Journal of High Energy Physics最新文献

We construct a (1+1)-dimension continuum model of 4-component fermions incorporating the exceptional Lie group symmetry G₂. Four gapped and five gapless phases are identified via the one-loop renormalization group analysis. The gapped phases are controlled by four different stable SO(8) Gross-Neveu fixed points, among which three exhibit an emergent triality, while the rest one possesses the self-triality, i.e., invariant under the triality mapping. The gapless phases include three SO(7) critical ones, a G₂ critical one, and a Luttinger liquid. Three SO(7) critical phases correspond to different SO(7) Gross-Neveu fixed points connected by the triality relation similar to the gapped SO(8) case. The G₂ critical phase is controlled by an unstable fixed point described by a direct product of the Ising and tricritical Ising conformal field theories with the central charges c = ( frac{1}{2} ) and c = ( frac{7}{10} ), respectively, while the latter one is known to possess spacetime supersymmetry. In the lattice realization with a Hubbard-type interaction, the triality is broken into the duality between two SO(7) symmetries and the supersymmetric G₂ critical phase exhibits the degeneracy between bosonic and fermionic states, which are reminiscences of the continuum model.

We construct maximal supergravity in five-dimensions by ‘oxidizing’ the four-dimensional ( mathcal{N} ) = 8 theory. The relevant symmetries, the unitary symplectic group USp(8) and the exceptional group E₆, are both presented in light-cone superspace and their connections with SU(8) and E₇ highlighted. We explain a procedure to derive higher-point interaction vertices in both the 4- and 5-dimensional supergravity theories using exclusively the exceptional symmetries. Specific forms for the quartic and quintic interaction vertices in light-cone superspace are derived.

We construct the unintegrated vertex operator at the first mass level of the open superstring from the OPE of massless vertices. Using BRST cohomology manipulations, the tree amplitude of two massless and one massive state is rewritten in terms of the pure spinor superspace kinematic expression of the massless four-point amplitude at the α^{′ 2} level. A generalization relating the partial n-point tree amplitudes with one massive state and linear combinations of the α^{′ 2} corrections to n+1 massless amplitudes is found and shown to be consistent with unitarity.

Recent calculations in both flat and de Sitter spacetimes have highlighted a tension between the decoupling of high-energy physics from low-energy degrees of freedom and the expectation that quantum systems decohere due to interactions with unknown environments. In effective field theory (EFT), integrating out heavy fields should lead to Hamiltonian time evolution, which preserves the purity of low-energy states. This is consistent with the fact that we never observe isolated quantum states spontaneously decohering in the vacuum due to unknown high-energy physics. However, when a heavy scalar of mass M is traced out, the resulting purity of a light scalar with mass m typically appears to scale as a power of 1/M (when m ≪ M), an effect that cannot be captured by a local effective Hamiltonian. We resolve this apparent paradox by showing that the purity depends on the resolution scale of the EFT and how the environment is traced out. We provide a practical method for diagnosing the purity of low-energy states consistent with EFT expectations, and briefly discuss some of the implications these observations have for how ultraviolet divergences can appear in decoherence calculations.

We perform an analysis of a number of approximations and methods used in numerical simulations of real-time Kadanoff-Baym equations based on truncations of the 2PI effective action. We compare the loop expansion to the 1/N expansion and compare their classical limit to classical-statistical simulations. We also compare implementations based on a space-time lattice discretization at the level of the action to an ad hoc momentum discretization at the level of the equations of motions. We extract some rules of thumb for performing 2PI-simulations of out-of-equilibrium systems.

The Hawking-Moss (HM) bounce solution implies that the tunneling amplitude between vacua is uniquely determined by the vacuum energy at the initial vacuum and the top of a potential barrier, regardless of the field distance between them ∆ϕ. This implausible conclusion was carefully discussed in [E. J. Weinberg, Phys. Rev. Lett. 98, 251303, (2007)], and it was concluded that the conventional HM amplitude is not reliable for a transition to the top of distant local maxima (hereinafter referred to as the remote HM transition). We revisit this issue and study the impact of the quantum tunneling effect on the remote HM transition. We demonstrate that the amplitude for such a distant transition is indeed smaller than the conventional HM amplitude by employing the Lorentzian path integral in a simple setup. We consider a linear potential, which allows for analytic treatments, and evaluate the up-tunneling probability of a homogeneous scalar field in de Sitter spacetime. The Picard-Lefschetz theory is employed to identify the relevant Lefschetz thimble, representing the relevant tunneling trajectory. We then compare the resulting transition amplitude with the conventional HM amplitude. We find that when the field separation |∆ϕ| is larger, the quantum-tunneling amplitude, estimated by our Lorentzian path integral, is smaller than that of the conventional HM amplitude. This implies that the transition amplitude may be significantly suppressed if the thermal interpretation is not applicable and the quantum-tunneling effect is dominant for the remote HM transition.

The free graviton theory given by linearising Einstein’s theory has a dual formulation in terms of a dual graviton field. The dual graviton theory has two gauge invariances giving rise to two conserved charges, while the ADM charges of the graviton theory become magnetic charges for the dual graviton theory. These charges can be ill-defined in topologically non-trivial settings and we find improvement terms that can be added to these to give gauge-invariant conserved charges. These gauge-invariant charges, which have local expressions in both the graviton and dual graviton formulation, give topological operators of the theory that should be considered as the generators of the genuine symmetries of the theory.

This paper represents a continuation of our previous work, where the Boltzmann weights (BWs) for several Interaction-Round-the Face (IRF) lattice models were computed using their relation to rational conformal field theories. Here, we focus on deriving solutions for the Boltzmann weights of the Interaction-Round the Face lattice model, specifically, the unrestricted face model, based on the ( mathfrak{su}{(3)}_k ) affine Lie algebra. The admissibility conditions are defined by the adjoint representation. We find the BWs by determining the quantum R matrix of the ( {U}_qleft(mathfrak{sl}(3)right) ) quantum algebra in the adjoint representation and then applying the so-called Vertex-IRF correspondence. The Vertex-IRF correspondence defines the BWs of IRF models in terms of R matrix elements.

In this paper we study various aspects of ghost resonances: the resummation that leads to the dressed propagator, the poles locations, the analytic continuation into the second Riemann sheet and the spectral representations in both first and second sheets. In particular, we show that for real masses above the multiparticle threshold the ghost propagator has a pair of complex conjugate poles in the first sheet, unlike the case of an ordinary unstable resonance which has no pole in the first sheet but a complex conjugate pair in the second sheet. Mathematical and physical implications of this feature are discussed. We also clarify an important point regarding the two absorptive contributions of a ghost propagator in the narrow-width approximation. Furthermore, we argue that finite-time quantum field theories are needed to consistently derive the dressed ghost propagator and capture the true physical properties of ghost resonances. Throughout the work, different prescriptions to define the ghost propagator on the real axis are considered: Feynman, anti-Feynman and fakeon prescriptions.

We study the coupling of axions to gauge bosons in heterotic string theory. The axion-gauge boson couplings in the low energy 4d theory are derived by matching mixed anomalies between higher-form global symmetries and the zero-form gauge symmetry in the 10d theory. When the standard model gauge group is embedded in a single simple group in the 10d theory — as is the case for almost all heterotic models studied in the literature — the ratio of the axion-photon coupling to the axion mass is bounded above by the QCD line. This bound is relevant for a large number of axion searches which have sensitivity to axion parameter space above this line. The discovery of an axion in these searches will rule out a large class of heterotic models, making such a signal challenging to explain within heterotic string theory.