Some debt securities saw record improvement Monday, as traders bet that rival ’s pending breakup could result in a combination of the two broadband heavyweights. The US junk-bond market’s biggest gainers were largely notes of Charter. Its note due in 2033 rose as much as 4.125 cents on the dollar, the most since the bond was sold in , and approached face value for the first time in two months, according to Trace . The Charter debt against default for five years fell as much as 0.66 percentage ...