We investigate a radiative electroweak gauge symmetry breaking scenario via the Coleman-Weinberg mechanism starting from a completely flat Higgs potential at the Planck scale (“flatland scenario”). In our previous paper, we showed that the flatland scenario is possible only when an inequality $K<1$ among the coefficients of the $\beta$ functions is satisfied. In this paper, we calculate the number $K$ in various models with an extra $U(1)$ gauge sector in addition to the standard model particles. We also show the renormalization group behaviors of a couple of the models as examples.

We analyze the unitarity of a modified QED with higher-order terms that violate Lorentz symmetry. We make an explicit calculation to verify unitarity at the one-loop level. As expected we find negative-norm states that could in principle lead to a violation of unitarity. However, we show that these states become massive in Euclidean space and do not contribute to the discontinuity.

Direct searches for electroweak pair production of new particles at the LHC are a difficult proposition, due to the large background and low signal cross sections. We demonstrate how these searches can be improved by a combination of new razor variables and shape analysis of signal and background kinematics. We assume that the pair-produced particles decay to charged leptons and missing energy, either directly or through a $W$ boson. In both cases the final state is a pair of opposite sign leptons plus missing transverse energy. We estimate exclusion reach in terms of sleptons and charginos as realized in minimal supersymmetry. We compare this super-razor approach in detail to analyses based on other kinematic variables, showing how the super-razor uses more of the relevant kinematic information while achieving higher selection efficiency on signals, including cases with compressed spectra.

Is the weak scale natural? This ever pending question makes the search for new particle production a highly motivated primary goal of the next LHC phase. These searches may or may not be successful. While waiting for a needed higher energy collider to extend the direct exploration, the search for signs of new physics might be confined to indirect tests for quite some time. In a few fully calculable models, weakly or semistrongly interacting, we compare the significance to measure the Higgs couplings versus the electroweak observables.

Motivated by the recent observation of the orbital excitation $B(5970)$ by the CDF Collaboration, we have performed a systematic study of the mass spectrum and strong decay patterns of the higher $B$ and $B_s$ mesons. Hopefully the present investigation may provide valuable clues to further experimental exploration of these intriguing excited heavy mesons.

We show that for the lower branch of the quark condensate and values higher than approximately $-(250\text{MeV}{)}^3$ the chiral critical endpoint in the Nambu–Jona-Lasinio model does not occur in the phase diagram. By using lattice motivated nonlocal quark interactions, we demonstrate that the critical endpoint can be recovered. We study this behavior for a range of condensate values and find that the variation in the position of the critical endpoint is more pronounced as the condensate is increased.

In the “Higgs basis” for a generic two-Higgs-doublet model, only one doublet gets a nonzero vacuum expectation value and, under the criterion of minimal flavor violation, the other one is fixed to be either color-singlet or color-octet, referred to, respectively, as the type-III and type-C models. Both of them can naturally avoid large FCNC transitions and provide very interesting phenomena in some low-energy processes. In this paper, we study their effects on exclusive radiative $B$-meson decays due to the exchange of colorless or colored charged Higgs. It is found that while constraints from the branching ratios are slightly weaker than the ones from the inclusive $B\to X_s\gamma$ decay, the isospin asymmetries in exclusive decays provide very complementary bounds on the model parameters. As the two models predict similar corrections to the dipole coefficient $C_7^{\text{eff}}$, but similar magnitudes with opposite signs to $C_8^{\text{eff}}$, the branching ratios cannot discriminate the two models, and we have to resort to the direct $CP$ and isospin asymmetries of $b\to s$ processes, which are more sensitive to $C_8^{\text{eff}}$. Due to the CKM factors $|{\lambda }_u^{(d)}|\sim |{\lambda }_t^{(d)}|$, the terms proportional to ${\lambda }_u^{(d)}$ make the observables of $b\to d$ processes exhibit a different dependence on the possible new physics phase. In addition, correlations between the various observables in the exclusive $B\to V\gamma$ and the inclusive $B\to X_{s,d}\gamma$ decays are investigated, which could provide further insights into the models with more precise experimental measurements and theoretical predictions for these decays.

