Massive Field Research Articles

Parity violation in the scalar trispectrum: no-go theorems and yes-go examples

We derive a set of no-go theorems and yes-go examples for the parity-odd primordial trispectrum of curvature perturbations. We work at tree-level in the decoupling limit of the Effective Field Theory of Inflation and assume scale invariance and a Bunch-Davies vacuum. We show that the parity-odd scalar trispectrum vanishes in the presence of any number of scalar fields with arbitrary mass and any parity-odd scalar correlator vanishes in the presence of any number of spinning fields with massless de Sitter mode functions, in agreement with the findings of Liu, Tong, Wang and Xianyu [1]. The same is true for correlators with an odd number of conformally-coupled external fields. We derive these results using both the (boostless) cosmological bootstrap, in particular the Cosmological Optical Theorem, and explicit perturbative calculations. We then discuss a series of yes-go examples by relaxing the above assumptions one at the time. In particular, we provide explicit results for the parity-odd trispectrum for (i) violations of scale invariance in single-clock inflation, (ii) the modified dispersion relation of the ghost condensate (non-Bunch-Davies vacuum), and (iii) interactions with massive spinning fields. Our results establish the parity-odd trispectrum as an exceptionally sensitive probe of new physics beyond vanilla inflation.

Islands and light gravitons in type IIB string theory

We consider the setup of a black hole in AdS4 coupled to an external bath, embedded in type IIB string theory. We study quantum extremal islands in these backgrounds, in relation to the existence of a massive graviton. Using explicit results of the microscopic embedding of AdS4 massive gravity in string theory, we investigate whether it is possible to achieve backgrounds with extremal islands, in which the lowest lying graviton is only slightly massive. For certain regions of the microscopic parameters, the graviton mass can be computed explicitly, and we explain how it directly affects the existence and the properties of the islands. We also show that islands can in principle exist within the regime of validity of the massive gravity effective field theory. However we see via numerical computations that the existence of quantum extremal islands at zero temperature is highly constrained, also when the dilaton is allowed to vary, so that the mass of the graviton cannot be made arbitrarily light. At finite temperature, we also identify a critical parameter, above and below which islands still exist but exhibit a different behavior. Our work supports recent proposals that the unitary evolution of black holes in higher dimensions, and more precisely their Page curve, relies on the presence of a massive graviton in the effective theory.

Gravitational wave probes of massive gauge bosons at the cosmological collider

We extend the reach of the “cosmological collider” for massive gauge boson production during inflation from the CMB scales to the interferometer scales. Considering a Chern-Simons coupling between the gauge bosons and the pseudoscalar inflaton, one of the transverse gauge modes is efficiently produced and its inverse decay leaves an imprint in the primordial scalar and tensor perturbations. We study the correlation functions of these perturbations and derive the updated constraints on the parameter space from CMB observables. We then extrapolate the tensor power spectrum to smaller scales consistently taking into account the impact of the gauge field on inflationary dynamics. Our results show that the presence of massive gauge fields during inflation can be detected from characteristic gravitational wave signals encompassing the whole range of current and planned interferometers.

Lorentz-covariant spin operator for spin 1/2 massive fields as a physical observable

Lorentz-covariant spin operator for spin 1/2 massive fields as a physical observable

Hydraulic resistances of eroded riverbed and assessment of their sustainability

In the world, due to the shortage of water resources, the most important issues are the rational use of water resources, the assessment, and the improvement of the capacity of riverbeds and channels. In this regard, research developments on improving the methods of the hydraulic calculation of the resistance and the stability of mobile river channels and channels are of particular importance. The results of some theoretical and experimental studies of hydraulic resistances and the stability of watercourses by scientists in the CIS and abroad are considered. The analysis of massive field data on the Darcy coefficient (Shezi) of earth channels covered in a sandy mobile bed is performed. With a change in the flow velocity field, the roughness of the channel surface changes, changing its size and shape, which determines the channel's resistance to flow movement. It is established that in stable channels with certain widths, the flow velocity is evenly distributed, having one maximum along the channel axis, and the movement is carried out in the form of a compact single jet along the flow cross-section. With changes in hydraulic conditions, the curvature of the isotopes is observed, the flow tends to split, and several closed systems of rotating the jet appear, which are signs of the development of channel deformations.

