Thu·Dec 9, 2021Thursday·December 9, 2021

1. 01*

   $x$-dependence reconstruction of pion and kaon PDFs from Mellin moments

   Constantia Alexandrou🇨🇾 · Simone Bacchio🇨🇾 · Ian Cloët🇺🇸 · Martha Constantinou🇺🇸 · Kyriakos Hadjiyiannakou🇨🇾 · Giannis Koutsou🇨🇾 · Colin Lauer🇺🇸

   We present a calculation of the connected-diagram contributions to the first three non-trivial Mellin moments for the pion and kaon, extracted using local operators with up to 3 covariant derivatives. We use one ensemble of gauge configurations with two degenerate light, a strange and a charm quark ($N_f$=2+1+1) of maximally twisted mass fermions with clover improvement. The ensemble has a pion mass $\sim$260 MeV, and a kaon mass $\sim$530 MeV. We reconstruct the $x$-dependence of the PDFs via fits to our results, and find that our lattice data favor a $(1-x{)}^2$-behavior in the large-$x$ region for both the pion and kaon PDFs. We integrate the reconstructed PDFs to extract the higher moments, $⟨x^n⟩$, with $4\le n\le 6$. Finally, we compare the pion and kaon PDFs, as well as the ratios of their Mellin moments, to address the effect of SU(3) flavor symmetry breaking.

   hep-lathep-phnucl-thPoS(2022)·2 citations
2. 02*

   Pion and kaon form factors using twisted-mass fermions

   Constantia Alexandrou🇨🇾 · Simone Bacchio🇨🇾 · Ian Cloët🇺🇸 · Martha Constantinou🇺🇸 · Joseph Delmar🇺🇸 · Kyriakos Hadjiyiannakou🇨🇾 · Giannis Koutsou🇨🇾 · Colin Lauer🇺🇸 · Alejandro Vaquero Avilés-Casco🇺🇸

   We present a calculation of the scalar, vector and tensor pion and kaon form factors using one ensemble of two degenerate light, a strange and a charm quark ($N_f=2+1+1$) of maximally twisted mass fermions with clover improvement. The quark masses are chosen so that they produce a pion mass of about 265 MeV, and a kaon mass of 530 MeV. The lattice spacing of the ensemble is 0.093 fm and the lattice has a spatial extent of 3 fm. We use a rest frame, as well as a boosted frame to obtain the form factors for a wider and denser set of four-vector momentum transfer squared, $Q^2$. To assess and eliminate excited-states contamination, we analyze several values of the source-sink time separation within the range of 1.12 - 2.23 fm (1.12 - 1.67 fm) for the rest (boosted) frame. The $Q^2$ dependence of the form factors is parametrized using a monopole fit, which leads to the extraction of the corresponding radius, and the tensor anomalous magnetic moment for the tensor form factor. The results for these parametrizations are compared for the pion and kaon to assess the level of the SU(3) flavor symmetry breaking.

   hep-lathep-phnucl-thPoS(2022)·1 citation
3. 03*

   A lattice QCD determination of the neutron electric dipole moment at the physical point

   Constantia Alexandrou🇨🇾 · Andreas Athenodorou🇨🇾 · Kyriakos Hadjiannakou🇨🇾 · Antonino Todaro🇨🇾

   Results are presented on the neutron electric dipole moment using an ensemble of $N_f=2+1+1$ twisted mass clover-improved fermions with lattice spacing of $a\simeq 0.08$ fm and physical pion mass ($m_{\pi }\simeq 139$ MeV). The approach followed in this work is to compute the $CP$-odd electromagnetic form factor $F_3(Q^2\to 0)$ at zero momentum transfer by expanding the action to leading order in $\theta$. This gives rise to correlation functions that involve the topological charge, for which we employ a fermionic definition by means of spectral projectors. We include a comparison between the results using the fermionic and the gluonic definition, where for the latter we employ the gradient flow. We show that using spectral projectors leads to half the statistical uncertainty on the evaluation of $F_3(0)$. Using the fermionic definition, we find a value of $|d_N|=0.0009(24)\theta \mathrm{e}\cdot \mathrm{fm}$.

   hep-latPoS(2022)·1 citation
4. 04*

   Elastic $\pi -N$ scattering in the $I=3/2$ channel

   Constantia Alexandrou🇨🇾 · Kyriakos Hadjiannakou🇨🇾 · Giannis Koutsou🇨🇾 · Srijit Paul🇩🇪 · Ferenc Pittler🇨🇾 · Marcus Petschlies🇩🇪 · Antonino Todaro🇨🇾

