Nuclear Theory·nucl-th

Monday·October 30, 2023

9 papers—5 primary·4 cross-listed

06
Improved Standard-Model prediction for $K_{L} \to ℓ^{+} ℓ^{-}$
Martin Hoferichter🇨🇭 · Bai-Long Hoid🇨🇭 · Jacobo Ruiz de Elvira🇪🇸
We present a comprehensive calculation of the $K_{L} \to γ^{*} γ^{*}$ form factor in dispersion theory, using input from the leptonic decays $K_{L} \to ℓ^{+} ℓ^{-} γ$ , $K_{L} \to ℓ_{1}^{+} ℓ_{1}^{-} ℓ_{2}^{+} ℓ_{2}^{-}$ , the hadronic mode $K_{L} \to π^{+} π^{-} γ$ , the normalization $K_{L} \to γ γ$ , and the matching to asymptotic constraints. As key result we obtain an improved determination of the long-distance contribution to $K_{L} \to ℓ^{+} ℓ^{-}$ , leading to the Standard-Model predictions $Br [K_{L} \to μ^{+} μ^{-}] = 7.4 4_{- 0.34}^{+ 0.41} \times 1 0^{- 9}$ , $Br [K_{L} \to e^{+} e^{-}] = 8.46 (37) \times 1 0^{- 12}$ , and more stringent limits on physics beyond the Standard Model. We provide a detailed breakdown of the current uncertainty, and delineate how future experiments and the interplay with lattice QCD could help further improve the precision.
↳ hep-phhep-exhep-latnucl-thJHEP(2024)·21 citations
07
Quark stars in $D_{3}$ - $D_{7}$ holographic model
M. Aleixo🇧🇷 · C.H. Lenzi🇧🇷 · W. de Paula🇧🇷 · R. da Rocha🇧🇷
This work investigates static and dynamical quark star properties within a $D_{3} - D_{7}$ holographic model. We solve the Tolman-Oppenheimer-Volkoff equations for the quark matter equation of state obtained from the brane configuration. We determine the mass-radius diagram for a range of model parameters and compare with recent NICER observational data for the pulsars PSR J $0030 + 0451$ and PSR J $0740 + 6620$ . Motivated by the GW170817 event detected by the LIGO-Virgo collaboration, we also calculate the tidal deformability parameter obtained for each component of the binary star system. We show that quark stars composed of flavor-independent quark matter derived from the $D_{3} - D_{7}$ holographic model are not able to satisfy simultaneously the LIGO-Virgo and NICER astrophysical bounds.
↳ hep-phastro-ph.HEnucl-thEPJC(2024)·5 citations
08
Symmetry breaking and restoration for many-body problems treated on quantum computers
Andres Ruiz🇫🇷
This thesis explores the application of the Symmetry-Breaking/Symmetry-Restoration methodology on quantum computers to better approximate a Hamiltonian's ground state energy within a variational framework in many-body physics. This involves intentionally breaking and restoring the symmetries of the wave function ansatz at different stages of the variational search for the ground state. The Variational Quantum Eigensolver (VQE) is utilized for the variational component together with an ansatz inspired by the Bardeen-Cooper-Schrieffer (BCS) theory. The applications were demonstrated using the pairing and Hubbard Hamiltonians. Two approaches were identified with the VQE method: varying the symmetry-breaking ansatz parameters before or after symmetry restoration, termed Quantum Projection After Variation and Quantum Variation After Projection, respectively. The main contribution of this thesis was the development of a variety of symmetry restoration techniques based on the principles of the Quantum Phase Estimation algorithm, the notion of a Quantum "Oracle," and the Classical Shadow formalism. In the final part, hybrid quantum-classical techniques were introduced to extract an approximation of the low-lying spectrum of a Hamiltonian. Assuming accurate Hamiltonian moment extraction from their generating function with a quantum computer, two methods were presented for spectral analysis: the t-expansion method and the Krylov method, which provides, in particular, information about the evolution of the survival probability. Furthermore, the Quantum Krylov method was introduced, offering similar insights without the need to estimate Hamiltonian moments, a task that can be difficult on near-term quantum computers.
↳ quant-phcond-mat.str-elnucl-th0 citations
09
Mass gaps of a $Z_{3}$ gauge theory with three fermion flavors in 1 + 1 dimensions
Adrien Florio🇺🇸 · Andreas Weichselbaum🇺🇸 · Semeon Valgushev🇺🇸 · Robert D. Pisarski🇺🇸
We consider a $Z_{3}$ gauge theory coupled to three degenerate massive flavors of fermions, which we term "QZD". The spectrum can be computed in $1 + 1$ dimensions using tensor networks. In weak coupling the spectrum is that of the expected mesons and baryons, although the corrections in weak coupling are nontrivial, analogous to those of non-relativistic QED in 1+1 dimensions. In strong coupling, besides the usual baryon, the singlet meson is a baryon anti-baryon state. For two special values of the coupling constant, the lightest baryon is degenerate with the lightest octet meson, and the lightest singlet meson, respectively.
↳ hep-thcond-mat.str-elhep-lathep-ph+1PRD(2024)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE

Improved Standard-Model prediction for KL​→ℓ+ℓ−

Quark stars in D3​-D7​ holographic model

Symmetry breaking and restoration for many-body problems treated on quantum computers

Mass gaps of a Z3​ gauge theory with three fermion flavors in 1 + 1 dimensions

Affiliations

Improved Standard-Model prediction for $K_{L} \to ℓ^{+} ℓ^{-}$

Quark stars in $D_{3}$ - $D_{7}$ holographic model

Mass gaps of a $Z_{3}$ gauge theory with three fermion flavors in 1 + 1 dimensions