String theories describe what cosmology was like before universe origin and what happened to begin universe. String theory allows more high-frequency gravity waves than inflation theory or ekpyrotic theory, so observing gravity waves can test string theories {pre-big-bang theory}. In fact, universe has few high-frequency gravity waves and some low-frequency gravity waves. Perhaps, universe has small-scale and large-scale strings. Perhaps, universe origins involve quantum-mechanical tunneling.
dilaton
Force strengths depend on string 11th-space-time-dimension length (dilaton). Short dilatons represent weak nuclear forces. Long dilatons represent strong nuclear forces. Dilaton lengths represent electromagnetism, and dilaton length variations change electromagnetic fields.
Before universe origin, dilatons are long, and forces are strong. At universe origin, dilatons are short, and forces are weak. Observing intergalactic magnetic-field changes is a test for dilatons and so can indicate universe-origin conditions.
axion
Magnetic-field photons can make dilaton-related strings (axion) that have less than one millionth electron mass, no charge, and zero average quantum field. Magnetic-field axions can make photons. Therefore, axions allow strong nuclear forces to maintain charge-parity (CP) symmetry between antiparticles and particles.
Cosmic-microwave-background temperature fluctuations are small, have Gaussian distribution, and have same amplitude for large space regions. Cosmic-microwave-background temperature fluctuations arise mostly from density differences and partly from gravity waves. However, string theories without axions allow no density differences. Axions determine large-scale universe temperature fluctuations [Adams, 2002].
Smaller strings have higher vibration frequencies and so higher masses. The smallest strings have highest mass and smallest size and so can be like black holes {string hole}.
Because many D-branes occupy high-dimensional space and D-branes attract each other, D-brane pairs collided, making universes' origins {ekpyrotic scenario} {conflagration scenario}. As D-branes mutually move closer, space contracts. If D-branes mutually move farther, space expands. Adjacent D-branes can repeatedly collide and separate, in contraction and expansion cycles.
Perhaps, before universe origin, time reversal and T-duality caused universe contraction, with matter accreting into string holes (pre-big-bang theory) {pre-big-bang scenario}. As space filled with string holes, universe was like string-hole gas. String-hole gas had smooth string-size distribution (unlike chaotic conditions at black-hole surfaces). Smooth size distribution allowed large string holes to form. Inside the largest string hole, matter reached maximum allowable density and temperature, causing an emission-singularity white-hole.
5-Astronomy-Universe-Cosmology-Theories
Outline of Knowledge Database Home Page
Description of Outline of Knowledge Database
Date Modified: 2022.0225