Soundness of the answer-reduced game: indifference #
The paper's second perturbation (II:10644): the oracle's polynomials are, with high probability,
block-local โ each codeword's polynomial involves only the variables of its slot's block
(Good), which is what reading them as a PCP (Pcp.ofPolys) needs.
The paper derives it from the indifference check (II:10465, check 3) through the low-degree test's
conclusions at lines. The seeded test's soundness in the model gives conclusions at points only
(LIDT.Simul.SoundIn), and the argument here uses points only, with two points of one
axis-parallel line:
- the question of type
ALinethe registers of a vectorwcarry is the same at every point of its line: moving the vector's point along its own direction (shiftW) keeps it (ldq_aline_shiftW); - at the type pair
(O, ALine), (O, Point), the low-degree check and the indifference check make the point values, in the codewords whose blocks miss the line's direction, the constant coefficients of the line answer's polynomials (kv_eq_pv_of_arDt); - so, through the line answer, Bob's point values at two points
u, u + s eแตขof one line agree with Alice's polynomials evaluated atu(a disagreement triangle), and Alice's polynomials evaluated atuand atu + s eแตขagree in those codewords (sum_ite_ne_le_dis_add); - a polynomial with a monomial in a variable outside its block changes value along most steps in
that direction (
MIPRE.LIDT.card_shift_ne_ge), on a1/Mfraction of the lines: so the weight of the outcomes that are not block-local is at most2Mtimes the errors (sum_badGood_le).
sum_ite_read_le and its mirror move an event between the two players' measurements, at the cost
of their disagreement.
Moving events between the players #
Two readings of the first player's outcome against one of the second's: the weight of the outcomes the two readings tell apart is at most the sum of the two disagreements.
An event of the first player's reading, bounded by the disagreement and the same event of the second player's reading.
An event of the second player's reading, bounded by the disagreement and the same event of the first player's reading.
Swapping a triple sum of an outcome's weight, kept on a condition.
Moving along the line a vector carries #
The direction of the axis-parallel line the registers of a low-degree vector carry.
Equations
- MIPRE.Tailored.AnsRed.Typed.dirIdx sel w = MIPRE.LIDT.CL.chi hM (sel.ฯ (w (MIPRE.Tailored.AnsRed.Typed.regs j).coord))
Instances For
A low-degree vector with its point moved by s along its own direction.
Equations
- MIPRE.Tailored.AnsRed.Typed.shiftW sel s w = w + s โข Pi.single ((MIPRE.Tailored.AnsRed.Typed.regs j).pt (MIPRE.Tailored.AnsRed.Typed.dirIdx sel w)) 1
Instances For
Moving along the line, as an equivalence.
Equations
- MIPRE.Tailored.AnsRed.Typed.shiftEquiv sel s = { toFun := MIPRE.Tailored.AnsRed.Typed.shiftW sel s, invFun := MIPRE.Tailored.AnsRed.Typed.shiftW sel (-s), left_inv := โฏ, right_inv := โฏ }
Instances For
The line question is the same at every point of the line.
The indifference check, read #
The codewords of the oracle whose slots' blocks miss the direction i, the others zeroed.
Equations
- MIPRE.Tailored.AnsRed.Typed.maskI j L hLM i v c = if i โ MIPRE.Tailored.AnsRed.Typed.blockM j hLM ((MIPRE.Tailored.AnsRed.slotsOf L MIPRE.Role.oracle).get c) then 0 else v c
Instances For
The constant coefficients of the codewords of an answer at an axis-parallel line.
Equations
- MIPRE.Tailored.AnsRed.Typed.kv t ht j d L a c = MIPRE.Tailored.AnsRed.Typed.cw t ht j d MIPRE.LIDT.CL.Ty.aline (โa) (โc) 0
Instances For
The low-degree and indifference checks at a line and a point, the line's answer Alice's: the point values in the codewords whose blocks miss the line's direction are the constant coefficients of the line's polynomials.
The low-degree and indifference checks at a point and a line, the line's answer Bob's.
Block-local polynomials #
An outcome of the oracle's polynomial measurement is block-local when no codeword's polynomial has a monomial in a variable outside its slot's block.
Equations
- One or more equations did not get rendered due to their size.
Instances For
A polynomial tuple that is not block-local changes, in some codeword whose block misses the line's direction, along many steps on the lines the registers carry.
The steps an outcome that is not block-local changes on, at least q^{2M+2} / (2M) of
them, once the field has 2 (M + 1) d elements.
The weight of the outcomes that are not block-local #
The steps along the lines where Alice's polynomials change, in the codewords whose blocks
miss the line's direction, weigh at most the extraction's error and twice the failure at the type
pair (O, ALine), (O, Point), 12 and 22 times, at one seed.
The oracle outcomes of Alice that are not block-local, at one seed: at most 2M times the
errors of sum_differ_le, per vector, once the field has 2 (M + 1) d elements.
The oracle outcomes of Alice that are not block-local, averaged over the seeds: at most
2M times 12 times the extraction's error plus 1782 times the typed failure.