What the program answers to

The local measurement of the Hubble constant: H₀ = 73.04 ± 1.04 km/s/Mpc from the Cepheid-calibrated supernova distance ladder, with the uncertainty brought to one km/s/Mpc. It differs from the Planck + ΛCDM value by 5σ — the “Hubble tension”.

Connection to WHD. The program uses the Hubble constant as an input, not a prediction: it decides which moment of the simulation is today. Both candidate values are carried — 67.4 from Planck and 73.0 from this measurement — and the prediction for the dark-energy density inherits whichever is used. WHD does not claim to explain the tension. The spread between the two is an uncertainty on the input, and the honest statement is that the model’s dark-energy density must come out right for the Hubble constant it is handed; it has one shot per choice and no parameter to absorb the difference. Filed as context for that reason.

The current best measurement of the effective number of relativistic species in the early universe, N_eff = 2.99 ± 0.17 — consistent with the Standard Model’s three neutrino species and no additional light relic, but with enough remaining uncertainty (ΔN_eff ≲ 0.3 at current precision) to leave room for a small extra contribution.

Connection to WHD. This is the external dataset the UV completion candidate’s one sharp, near-term prediction has to answer to: a small, positive excess ΔN_eff from vents leaking preferentially into the program’s forced hidden sector. Filed as context rather than supports or threatens because the current measurement neither confirms nor rules out WHD’s predicted small excess yet — it only excludes the large, “democratic” leak a symmetric mechanism would predict, which WHD already doesn’t predict. This entry should be revisited (and likely reclassified) once the one owed number — the vent’s hidden-vs-visible branching ratio — is computed, and again once CMB-S4-class data (roughly ten times more precise) is available.

Three more of the program’s tests run through this paper. Its Hubble constant, 67.4 ± 0.5 km/s/Mpc, is one of the two values used to set the model’s clock (the other is the local measurement, riess2022sh0es); with Newton’s constant it fixes the units for the prediction of the dark-energy density, which then has no freedom left. Its densities Ω_c h² = 0.120 and Ω_b h² = 0.0224 give the observed ratio of dark to ordinary matter, about 5.4, which a valid census of vents must reproduce with no adjustable parameter. None of these has been evaluated on a complete run of the model yet; this entry is the measurement they will be judged against.

The Pantheon+ compilation: 1701 light curves of 1550 spectroscopically confirmed Type Ia supernovae from z = 0.001 to 2.26, the supernova leg of most current dark-energy fits. On their own the supernovae give Ω_M = 0.334 ± 0.018 in a flat ΛCDM universe and a constant equation of state w = −0.90 ± 0.14; with the CMB and BAO the equation of state tightens to w = −0.978 (+0.024 / −0.031). Both are consistent with a cosmological constant.

Connection to WHD. Supernovae fix the low-redshift end of the range in which WHD’s w(z) drift is read, and they are the dataset DESI’s evolving-dark-energy significance depends on — 2.5σ with this sample, higher with Union3 and DES-SN5YR (desi2024bao). The program’s own number is not on the table yet, so this is filed as context: the measurement WHD’s drift has to pass through at redshifts below about one, not a verdict. When the run exists the comparison is made against the combined BAO, supernova and CMB fit, not against supernovae alone.

The paper that introduced the equation of state linear in the scale factor, now written w(a) = w₀ + wₐ(1 − a) and known — with Linder’s 2003 paper — as the CPL parametrization. It is the two-number language every dark-energy survey reports in: w₀ is the equation of state today, wₐ its slope back in time, and (−1, 0) is a cosmological constant.

Connection to WHD. The program does not predict two numbers; it predicts a function — the drift of w(z) set by the wall’s shedding exponent. To compare it with survey results the function has to be projected onto (w₀, wₐ). WHD’s pipeline does that by least squares with uniform weight in the scale factor over redshifts from 0.05 to 2, and carries a caveat of its own: a real survey fit weights redshifts by their information content, so the uniform projection is a stated convention until a data-weighted one replaces it. The residual between WHD’s w(z) and its best two-parameter fit is itself a future test — a drift that is not of this form would show up as exactly that.

