Evolution of the Primordial Substrate

For most of the past century, cosmology presented a remarkably coherent picture. The standard Big Bang framework, refined through the Cold Dark Matter model of the 1980s, brought together the universe’s expansion, the cosmic microwave background, and the large-scale distribution of galaxies into an elegant whole. For a time, the cosmic puzzle seemed nearly complete: each piece in place, the edges neatly defined.

Yet as the twentieth century gave way to the twenty-first, new observations began to add puzzle pieces that refused to fit. What once appeared a tidy image has become a puzzle with gaps that widen each decade. Some of these gaps are old and familiar landmarks in modern cosmology. Zwicky’s observation of unexpectedly rapid galactic motion (Zwicky 1933) hinted at unseen mass; supernova surveys later revealed that cosmic expansion was not slowing but accelerating (Riess 1998; Perlmutter 1999). The Hubble constant measured by local methods diverges from its value inferred from the early universe (Planck 2018; Riess 2021), and large-scale structure appears to form faster than expected. Most recently, the James Webb Space Telescope has revealed galaxies and black holes that seem to have formed too early and grown too massive for hierarchical models to explain. The once-clear picture began to blur.

Each of these discoveries was met with skillful adaptation: new parameters, new particles, new epochs of unknown physics. Yet for all their differences in scale, from galaxies to the cosmic horizon, their common theme is striking. Each touches, directly or indirectly, on the behavior of the vacuum itself. In standard cosmology, the large-scale uniformity of the universe poses a distinct challenge, requiring special mechanisms to enforce causal coordination across regions that appear disconnected. In contrast, if the universe began as a single, coherent physical system, large-scale correlations do not require later synchronization. Uniformity, alignment, and shared boundary conditions arise naturally as inherited properties of a common origin rather than as outcomes imposed after the fact. When so many puzzles converge on the same background, it becomes reasonable to ask whether the difficulty lies not with the observations themselves, but with the physical frame on which they rest.

The idea that the vacuum might possess traits of its own is hardly new. Decades ago, Zel’dovich (1968) and Weinberg (1989) articulated the cosmological-constant problem, the profound mismatch between the energy density expected from quantum field theory and the value permitted by cosmic expansion. The difficulty was not the presence of vacuum energy but its magnitude: the vacuum appeared to possess energy, yet in the wrong amount by an inconceivable margin. That recognition quietly transformed the vacuum from a passive emptiness into an active participant in cosmic dynamics.

The conceptual boundary shifted further when Jacobson (1995) showed that Einstein’s equations can be derived as an equation of state. In that view, spacetime geometry is not fundamental but thermodynamic, an emergent behavior of underlying degrees of freedom within the vacuum itself. Padmanabhan (2003) extended this perspective, describing the cosmological constant as “the weight of the vacuum,” an imprint of whatever microstructure underlies spacetime. The same decade saw the rise of analogue-gravity research, in which laboratory media reproduce gravitational effects such as horizons and Hawking radiation (Barceló 2005), demonstrating that curvature and metric phenomena can arise from collective behavior in a continuous substrate. Volovik (2003) developed this vision further, treating the quantum vacuum as a condensed-matter-like system in which particles and forces emerge as quasiparticle excitations.

Together these works present a picture of deepening richness: what we call spacetime may be the macroscopic expression of an ordered vacuum, one capable of storing and transmitting information, stress, and spin. This possibility has precedents in the Einstein–Cartan extension of general relativity, where intrinsic spin contributes directly to geometry through torsion (Einstein–Cartan 1929; Hehl 1976). Observational tensions have only sharpened that suspicion. A number of modern approaches—from spin-torsion cosmologies and spinor-vacuum models (Shapiro 2002; Popławski 2010) to later analog-gravity systems that mimic rotational stress in quantum condensates (Barceló 2011), suggest that spin and geometric structure may be more deeply intertwined than once assumed. Reviews by Verde et al. (2019) and subsequent analyses (Di Valentino 2021; Perivolaropoulos 2022) emphasize that current anomalies, such as the Hubble-rate and structure-growth discrepancies, and possibly even early-formation phenomena, may indicate that the vacuum sector of cosmology is incomplete or evolving. If so, then the modern puzzles of dark matter, dark energy, and early structure may share a common root: they all concern how the vacuum responds to energy, motion, and boundary conditions.

