ${\mu }_{K=2}$. The obtained mass degeneracies and mixing pattern constitute a signature of the contracted spin-flavor symmetry for baryons in the large $N_c$ limit.

We discuss some aspects of soft hairy black holes and a new kind of “soft hairy cosmologies,” including a detailed derivation of the metric formulation, results on flat space, and novel observations concerning the entropy. Remarkably, like in the case with negative cosmological constant, we find that the asymptotic symmetries for locally flat spacetimes with a horizon are governed by infinite copies of the Heisenberg algebra that generate soft hair descendants. It is also shown that the generators of the three-dimensional Bondi-Metzner-Sachs algebra arise from composite operators of the affine $\widehat{u}(1)$ currents through a twisted Sugawara-like construction. We then discuss entropy macroscopically and microscopically and discover that a microscopic formula derived recently for boundary conditions associated with the Korteweg–de Vries hierarchy fits perfectly our results for entropy and ground state energy. We conclude with a comparison to related approaches.

We present a manifestly local and general coordinate invariant formulation of a nonlocal approach to the cosmological constant problem which has been recently proposed by Carroll and Remmen. To do that, we need to introduce a topological term involving a new 3-form gauge field. The equations of motion for this new 3-form gauge field lead to a constant Lagrange multiplier parameter and the resulting action becomes equivalent to that of Carroll and Remmen. In our formulation, nonlocal information is encoded via the procedure of taking the space-time average at the stage of the equations of motion. Consequently, our theory evades a no-go theorem by Weinberg and provides a new solution to the cosmological constant problem in almost exactly the same way as the original proposal by Carroll et al.

We present first the equation of motion for the photon coupled to a Weyl tensor in a Kerr black hole spacetime and then study further the corresponding strong gravitational lensing. We find that black hole rotation makes propagation of the coupled photons more complicated, which brings about some new features for physical quantities, including the marginally circular photon orbit, the deflection angle, the observational gravitational lensing variables, and the time delay between two relativistic images. There is a critical value of the coupling parameter for existence of the marginally circular photon orbit outside the event horizon, which depends on the rotation parameter of the black hole and the polarization direction of the photons. As the value of the coupling parameter nears the critical value, we find that the marginally circular photon orbit for the retrograde photon increases with the rotation parameter, which modifies a common feature of the marginally circular photon orbit in a rotating black hole spacetime since it always decreases monotonously with the rotation parameter in the case without Weyl coupling. Modeling the supermassive central object in our Galaxy as a Kerr black hole, we estimate the numerical values of the observables including time delays between the relativistic images in the strong gravitational lensing of the photons coupled to Weyl tensor.

We propose a derivation of the inflaton scalar potential from the higher ($D$) dimensional $(R+\gamma R^n-2\mathrm{\Lambda })$ gravity, with the new coupling constant $\gamma$ and the cosmological constant $\mathrm{\Lambda }$. We assume that a compactification of extra dimensions happened before inflation, so that the inflaton scalar potential in four spacetime dimensions appears to be dependent upon the parameters $(\gamma ,\mathrm{\Lambda },D,n)$. We find that phenomenology and consistency require $n=D/2$, while the dimension $D$ has to be a multiple of four. We calculate the potential for any $D$, and determine the values of $\gamma$ and $\mathrm{\Lambda }$ from observations. The cases of $D=8$ and $D=12$ are considered in more detail. Our approach results in the viable models of chaotic large-field inflation, and leads to the sharp predictions of an observable value of the tensor-to-scalar ratio $r$ of the cosmic microwave background radiation.

We show that solving the flavor problem of the Standard Model with a simple $U(1{)}_H$ flavor symmetry naturally leads to an axion that solves the strong $CP$ problem and constitutes a viable Dark Matter candidate. In this framework, the ratio of the axion mass and its coupling to photons is related to the SM fermion masses and predicted within a small range, as a direct result of the observed hierarchies in quark and charged lepton masses. The same hierarchies determine the axion couplings to fermions, making the framework very predictive and experimentally testable by future axion and precision flavor experiments.

Secret coupling of neutrinos to a new light vector boson, $Z^{\prime }$, with a mass smaller than 100 MeV is motivated within a myriad of scenarios which are designed to explain various anomalies in particle physics and cosmology. Due to the longitudinal component of the massive vector boson, the rates of three-body decay of charged mesons ($M$) such as the pion and the kaon to the light lepton plus neutrino and $Z^{\prime }$ ($M\to l\nu Z^{\prime }$) are enhanced by a factor of $(m_M/m_{Z^{\prime }}{)}^2$. On the other hand, the standard two body decay $M\to l\nu$ is suppressed by a factor of $(m_l/m_M{)}^2$ due to chirality. We show that in the case of ($M\to e\nu Z^{\prime }$), the enhancement of $m_M^4/m_e^2{m}_{Z^{\prime }}^2\sim 10^8–10^{10}$ relative to two-body decay ($M\to e\nu$) enables us to probe very small values of gauge coupling for ${\nu }_e$. The strongest bound comes from the $R_K\equiv \mathrm{Br}(K\to e+\nu )/\mathrm{Br}(K\to \mu +\nu )$ measurement in the NA62 experiment. The bound can be significantly improved by customized searches for signals of three-body charged meson decay into the positron plus missing energy in the NA62 and/or PIENU data.

The octant of the atmospheric mixing angle ${\theta }_{23}$ is still undetermined by neutrino oscillation experiments. Long-baseline experiments like $\mathrm{NO}\nu \mathrm{A}$, T2K, and DUNE offer good prospects for determining the octant of ${\theta }_{23}$. However, their capability to do so may be compromised by the possible presence of nonunitarity in the leptonic mixing matrix. In this paper, we study in detail the octant degeneracy with and without nonunitarity at the level of oscillation probabilities and events for these experiments. We also analyze their octant sensitivity and discovery reach and show that they are hampered in the presence of nonunitarity.

