The measured (central) values of the Higgs and top quark masses indicate that the standard model (SM) effective potential develops an instability at high field values. The scale of this instability, determined as the Higgs field value at which the potential drops below the electroweak minimum, is about $10^{11}\mathrm{GeV}$. However, such a scale is unphysical as it is not gauge invariant and suffers from a gauge-fixing uncertainty of up to 2 orders of magnitude. Subjecting our system, the SM, to several probes of the instability (adding higher order operators to the potential, letting the vacuum decay through critical bubbles, heating up the system to very high temperature, and inflating it) and asking in each case physical questions, we are able to provide several gauge-invariant scales related with the Higgs potential instability.

If the flavor-dependent nonstandard interactions (NSIs) in neutrino propagation exist, then the matter effect is modified, and the modification is parametrized by the dimensionless parameter ${\epsilon }_{\alpha \beta }$ ($\alpha$, $\beta =e$, $\mu$, $\tau$). In this paper, we discuss the sensitivity of the T2HKK experiment, the possibility of which is now seriously discussed as a future extension of the T2K experiment, to such NSIs. On the assumption that ${\epsilon }_{\alpha \mu }=0$ ($\alpha =e$, $\mu$, $\tau$) and ${\epsilon }_{\tau \tau }=|{\epsilon }_{e\tau }|/(1+{\epsilon }_{ee})$, which are satisfied by other experiments to a good approximation, we find that, among the possible off-axis flux configurations of 1.3°, 1.5°, 2.0°, and 2.5°, the case of the off-axis angle 1.3° gives the highest sensitivity to ${\epsilon }_{ee}$ and $|{\epsilon }_{e\tau }|$. Our results show that the 1.3° off-axis configuration can exclude NSIs for $|{\epsilon }_{ee}|\gtrsim 1$ or $|{\epsilon }_{e\tau }|\gtrsim 0.2$ at $3\sigma$. We also find that in the presence of NSIs T2HKK (for the off-axis angle 1.3°) has better sensitivity to the two $CP$ phases [${\delta }_{CP}$ and arg(${\epsilon }_{e\tau }$)] than DUNE. This is because of the synergy between the two detectors, i.e., one in Kamioka and one in Korea. T2HKK has better sensitivity to the $CP$ phases than the atmospheric neutrino experiment at Hyper-Kamiokande in inverted hierarchy, but in normal hierarchy, the atmospheric neutrino experiment has the best sensitivity to the $CP$ phases.

In the lepton-specific version of two Higgs doublet models, a discrete symmetry is used to couple one Higgs boson, ${\mathrm{\Phi }}_2$, to quarks and the other, ${\mathrm{\Phi }}_1$, to leptons. The symmetry eliminates tree level flavor changing neutral currents. Motivated by strong constraints on such currents in the quark sector from meson-antimeson mixing, and by hints of $h\to \mu \tau$ in the lepton sector, we study a simple three Higgs doublet model in which one doublet couples to quarks and the other two to leptons. Unlike most other studies of three Higgs doublet models, we impose no flavor symmetry and just use a $Z_2$ symmetry to constrain the Yukawa couplings. We present the model and discuss the various mixing angles. Constraining the parameters to be consistent with observations of the Higgs boson at the LHC, we study the properties of the charged Higgs boson(s) in the model, focusing on the case in which the charged Higgs boson is above the top threshold. It is found that one can have the branching fraction of the charged Higgs boson into $\tau {\nu }_{\tau }$ comparable to $t\overline{b}$ decay without needing very large values for the ratios of vacuum expectation values. One can also get a large branching fraction for the much more easily observable $\mu {\nu }_{\tau }$ decay.

We propose a simple extension of the Standard Model (SM) which has a viable dark matter (DM) candidate and can explain the generation of tiny neutrino masses. The DM is an electroweak (EW) singlet scalar $S$, odd under an imposed exact $Z_2$ symmetry, that interacts with the SM through the “Higgs portal” coupling, while all other particles are even under $Z_2$. The model also has an EW isospin $3/2$ scalar $\mathrm{\Delta }$ and a pair of EW isospin vectors $\mathrm{\Sigma }$ and $\overline{\mathrm{\Sigma }}$, which are responsible for generating tiny neutrino mass via the effective dimension-seven operator. Thanks to the additional interactions with $\mathrm{\Delta }$, the scalar singlet DM $S$ survives a large region of parameter space by relic density constraints from WMAP/Planck and direct search bounds from updated LUX data. Constraints on the model from the LHC are also discussed.

