Decoherence-free subspaces are defined relative to a specified noise algebra. Dipositronium, \( Ps_2=e^-e^-e^+e^+ \), is the minimal positronium molecule in which the fixed-pair picture becomes inadequate: it contains two electrons and two positrons, but no permanent electron–positron pairs. A fixed-pair picture of two positronium atoms can suggest a collective-spin protected sector. In the true molecule, however, annihilation must be summed over all electron–positron contacts. This paper compares two scalarity tests on the same finite spin space: protection under modeled collective generators and undistorted conditional survival under the exchange-summed no-jump sink. In an equal-contact spin approximation, the operator governing conditional annihilation loss takes the form \( \begin{equation} K_{\rm ann}=C\left[\Gamma_2+3\Gamma_3+(\Gamma_3-\Gamma_2)\mathbf S_e\cdot\mathbf S_p\right]\end{equation} \) (1). It is therefore scalar on fixed \( (S_e,S_p;F) \) sectors. The two spin sectors (0,0;0) and (1,1;0) are both annihilated by the modeled collective generators, but the same two sectors have no-jump sink eigenvalues \( (C(\Gamma_2+3\Gamma_3) \) and \( C(3\Gamma_2+\Gamma_3) \), respectively. Thus the collective protected \( F=0 \) spin space is generally not scalar for conditional survival. The calculation is a channel-level comparison, not a molecular rate calculation. It shows that collective protection and conditional no-jump survival define different scalar decompositions.

Everettian branch multiplicity is often discussed as though it were a count of wavefunction terms or decoherent alternatives. This paper argues that the relevant object is an algebra-relative packing number on physically admissible history classes. Candidate histories, already assumed to belong to a decoherent or approximately decoherent family, are first quotiented by exact physical symmetries and then compared only through distinctions visible in a specified operator system of admissible effects. The resulting effective branch packing number \( N_{\mathrm{eff}}(t;{\mathcal A},\varepsilon) \) is the maximal number of mutually \( \varepsilon \)-distinguishable symmetry classes of histories relative to \( \mathcal A \). The paper proves a sequence of structural results: an orbit-packing reduction theorem; monotonicity under refinement of the admissible operator system; metric packing bounds; polynomial and, under the natural affine-rank condition, sharp asymptotic record-compression theorems for collective linear records of identical bosonic qudits; contraction of channel distinguishability under recovery; and a logical cluster theorem for recovered channels. In particular, \( r_0 \) independent collective record directions give \( \Theta(N^{r_0}) \) record growth rather than the labeled \( d^N \) growth; and separated clusters of recovered logical channels, rather than microscopic histories, determine logical branch multiplicity. Applications include the three-qubit bit-flip code, bosonic qudit occupation sectors, and a formal orbit-record model for dipositronium annihilation histories. The framework relates decoherent histories, Quantum Darwinism, exchange symmetry, and quantum error correction without asserting literal merger of globally orthogonal branches.

Living matter uses energy and material to maintain and replace the structures that sustain its activity. This monograph asks when quantum mechanics contributes measurably to that continuity. It examines local electronic, nuclear, photochemical, and spin-dependent events whose products can persist as chemical, electrical, or conformational records. The cases include respiratory electron and proton transfer, enzyme hydrogen tunnelling, photosynthetic energy transfer, vision, radical-pair chemistry, DNA maintenance, and protein-based inheritance. Established molecular mechanisms are distinguished from claims about their necessity for biological function.The proposed test follows a quantum-sensitive step through an intermediate record to a functional output, then asks whether it changes the work, fidelity, or renewal a system can sustain. Comparisons must give physically admissible alternatives the same limits on power, material, space, time, and error, including the cost of compensation. Models of completion before loss and coupled production show how a local effect could shift a threshold for renewal; they do not establish that such a shift occurs in a particular organism. Classical kinetic networks and alternative architectures provide controls. Evidence for extended coherence and neural quantum proposals is assessed separately. The book develops experimental designs in catalysis, bioenergetics, DNA maintenance, radical-pair sensing, and artificial cells. Its central claim is conditional: a quantum-sensitive mechanism matters to living organization when its measured contribution changes what a system can sustain under specified constraints.

