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THE STANDARD MODEL OF PARTICLE COSMOLOGY
AND ITS UNSOLVED PROBLEMS
A.M. Otajanov
Berdakh Karakalpak State University
Abstract:
Modern cosmology is based on the synthesis of general relativity (GR)
and the Standard Model (SM) of particle physics, known as the ΛCDM model. Despite
successes in describing the evolution of the Universe, fundamental questions remain:
the nature of dark matter and dark energy, the mechanism of cosmic inflation, and the
unification of quantum theory with gravity. This work analyzes key aspects of the
ΛCDM model, its connection to particle physics, and prospects for addressing
unresolved issues.
1. Introduction. Particle cosmology is an interdisciplinary field that studies the
evolution of the Universe through the lens of elementary particle physics. The
foundation is the ΛCDM model, which includes [1-2]:
▪ Dark matter (26.7% energy density), explaining anomalies in galactic rotation
curves;
▪ Dark energy (68.5%), responsible for accelerated expansion;
▪ Baryonic matter (4.8%) and cosmic inflation—rapid expansion in the early
stages.
However, the model faces challenges: the absence of direct dark matter detections,
uncertainty in the inflation mechanism, and the incompatibility of GR with quantum
mechanics [3].
2. Methodology and Key Results [4-5].
2.1. From Newtonian Cosmology to ΛCDM.
Classical Newtonian cosmology, relying on a static Universe model, failed to
explain Hubble’s observations (1929) of expansion. The solution emerged from
Friedmann’s equations derived from the Friedmann–Robertson–Walker (FRW) metric:
(
𝑎̇
𝑎
)
2
=
8𝜋𝐺
3
𝜌 −
𝑘
𝑎
2
+
𝛬
3
.
where
𝑎(𝑡)
is the scale factor,
𝜌
is energy density, and
𝛬
is the cosmological
constant.
2.2. The Standard Model of Particles and Its Limitations.
The SM describes three of the four fundamental interactions (excluding gravity)
via the gauge group,
𝑆𝑈(3) × 𝑆𝑈(2) × 𝑈(1)
. Despite the Higgs boson discovery
(2012), the SM fails to explain:
▪ Dark matter: Hypotheses include WIMPs (weakly interacting massive particles)
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and actions:
▪ Baryon asymmetry: CP-violation in the SM is insufficient to explain matter-
antimatter dominance.
2.3. Inflation and Its Problems [6-7].
Inflation solves the horizon and flatness problems by postulating exponential
expansion within the first
10
−32
s. Remaining questions include:
▪ Inflation nature: The scalar field driving inflation remains undetected;
▪ Initial conditions: The trigger mechanism for inflation is unknown.
2.4. Beyond the Standard Model.
▪ Supersymmetry (SUSY): Predicts SM particle partners but lacks confirmation
at the LHC;
▪ Grand Unified Theories (GUTs): Unify interactions at
10
16
GeV energies but
predict unobserved proton decay.
3. Unsolved Problems and Prospects [8-11].
▪ Dark matter: Ongoing searches in XENONnT and LZ experiments.
▪ Quantum gravity: String theory and loop quantum gravity are leading
candidates.
▪ Inflation: Data from the JWST telescope and LISA mission may clarify early
expansion [12].
4. Conclusion. The ΛCDM model successfully describes the Universe’s large-
scale structure but requires extensions to resolve fundamental issues. Integrating new
theories (SUSY, GUTs) with next-generation observatories (JWST, LISA) will
advance the quest for a complete quantum gravity theory.
References:
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of luminosities and radii. Astrophysical Journal, 238, 471–487.
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Astrophysical Journal, 517(2), 565–586.
3. Guth, A. H. (1981). Inflationary universe: A possible solution to the horizon and flatness
problems. Physical Review D, 23(2), 347–356.
5. ATLAS Collaboration (2012). Observation of a new particle in the search for the Standard
Model Higgs boson. Nature, 490(7418), 486–494.
6. Bertone, G., Hooper, D. (2018). History of dark matter. Reviews of Modern Physics, 90(4),
045002.
7. Linde, A. D. (1983). Chaotic inflation. Physics Letters B, 129(3–4), 177–181.
8. Wess, J., Zumino, B. (1974). Supergauge transformations in four dimensions. Nuclear
Physics B, 70(1), 39–50.
9. Georgi, H., Glashow, S. L. (1974). Unity of all elementary-particle forces. Physical Review
Letters, 32(8), 438–441.
10. April, E., et al. (XENON Collaboration) (2023). First Dark Matter Search Results from the
XENONnT Experiment. Physical Review D, 107(5), 052014.
11. Planck Collaboration (2020). Planck 2018 results. VI. Cosmological parameters.
Astronomy & Astrophysics, 641, A6.
12. Gell-Mann, M. (1964). A schematic model of baryons and mesons. Physics Letters, 8(3),
214–215.