Result on locations of the tricritical points of $N_f=2$ lattice QCD with imaginary chemical potential is presented. Simulations are carried out with Symanzik improved gauge action and Asqtad fermion action. With imaginary chemical potential $i{\mu }_I=i\pi T$, previous studies show that the Roberge-Weiss (RW) transition endpoints are triple points at both large and small quark masses, and second order transition points at intermediate quark masses. The triple and second order endpoints are separated by two tricritical ones. Our simulations are carried out at 7 values of quark mass $am$ ranging from 0.024 to 0.070 on lattice volume $12^3\times 4$, $16^3\times 4$, $20^3\times 4$. The susceptibility and Binder cumulant of the imaginary part of the Polyakov loop are employed to determine the nature of RW transition endpoints. The simulations suggest that the two tricritical points are within the range 0.024–0.026 and 0.040–0.050, respectively.

We compute the topological charge and its susceptibility in finite temperature ($2+1$)-flavor QCD on the lattice applying a gradient flow method. With the Iwasaki gauge action and nonperturbatively $O(a)$-improved Wilson quarks, we perform simulations on a fine lattice with $a\simeq 0.07\mathrm{fm}$ at a heavy $u$, $d$ quark mass with $m_{\pi }/m_{\rho }\simeq 0.63$, but approximately physical $s$ quark mass with $m_{{\eta }_{ss}}/m_{\varphi }\simeq 0.74$. In a temperature range from $T\simeq 174\mathrm{MeV}$ ($N_t=16$) to 697 MeV ($N_t=4$), we study two topics on the topological susceptibility. One is a comparison of gluonic and fermionic definitions of the topological susceptibility. Because the two definitions are related by chiral Ward-Takahashi identities, their equivalence is not trivial for lattice quarks which violate the chiral symmetry explicitly at finite lattice spacings. The gradient flow method enables us to compute them without being bothered by the chiral violation. We find a good agreement between the two definitions with Wilson quarks. The other is a comparison with a prediction of the dilute instanton gas approximation, which is relevant in a study of axions as a candidate of the dark matter in the evolution of the Universe. We find that the topological susceptibility shows a decrease in $T$ which is consistent with the predicted ${\chi }_{\mathrm{t}}(T)\propto (T/T_{\mathrm{pc}}{)}^{-8}$ for three-flavor QCD even at low temperature $T_{\mathrm{pc}}<T\lesssim 1.5T_{\mathrm{pc}}$.

We study several types of tree-level improvement in the Yang-Mills gradient flow method in order to reduce the lattice discretization errors in line with Fodor et al. [J. High Energy Phys. 09 (2014) 018.]. The tree-level $\mathcal{O}(a^2)$ improvement can be achieved in a simple manner, where an appropriate weighted average is computed between the plaquette and clover-leaf definitions of the action density $⟨E(t)⟩$ measured at every flow time $t$. We further develop the idea of achieving the tree-level $\mathcal{O}(a^4)$ improvement within a usage of actions consisting of the $1\times 1$ plaquette and $1\times 2$ planar loop for both the flow and gauge actions. For testing our proposal, we present numerical results for $⟨E(t)⟩$ obtained on gauge configurations generated with the Wilson and Iwasaki gauge actions at three lattice spacings ($a\approx 0.1,0.07$, and 0.05 fm). Our results show that tree-level improved flows significantly eliminate the discretization corrections on $t^2⟨E(t)⟩$ in the relatively small-$t$ regime for up to $t\gtrsim a^2$. To demonstrate the feasibility of our tree-level improvement proposal, we also study the scaling behavior of the dimensionless combinations of the ${\mathrm{\Lambda }}_{\overline{\mathrm{MS}}}$ parameter and the new reference scale $t_X$, which is defined through $t_X^2⟨E(t_X)⟩=X$ for the smaller $X$, e.g., $X=0.15$. It is found that $\sqrt{t_{0.15}}{\mathrm{\Lambda }}_{\overline{\mathrm{MS}}}$ shows a nearly perfect scaling behavior as a function of $a^2$ regardless of the types of gauge action and flow, after tree-level improvement is achieved up to $\mathcal{O}(a^4)$. Further detailed study of the scaling behavior exposes the presence of the remnant $\mathcal{O}(g^{2n}{a}^2)$ corrections, which are beyond the tree level. Although our proposal is not enough to eliminate all $\mathcal{O}(a^2)$ effects, we show that the $\mathcal{O}(g^{2n}{a}^2)$ corrections can be well under control even by the simplest tree-level $\mathcal{O}(a^2)$ improved flow.