Seen in that light, the history of cosmology can be read as an expanding dialogue about the vacuum. At first it was empty; then energetic; then emergent; and now, perhaps, structured. Within such a framework, several long-standing cosmological puzzles are no longer independent problems but different expressions of how a real background responds to motion, stress, and dilution. The arrow of time follows naturally from the irreversible relaxation of spin and internal stress in an expanding medium, rather than from statistical assumptions imposed after the fact. The apparent acceleration of cosmic expansion reflects changing substrate response as density declines, not the action of a separate repulsive agent. Even the phenomena grouped under dark matter and dark energy may be reinterpreted as manifestations of residual structure and stress within that background, not as missing substances. In this view, the apparent fine-tuning of cosmic parameters is replaced by a simpler criterion: only configurations that satisfy mechanical stability and coherence constraints persist. The question that follows, then, is not whether the vacuum is real, but what kind of real thing it is, and whether its earliest state carried internal motion capable of imprinting order across every subsequent scale of cosmic evolution.

The Question of a Substrate

Every generation of physics has asked in one form or another, what lies beneath space itself. To Newton, the answer was simple: space was absolute, a passive stage upon which matter acted. By the late nineteenth century, that stage had become populated with an invisible medium—the luminiferous ether—invoked to carry electromagnetic waves and perhaps even the forces of gravitation. When the Michelson–Morley experiment failed to detect its motion, and relativity dispensed with the need for a preferred frame, the ether was quietly retired. What remained was geometry—elegant, dynamic, but immaterial.

Yet the vacuum refused to stay empty. With the rise of quantum field theory, “empty space” gained energy, fluctuations, and virtual excitations. Even after the ether was gone, something remarkably like it had returned in new clothing. The electromagnetic, weak, and strong fields filled space entirely; the Higgs field endowed particles with mass through its ever-present background value; and zero-point energy permeated all of them. By mid-century, the vacuum was once again crowded with entities that could not be seen but that carried unmistakable influence.

This gradual rehabilitation of the vacuum is one of the quieter revolutions of modern physics. It reintroduced an active background while keeping the geometric purity of relativity intact. The ether had been mechanical; the quantum vacuum was statistical. But both served the same role: they made “empty” space a participant rather than a void.

Still, key questions linger. If the vacuum carries energy, why does its gravitational effect not overwhelm the universe? Weinberg (1989) formalized that tension in what remains one of the deepest unsolved problems in physics. A decade later, the discovery of cosmic acceleration placed the same issue on observational footing: the universe was expanding faster because the vacuum itself—whatever it is—exerts pressure. The theoretical and observational puzzles had merged.

By the mid-1990s, new frameworks began to treat spacetime not as fundamental but as emergent. Jacobson (1995) recovered Einstein’s equations from thermodynamic reasoning applied to local causal horizons, implying that curvature reflects the statistical behavior of hidden degrees of freedom. Padmanabhan (2003) interpreted the cosmological constant as the gravitational imprint of that concealed structure, the “weight of the vacuum.” Laboratory analogues soon reinforced the point: Barceló et al. (2005) demonstrated how acoustic waves in condensed-matter media obey equations identical to those of fields in curved spacetime, while Volovik (2003) advanced a similar insight from the condensed-matter side, proposing that our universe may resemble a superfluid whose excitations manifest as particles and fields.

Through these developments, the conceptual pendulum swung back toward substance. Spacetime, once stripped of materiality, began to look again like a medium, albeit one of subtle character. It could carry stress and curvature, exchange energy with matter, and sustain fluctuations that respond to boundaries and acceleration. Experiments such as Casimir-force measurements and Unruh-type analogues confirmed that the vacuum behaves differently when constrained or disturbed, further eroding the notion of emptiness.

The implications reach far beyond quantum corrections. If spacetime possesses internal degrees of freedom, then geometry itself may be a macroscopic manifestation of an underlying state of organization. Its apparent smoothness would be the large-scale limit of a coherent substrate whose microscopic behavior remains invisible at accessible energies. Such a view does not contradict relativity; it supplies the physical continuity that relativity leaves undefined (Einstein 1920; Sakharov 1967; Jacobson 1995).

In recent years, this question has gained new urgency. Persistent tensions in cosmological data, such as the Hubble-rate and structure-growth discrepancies summarized by Verde et al. (2019) and the unexpectedly mature galaxies revealed by JWST, may signal that the vacuum sector of cosmology is incomplete or evolving (Solà 2022; Capozziello et al. 2024). These anomalies do not necessarily require new particles or forces; they may instead reflect unrecognized traits of the background itself. The vacuum may be dynamic, history-dependent, or capable of storing angular momentum on a cosmic scale.

If so, it becomes legitimate to ask whether that underlying continuum possesses characteristics usually reserved for matter: elasticity, coherence, perhaps even intrinsic spin. Such traits could reconcile the vacuum’s gravitational influence with its apparent neutrality and might explain how structure arises without invoking new forms of mass or energy. The question, then, is not whether the vacuum is real, it clearly is, but what kind of real thing it is. In this work, “vacuum” refers to the macroscopic manifestation of a deeper physical substrate.