The first cosmological results from DESI’s first year of data: baryon acoustic oscillations measured in seven redshift bins from more than 6 million galaxies, quasars and Lyman-α forest spectra over 0.1 < z < 4.2. On their own the BAO give Ω_m = 0.295 ± 0.015; with a nucleosynthesis prior and the CMB acoustic scale they give H₀ = 68.52 ± 0.62 km/s/Mpc. Combined with the CMB and supernovae the data prefer a dark-energy equation of state that evolves — w₀ > −1 today, wₐ < 0 — over a cosmological constant, at 2.5σ to 3.9σ depending on which supernova sample is used.

Connection to WHD. The first of the two DESI results the program’s dark-energy prediction will be read against, over the redshifts between about 0.3 and 2 where the drift is expected to show. The direction the data favours — w₀ > −1, wₐ < 0 — is the shape a complete run of the model must either reproduce or contradict; it is recorded here without a verdict, because no such run has produced WHD’s own w(z) yet. Superseded in precision by the second data release (desi2025dr2bao); kept because the sample-by-sample breakdown shows how much the conclusion leans on the supernova anchor at low redshift.

The second data release of the Dark Energy Spectroscopic Instrument: baryon acoustic oscillation distances from more than 14 million galaxies and quasars, the largest such measurement made. The BAO scale agrees with the acoustic angular scale Planck measures, but the ΛCDM parameters it prefers sit in a mild 2.3σ tension with the CMB, and a dark-energy density allowed to change with time — the w₀wₐ parametrization — is preferred over a constant one at 3.1σ with the CMB alone and at 2.8–4.2σ with supernovae. It is the sharpest indication so far that dark energy may not be a constant.

Connection to WHD. The drift of w(z) is the program’s external test of how fast the loaded wall sheds its stored energy back into the bulk. The shedding exponent is derived to be 3/2, and the same drift appears as a slow change in Newton’s constant. A complete run of the model produces a w(z) shape with nothing left to adjust, and this is the dataset it is compared with. Filed as context rather than supports because WHD’s own w(z) has not yet been computed on a run that counts; a hint of evolving dark energy is not evidence for or against the program until it has. A run whose drift disagrees with DESI-class w(z), or whose exponent leaves its band around 3/2, rules the mechanism out.

The overview paper of ESA’s Euclid mission: a space telescope surveying about 14 000 square degrees of extragalactic sky with visible imaging and near-infrared imaging and spectroscopy, built to measure the geometry of the universe and the growth of its structure through weak lensing and galaxy clustering, and so to constrain the dark-energy equation of state and its evolution.

Connection to WHD. The survey after DESI. The program’s w(z) drift is a single derived function with a fixed exponent behind it, and a survey that maps the expansion history over a wider redshift range with independent systematics is where an agreement with DESI would be confirmed or a tension resolved. Filed as context and as a forecast: no WHD number exists yet to compare, and Euclid’s cosmology results are still to come.

The tightest lunar-laser-ranging analysis: forty-five years of data (1970 to January 2015) give a drift of Newton’s constant of Ġ/G = (7.1 ± 7.6) × 10⁻¹⁴ per year — an order of magnitude below the 2004 bound — with the equivalence principle, the post-Newtonian parameters β and γ, and the geodetic precession all within their general-relativistic values.

Connection to WHD. The current ceiling on the Ġ/G side of the twin measurement. A complete run of the model reports the drift of the wall’s tension, and it has to fit under this bound — about one part in 10¹³ per year — while the same drift, read as w(z), matches the survey data. Filed as context until the run exists.

The second parent of the CPL convention. Linder shows that the two-parameter form w(a) = w₀ + wₐ(1 − a) reproduces the expansion history of a wide class of scalar-field dark-energy models to high accuracy over the redshifts surveys can reach, and argues that the slope of the equation of state — how w changes with the logarithm of the scale factor — is the quantity that separates a cosmological constant from a dynamical field.

Connection to WHD. The wall’s stored energy drains at a rate the derivation fixes, and an observer on the brane reads that drain as a changing w. Linder’s argument is why the slope, not the value, is where the program’s signature sits: a constant w = −1 is the one thing the mechanism cannot produce while the wall is still shedding energy. The two-parameter form is used here as an interpreter between WHD’s function and the surveys’ two numbers, not as a model of the physics.