We investigate the $a_0(980)$ resonance within chiral effective field theory through a three-coupled-channel analysis, namely, $\pi \eta$, $K\overline{K}$, and $\pi {\eta }^{\prime }$. A global fit to recent lattice finite-volume energy levels from $\pi \eta$ scattering and relevant experimental data on a $\pi \eta$ event distribution and the $\gamma \gamma \to \pi \eta$ cross section is performed. Both the leading and next-to-leading-order analyses lead to similar and successful descriptions of the finite-volume energy levels and the experimental data. However, these two different analyses yield different $\pi \eta$ scattering phase shifts for the physical masses for the $\pi$, $K$, $\eta$, and ${\eta }^{\prime }$ mesons. The inelasticities, the pole positions in the complex energy plane, and their residues are calculated both for unphysical and physical meson masses.

We give a detailed account of the phenomenology of all-order resummations of logarithmically enhanced contributions at small momentum fraction of the observed hadron in semi-inclusive electron-positron annihilation and the timelike scale evolution of parton-to-hadron fragmentation functions. The formalism to perform resummations in Mellin moment space is briefly reviewed, and all relevant expressions up to next-to-next-to-leading logarithmic order are derived, including their explicit dependence on the factorization and renormalization scales. We discuss the details pertinent to a proper numerical implementation of the resummed results comprising an iterative solution to the timelike evolution equations, the matching to known fixed-order expressions, and the choice of the contour in the Mellin inverse transformation. First extractions of parton-to-pion fragmentation functions from semi-inclusive annihilation data are performed at different logarithmic orders of the resummations in order to estimate their phenomenological relevance. To this end, we compare our results to corresponding fits up to fixed, next-to-next-to-leading order accuracy and study the residual dependence on the factorization scale in each case.

We study the processes $e^{+}{e}^{-}\to K_S^0{K}_L^0{\pi }^0\gamma$, $K_S^0{K}_L^0\eta \gamma$, and $K_S^0{K}_L^0{\pi }^0{\pi }^0\gamma$, where the photon is radiated from the initial state, providing cross section measurements for the hadronic final states over a continuum of center-of-mass energies. The results are based on $469{\mathrm{fb}}^{-1}$ of data collected at or near the $\mathrm{{\rm Y}}(4S)$ resonance with the BABAR detector at SLAC. We present the first measurements of the $e^{+}{e}^{-}\to K_S^0{K}_L^0{\pi }^0$, $K_S^0{K}_L^0\eta$, and $K_S^0{K}_L^0{\pi }^0{\pi }^0$ cross sections up to a center-of-mass energy of 4 GeV and study their intermediate resonance structures. We observe $J/\psi$ decays to all of these final states for the first time, present measurements of their $J/\psi$ branching fractions, and search for $\psi (2S)$ decays.

We study the role of composite operators in the asymptotic safety program for quantum gravity. By including in the effective average action an explicit dependence on new sources, we are able to keep track of operators which do not belong to the exact theory space and/or are normally discarded in a truncation. Typical examples are geometric operators such as volumes, lengths, or geodesic distances. We show that this setup allows us to investigate the scaling properties of various interesting operators via a suitable exact renormalization group equation. We test our framework in several settings including quantum Einstein gravity, the conformally reduced Einstein-Hilbert truncation, and two-dimensional quantum gravity. Finally, we briefly argue that our construction paves the way to approach observables in the asymptotic safety program.

We study the butterfly effect of the AdS planar black holes in the framework of Einstein’s general relativity. We find that the butterfly velocities can be expressed by a universal formula $v_{\mathrm{B}}^2=TS/(2V_{\text{th}}P)$. In doing so, we come upon a near-horizon geometrical formula for the thermodynamical volume $V_{\text{th}}$. We verify the volume formula by examining a variety of AdS black holes. We also show that the volume formula implies that the conjectured reverse isoperimetric inequality follows straightforwardly from the null-energy condition, for static AdS black holes. The inequality is thus related to an upper bound of the butterfly velocities.

