Holographic Dark Matter

• Holographic dark matter is an emergent phenomenon where dark matter effects arise from the holographic principle and UV/IR duality, bypassing the need for new particles.
• Models employ techniques like holographic screens, geometric IR cutoffs, and information-theoretic bounds to derive energy densities that mimic cold dark matter behavior.
• These approaches offer testable predictions on structure formation, Tully–Fisher relations, and unified dark sector behavior, providing alternatives to standard ΛCDM.

Holographic dark matter refers to a broad class of models in which the dark matter phenomenon—traditionally attributed to new, weakly interacting particle species or compact primordial objects—is instead explained as an emergent effect of the holographic principle in gravitational or cosmological frameworks. These models leverage the UV/IR duality, entropy bounds, or holographic screen dynamics to account for missing mass and related phenomena. The holographic approach generates dark-matter-like effects by associating components of the cosmic energy budget with nonlocal features of spacetime, boundary stress tensors, geometric invariants, or information-theoretic constructs, often with minimal or no reference to conventional particle content.

1. Holographic Principle and Theoretical Frameworks

At the foundational level, the holographic principle posits that the maximum information content of a spatial region is determined by its bounding area, not its volume. Explicitly, the entropy $S$ in a region is $S \leq A/(4G)$ in Planck units. This principle, articulated in contexts such as AdS/CFT correspondence and causal diamonds, underpins most holographic dark matter proposals and yields new constraints and interpretations for gravitational dynamics.

Several frameworks employ the holographic principle for dark matter modeling:

• Holographic Screens and Boundary Stress Tensors: Models based on the Brown–York tensor on holographic screens (often de Sitter hypersurfaces in higher-dimensional Minkowski space) allocate dark energy and dark matter contributions directly to the boundary rather than local bulk content. The Hamiltonian constraint in the bulk leads to nontrivial algebraic relationships among energy densities on the screen, with emergent dark matter manifest as part of the holographic stress-energy tensor (Cai et al., 2017).
• Geometrical IR Cutoff Approaches: In these, the infrared cutoff $L$ is specified as a function of geometric scalars, e.g., $L^{-2} \sim H^2$ or $L^{-2}\propto R_{\mu\nu}R^{\mu\nu}$, resulting in holographic energy densities that dynamically interpolate between radiation, dust (dark matter), and cosmological constant behavior (Aviles et al., 2011, Trivedi et al., 13 Nov 2025).
• Information-Theoretic Constructions: These employ a mapping between information/entropy bounds and cosmological energy densities (via Landauer’s principle and Bekenstein bounds). The Holographic Dark Information Energy (HDIE) model is representative, linking the information content of hot baryons to a clumped energy component that mimics cold dark matter (Gough, 2016, Ng, 2016).

2. Model Implementations and Mathematical Structures

Holographic dark matter arises in diverse mathematical realizations, each encoding the dark sector in terms of boundary or bulk data:

A. IR Cutoff and Emergent Dust

• The "Ricci cutoff" class sets $L^{-2} = \alpha H^2 + \beta \dot{H}$ and postulates $\rho_{\rm holo} = 3 c^2 L^{-2}$ (often, $c=1$ by convention). The special case $\beta = \alpha/2$ (the Ricci scalar) produces an effective dark matter density

$$\rho_{\rm HDM}(a) = \frac{\alpha}{4-\alpha} \rho_{B0} a^{-3} + 3K a^{4(1-\alpha)/\alpha}$$

with the dust-like first term tracking the baryons at a fixed ratio for $\alpha \approx 3.3 - 3.4$, reproducing the observed $\rho_{DM}/\rho_B\approx5.3$ (Trivedi et al., 13 Nov 2025).

B. Geometric Invariants and Unified Dark Sector

• By expressing the IR cutoff in terms of curvature invariants, e.g., $$I_1 = R_{\alpha\beta\gamma\delta}R^{\alpha\beta\gamma\delta}$$, holographic energy densities are constructed as

$\rho_X = \frac{3\alpha}{8\pi G} \sqrt{|I_i|}$

The resulting $w_{\rm eff}(z)$ evolves from radiation-like ($w=1/3$) at high $z$, to dust ($w=0$) at moderate $z$, to DE-like ($w=-1$) at late times, unifying cosmological eras with no explicit particle species for dark matter (Aviles et al., 2011).