Conformal-type energy estimates on hyperboloids and the wave-Klein-Gordon model of self-gravitating massive fields

<abstract><p>In this article we revisit the global existence result of the wave-Klein-Gordon model of the system of the self-gravitating massive field. Our new observation is that, by applying the conformal energy estimates on hyperboloids, we obtain mildly increasing energy estimate up to the top order for the Klein-Gordon component, which clarify the question on the hierarchy of the energy bounds of the Klein-Gordon component in our previous work. Furthermore, a uniform-in-time energy estimate is established for the wave component up to the top order, as well as a scattering result. These improvements indicate that the partial conformal symmetry of the Einstein-massive scalar system will play an important role in the global analysis.</p></abstract>

Evolution of Lifshitz metric anisotropies in Einstein–Proca theory under the Ricci–DeTurck flow

By starting from a Perelman entropy functional and considering the Ricci–DeTurck flow equations, we analyze the behavior of Einstein–Hilbert and Einstein–Proca theories with Lifshitz geometry as functions of a flow parameter. In the former case, we found one consistent fixed point that represents flat space-time as the flow parameter tends to infinity. Massive vector fields in the latter theory enrich the system under study and have the same fixed point achieved at the same rate as in the former case. The geometric flow is parametrized by the metric coefficients and represents a change in anisotropy of the geometry toward an isotropic flat space-time as the flow parameter evolves. Indeed, the flow of the Proca fields depends on certain coefficients that vanish when the flow parameter increases, rendering these fields constant. We have been able to write down the evolving Lifshitz metric solution with positive, but otherwise arbitrary, critical exponents relevant to geometries with spatially anisotropic holographic duals. We show that both the scalar curvature and matter contributions to the Ricci–DeTurck flow vanish under the flow at a fixed point consistent with flat space-time geometry. Thus, the behavior of the scalar curvature always increases, homogenizing the geometry along the flow. Moreover, the theory under study keeps positive-definite, but decreasing, the entropy functional along the Ricci–DeTurck flow.

Circuit Complexity in Z2 EEFT

Motivated by recent studies of circuit complexity in weakly interacting scalar field theory, we explore the computation of circuit complexity in Z2 Even Effective Field Theories (Z2 EEFTs). We consider a massive free field theory with higher-order Wilsonian operators such as ϕ4, ϕ6, and ϕ8. To facilitate our computation, we regularize the theory by putting it on a lattice. First, we consider a simple case of two oscillators and later generalize the results to N oscillators. This study was carried out for nearly Gaussian states. In our computation, the reference state is an approximately Gaussian unentangled state, and the corresponding target state, calculated from our theory, is an approximately Gaussian entangled state. We compute the complexity using the geometric approach developed by Nielsen, parameterizing the path-ordered unitary transformation and minimizing the geodesic in the space of unitaries. The contribution of higher-order operators to the circuit complexity in our theory is discussed. We also explore the dependency of complexity on other parameters in our theory for various cases.

Simplified models of vector SU(4) leptoquarks at the TeV

Assuming confirmation of the anomalies in semi-leptonic B-decays, their explanation in terms of the exchange of a massive vector leptoquark field, U_{mu }^a, of charge 2/3, appears to require the inclusion of U_{mu }^a in the vector multiplet of the adjoint of Pati–Salam SU(4), {mathcal {G}}_{mu }^A, as well as the introduction of vector-like fermions, F_j, in the fundamental of SU(4). We consider simplified models characterised by the nature of the SU(4) symmetry (global or local), by the number of vector-like fermions, and by the couplings of the Higgs boson to SM fermions (direct or induced by mixing with the vector-like fermions). In all cases, we implement a minimal breaking of a U(2)^n_f flavour symmetry, with a single motivated exception. We then perform a global fit including the main observables sensitive to exchanges of the {mathcal {G}}_{mu }^A at tree level and in loops dominated by logs insensitive to the UV completion.

Massive fermion between two parallel chiral plates

Abstract We study the system of a massive fermion field confined between two parallel plates, where the properties of both plates are discussed under chiral MIT boundary conditions. We investigate the effects of the chiral angle on the Casimir energy for a massive fermion field with the general momentum. We find that the Casimir energy as a function of the chiral angle is generally symmetric, and the attractive Casimir force in the chiral case is stronger than that in the nonchiral case. In addition, we investigate the approximate Casimir energy for light and heavy mass cases. The behavior of the discrete momentum and changes of spin orientation are also discussed.