We derive the secular evolution of the orbital elements of a stellar-mass object orbiting a spinning massive black hole. We use the post-Newtonian (PN) approximation in harmonic coordinates, with test-body equations of motion for the conservative dynamics that are valid through 3PN order, including spin-orbit, quadrupole and ${(\mathrm{spin})}^2$ effects, and with radiation-reaction contributions linear in the mass of the body that are valid through 4.5PN order, including the 4PN damping effects of spin-orbit coupling. The evolution equations for the osculating orbit elements are iterated to high PN orders using a two-time-scale approach and averaging over orbital time scales. We derive a criterion for terminating the orbit when its Carter constant drops below a critical value, whereupon the body plunges across the event horizon at the next closest approach. The results are valid for arbitrary eccentricities and arbitrary inclinations. We then analyze numerically the orbits of objects injected into high-eccentricity orbits via interactions within a surrounding star cluster, obtaining the number of orbits and the elapsed time between injection and plunge, and the residual orbital eccentricity at plunge as a function of inclination. We derive an analytic approximation for the time to plunge in terms of initial orbital variables. We show that, if the black hole is spinning rapidly, the flux of gravitational radiation during the final orbit before plunge may be suppressed by as much as 3 orders of magnitude if the orbit is retrograde on the equatorial plane compared to its prograde counterpart.

Thermodynamic fluctuation metrics in Ruppeiner’s formalism are worked out for Kerr-AdS black holes in the extended state space. The implications of constraints upon the state space geometry and their correspondence with thermodynamical ensembles are explicitly worked out in the most general setting. The state space scalar curvature for a given ensemble is found to be sensitive to the instabilities or phase transitions therein. In particular, it is found that the appropriate Ruppeiner scalar curvature does encode critical phenomena in the Kerr-AdS black holes. A detailed study is undertaken of the curvature contour of the state space of the 4D Kerr-AdS black hole, and suitable inferences are drawn. In particular, thermodynamic geometry suggests an instability in the Schwarzschild-AdS limit for all the ensembles except the pressure ensemble, which is equivalent to the unextended state space of the Kerr-AdS black holes. The extrinsic geometry of the ensemble hypersurfaces is introduced, and its relevance to constrained thermodynamic fluctuations is discussed. A new interpretation for the thermodynamic curvature of black hole systems is suggested.

We calculate Boltzmann neutrino energy transport with self-consistently coupled nuclear reactions through the weak-decoupling-nucleosynthesis epoch in an early universe with significant lepton numbers. We find that the presence of lepton asymmetry enhances processes which give rise to nonthermal neutrino spectral distortions. Our results reveal how asymmetries in energy and entropy density uniquely evolve for different transport processes and neutrino flavors. The enhanced distortions in the neutrino spectra alter the expected big bang nucleosynthesis light element abundance yields relative to those in the standard Fermi-Dirac neutrino distribution cases. These yields, sensitive to the shapes of the neutrino energy spectra, are also sensitive to the phasing of the growth of distortions and entropy flow with time/scale factor. We analyze these issues and speculate on new sensitivity limits of deuterium and helium to lepton number.

The next generation of surveys will greatly improve our knowledge of cosmological gravity. In this paper we focus on how Stage IV photometric redshift surveys, including weak lensing and multiple tracers of the matter distribution and radio experiments combined with measurements of the cosmic microwave background will lead to precision constraints on deviations from general relativity. We use a broad subclass of Horndeski scalar-tensor theories to forecast the accuracy with which we will be able to determine these deviations and their degeneracies with other cosmological parameters. Our analysis includes relativistic effects, does not rely on the quasistatic evolution and makes conservative assumptions about the effect of screening on small scales. We define a figure of merit for cosmological tests of gravity and show how the combination of different types of surveys, probing different length scales and redshifts, can be used to pin down constraints on the gravitational physics to better than a few percent, roughly an order of magnitude better than present probes. Future cosmological experiments will be able to constrain the Brans-Dicke parameter at a level comparable to Solar System and astrophysical tests.

The single-field consistency conditions and the local ansatz have played separate but important roles in characterizing the non-Gaussian signatures of single- and multifield inflation respectively. We explore the precise relationship between these two approaches and their predictions. We demonstrate that the predictions of the single-field consistency conditions can never be satisfied by a general local ansatz with deviations necessarily arising at order $(n_s-1{)}^2$. This implies that there is, in principle, a minimum difference between single- and (fully local) multifield inflation in observables sensitive to the squeezed limit such as scale-dependent halo bias. We also explore some potential observational implications of the consistency conditions and its relationship to the local ansatz. In particular, we propose a new scheme to test the consistency relations. In analogy with delensing of the cosmic microwave background, one can deproject the coupling of the long wavelength modes with the short wavelength modes and test for residual anomalous coupling.

