This short paper summarizes the results we presented at the LEHTSC2007 conference. Recent doping and temperature dependence of angle-resolved photoemission data of underdoped superconducting cuprate Bi2Sr2CaCu2O8 (Bi2212) have revealed the presence of two energy scales exhibiting distinct behaviours [1,2]. One, which dominates the antinodal region, increases with underdoping and does not show obvious temperature dependence across Tc. This is a behaviour known for more than a decade and considered as the general gap behaviour in the underdoped regime. The other, which dominates the near-nodal regime, does not increase with less doping and opens near Tc via a BCS-like temperature dependence. This is a behaviour not previously observed in the single particle spectra. We propose a momentum space picture of these two energy scales or energy gaps that could resolve the seemingly contradictory gap measurements among different experimental techniques. Our results have also further constrained the theory for high-Tc superconducting cuprates.

The AR5 was published in 2014. The Paris Agreement and the 17 Sustainable Development Goals (SDGs) were adopted in 2015. An increasing number of countries have since announced ambitions to be carbon neutral by 2045–2060. The COVID-19 pandemic shocked the global economy in 2020 and motivated economic stimulus with demands for green recovery and concerns for economic security. All this has created a new context and a growing recognition that all industry, including the energy and emissions intensive industries, need to reach net zero GHG emissions. There is an ongoing mind shift around the opportunities to do so, with electrification and hydrogen emerging among key mitigation options as a result of renewable electricity costs falling rapidly. On the demand side there has been renewed attention to end-use demand, material efficiency, and more and better-quality recycling measures. This chapter takes its starting point in this new context and emphasises the need for deploying innovative processes and practices in order to limit the global warming to 1.5°C or 2°C (IPCC 2018a).

This report is based on a ten-week program on "Gluons and the quark sea at high-energies", which took place at the Institute for Nuclear Theory in Seattle in Fall 2010. The principal aim of the program was to develop and sharpen the science case for an Electron-Ion Collider (EIC), a facility that will be able to collide electrons and positrons with polarized protons and with light to heavy nuclei at high energies, offering unprecedented possibilities for in-depth studies of quantum chromodynamics. This report is organized around four major themes: i) the spin and flavor structure of the proton, ii) three-dimensional structure of nucleons and nuclei in momentum and configuration space, iii) QCD matter in nuclei, and iv) Electroweak physics and the search for physics beyond the Standard Model. Beginning with an executive summary, the report contains tables of key measurements, chapter overviews for each of the major scientific themes, and detailed individual contributions on various aspects of the scientific opportunities presented by an EIC.