Thirty-five years of laser ranging to the retroreflectors on the Moon, turned into tests of gravity: no drift of Newton’s constant, Ġ/G = (4 ± 9) × 10⁻¹³ per year; the equivalence principle holding to Δ(M_G/M_I) = (−1.0 ± 1.4) × 10⁻¹³; the geodetic precession of the lunar orbit within 0.6% of general relativity.

Connection to WHD. On the brane, Newton’s constant is set by the wall’s effective tension, so any drift in that tension appears directly as a drift in G. It is the same drift the program reads elsewhere as the change of w(z) with time — one physical quantity with two readouts. A complete run of the model therefore has to satisfy both at once: its Ġ/G inside the lunar-ranging band, its w(z) matching the surveys. If the two readouts disagree the mechanism is wrong, whatever each fit says on its own. This is the classic bound; the tighter one is hofmannmuller2018llr.

The current best measurement of the effective number of relativistic species in the early universe, N_eff = 2.99 ± 0.17 — consistent with the Standard Model’s three neutrino species and no additional light relic, but with enough remaining uncertainty (ΔN_eff ≲ 0.3 at current precision) to leave room for a small extra contribution.

Connection to WHD. This is the external dataset the UV completion candidate’s one sharp, near-term prediction has to answer to: a small, positive excess ΔN_eff from vents leaking preferentially into the program’s forced hidden sector. Filed as context rather than supports or threatens because the current measurement neither confirms nor rules out WHD’s predicted small excess yet — it only excludes the large, “democratic” leak a symmetric mechanism would predict, which WHD already doesn’t predict. This entry should be revisited (and likely reclassified) once the one owed number — the vent’s hidden-vs-visible branching ratio — is computed, and again once CMB-S4-class data (roughly ten times more precise) is available.

Three more of the program’s tests run through this paper. Its Hubble constant, 67.4 ± 0.5 km/s/Mpc, is one of the two values used to set the model’s clock (the other is the local measurement, riess2022sh0es); with Newton’s constant it fixes the units for the prediction of the dark-energy density, which then has no freedom left. Its densities Ω_c h² = 0.120 and Ω_b h² = 0.0224 give the observed ratio of dark to ordinary matter, about 5.4, which a valid census of vents must reproduce with no adjustable parameter. None of these has been evaluated on a complete run of the model yet; this entry is the measurement they will be judged against.

The Atacama Cosmology Telescope’s sixth data release, tested against models beyond ΛCDM: the effective number of relativistic species comes out at N_eff = 2.86 ± 0.13 (2.89 ± 0.11 with nucleosynthesis data), the sum of neutrino masses below 0.082 eV, self-interacting dark radiation limited to N_idr < 0.134, no neutrino self-interactions, and no statistically significant preference for any departure from the baseline model.

Connection to WHD. The most recent measurement of the number the string completion’s one sharp prediction lives in. With the Standard Model at N_eff = 3.044 and ACT’s central value slightly below it, the room left for a positive excess is now roughly 0.2 to 0.3 at two standard deviations — far below the excess of about one that is already excluded, and a tighter box than Planck’s for the still-to-be-computed size to land in. The limit on self-interacting dark radiation is a separate bound the hidden sector must respect, since its only connection to us is gravitational. Filed as context: the prediction is a sign and a ceiling until the size is computed.

The reference design and project plan for CMB-S4: the survey strategy, instrument configuration and schedule that turn the 2016 science case into numbers. For light relics the conceptual design reaches σ(N_eff) < 0.03 over the seven-year survey, against Planck’s ±0.17 today — precise enough that any light particle that was ever in thermal equilibrium with the Standard Model leaves a detectable trace in N_eff.

Connection to WHD. This is the precision that makes the dark-radiation prediction decidable. Today the prediction is a sign and a ceiling: a small positive excess, bounded by Planck’s N_eff = 2.99 ± 0.17 (room for about 0.3 or less), with its size still to be computed from the fraction of a vent’s output that goes into the hidden sector. At σ(N_eff) < 0.03 that computed size becomes a target the survey either finds or excludes; a computed excess that CMB-S4 then excludes rules the string completion out. Filed as context because it is a forecast, not a measurement; it will move once the fraction is computed and again once CMB-S4 reports.

The first edition of the science case for CMB-S4, the Stage-4 ground-based cosmic microwave background experiment: a search for the B-mode signature of primordial gravitational waves, a determination of the number and masses of the neutrinos, a search for light relics beyond the Standard Model through the effective number of relativistic species, and constraints on dark energy and on gravity at cosmological scales.