We derive an explicit test of whether a reduced quantum-memory model overstates recoverability. For channels with orthogonal logical outputs in distinguishable sectors, the minimum recovery error follows directly from differences between environmental record amplitudes, without numerical recovery optimization. Applying this test to two-excitation oscillator–qubit and four-qubit encodings reveals that matching single-loss responses need not preserve finite-time recoverability. Under collective loss, the four-qubit encoding is perfectly recoverable, whereas oscillator emission records reveal logical information. The resulting unavoidable error initially grows as the cube of storage time. The test quantifies omitted-level effects and benchmarks reduced models and recovery algorithms.

Varying the probabilities of the branches in a massive spatial superposition provides a controlled way to test gravitational response models. We develop this comparison for fixed source configurations and calibrated probe measurements. The between-branch covariance obeys a pairwise-distance law on the probability simplex and has rank at most one less than the number of occupied branches. Higher cumulants and ensemble-size scans constrain the same response model, although their statistics can also be produced by classical branch mixtures. Coherence recovery adds information when its permitted operations and accessible records are specified independently. For a branch-preserving measurement that produces an irreversible classical record and drives a common feed-forward response, we derive an upper bound on recovered source coherence in terms of record overlaps. A calibrated response diameter converts this into a response--recovery inequality. A second bound relates recovery to the conditional response variances and remains applicable to unbounded feedback with finite second moments. An explicit binary model saturates both inequalities. Coherent momentum transfer provides a contrasting example in which the probe statistics remain branch resolved while an eraser measurement restores source coherence. These comparisons require separate measurements of conditional probe noise, trajectories, and calibration parameters. The bounds apply to the stated classical-record channel; their application to a gravitational theory requires a derivation of that channel from the theory. Branch-weight scans therefore support quantitative tests of specified models without providing a theory-independent criterion for quantized gravity.

Background and objectives: Cannabis-related harms vary across psychiatric, cognitive, neurological, developmental and functional outcomes. This monograph combines a critical evidence review with original secondary meta-analyses and probability modeling to assess harm, susceptibility and recovery, and to develop a literature-derived risk questionnaire.Methods: Original frequentist and Bayesian random-effects meta-analyses of published longitudinal estimates were conducted under six selected specifications for psychosis, depression and anxiety, with source-verification, cohort-overlap and prior-sensitivity analyses. Published reviews, cohorts and experiments were critically synthesized. Eight MEDLINE-source queries with a publication cutoff of 18 October 2026 yielded 1,719 title assessments and 292 documented abstract assessments. Twenty-five principal regression specifications and two alternative cannabis use disorder models were fitted to published longitudinal aggregates to support a forty-five-item questionnaire. Cannabis use disorder models underwent internal held-out comparisons and 500 bootstrap replications. Prenatal associations underwent dependence and numerical-precision analyses.Results: The original two-cohort synthesis of higher adolescent exposure and psychotic disorder yielded a pooled relative association of 2.67 (modified Hartung–Knapp 95% CI 0.06–115.26); the Bayesian pooled median was 2.38 (95% credible interval 1.05–4.80). All six selected frequentist intervals included unity, and strict primary-source verification left insufficient studies for an anxiety pool. Across the broader literature, evidence was strongest for acute psychiatric and cognitive effects, cannabis use disorder and withdrawal, and psychosis-related harm. Published pooled cannabis use disorder prevalence among users was 22% (95% CI 18–26%); educational disruption included increased school dropout (odds ratio 2.19; 95% CI 1.73–2.78). Cognitive differences were small on average and smaller in studies requiring abstinence. Depression, suicidality and mania showed adverse observational associations; anxiety, motivation, employment, interpersonal and neurological findings were less consistent. Prenatal associations were most consistent for impaired fetal growth and prematurity; malformation and later developmental findings were heterogeneous. Internal predictive performance varied substantially by subgroup, and modeled uncertainty frequently prevented stable risk-category assignment.Interpretation: Original meta-analyses and probability models quantify selected associations and their uncertainty within a broader assessment of cannabis-related harm. Frequent high-THC exposure, early initiation, established psychiatric illness and pregnancy warrant particular concern; causal certainty varies by outcome. Questionnaire reports provide outcome-specific source projections with uncertainty estimates. External clinical and psychometric validation has not been performed.