We derive in detail several universal features in the time evolution of entanglement entropy and other nonlocal observables in quenched holographic systems. The quenches are such that a spatially uniform density of energy is injected at an instant in time, exciting a strongly coupled conformal field theory which eventually equilibrates. Such quench processes are described on the gravity side by the gravitational collapse of a thin shell that results in a black hole. Various nonlocal observables have a unified description in terms of the area of extremal surfaces of different dimensions. In the large distance limit, the evolution of an extremal surface, and thus the corresponding boundary observable, is controlled by the geometry around and inside the event horizon of the black hole, allowing us to identify regimes of pre-local-equilibration quadratic growth, post-local-equilibration linear growth, a memory loss regime, and a saturation regime with behavior resembling those in phase transitions. We also discuss possible bounds on the maximal rate of entanglement growth in relativistic systems.

In the conventional formalism of physics, with one time, systems with different Hamiltonians or Lagrangians have different physical interpretations and are considered to be independent systems unrelated to each other. However, in this paper we construct explicitly canonical maps in one-time (1T) phase space (including timelike components, specifically the Hamiltonian) to show that it is appropriate to regard various 1T physics systems, with different Lagrangians or Hamiltonians, as being duals of each other. This concept is similar in spirit to dualities discovered in more complicated examples in field theory or string theory. Our approach makes it evident that such generalized dualities are widespread. This suggests that, as a general phenomenon, there are hidden relations and hidden symmetries that conventional 1T physics does not capture, implying the existence of a more unified formulation of physics that naturally supplies the hidden information. In fact, we show that two-time (2T) physics in ($d+2$) dimensions is the generator of these dualities in 1T physics in $d$ dimensions by providing a holographic perspective that unifies all the dual 1T systems into one. The unifying ingredient is a gauge symmetry in phase space. Via such dualities it is then possible to gain new insights toward new physical predictions not suspected before, and suggest new methods of computation that yield results not obtained before. As an illustration, we will provide concrete examples of 1T systems in classical mechanics that are solved analytically for the first time via our dualities. These dualities in classical mechanics have counterparts in quantum mechanics and field theory, and in some simpler cases they have already been constructed in field theory. We comment on the impact of our approach on the meaning of space-time and on the development of new computational methods based on dualities.

We study spatially localized, time-periodic solutions (breathers) of scalar field theories with various self-interacting potentials on anti–de Sitter (AdS) spacetimes in $D$ dimensions. A detailed numerical study of spherically symmetric configurations in $D=3$ dimensions is carried out, revealing a rich and complex structure of the phase-space (bifurcations, resonances). Scalar breather solutions form one-parameter families parametrized by their amplitude, $\epsilon$, while their frequency, $\omega =\omega (\epsilon )$, is a function of the amplitude. The scalar breathers on AdS we find have a small amplitude limit, tending to the eigenfunctions of the linear Klein-Gordon operator on AdS. Importantly most of these breathers appear to be generically stable under time evolution.

In this paper, we present and analyze the simplest physically meaningful model for stationary black diholes—a binary configuration of counterrotating Kerr-Newman black holes endowed with opposite electric charges—elaborated in a physical parametrization on the basis of one of the Ernst-Manko-Ruiz equatorially antisymmetric solutions of the Einstein-Maxwell equations. The model saturates the Gabach-Clement inequality for interacting black holes with struts, and in the absence of rotation, it reduces to the Emparan-Teo electric dihole solution. The physical characteristics of each dihole constituent satisfy identically the well-known Smarr’s mass formula.