Finite temperature charge and current densities around a cosmic string in AdS spacetime with compact dimension

For a massive scalar field with a general curvature coupling parameter, we investigate the finite temperature contributions to the Hadamard function and to the charge and current densities in the geometry of a magnetic flux carrying generalized cosmic string embedded in ($D+1$)-dimensional locally AdS spacetime with a compactified spatial dimension. For $D=4$, the geometry on the AdS boundary, in the context of the AdS/CFT duality, corresponds to a cosmic string as a linear defect, compactified along its axis. In contrast to the case of the Minkowski bulk, the upper bound on the chemical potential does not depend on the field mass and is completely determined by the length of compact dimension and by the enclosed magnetic flux. The only nonzero components correspond to the charge density, to the azimuthal current, and to the current along the compact dimension. They are periodic functions of magnetic fluxes with the period equal to the flux quantum. The charge density is an odd function and the currents are even functions of the chemical potential. At high temperatures the influence of the gravitational field and topology on the charge density is subdominant and the leading term in the corresponding expansion coincides with that for the charge density in the Minkowski spacetime. The current densities are topology-induced quantities and their behavior at high temperatures is completely different with the linear dependence on the temperature. At small temperatures and for chemical potentials smaller than the critical value, the thermal expectation values are exponentially suppressed for both massive and massless fields.

Constructing generic effective field theory for all masses and spins

We solve the long-standing problem of operator basis construction for fields with all masses and spins. Based on the on-shell method, we propose a novel method to systematically construct a complete set of lowest dimensional amplitude bases at any given dimension through semistandard Young tableaus of Lorentz subgroup $SU(2{)}_{r}$ and global symmetry $U(N)$ ($N$ is the number of external legs), which can be directly mapped into physical operator bases. We first construct a complete set of independent monomial bases whose dimension is not the lowest and a redundant set of bases that always contains a complete set of amplitude bases with the lowest dimension. Then we decompose the bases of the redundant set into the complete monomial bases from low to high dimension and eliminate the linear correlation bases. Finally, the bases with the lowest dimension can be picked up. We also propose a matrix projection method to construct the massive amplitude bases involving identical particles. The operator bases of a generic massive effective field theory can be efficiently constructed by the computer programs. A complete set of four-vector operators at dimensions up to six is presented.

Chiral Approach to Massive Higher Spins.

We propose a new, chiral description for massive higher-spin particles in four spacetime dimensions, which facilitates the introduction of consistent interactions. As proof of concept, we formulate three theories, in which higher-spin matter is coupled to electrodynamics, non-Abelian gauge theory, or gravity. The theories are chiral and have simple Lagrangians, resulting in Feynman rules analogous to those of massive scalars. Starting from these Feynman rules, we derive tree-level scattering amplitudes with two higher-spin matter particles and any number of positive-helicity photons, gluons, or gravitons. The amplitudes reproduce the arbitrary-multiplicity results that were obtained via on-shell recursion in a parity-conserving setting, and which chiral and nonchiral theories thus have in common. The presented theories are currently the only examples of consistent interacting field theories with massive higher-spin fields.

Supersymmetric quantum chiral higher spin gravity

We study quantum properties of supersymmetric mathcal{N} = 1 and mathcal{N} = 4 extensions of the four dimensional bosonic Chiral Higher Spin Gravities (HiSGRAs). We discuss the spectra, the classical actions and define the Feynman rules in mathcal{N} = 1 and mathcal{N} = 4 superspaces in the light-front gauge. Using these Feynman rules, we compute tree and one-loop amplitudes for these systems. A dimensional reduction to a system with mathcal{N} = 2 supersymmetry and with massive higher spin fields is performed and quantum properties of this system are discussed.

