Diablo – Is the hardcore auction house separate from the normal auction house

Since it seems that this question hasn't received a comprehensive answer, here's my best attempt at a full list of all of the differences between Hardcore and Normal (Softcore) modes:

In Hardcore, you:

• Will lose the ability to play your character permanently upon your character's death. You will also have the option to archive a profile of your dead character (playtime, level, appearance, cause of death) in your "Hall of Fallen Heroes" for posterity.

• Will lose all of your character's equipped items, all items in your character's inventory, and all items equipped on your Followers when your character dies. Any items in your Stash, as well as your Gold and Blacksmith/Jeweler status, are retained (and are shared between all of your present and future Hardcore characters).

• Have a separate stash, gold pool, and Blacksmith/Jeweler than your Normal mode characters. There is a dedicated Hardcore-only Auction House, and Blizzard has stated that there will not be a Real-Money Hardcore Auction House. Hardcore mode is an entirely separate ecosystem than Normal mode.

• Cannot trade items back and forth between Hardcore and Normal characters.

• Cannot join a game with non-Hardcore characters (and they cannot join yours).

• Can earn special Achievements for killing bosses and reaching level thresholds on a Hardcore character. Many of these Achievements have special rewards, such as banner designs.

Additionally:

• There are no innate differences in the strength of a Hardcore character versus a Normal character.

• So far, there is no evidence of any difference in the strength of monsters, quality of loot drops, or anything else that affects gameplay aside from the fact that your character cannot be resurrected upon death.

Unfortunately the Auction Houses are only accessible from the menus, not anywhere in the game via your character.

The Auction House is a new trading system introduced in Diablo III which shares many features with similar systems found in other games, such as World of Warcraft. Accessed through Battle.net and not from in-game, the auction house allows all players within a region (US, EU etc.) to buy and sell items easily and conveniently between each other. Almost all items other than quest items can be sold between players, and everything is run by the players: Blizzard will not sell any items.

http://www.diablowiki.com/Auction_House

Edit: Blizzard has since confirmed that this is a deliberate design decision (Source).

Contrary to MMOs like World of Warcraft Diablo III is not a game where the auction house meta-game is part of the in-game story.