C. Boundary/Screen Tensor Dynamics

• The emergent screen scenario assigns the Brown–York tensor $T^{\rm BY}_{\mu\nu}$ as the source for both dark matter and dark energy:

$$T^{\rm BY}_{\mu\nu} = \frac{1}{\kappa_{d+1}}(K_{\mu\nu} - K g_{\mu\nu})$$

The Hamiltonian constraint yields a quadratic relation among normalized densities:

$$\Omega_D^2 = \frac{1}{2} \Omega_\Lambda (\Omega_D - \Omega_B)$$

This scenario is distinct from standard braneworld or DGP models in its one-sided (non-$Z_2$) construction and the entire dark sector being boundary-induced (Cai et al., 2017).

D. Vortex Solutions and Holographic Superconductors

• In AdS/CFT-based holographic superconductors, the inclusion of a second, "dark" U(1) field with kinetic mixing $\alpha$ modifies both the formation and stability of vortices in the boundary (superconducting) theory. The free energy of vortex configurations is lowered by the presence of the dark sector:

$$\Delta F \sim -\frac{\epsilon^2}{2}\Big[ B_{c2} \int \Theta(x,y) + \alpha \int A^{(1)} \beta(\alpha) \Big]$$

For $\alpha>0$, the stabilization of vortices is enhanced, providing a mechanism for early-universe string-like dark structures on which baryonic clustering occurs (Rogatko et al., 2015).

E. Holographic Black Hole Remnants and Discretely Charged Relics

• The Holographic Space-Time (HST) program posits that the end of inflation produces a dilute gas of primordial black holes (IBHs). If a small fraction $f\sim2\times10^{-9}$ of these carry discrete gauge charges (e.g., $Z_N$), Hawking evaporation leaves Planck-mass remnants, thermodynamically stable and effectively neutral apart from gravitational plus Aharonov–Bohm interactions (Banks et al., 2022, Barrau, 2022). The relative abundance of such dark relics naturally matches $\Omega_{DM}$ when $f$ is fixed by the radiation-to-matter equality temperature.

3. Clustering, Observational Phenomenology, and Constraints

Holographic dark matter models predict cold, pressureless matter-like clustering at linear order when the effective equation of state is $w=0$, and when the effective sound speed $c_s^2\to0$. This is satisfied in the geometric-invariant models (Aviles et al., 2011), Ricci-cutoff models (Trivedi et al., 13 Nov 2025), and in all cases where the holographic energy density term scales as $a^{-3}$. To ensure consistency with structure formation and CMB constraints, it is necessary that any subdominant "non-dust" components (e.g., terms scaling as $a^{-0.8}$) are sufficiently suppressed (integration constant $K$ small or zero).

Observationally, these models:

• Match expansion histories and fit SNe Ia, BAO, and CMB data with accuracy close to or marginally favoring them over standard $\Lambda$CDM, particularly in models that allow for a mild $w(z)$ evolution or phantom crossing (Aviles et al., 2011, Gough, 2016).
• Reproduce or mildly deviate from standard matter and CMB power spectra, with distinctions at the few percent level at $k\sim0.1\,h\,\mathrm{Mpc}^{-1}$, potentially testable with high-precision BAO and LSS measurements (Aviles et al., 2011).
• For emergent models based on the Brown–York tensor or the Hamiltonian constraint, Tully–Fisher-like relations emerge robustly (e.g., $v_f^4 \propto M_B$) (Cai et al., 2017).
• In PBH-remnant–based HST scenarios, the dark matter is entirely noninteracting except gravitationally and via extremely rare Aharonov–Bohm effects. This places it beyond direct-detection limits while maintaining consistency with BBN and microlensing constraints due to the low number density and small mass (Banks et al., 2022, Barrau, 2022).

4. Unified Dark Sector and Information-Theoretic Models

The HDIE model connects holography to information theory by linking the energy stored in bits associated with hot baryons to an effective dark sector component. The HDIE energy density tracks

$\rho_{\rm HDIE}(a) \propto a^{-1} T(a)$

with $T(a)$ the mean baryonic temperature. When $T(a)\propto a^{n}$, the HDIE equation of state transitions from $w\approx-1.8$ in the early universe ($z>1.35$) to $w\approx-1.03$ at late times, naturally unifying dark matter and dark energy as a function of stellar feedback and entropy generation. The model matches key cosmological observables, and the present-day ratio of HDIE to baryon energy, $2.15$, yields a total "dark fraction" of roughly $68\%$ (Gough, 2016).