Most calculations of the gravitational wave signal from merging compact binaries limit attention to the leading-order quadrupole when constructing models for detection or parameter estimation. Some studies have claimed that if additional “higher harmonics” are included consistently in the gravitational wave signal and search model, binary parameters can be measured much more precisely. Using the lalinference Markov-chain Monte Carlo parameter estimation code, we construct posterior parameter constraints associated with two distinct nonprecessing black hole–neutron star (BH-NS) binaries, each with and without higher-order harmonics. All simulations place a plausible signal into a three-detector network with Gaussian noise. Our simulations suggest that higher harmonics provide little information, principally allowing us to measure a previously unconstrained angle associated with the source geometry well but otherwise improving knowledge of all other parameters by a few percent for our loud fiducial signal ($\rho =20$). Even at this optimistic signal amplitude, different noise realizations have a more significant impact on parameter accuracy than higher harmonics. We compare our results with the “effective Fisher matrix” introduced previously as a method to obtain robust analytic predictions for complicated signals with multiple significant harmonics. We find generally good agreement with these predictions, confirm that intrinsic parameter measurement accuracy is nearly independent of detector network geometry, and show that uncertainties in extrinsic and intrinsic parameters can, to a good approximation, be separated. For our fiducial example, the individual masses can be determined to lie between $7.11–11.48M_{\odot }$ and $1.77–1.276M_{\odot }$ at greater than 99% confidence level, accounting for unknown BH spin. Assuming comparable control over waveform systematics, measurements of BH-NS binaries can constrain the BH and perhaps NS mass distributions. Using analytic arguments to guide extrapolation, we anticipate that higher harmonics should provide little new information about nonprecessing BH-NS binaries, for the signal amplitudes expected for the first few detections. Though our study focused on one particular example—higher harmomics—any study of subdominant degrees of freedom in gravitational wave astronomy can adopt the tools presented here ($V/V_{\text{prior}}$ and $D_{\mathrm{KL}}$) to assess whether new physics is accessible (e.g., modifications of gravity, spin-orbit misalignment) and if so precisely what information those new parameters provide.

We consider an approach to the Brans-Dicke theory of gravity in which the scalar field has a geometrical nature. By postulating the Palatini variation, we find out that the role played by the scalar field consists in turning the space-time geometry into a Weyl integrable manifold. This procedure leads to a scalar-tensor theory that differs from the original Brans-Dicke theory in many aspects and presents some new features.

We study the structure of scalar-tensor theories of gravity based on derivative couplings between the scalar and the matter degrees of freedom introduced through an effective metric. Such interactions are classified by their tensor structure into conformal (scalar), disformal (vector), and extended disformal (traceless tensor), as well as by the derivative order of the scalar field. Relations limited to first derivatives of the field ensure second-order equations of motion in the Einstein frame and hence the absence of Ostrogradski ghost degrees of freedom. The existence of a mapping to the Jordan frame is not trivial in the general case, and can be addressed using the Jacobian of the frame transformation through its eigenvalues and eigentensors. These objects also appear in the study of different aspects of such theories, including the metric and field redefinition transformation of the path integral in the quantum mechanical description. Although second-order in the Einstein frame, generic disformally coupled theories are described by higher-order equations of motion in the Jordan frame. This apparent contradiction is solved by the use of a hidden constraint: the contraction of the metric equations with a Jacobian eigentensor provides a constraint relation for the higher field derivatives, which allows one to express the dynamical equations in a second-order form. This signals a loophole in Horndeski’s theorem and allows one to enlarge the set of scalar-tensor theories which are Ostrogradski stable. The transformed Gauss-Bonnet terms are also discussed for the simplest conformal and disformal relations.

