( ( ( ( ( ( The field ) ( contains ( a ( certain ( energy density ) ) ) ) ) , ) but ) ( ( unlike ( ( the density ) ( of ( ( the ( matter ( or ( radiation present ) ) ) ) ( in ( ( ( the ( late universe ) ) , ) ( which ( ( decrease over ) time ) ) ) ) ) ) ) ) ( , ( ( ( the density ) ( of ( the ( inflationary field ) ) ) ) ( ( remains ( roughly constant ) ) ( as ( space expands ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (DT The) (NN field)) (VP (VBZ contains) (NP (DT a) (JJ certain) (NN energy) (NN density)))) (, ,) (CC but) (S (PP (IN unlike) (NP (NP (DT the) (NN density)) (PP (IN of) (NP (NP (DT the) (NN matter) (CC or) (NN radiation) (NN present)) (PP (IN in) (NP (NP (DT the) (JJ late) (NN universe)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VB decrease) (PRT (RP over)) (NP (NN time))))))))))) (, ,) (NP (NP (DT the) (NN density)) (PP (IN of) (NP (DT the) (JJ inflationary) (NN field)))) (VP (VBZ remains) (ADJP (RB roughly) (JJ constant)) (SBAR (IN as) (S (NP (NN space)) (VP (VBZ expands)))))) (. .)))
The field contains a certain energy density, but unlike the density of the matter or radiation present in the late universe, which decrease over time, the density of the inflationary field remains roughly constant as space expands.
(ROOT (S (NP (NNP Density)) (VP (VBZ describes) (SBAR (WHADJP (WRB how) (JJ much)) (S (NP (NN matter)) (VP (VBZ is) (PP (IN in) (NP (NP (DT a) (JJ certain) (NN amount)) (PP (IN of) (NP (NN space))))))))) (. .)))