A related class, the "holographic unification" models, uses a generalized IR cutoff $L$ with a constant term and Hubble-derivative corrections in the holographic energy density. This allows simultaneous recovery of both the cold dark matter and the cosmological constant behaviors without explicit matter content, with the dominant (1+z)$^3$ term playing the role of dust purely geometrically. The solution structure supports transitions between radiation, dust, and dark energy components and allows for a controlled departure from $\Lambda$CDM (e.g., via $w(z)$ evolution or quintom behavior) (Granda, 2011).

5. Holographic Dark Sectors in Condensed Matter and Particle Models

In the context of strongly coupled gauge theories, bottom-up holographic constructions extend the dictionary to accommodate hidden sectors and new composite states:

• Holographic superconductors with an additional U(1) gauge field (the "dark photon") incorporate dark-sector effects via kinetic mixing. While the supercurrent–temperature law remains unaffected, critical properties such as the transition temperature or chemical potential can shift according to the mixing $\alpha$ and dark-sector chemical potential $\mu_D$ or superflow $S_D$ (Rogatko et al., 2016).
• In technicolor contexts, the AdS/QCD dual of minimal walking technicolor predicts technibaryon dark-matter candidates (TIMPs), whose masses (2–4 TeV) and scattering cross-sections fall within reach of upcoming direct detection experiments. Here the holographic setup tightly connects the dark matter and Higgs phenomena via the soft wall parameter $\mu$ (Chen et al., 2019).

6. Distinctive Predictions, Limitations, and Open Issues

Holographic dark matter models entail several distinctive predictions and constraints:

• Non-particle Nature: Many of these models do not require new fundamental particles in the bulk or visible brane world; instead, the dark sector is encoded in geometric, informational, or boundary quantities.
• Testable Deviations: Subdominant power-law components or step-like changes in $w(z)$, if detected, could falsify these models or distinguish them from standard cold dark matter. Specifically, any measurable extra component scaling as $a^{-0.8}$ (for Ricci cutoff with nonzero $K$) would be a "smoking gun" (Trivedi et al., 13 Nov 2025).
• Implications for Vacuum Energy: The Ricci cutoff approach provides a mechanism for sign reversal of a bare vacuum energy, addressing the "string theory negative $\rho_\Lambda$" puzzle by flipping it to positive at the effective level (Trivedi et al., 13 Nov 2025).
• PBH/Remnant Models: Unique signals may include gravitational-wave backgrounds from relic cosmic string networks or ultra-high-energy quanta from rare Planck-mass remnant mergers.
• Clustering Physics: Ensuring the correct growth of linear and nonlinear structure requires the dark fluid to be cold ($c_s^2\to0$) and pressureless at late times. The construction of an explicit microphysical Lagrangian for such a component remains a key open question.

A plausible implication is that if any observed departure from $\Lambda$CDM in $w(z)$ or matter power spectrum is correlated with features predicted by the geometric, boundary, or information-based holographic models, this would favor emergent holographic dark matter explanations over particle-based candidates.

7. Comparative Overview of Model Classes

Model Type	Microphysics	Clustering	Key Prediction/Signature
IR Cutoff (Ricci, invariants)	Geometric	CDM-like	DM/baryon ratio fixed by cutoff
Information/Holographic Energy	Entropy/Info theory	Clumped DM	HDIE/baryon = 2.15; $w(z)$ step
HST PBH Remnants	Planck relics	CDM-like	$f$ fixed by $T_{eq}$; Z$_N$ strings
Boundary Stress (BY tensor)	Extrinsic geometry	Modified DM	$\Omega_D^2\sim\Omega_\Lambda(\Omega_D-\Omega_B)$
Holographic Vortices	U(1) mixing	Nucleation	Lower vortex free energy; clustering seeds

*Editor's term: "Holographic DM" generalizes across these model classes for clarity.

The landscape of holographic dark matter proposals thus encompasses models with strictly geometric origins, information-theoretic content, emergent stress tensors on holographic screens, and concrete particle-physics duals. While sharing the absence of a new fundamental CDM particle, these models provide a wide spectrum of novel cosmological phenomenology, distinct signatures, and theoretical challenges anchored in the deep structure of gravitational theories, holography, and the quantum information content of spacetime.