Managerless Arsenal's season plummeted to a new low as they were beaten at home by Brighton in interim manager Freddie Ljungberg's first home match in charge.Alexandre Lacazette marked his 100th Arsenal appearance by heading his side level after Adam Webster had given the visitors a first-half lead.With the score 1-1, there was frustration for Ljungberg and Arsenal when David Luiz thought he had scored the winner with a volley but it was correctly ruled out following a VAR check for offside.Neal Maupay headed Brighton's winner from Aaron Mooy's cross to leave Arsenal 10th in the table - 10 points off a Champions League spot.