Connection to WHD. The effective number of light species is the one sharp observational handle on the hidden sector the string completion forces into existence. Vents deposit their energy toward the brane, so a leak into that sector heats it less than it heats us, and the prediction is a small, positive excess — never the excess of about one a symmetric leak would give, which Planck already excludes. This is where N_eff enters the next generation’s design as a primary target; the precision the program relies on, σ(N_eff) < 0.03, is in the 2019 reference design (cmbs4referencedesign2019). Filed as context: a forecast the prediction will be judged by, once the one missing number — the fraction of a vent’s output that goes into the hidden sector — turns the sign into a size.

Standard big-bang nucleosynthesis re-evaluated with the Planck baryon density: the predicted light-element abundances against the observed ones (deuterium is now measured more precisely than theory predicts it; the lithium discrepancy remains), and an independent early-time determination of the number of relativistic species, N_ν = 2.86 ± 0.15 at the epoch of nucleosynthesis — a few minutes into the hot phase, long before the CMB.

Connection to WHD. Two constraints in one. The light-element abundances must come out as observed: reheating vent by vent has to deliver an ordinary hot big bang whose nuclear history matches, and the census of vents will decide whether it does. And the number of light species at nucleosynthesis is a second, earlier bound on dark radiation, complementary to the microwave background: the small positive excess the string completion predicts has to be present already at this epoch and consistent with both readings. Filed as context until the census and the size of the excess exist.

The current best measurement of the effective number of relativistic species in the early universe, N_eff = 2.99 ± 0.17 — consistent with the Standard Model’s three neutrino species and no additional light relic, but with enough remaining uncertainty (ΔN_eff ≲ 0.3 at current precision) to leave room for a small extra contribution.

Connection to WHD. This is the external dataset the UV completion candidate’s one sharp, near-term prediction has to answer to: a small, positive excess ΔN_eff from vents leaking preferentially into the program’s forced hidden sector. Filed as context rather than supports or threatens because the current measurement neither confirms nor rules out WHD’s predicted small excess yet — it only excludes the large, “democratic” leak a symmetric mechanism would predict, which WHD already doesn’t predict. This entry should be revisited (and likely reclassified) once the one owed number — the vent’s hidden-vs-visible branching ratio — is computed, and again once CMB-S4-class data (roughly ten times more precise) is available.

Three more of the program’s tests run through this paper. Its Hubble constant, 67.4 ± 0.5 km/s/Mpc, is one of the two values used to set the model’s clock (the other is the local measurement, riess2022sh0es); with Newton’s constant it fixes the units for the prediction of the dark-energy density, which then has no freedom left. Its densities Ω_c h² = 0.120 and Ω_b h² = 0.0224 give the observed ratio of dark to ordinary matter, about 5.4, which a valid census of vents must reproduce with no adjustable parameter. None of these has been evaluated on a complete run of the model yet; this entry is the measurement they will be judged against.

The neutron-star merger seen in both gravitational waves and gamma rays: GRB 170817A followed GW170817 by 1.74 ± 0.05 seconds after a journey of about 130 million years, which pins the speed of gravity to the speed of light to between −3 × 10⁻¹⁵ and +7 × 10⁻¹⁶ of c. Any theory in which gravitational waves travel at a different speed from light over cosmological distances was ruled out that day.

Connection to WHD. The graviton bound to the wall in the brane picture is not quite massless, but it travels at the speed of light to every precision tested — the model has no room for a difference. This is a constraint the program passes by construction rather than a test that singles it out, since general relativity passes it too, which is why it is filed as supports at weak strength: consistent, not decisive. The decisive statement in this group is the graviton mass, √2 times the Hubble rate, and what would rule it out is a confirmed mass different from that (ligo2025gwtc3tgr).

The standard map of how heavy a graviton is allowed to be: the review collects the bounds from planetary orbits and binary pulsars, from gravitational-wave dispersion, from the growth of cosmic structure and the expansion history, and lays out the theoretical constraints — ghosts, strong coupling, the Vainshtein screening — that any consistent theory of a massive graviton has to satisfy.