In this framework, the primordial substrate is neither spacetime itself, nor a conventional quantum field, nor a fluid in the classical sense. It is a physically real, spin-coherent, stress-responsive continuum whose organized internal motion later gives rise to all three as effective descriptions. Spacetime geometry emerges as the large-scale expression of its curvature and tension; quantum fields arise as structured excitations within it; and fluid or elastic analogies serve only as limited metaphors for its ability to transmit motion and store angular momentum. The substrate is thus not an abstract mathematical stage but the causal physical medium from which geometry, particles, and forces subsequently unfold. In what follows, this primordial, spin-coherent, stress-responsive continuum will be referred to for brevity as the Penergy substrate.

The following section turns to that problem directly. If the universe began as a finite, spinning concentration of this substrate, what forms of motion and instability would follow? What natural structures would such a medium produce as it evolved, expanded, and lost density? Those questions define the search that follows.

[Footnote] All substrate densities are expressed as dimensionless fractions of the initial primordial substrate, defined as 1.00. These thresholds should be understood as approximate stability regimes rather than universal or temporally fixed transition points; collapse and persistence occur locally when rotational and coherence conditions are met.

Minimal Physical Conditions for a Coherent Early Universe

Any cosmological model that attempts to describe the earliest stages of the universe must begin with a set of physically defensible initial conditions. The present approach requires only three, each of which follows directly from observation or conservation principles rather than speculative additions.

(1) The universe must have originated from a real physical medium.
Modern field theory already assigns non-zero energy density, fluctuations, and stress–energy to the vacuum. These traits make the notion of a completely empty, structureless “nothing” physically incoherent. If curvature, acceleration, and particle excitations all elicit responses from the vacuum (Unruh 1981; Birrell and Davies 1982), then the simplest assumption is that the early universe consisted of a continuous substrate capable of storing energy, transmitting stress, and supporting collective modes. This parallels the starting point of many emergent-gravity frameworks and avoids the need for ad hoc initial fields or potentials.

(2) That medium must have possessed angular momentum.
Angular momentum is conserved globally and locally in every known physical system. Its ubiquity in cosmic structure, from the spin of elementary particles to the rotation of galaxies, raises a natural inference: spin is not an emergent late-time feature but a fundamental property of the early medium itself. Models ranging from Kerr-based cosmologies to analog-gravity systems show that rotation is the most natural and efficient way for a coherent medium to store motion. If the early substrate carried internal degrees of freedom, it would have been capable of sustaining intrinsic rotation.

(3) The universe must have undergone expansion driven by internal stress.
This is not an assumption but an observation: distant galaxies recede, redshifts grow with distance, and the expansion history is encoded in multiple independent datasets. Any early-universe model must therefore be compatible with the fact that the universe has been expanding since its earliest observable epochs. No mechanism need be specified at this stage; expansion simply provides a boundary condition that any physical model must respect.

Throughout this chapter, the term “spin” does not refer to the literal rotation of a material object within an already existing space, as a planet turns or a fluid swirls in a container. It refers instead to conserved intrinsic angular momentum carried by a coherent physical substrate whose internal degrees of freedom possess orientation and circulation. The primordial medium did not rotate as a classical body embedded in space; rather, its spin was a structural property of the substrate itself, later manifesting geometrically as curvature, vortices, and ultimately as the dynamical spacetime described by general relativity. In this sense, rotation is not imposed upon the universe from without, but arises from within as an organized mode of motion of the medium from which space, matter, and fields subsequently emerge.

Taken together, these three assumptions satisfy the criteria of minimality and physical plausibility. They require no exotic fields, finely tuned potentials, or special boundary conditions. Instead, they recognize the vacuum as a real, dynamical system whose early configuration supplied the motion, stress, and coherence that later appeared as curvature, structure, and matter.

Formation of a Substrate

If the early universe consisted of a real, continuous substrate, as suggested by modern field theory and the minimal conditions outlined above, then that substrate must have emerged alongside the universe itself. The question here is not whether such a medium existed; its physical necessity has already been established. The question is how a structured background could first appear and what initial properties it is likely to have possessed.

Modern cosmology cannot avoid this issue. Classical mechanics assumed the stage already built; relativity described its curvature but not its construction. Inflationary models introduce fields whose energy density fills all of space (Guth 1981; Linde 1982), while quantum-cosmology approaches consider vacuum fluctuations from which the universe might tunnel into being (Vilenkin 1982; Hartle and Hawking 1983). Though differing in mechanism, each begins by assuming the presence of a background medium upon which expansion can act and within which structure can emerge.

