We present an analytical expression for the static many-body local field factor G+(q) of a homogeneous two-dimensional electron gas, which reproduces Diffusion Monte Carlo data and embodies the exact asymptotic behaviors at both small and large wave number q. This allows us to also provide a closed-form expression for the exchange and correlation kernel Kxc(r), which represents a key input for density functional studies of inhomogeneous systems.PACS number: 71.10. Ca, 71.15.Mb The static charge-charge response function χ C (q) of a paramagnetic electron gas (EG) can be written in terms of the Lindhard function χ 0 (q) by means of the spin-symmetric many-body local field G + (q) through the relationshipThus G + (q) is a fundamental quantity for the determination of many properties of a general electron system. By definition G + (q) is meant to represent the effects of the exchange and correlation hole surrounding each electron in the fluid and is therefore a key input in the density functional theory (DFT) of the inhomogeneous electron gas 1 and in studies of quasiparticle properties (such as the effective mass and the effective Landè g-factor) in the electronic Fermi liquid 2 . For what concerns DFT calculations, a common approximation to the unknown exchange-correlation energy functional E xc [n] appeals to its second functional derivative,wheren is the average local density of the EG. The local field factor and the exchange-correlation kernel are simply related in Fourier transform bywhere d is the dimensionality of the system and v q is the Fourier transform of the Coulomb potential e 2 /r. In what follows we shall only consider the case of two spatial dimensions, with d = 2 and v q = 2πe 2 /q. The corresponding three-dimensional case was discussed in Ref. [3]. A number of exact asymptotic properties of the static local field factor in two dimensions are readily proven. In particular,withwhere k F = √ 2πn = √ 2/r s a B is the Fermi wave number, r s = πna 2 B is the usual EG density parameter with a B the Bohr radius, κ 0 = πr 4 s /2 is the compressibility of the ideal gas in units of a 2 B /Ryd, while κ is the compressibility of the interacting system. By making use of the thermodynamic definition of κ we can write1 where ǫ c (r s ) is the correlation energy per particle. Once this function is known, it is possible to calculate A + . For the present purpose ǫ c (r s ) can be taken from the Monte Carlo data of Ref. [4]. The asymptotic behavior of G + (q) at large q is also known exactly 5,6 :where C + is proportional to the difference in kinetic energy between the interacting and the ideal gas,Moreover B + = 1 − g(0), g(0) being the value of the pair-correlation function at the origin. For g(0) we use the simple expressionwhich has been derived 7 by an interpolation between the result of a low-r s expansion, including the second order direct and exchange contributions to the energy in the paramagnetic state, and the result of a partial-wave phase-shift analysis near Wigner crystallization. This interpolatio...