Connection to WHD. The program’s graviton mass is set by the Hubble rate itself, which puts it in the one corner of this map where the observational bounds are weakest and the theoretical questions are sharpest: a mass of order H₀ is invisible to laboratory and solar-system tests and can only be reached through cosmology. This review is the reference for what a graviton of that mass is and is not allowed to do, and for the consistency conditions the brane’s gravitational sector will be held to when its perturbation theory is written out. Filed as context: it bounds the space the derived value lives in without yet testing the value.

The LIGO–Virgo–KAGRA battery of general-relativity tests on the third gravitational-wave catalog: waveform residuals consistent with noise, post-Newtonian deformation coefficients at their GR values, Kerr spin-induced quadrupoles, no extra polarizations, no echoes, ringdown frequencies and damping times as predicted, and — from the absence of dispersion in the propagating waves — a graviton mass bound of m_g ≤ 2.42 × 10⁻²³ eV/c² at 90% credibility.

Connection to WHD. The program’s graviton is the wall-bound mode with a mass of √2 times the Hubble rate, tracking the expansion so that it keeps that value in every epoch. Today that is about 2 × 10⁻³³ eV — ten orders of magnitude below this bound, so the bound is a ceiling the derived value clears easily, not a test it is close to failing. What would rule the derivation out is sharper than any bound: a confirmed graviton mass that differs from √2 times the Hubble rate. Filed as context because current data cannot resolve a mass this small in either direction.

The reference compilation of what the universe allows primordial black holes to be: limits from their Hawking evaporation (γ-ray backgrounds, light-element abundances, CMB anisotropies), from micro- and millilensing, from the dynamics of stars and galaxies, from accretion, and from gravitational waves, assembled across some twenty decades in mass, with the windows in which primordial black holes could still be a significant part of the dark matter.

Connection to WHD. The program’s vents are black holes that evaporate into the bulk, not into four dimensions, and that changes the exponents this whole map is built on: a vent’s lifetime scales with the square of its mass rather than the cube, so the light end of the delivered mass distribution rises linearly in mass where a four-dimensional population would rise quadratically, and the terminal flare brightens as (t_f − t)^(−1/2) while its temperature rises as (t_f − t)^(−1/4). Those exponents have no adjustable parameter; the absolute spectrum waits on a valid census of vents and on the model’s overall scale. This review is the four-dimensional constraint map the five-dimensional spectrum has to be re-derived against once that census exists — every evaporation bound here assumes the four-dimensional law and has to be recomputed, not copied. Filed as context.

The local measurement of the Hubble constant: H₀ = 73.04 ± 1.04 km/s/Mpc from the Cepheid-calibrated supernova distance ladder, with the uncertainty brought to one km/s/Mpc. It differs from the Planck + ΛCDM value by 5σ — the “Hubble tension”.

Connection to WHD. The program uses the Hubble constant as an input, not a prediction: it decides which moment of the simulation is today. Both candidate values are carried — 67.4 from Planck and 73.0 from this measurement — and the prediction for the dark-energy density inherits whichever is used. WHD does not claim to explain the tension. The spread between the two is an uncertainty on the input, and the honest statement is that the model’s dark-energy density must come out right for the Hubble constant it is handed; it has one shot per choice and no parameter to absorb the difference. Filed as context for that reason.

The CODATA least-squares adjustment of the fundamental constants for 2018 — the first after the SI was redefined in terms of fixed constants. Newton’s constant is the odd one out: G = 6.674 30(15) × 10⁻¹¹ m³ kg⁻¹ s⁻², known to only 22 parts per million and the least precise of the fundamental constants, a value the 2022 adjustment left unchanged.

Connection to WHD. In the solver’s units every quantity is a power of one unknown length scale. On the brane, Newton’s constant is set by the wall’s tension, and the measured value of G fixes that scale — the ruler, as the Hubble constant is the clock. An input, not a prediction: once G and H₀ are spent, the dark-energy density has no freedom left, which is what makes its prediction a real test. The 22-parts-per-million uncertainty on G is far below anything that test can resolve today; the entry is here so the input’s provenance is on the page.

The current best measurement of the effective number of relativistic species in the early universe, N_eff = 2.99 ± 0.17 — consistent with the Standard Model’s three neutrino species and no additional light relic, but with enough remaining uncertainty (ΔN_eff ≲ 0.3 at current precision) to leave room for a small extra contribution.