Given the extreme accuracy of modern space science, a precise relativistic modeling of observations is required. In particular, it is important to properly describe light propagation through the Solar System. For two decades, several modeling efforts based on the solution of the null geodesic equations have been proposed, but they are mainly valid only for the first-order post-Newtonian approximation. However, with the increasing precision of ongoing space missions such as Gaia, GAME, BepiColombo, JUNO, and JUICE, we know that some corrections up to the second order have to be taken into account for future experiments. We present a procedure to compute the relativistic coordinate time delay, Doppler, and astrometric observables avoiding the integration of the null geodesic equation. This is possible using the time transfer function formalism, a powerful tool providing key quantities such as the time of flight of a light signal between two point events and the tangent vector to its null geodesic. Indeed, we show how to compute the time transfer functions and their derivatives (and thus range, Doppler, and astrometric observables) up to the second post-Minkowskian order. We express these quantities as quadratures of some functions that depend only on the metric and its derivatives evaluated along a Minkowskian straight line. This method is particularly well adapted for numerical estimations. As an illustration, we provide explicit expressions in static and spherically symmetric space-time up to second post-Minkowskian order. Then we give the order of magnitude of these corrections for the range and Doppler on the BepiColombo mission and for astrometry in a GAME-like observation.

We develop the basics of twistor theory in de Sitter space, up to the Penrose transform for free massless fields. We treat de Sitter space as fundamental, as one does for Minkowski space in conventional introductions to twistor theory. This involves viewing twistors as spinors of the de Sitter group $SO(4,1)$. When attached to a spacetime point, such a twistor can be reinterpreted as a local $SO(3,1)$ Dirac spinor. Our approach highlights the antipodal map in de Sitter space, which gives rise to doublings in the standard relations between twistors and spacetime. In particular, one can generate a field with both handedness signs from a single twistor function. Such fields naturally live on antipodally identified de Sitter space $d{S}_4/{\mathbb{Z}}_2$, which has been put forward as the ideal laboratory for quantum gravity with a positive cosmological constant.

We consider the generic scenario of dark energy that arises through the latent heat of a hidden sector first-order cosmological phase transition. This field could account for the extra radiation degree of freedom suggested by the CMB. We present the bubble nucleation solution for the viscous limit. The decay rate of the field is constrained by published kSZ data. This model may provide an explanation of current excess ISW correlations. Cross correlation of current and future surveys can further constrain or test the parameter space. The decay model is plausibly in the observable range and avoids anthropic problems. This class of models is not well constrained by the popular dark energy figure of merit.

The predictions of different relativistic descriptions of final-state interactions are compared with the neutral-current elastic neutrino- and antineutrino-nucleus differential cross sections recently measured by the MiniBooNE Collaboration. The results of the relativistic Green’s function model describe the data without the need to increase the standard value of the nucleon axial mass.

We propose a new nonuniversal $U(1{)}^{\prime }$ extension of the standard model with the addition of three exotic quark singlets, two scalar singlets and one additional scalar doublet. We obtain family-dependent couplings with a new $Z^{\prime }$ boson in the quark sector and universal couplings in the lepton sector. From experimental data on $Z^{\prime }$ research at the CERN LHC, we find limit regions in the $U(1{)}^{\prime }$ free parameters ($Z^{\prime }$ mass and coupling constant), which we use to obtain the total decay width and invariant-mass distributions. By introducing discrete symmetries and mixing couplings between ordinary and exotic fermions, we obtain predictable mass relations in the quark sector compatible with the phenomenological values without large fine-tuning of the Yukawa couplings and with few free parameters, where hierarchies between quark families can be understood from the existence of heavy beyond-standard-model particles.

The parameter space of the phenomenological minimal supersymmetric standard model is explored by means of Markov chain Monte Carlo methods, taking into account the latest LHC results on the Higgs signal at 125 GeV in addition to relevant low-energy observables and LEP constraints. We use a Bayesian approach to derive posterior densities for the parameters and observables of interests. We find in particular that the Higgs measurements have a significant impact on the parameters $\mu$ and $\tan \beta$ due to radiative corrections to the bottom Yukawa coupling. We show moreover the impact of the most recent dark matter measurements on the probability distributions, and we discuss prospects for the next run of the LHC at 13–14 TeV.