Unified field theory of basic forces and elementary particles with gravitational origin of gauge symmetry in hyper-spacetime

The theory of general relativity(GR)[1,2]has successfully built a relation between the geometry of spacetime and the energymomentum tensor of matter.Einstein has extensively quested for potential unified models of electromagnetism and gravity at a classical unified field theory and spent the last two decades of his

Taiji data challenge for exploring gravitational wave universe

The direct observation of gravitational waves(GWs)opens a new window for exploring new physics from quanta to cosmos and provides a new tool for probing the evolution of universe.GWs detection in space covers a broad spectrum ranging over more than four orders of magnitude and enables us to study rich physical and astronomical phenomena.Taiji is a proposed space-based gravitational wave(GW)detection mission that will be launched in the 2030s.Taiji will be exposed to numerous overlapping and persistent GW signals buried in the foreground and background,posing various data analysis challenges.In order to empower potential scientific discoveries,the Mock Laser Interferometer Space Antenna(LISA)data challenge and the LISA data challenge(LDC)were developed.While LDC provides a baseline framework,the first LDC needs to be updated with more realistic simulations and adjusted detector responses for Taiji’s constellation.In this paper,we review the scientific objectives and the roadmap for Taiji,as well as the technical difficulties in data analysis and the data generation strategy,and present the associated data challenges.In contrast to LDC,we utilize second-order Keplerian orbit and second-generation time delay interferometry techniques.Additionally,we employ a new model for the extreme-mass-ratio inspiral waveform and stochastic GW background spectrum,which enables us to test general relativity and measure the non-Gaussianity of curvature perturbations.Furthermore,we present a comprehensive showcase of parameter estimation using a toy dataset.This showcase not only demonstrates the scientific potential of the Taiji data challenge(TDC)but also serves to validate the effectiveness of the pipeline.As the first data challenge for Taiji,we aim to build an open ground for data analysis related to Taiji sources and sciences.More details can be found on the official website(taiji-tdc.ictp-ap.org).

Maximal symmetry and mass generation of Dirac fermions and gravitational gauge field theory in six-dimensional spacetime

The relativistic Dirac equation in four-dimensional spacetime reveals a coherent relation between the dimensions of spacetime and the degrees of freedom of fermionic spinors. A massless Dirac fermion generates new symmetries corresponding to chirality spin and charge spin as well as conformal scaling transformations. With the introduction of intrinsic W-parity, a massless Dirac fermion can be treated as a Majorana-type or Weyl-type spinor in a six-dimensional spacetime that reflects the intrinsic quantum numbers of chirality spin. A generalized Dirac equation is obtained in the six-dimensional spacetime with a maximal symmetry. Based on the framework of gravitational quantum field theory proposed in Ref. [1] with the postulate of gauge invariance and coordinate independence, we arrive at a maximally symmetric gravitational gauge field theory for the massless Dirac fermion in six-dimensional spacetime. Such a theory is governed by the local spin gauge symmetry SP（1,5） and the global Poincar′e symmetry P（1,5）= SO（1,5） P^1,5 as well as the charge spin gauge symmetry SU（2）. The theory leads to the prediction of doubly electrically charged bosons. A scalar field and conformal scaling gauge field are introduced to maintain both global and local conformal scaling symmetries. A generalized gravitational Dirac equation for the massless Dirac fermion is derived in the six-dimensional spacetime. The equations of motion for gauge fields are obtained with conserved currents in the presence of gravitational effects. The dynamics of the gauge-type gravifield as a Goldstone-like boson is shown to be governed by a conserved energy-momentum tensor, and its symmetric part provides a generalized Einstein equation of gravity. An alternative geometrical symmetry breaking mechanism for the mass generation of Dirac fermions is demonstrated.

Equation of state and chiral transition in soft-wall AdS/QCD with a more realistic gravitational background

We construct an improved soft-wall AdS/QCD model with a cubic coupling term of the dilaton and the bulk scalar field.The background fields in this model are solved by the Einstein-dilaton system with a nontrivial dilaton potential,which has been shown to reproduce the equation of state from the lattice QCD with two flavors.The chiral transition behaviors are investigated in the improved soft-wall AdS/QCD model with the solved gravitational background,and the crossover transition can be realized.Our study provides the possibility to address the deconfining and chiral phase transitions simultaneously in the bottom-up holographic framework.