Connection to WHD. This is the external dataset the UV completion candidate’s one sharp, near-term prediction has to answer to: a small, positive excess ΔN_eff from vents leaking preferentially into the program’s forced hidden sector. Filed as context rather than supports or threatens because the current measurement neither confirms nor rules out WHD’s predicted small excess yet — it only excludes the large, “democratic” leak a symmetric mechanism would predict, which WHD already doesn’t predict. This entry should be revisited (and likely reclassified) once the one owed number — the vent’s hidden-vs-visible branching ratio — is computed, and again once CMB-S4-class data (roughly ten times more precise) is available.

Three more of the program’s tests run through this paper. Its Hubble constant, 67.4 ± 0.5 km/s/Mpc, is one of the two values used to set the model’s clock (the other is the local measurement, riess2022sh0es); with Newton’s constant it fixes the units for the prediction of the dark-energy density, which then has no freedom left. Its densities Ω_c h² = 0.120 and Ω_b h² = 0.0224 give the observed ratio of dark to ordinary matter, about 5.4, which a valid census of vents must reproduce with no adjustable parameter. None of these has been evaluated on a complete run of the model yet; this entry is the measurement they will be judged against.

Standard big-bang nucleosynthesis re-evaluated with the Planck baryon density: the predicted light-element abundances against the observed ones (deuterium is now measured more precisely than theory predicts it; the lithium discrepancy remains), and an independent early-time determination of the number of relativistic species, N_ν = 2.86 ± 0.15 at the epoch of nucleosynthesis — a few minutes into the hot phase, long before the CMB.

Connection to WHD. Two constraints in one. The light-element abundances must come out as observed: reheating vent by vent has to deliver an ordinary hot big bang whose nuclear history matches, and the census of vents will decide whether it does. And the number of light species at nucleosynthesis is a second, earlier bound on dark radiation, complementary to the microwave background: the small positive excess the string completion predicts has to be present already at this epoch and consistent with both readings. Filed as context until the census and the size of the excess exist.

Planck’s constraints on the primordial perturbations: a nearly scale-invariant, red spectrum with n_s = 0.9649 ± 0.0042 and no measurable running; primordial gravitational waves limited to r₀.₀₀₂ < 0.10 (< 0.056 with BICEP2/Keck); polarization data that test the adiabaticity of the initial conditions stringently; and no evidence for oscillatory or other parameterized features in the spectrum.

Connection to WHD. Two of the program’s tests meet this paper. The first is a constraint that must hold: reheating in WHD happens vent by vent — many small hot big bangs — and the observed smoothness and adiabaticity of the microwave background bound how numerous and how close-packed the vents must have been to blend. The second is not yet a claim: the model’s computation of the birth produces a red first spectrum and a universe lopsided at birth, but the program has not accepted that computation, pending a decision on how the birth is to be read. This entry records the measurement both will face; it does not score either.

The LUX-ZEPLIN experiment’s 4.2 tonne-year search: no evidence of weakly interacting massive particles scattering off xenon nuclei, and the strongest exclusion to date on the spin-independent WIMP–nucleon cross section, 2.2 × 10⁻⁴⁸ cm² at 40 GeV/c², with world-leading limits for every mass above 9 GeV/c².

Connection to WHD. Listed so that a null result is not misread. The hidden sector the string completion forces into existence is not a weakly interacting massive particle: its only connection to our sector is gravity and exchanges suppressed at the string scale, so a detector built to catch a particle scattering off a xenon nucleus does not test it, and any signal would sit far below the neutrino background these experiments already face. Neither this exclusion nor a future detection at these cross sections bears on the program. The observational handle on the hidden sector is the dark-radiation excess (act2025dr6extended, cmbs4referencedesign2019).

The first WIMP search of the XENONnT detector: nuclear-recoil events between 3.3 and 60.5 keV, no excess above the expected background, and an upper limit on the spin-independent WIMP–nucleon cross section of 2.58 × 10⁻⁴⁷ cm² at 28 GeV/c² — an improvement on XENON1T at equal exposure.

Connection to WHD. As with lz2025results, this experiment is listed because a reader will expect a dark-matter claim to answer to it, and the answer is that it does not apply. The hidden sector couples to us through gravity and string-scale exchange only; a direct-detection null result is neither evidence against it nor room for it. Its test is elsewhere: the sign and size of the dark-radiation excess, and the existence of the decoupled sector itself.