The simplest starting point is that the primordial state was uniform and featureless. Yet a perfectly featureless continuum would contain no internal gradients and no direction for evolution to begin. For change to occur, some asymmetry, some strain, motion, or internal degree of freedom, must have been present from the outset. Conservation principles suggest that once motion existed it could not simply disappear but only redistribute. This observation raises a natural possibility: that the universe began not as a fluctuation within emptiness, but as a finite concentration of vacuum-like substance already capable of sustaining angular momentum. Expansion and structure formation would then follow from that initial rotation seeking equilibrium through redistribution.

Hints that the vacuum possesses mechanical character have long been recognized. Unruh (1981) showed that uniform acceleration through empty space produces radiation, implying that the vacuum responds to motion as a medium would. Birrell and Davies (1982) demonstrated that curved spacetime can convert virtual excitations into real particles, a phenomenon indistinguishable from stress release in an elastic continuum. Analog-gravity studies (Barceló et al. 2005) reproduce similar effects in condensed-matter systems, showing how gravitational behavior can emerge from underlying flow or coherence. Volovik (2003) approached the issue from the condensed-matter side, proposing that the vacuum behaves like a structured medium whose excitations constitute particles and fields. Taken together, these findings make it increasingly plausible that the early universe’s “vacuum field” was not an abstraction but a real substrate capable of deformation and rotation.

If such a substrate existed, it must have possessed at least two fundamental traits. First, it had to be coherent, capable of transmitting stresses and maintaining correlations across regions larger than any emerging quantum or thermal fluctuations. Second, it had to be conservative, retaining angular momentum and energy so that once imparted, they remained stored within the medium. A coherent, conservative continuum naturally supports rotational modes, such as vortices, waves, standing patterns, just as condensed-matter systems do when disturbed. As density declined, regions of instability would appear, and rotational domains could condense out of the background.

The notion of a spin-structured or rotationally coherent vacuum aligns with insights from several disciplines. In superfluid and analog-gravity research, quantized circulation and vortex stability arise from phase coherence within a continuous order parameter (Volovik 2003). In cosmology, similar coherence is present in models where large-scale magnetic or velocity fields are frozen into the early plasma (Widrow 2002; Subramanian 2016). Even in general relativity, rotation enters naturally through the Kerr family of solutions, suggesting that angular momentum is an intrinsic mode of energy organization in spacetime.

What distinguishes a substrate interpretation is its emphasis on the medium’s internal motion rather than on geometrically imposed evolution. Instead of spacetime expanding as an abstract metric, the substrate itself changes state as its internal stresses redistribute through outward flow. In this view, the observed expansion may reflect the macroscopic expression of microscopic energy rearrangement, a perspective consistent with emergent-spacetime ideas in which gravitational dynamics arise from hidden degrees of freedom (Jacobson 1995; Padmanabhan 2003). Laboratory and theoretical analogy models reinforce this picture, showing that curvature and horizon phenomena can emerge from collective motion in continuous media (Barceló et al. 2005). Volovik (2003) similarly described the vacuum as a structured medium whose excitations manifest as particles and fields, while hydrodynamic approaches such as Rizzo (2023) explicitly treat the vacuum as a compressible continuum whose internal flows reproduce gravitational effects.

This perspective reframes cosmological causation. Standard theory treats spacetime curvature as primary and matter as secondary; a substrate model reverses that hierarchy. Structure and curvature arise because the medium evolves, not because geometry dictates evolution. The apparent expansion of space becomes a collective response, a gradual relaxation of internal stress within a continuous background whose energy and coherence adjust as the universe evolves. This view resonates with running-vacuum and evolving-vacuum models, which propose that the vacuum energy density changes over cosmic history (Solà 2022; Capozziello et al. 2024).

At the same time, persistent tensions in cosmological data suggest the vacuum sector itself may be dynamic rather than static (Verde et al. 2019; Di Valentino 2021; Perivolaropoulos 2022). Within this broader context, the substrate framework becomes a physical realization of that evolving background: a medium that conserves angular momentum and energy locally while redistributing them globally as it relaxes toward large-scale equilibrium. General relativity describes this behavior geometrically; the substrate model expresses it dynamically.

The next section now follows naturally. If the substrate possessed internal rotation, what specific behaviors would conservation and coherence enforce? Rotating continua exhibit rich organizations and instabilities when their angular momentum can no longer remain evenly distributed (Chandrasekhar 1961; Greenspan 1968). Laboratory and astrophysical systems alike show that rotational stress triggers vortex formation and cascades into hierarchical patterns (Davidson 2015; Libeskind et al. 2018; Kraljic et al. 2020). The following section examines whether the same principles, acting within a coherent substrate, could have guided the universe’s earliest self-organization into the cascading hierarchy seen in cosmic structure today.