   We present our study of $\pi -N$ scattering in the iso-spin $I=3/2$ channel for the first time at the physical point. The calculation is performed using $N_f=2+1+1$ flavors of twisted mass fermions with clover improvement at physical pion mass. We compute energy levels for the rest frame and moving frames up to a total momentum of $|\vec{P}|=\sqrt{3}\frac{2\pi }{L}$, and for all the relevant ireducible representations of the lattice symmetry groups. We perform a phase-shift analysis including $s(\ell =0)$ and $p(\ell =1)$ wave phase shifts assuming a Breit-Wigner form and determine the parameters of the $\Delta$ resonance.

   hep-latPoS(2022)·9 citations
5. 05*

   The upper right corner of the Columbia plot with staggered fermions

   Ruben Kara🇩🇪 · Szabolcs Borsanyi🇩🇪 · Zoltan Fodor🇩🇪 · Jana N. Guenther🇩🇪 · Paolo Parotto🇩🇪 · Attila Pasztor🇭🇺 · Denes Sexty🇦🇹

   QCD with heavy dynamical quarks exhibits a first order thermal transition which is driven by the spontaneous breaking of the global ${\mathcal{Z}}_3$ center symmetry. Decreasing the quark masses weakens the transition until the corresponding latent heat vanishes at the critical mass. We explore the heavy mass region with three flavors of staggered quarks and analyze the Polyakov loop and its moments in a finite volume scaling study. We calculate the heavy critical mass in the three flavor theory in the infinite volume limit for $N_t=8$.

   hep-latPoS(2022)·11 citations
6. 06*

   A comparison of spectral reconstruction methods applied to non-zero temperature NRQCD meson correlation functions

   Thomas Spriggs🇬🇧 · Gert Aarts🇬🇧 · Chris Allton🇬🇧 · Timothy Burns🇬🇧 · Rachel Horohan D'Arcy🇮🇪 · Benjamin Jäger🇩🇰 · Seyong Kim🇰🇷 · Maria-Paola Lombardo🇮🇹 · Sam Offler🇬🇧 · Ben Page🇬🇧 · Sinead M. Ryan🇮🇪 · Jon-Ivar Skullerud🇮🇪

   We present results from the fastsum collaboration's programme to determine the spectrum of the bottomonium system as a function of temperature. Three different methods of extracting spectral information are discussed: a Maximum Likelihood approach using a Gaussian spectral function for the ground state, the Backus Gilbert method, and the Kernel Ridge Regression machine learning procedure. We employ the fastsum anisotropic lattices with 2+1 dynamical quark flavours, with temperatures ranging from 47 to 375 MeV.

   hep-latEPJ Web Conf.(2022)·14 citations
7. 07*

   Search for continuous phase transitions in 5D pure SU(2) lattice gauge theory

   José Matos🇵🇹

   The Renormalization Group (RG) is one of the central and modern techniques in quantum field theory. Indeed, quantum field theories can be understood as flows between fixed points of the RG flow, which represent Conformal Field Theories (CFT's). Hence, the search and classification of yet unknown non-trivial CFT's is a legitimate endeavor. Analytical considerations point to the existence of such a fixed point in pure SU(2) Yang-Mills fields in 5D. This issue has already been addressed, although inconclusively. We search for this putative fixed point using lattice Monte Carlo methods. An extended discussion can be found in [1].

   hep-lathep-thPoS(2022)·0 citations
8. 08*

   Patterns of flavour symmetry breaking in hadron matrix elements involving u, d and s quarks

   J.M. Bickerton🇦🇺 · A.N. Cooke🇬🇧 · R. Horsley🇬🇧 · Y. Nakamura🇯🇵 · H. Perlt🇩🇪 · D. Pleiter🇸🇪 · P.E.L. Rakow🇬🇧 · G. Schierholz🇩🇪 · H. Stüben · R.D. Young🇦🇺 · J.M. Zanotti🇦🇺

   Using an SU(3)-flavour symmetry breaking expansion between the strange and light quark masses, we determine how this constrains the extrapolation of baryon octet matrix elements and form factors. In particular we can construct certain combinations, which fan out from the symmetric point (when all the quark masses are degenerate) to the point where the light and strange quarks take their physical values. As a further example we consider the vector amplitude at zero momentum transfer for flavour changing currents.