We present neutrino bulb model simulations of Majorana neutrino coherent spin transformation (i.e., neutrino-antineutrino transformation), coupled to neutrino flavor evolution, for conditions corresponding to the neutronization burst epoch of an oxygen-neon-magnesium core collapse supernova. Significant neutrino spin transformation in, for example, the neutronization burst could alter the fluences of neutrinos and antineutrinos in a way which is potentially detectable for a Galactic core collapse supernova. Our calculations for the first time incorporate geometric dilution in the spin evolution of the neutrinos and combine two-flavor and three-flavor evolution with spin mixing physics. We find that significant spin transformations can occur, but only with a large neutrino luminosity and an electron fraction ($Y_e$) profile which facilitates adiabatic conditions for the spin-channel resonance. Using our adopted parameters of neutrino energy spectra, luminosity, density and $Y_e$ profiles, our calculations require an unrealistically large neutrino rest mass to sustain the spin transformation. It is an open question whether examining different density profiles or incorporating other sources of nonlinear feedback, such as $Y_e$ feedback, could mitigate this need. We find that spin transformations are not sensitive to the flavor structure of neutrinos; i.e., the spin transformations occur regardless of whether we simulate two- or three-flavor transformations. In the two-flavor case, spin transformations were insensitive to the choice of solar or atmospheric mass-squared splitting as well as the choice of the Majorana phase. Importantly, our three-flavor simulations, as well as our two-flavor simulations done with the atmospheric mass-squared splitting, show that the inclusion of spin degrees of freedom can significantly and qualitatively alter neutrino flavor evolution.

The interaction properties of cold dark matter (CDM) particle candidates, such as those of weakly interacting massive particles (WIMPs), generically lead to the structuring of dark matter on scales much smaller than typical galaxies, potentially down to $\sim {10}^{-10}{M}_{\odot }$. This clustering translates into a very large population of subhalos in galaxies and affects the predictions for direct and indirect dark matter searches (gamma rays and antimatter cosmic rays). In this paper, we elaborate on previous analytic works to model the Galactic subhalo population, while keeping consistent with current observational dynamical constraints on the Milky Way. In particular, we propose a self-consistent method to account for tidal effects induced by both dark matter and baryons. Our model does not strongly rely on cosmological simulations, as they can hardly be fully matched to the real Milky Way, apart from setting the initial subhalo mass fraction. Still, it allows us to recover the main qualitative features of simulated systems. It can further be easily adapted to any change in the dynamical constraints, and can be used to make predictions or derive constraints on dark matter candidates from indirect or direct searches. We compute the annihilation boost factor, including the subhalo-halo cross product. We confirm that tidal effects induced by the baryonic components of the Galaxy play a very important role, resulting in a local average subhalo mass density $\lesssim 1\%$ of the total local dark matter mass density, while selecting the most concentrated objects and leading to interesting features in the overall annihilation profile in the case of a sharp subhalo mass function. Values of global annihilation boost factors range from $\sim 2$ to $\sim 20$, while the local annihilation rate is about boosted half as much.

A new detector, the Fermilab Holometer, consists of separate yet identical 39-meter Michelson interferometers. Strain sensitivity achieved is better than ${10}^{-21}/\sqrt{\mathrm{Hz}}$ between 1 to 13 MHz from a 130-h data set. This measurement exceeds the sensitivity and frequency range made from previous high frequency gravitational wave experiments by many orders of magnitude. Constraints are placed on a stochastic background at 382 Hz resolution. The $3\sigma$ upper limit on ${\mathrm{\Omega }}_{\mathrm{GW}}$, the gravitational wave energy density normalized to the closure density, ranges from $5.6\times 10^{12}$ at 1 MHz to $8.4\times 10^{15}$ at 13 MHz. Another result from the same data set is a search for nearby primordial black hole binaries (PBHB). There are no detectable monochromatic PBHBs in the mass range $0.83–3.5\times 10^{21}\mathrm{g}$ between the Earth and the Moon. Projections for a chirp search with the same data set increase the mass range to $0.59-2.5\times 10^{25}\mathrm{g}$ and distances out to Jupiter. This result presents a new method for placing limits on a poorly constrained mass range of primordial black holes. Additionally, solar system searches for PBHBs place limits on their contribution to the total dark matter fraction.