BRST formalism of Weyl conformal gravity

We present the BRST formalism of a Weyl conformal gravity in Weyl geometry. Choosing the extended de Donder gauge-fixing condition (or harmonic gauge condition) for the general coordinate invariance and the new scalar gauge-fixing for the Weyl invariance we find that there is a Poincar${\rm{\acute{e}}}$-like $\IOSp(10|10)$ supersymmetry as in a Weyl invariant scalar-tensor gravity in Riemann geometry. We also point out that there is a gravitational conformal symmetry in quantum gravity although there is a massive Weyl gauge field as a result of spontaneous symmetry breakdown of Weyl gauge symmetry and account for how the gravitational conformal symmetry is spontaneously broken to the Poincar\'e symmetry. The corresponding massless Nambu-Goldstone bosons are the graviton and the dilaton. We also prove the unitarity of the physical S-matrix on the basis of the BRST quartet mechanism.

Renormalization group and approximate error correction

In renormalization group (RG) flow, the low energy states form a code subspace that is approximately protected against the local short-distance errors. We motivate this connection with an example of spin-blocking RG in classical spin models. We consider the continuous multi-scale renormalization ansatz (cMERA) for massive free fields as a concrete example of real-space RG in quantum field theory (QFT) and show that the low-energy coherent states are approximately protected from the errors caused by the high-energy localized coherent operators. In holographic RG flows, we study the phase transition in the entanglement wedge of a single region and argue that one needs to define the price and the distance of the code with respect to the reconstructable wedge.

Geometric Proca with matter in metric-Palatini gravity

In the present work, we study linear, torsion-free metric-Palatini gravity, extended by the quadratics of the antisymmetric part of the Ricci tensor and extended also by the presence of the affine connection in the matter sector. We show that this extended metric-Palatini gravity reduces dynamically to the general relativity plus a geometrical massive vector field corresponding to non-metricity of the connection. We also show that this geometric Proca field couples to fermions universally. We derive static, spherically symmetric field equations of this Einstein-geometric Proca theory. We study possibility of black hole solutions by taking into account the presence of a dust distribution that couples to the geometric Proca. Our analytical and numerical analyses show that the presence of this dust worsens the possibility of horizon formation. We briefly discuss possible roles of this universally-coupled geometric Proca in the astrophysical and collider processes.

Shift symmetries for p-forms and mixed symmetry fields on (A)dS

Massive fields on (anti) de Sitter space realize extended shift symmetries at particular values of their masses. We find these symmetries for all bosonic p-forms and mixed symmetry fields, in arbitrary spacetime dimension. These shift symmetric fields correspond to the missing longitudinal modes of mixed symmetry partially massless fields where the top row of the Young tableau is activated.

Inclusive entrepreneurship: A call for a shared theoretical conversation about unconventional entrepreneurs

Entrepreneurship has the potential to be an inclusive space comprising many types of conventional as well as unconventional entrepreneurs. In this essay we will argue that when it comes to unconventional entrepreneurs—ranging from refugee entrepreneurs and entrepreneurs with a physical or cognitive disability, to elder entrepreneurs, former convict entrepreneurs, and many others—there are important questions we are not asking because we tend to look at each subgroup in isolation. Our central message is that looking for shared wisdom across various groups of unconventional entrepreneurs may facilitate a shared theoretical conversation that aids the transfer of knowledge, prevents silos and the unnecessary reinventing of the wheel, boosts the field's appeal and critical mass, and facilitates a broader exchange of ideas. To facilitate that conversation, we identify who unconventional entrepreneurs are; identify obstacles to a common theoretical conversation and how these obstacles could be overcome; outline a set of common theoretical themes that apply across various groups of unconventional entrepreneurs; and show how further theorizing unconventional entrepreneurs could challenge the community to reach beyond our existing knowledge horizons to develop pioneering entrepreneurship research.

Large spin-2 signals at the cosmological collider

We study the theory and phenomenology of massive spin-2 fields during the inflation with nonzero background chemical potential, and extend the cosmological collider physics to tensor modes. We identify a unique dimension-5 and parity-violating chemical potential operator for massive spin-2 fields, which leads to a ghost-free linear theory propagating one scalar mode and two tensor modes. The chemical potential greatly boosts the production of one tensor mode even for very heavy spin-2 particles, and thereby leads to large and distinct cosmological collider signals for massive spin-2 particles. The large signals show up at the tree-level in both the curvature trispectrum and the tensor-curvature mixed bispectrum.