   hep-lathep-phPoS(2022)·3 citations
9. 09*

   Quantum Simulation of Chiral Phase Transitions

   Alexander M. Czajka🇺🇸 · Zhong-Bo Kang🇺🇸 · Henry Ma🇺🇸 · Fanyi Zhao🇺🇸

   The Nambu-Jona-Lasinio (NJL) model has been widely studied for investigating the chiral phase structure of strongly interacting matter. The study of the thermodynamics of field theories within the framework of Lattice Field Theory is limited by the sign problem, which prevents Monte Carlo evaluation of the functional integral at a finite chemical potential. Using the quantum imaginary time evolution (QITE) algorithm, we construct a quantum simulation for the $(1+1)$ dimensional NJL model at finite temperature and finite chemical potential. We observe consistency among digital quantum simulation, exact diagonalization, and analytical solution, indicating further applications of quantum computing in simulating QCD thermodynamics.

   ↳ hep-phhep-exhep-latnucl-th+1JHEP(2022)·40 citations
10. 10*

    On propagation in Loop Quantum Gravity

    Thomas Thiemann🇩🇪 · Madhavan Varadarajan🇮🇳

    A rigorous implementation of the Wheeler-Dewitt equations was derived in the context of Loop Quantum Gravity (LQG) and was coined Quantum Spin Dynamics (QSD). The Hamiltonian constraint of QSD was criticised as being too local and to prevent "propagation" in canonical LQG. That criticism was based on an algorithm developed for QSD for generating solutions to the Wheeler-DeWitt equations. The fine details of that algorithm could not be worked out because the QSD Hamiltonian constraint makes crucial use of the volume operator which cannot be diagonalised analytically. In this paper, we consider the U(1)${}^3$ model for Euclidean vacuum LQG which consists in replacing the structure group SU(2) by U(1)${}^3$ and otherwise keeps all properties of the SU(2) theory intact. This enables analytical calculations and the fine details of the algorithm {\it can} be worked out. By considering one of the simplest possible non-trivial class of solutions based on very small graphs, we show that 1. an infinite number of solutions {\it exist} which are 2. generically {\it not normalisable} with respect to the inner product on the space of spatially diffeomorphism invariant distributions and 3. generically display {\it propagation}. Due to the closeness of the U(1)${}^3$ model to Euclidean LQG, it is extremely likely that all three properties hold also in the SU(2) case and even more so in physical Lorentzian LQG. These arguments can in principle be made water tight using modern numerical (e.g. ML or QC) methods combined with the techniques developed in this paper which we reserve for future work.

    ↳ gr-qchep-lathep-thmath-ph+1Universe(2022)·10 citations
11. 11*

    Achieving the quantum field theory limit in far-from-equilibrium quantum link models

    Jad C. Halimeh🇮🇹 · Maarten Van Damme🇧🇪 · Torsten V. Zache🇦🇹 · Debasish Banerjee🇮🇳 · Philipp Hauke🇮🇹

    Realizations of gauge theories in setups of quantum synthetic matter open up the possibility of probing salient exotic phenomena in condensed matter and high-energy physics, along with potential applications in quantum information and science technologies. In light of the impressive ongoing efforts to achieve such realizations, a fundamental question regarding quantum link model regularizations of lattice gauge theories is how faithfully they capture the quantum field theory limit of gauge theories. Recent work [Zache, Van Damme, Halimeh, Hauke, and Banerjee, at https://journals.aps.org/prd/abstract/10.1103/PhysRevD.106.L091502 has shown through analytic derivations, exact diagonalization, and infinite matrix product state calculations that the low-energy physics of $1+1$D $\mathrm{U}(1)$ quantum link models approaches the quantum field theory limit already at small link spin length $S$. Here, we show that the approach to this limit also lends itself to the far-from-equilibrium quench dynamics of lattice gauge theories, as demonstrated by our numerical simulations of the Loschmidt return rate and the chiral condensate in infinite matrix product states, which work directly in the thermodynamic limit. Similar to our findings in equilibrium that show a distinct behavior between half-integer and integer link spin lengths, we find that criticality emerging in the Loschmidt return rate is fundamentally different between half-integer and integer spin quantum link models in the regime of strong electric-field coupling. Our results further affirm that state-of-the-art finite-size ultracold-atom and NISQ-device implementations of quantum link lattice gauge theories have the real potential to simulate their quantum field theory limit even in the far-from-equilibrium regime.

    ↳ cond-mat.quant-gascond-mat.str-elhep-latquant-phQuantum(2022)·34 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.