Questions on DankSharding

Hi All,

Can someone help me answer the following questions:

1. If there will be only one proposer in the Proposer/builder split, won't that make it more centralized?
2. What is meant by the term "bid" in this sentence: " a specialized class of actors called block builders bid on the right to choose the contents of the slot, and the proposer need only select the valid header with the highest bid "
3. And to clarify, the "header" is a data attribute, right?
4. What role will the validators play in the dank sharding process? How I understand it currently, a layer 2 rollup will process transactions and pass a proof down to layer 1. The proofs (and therefore, the stripped transaction data) will be bundled into blobs by builders. The builders will pass them to a single proposer who will order them appropriately and do they then go through the validator selection process in which a validator is then selected and comes to consensus on the validity of the transactions?

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Thank you much!