Nechť A je Banachova algebra bez jednotky s regulární normou. Je známo, že existuje minimální a maximální rozšíření této normy na unitizaci A. Je ukázáno, že nejlepší odhad podílu těchto dvou norem je 3. (cs)
Let A be a Banach algebra without unit with a regular norm. It is known that there are a minimal and a maximal extension of this norm to the unitization of A. It is shown that the best upper bound for the ratio of these two extensions is equal to 3.
Let A be a Banach algebra without unit with a regular norm. It is known that there are a minimal and a maximal extension of this norm to the unitization of A. It is shown that the best upper bound for the ratio of these two extensions is equal to 3. (en)