Given a Wigner distribution simultaneously characterizing quark transverse positions and momenta in a proton, one can directly evaluate their cross product, i.e., quark orbital angular momentum. The aforementioned distribution can be obtained by generalizing the proton matrix elements of quark bilocal operators which define transverse momentum-dependent parton distributions (TMDs); the transverse momentum information is supplemented with transverse position information by introducing an additional nonzero momentum transfer. A gauge connection between the quarks must be specified in the quark bilocal operators; the staple-shaped gauge link path used in TMD calculations yields the Jaffe-Manohar definition of orbital angular momentum, whereas a straight path yields the Ji definition. An exploratory lattice calculation, performed at the pion mass $m_{\pi }=518\mathrm{MeV}$, is presented which quasicontinuously interpolates between the two definitions and demonstrates that their difference can be clearly resolved. The resulting Ji orbital angular momentum is confronted with traditional evaluations based on Ji’s sum rule. Jaffe-Manohar orbital angular momentum is enhanced in magnitude compared to its Ji counterpart.

We study the constraints coming from the local causality requirement in various $2+1$ dimensional dynamical theories of gravity. In topologically massive gravity, with a single parity noninvariant massive degree of freedom, and in new massive gravity, with two massive spin-2 degrees of freedom, causality and unitarity are compatible with each other and both require the Newton’s constant to be negative. In their extensions, such as the Born-Infeld gravity and the minimal massive gravity the situation is similar and quite different from their higher dimensional counterparts, such as quadratic (e.g., Einstein-Gauss-Bonnet) or cubic theories, where causality and unitarity are in conflict. We study the problem both in asymptotically flat and asymptotically anti–de Sitter spaces.

Within the framework of tachyon inflation, we consider different steep potentials and check their viability in light of the Planck 2015 data. We see that in this scenario, the inverse power-law potential $V(\varphi )=V_0(\varphi /{\varphi }_0{)}^{-n}$ with $n=2$ leads to the power-law inflation with the scale factor $a(t)\propto t^q$ where $q>1$, while with $n<2$, it gives rise to the intermediate inflation with the scale factor $a(t)\propto \exp (A{t}^f)$ where $A>0$ and $0<f<1$. We find that, although the inverse power-law potential with $n\le 2$ is completely ruled out by the Planck 2015 data, the result of this potential for $n>2$ can be compatible with the 95% CL region of Planck 2015 TT, TE, $\mathrm{EE}+\mathrm{lowP}$ data. We further conclude that the exponential potential $V(\varphi )=V_0{e}^{-\varphi /{\varphi }_0}$, the inverse cosh potential $V(\varphi )=V_0/\cosh (\varphi /{\varphi }_0)$, and the mutated exponential potential $V(\varphi )=V_0[1+(n-1{)}^{-(n-1)}(\varphi /{\varphi }_0{)}^n]e^{-\varphi /{\varphi }_0}$ with $n=4$, can be consistent with the 95% CL region of Planck 2015 TT, TE, $\mathrm{EE}+\mathrm{lowP}$ data. Moreover, using the $r-n_s$ constraints on the model parameters, we also estimate the running of the scalar spectral index $d{n}_s/d\ln k$ and the local non-Gaussianity parameter $f_{\mathrm{NL}}^{\text{local}}$. We find that the lower and upper bounds evaluated for these observables are compatible with the Planck 2015 results.

Observed baryon asymmetry can be achieved not only by the decay of right-handed neutrinos but also by the scattering processes in the reheating era. In the latter scenario, new physics in high energy scale does not need to be specified, but only two types of the higher dimensional operator of the standard model particles are assumed in the previous work. In this paper, we examine the origin of the higher dimensional operators assuming models with a certain seesaw mechanism at the high energy scale. The seesaw mechanism seems to be a simple realization of the reheating era leptogenesis because the lepton number violating interaction is included. We show that the effective interaction giving $CP$ violating phases is provided in the several types of models and also the reheating era leptogenesis actually works in such models. Additionally, we discuss a possibility for lowering the reheating temperature in the radiative seesaw models, where the large Yukawa coupling is naturally realized.

The massive neutron star (NS) or black hole (BH) accretion disk resulting from NS–NS or NS–BH mergers is dense in neutrinos. We present the first study on the role of angular distributions in the neutrino flavor conversion above the remnant disk. In particular, we focus on “fast” pairwise conversions whose rate depends on the local angular intensity of the electron lepton number carried by neutrinos. Because of the emission geometry and the flux density of ${\overline{\nu }}_e$ being larger than that of ${\nu }_e$, fast conversions prove to be a generic phenomenon in NS–NS and NS–BH mergers for physically motivated disturbances in the mean field of flavor coherence. Our findings suggest that, differently from the core-collapse supernova case, fast flavor conversions seem to be unavoidable in compact mergers and could have major consequences for the jet dynamics and the synthesis of elements above the remnant disk.

We investigate the effect of the redshift drift in strong gravitational lensing. The redshift drift produces a time variation of (i) the apparent position of a lensed source and (ii) the time delay among incoming signals from different images. We dub these effects as angular drift and time delay drift and show that they are of order of ${10}^{-10}$ arc seconds per year and ${10}^{-3}$ seconds per year, respectively. With present techniques there is apparently no hope of detecting such small changes for time intervals smaller than $10^9\mathrm{years}$.