Unveiling the Invisible: The Interplay Between Dark Matter and

Dark Energy in Cosmic Evolution

Daniel Yikai Qiu

The Peddie School, 21 South Main Street, Hightstown, U.S.A.

Keywords: Dark Matter, Dark Energy, Cosmic Evolution, Cosmic Expansion.

Abstract: In astrophysics, a lot of astrophysical phenomena seem to act differently than what is predicted by typical

understandings of regular physics. For example, in reference to the expansion of the universe, the expansion

rate should be slowing down due to the force of gravity, yet it does not, and through measurements of Standard

candles, the universe is observed to be expanding at an increasingly fast rate. This implies the existence of

another force or energy counteracting and overpowering the force of predicted gravity. Dark matter and dark

energy play the crucial roles in the formation of all cosmic structures. The former study reveals that there are

some things that cannot be directly observed that have significant impact on cosmic evolution: dark matter

and dark energy. In this paper, the author will demonstrate the interplay between dark matter and dark energy,

which will eventually play important role on the cosmic evolution.

1 INTRODUCTION

In the universe, everything seemed to make sense in

accordance to Newtonian physics, yet when looking

at astronomical objects, certain obejcts behave

differently, and eventually patterns emerge.

Following the Big Bang, the universe had expanded

at a rapid rate, and contrary to prediction of the force

of gravity slowing down said expansion, an unknown

energy or force was driving the expansion to speed

up. Once observing certain astronomical objects, it

can be noted that certain objects seemed to be moving

on its own, which does not make sense, implying an

unseen gravitational influence on these objects, which

is considered as dark matter. Due to its obvious

significance in cosmic evolution and expansion,

scientists have come up with a vast number of

theories and models to predict the behvaiors and

properties of dark matter and dark energy. Dark

matter and dark energy’s properties make it hard to

work with, and as a result it is a theoretical form of

matter and energy.

https://orcid.org/0009-0009-1467-9345

2 THEORETICAL FRAMEWORK

Matter is described as anything that has mass and

occupies space. However, there are 2 kinds of

matters, normal matter, something people are more

accustomed to, since light of different wavelengths

can typically reflect off it, and dark matter. Dark

matter is a theoretical type of matter that is

“invisible”, meaning it does not emit, reflect, or

absorb any kind of electromagnetic radiation (e.g. X-

rays, radio waves) or light, and moves slowly relative

to the speed of light. Based on the ΛCDM model,

95% of the universe is dark matter and dark energy,

and 5% of the universe consists of atomic matter

(NASA).

Dark energy, on the other hand, is predicted to be

a hypothetical type of energy that is primarily thought

to contribute to the universe’s expansion (NASA). It

produces a negative pressure which drives the

acceleration of the universe, disproving the belief that

gravity will eventually slow down the expansion.

Despite having a very low density, its widespread

presence across the universe makes it dominant in the

mass-energy content.

Free streaming length is an important distance in

astrophysics in regard to dark matter, since it

330

Qiu, D.

Unveiling the Invisible: The Interplay Between Dark Matter and Dark Energy in Cosmic Evolution.

DOI: 10.5220/0013075900004601

Paper published under CC license (CC BY-NC-ND 4.0)

In Proceedings of the 1st International Conference on Innovations in Applied Mathematics, Physics and Astronomy (IAMPA 2024), pages 330-334

ISBN: 978-989-758-722-1

describes the maximum distance dark matter can

travel before being slowed down by gravitational

interactions (Einasto, 2009). Dark matter can then be

divided into three categories, which, contrary to the

name of the three categories has nothing to do with

the temperature and more so to do with the velocity:

CDM (Baudis & Promufo, 2021), WDM, and HDM,

cold, warm, and hot. In simple terms, CDM would

result in structural formation that follows galaxies

forming before galaxy clusters, while HDM will

result in large-scale matter congregations, followed

by a separation into galaxies (Primack & Gross,

2000).

2.1 WIMPS

There are several theories about dark matter and dark

energy, one of which are weakly interacting massive

particles, or WIMPs. WIMPs are defined as heavy,

electromagnetically neutral subatomic particles. It is

theorized to be a major constituent of dark matter. It

is seen as an elementary particle, not necessarily from

the Standard Model, that interacts with gravity and

the weak nuclear force, and is predicted by

supersymmetry, universal extra dimension models,

and the little Higgs model. Other traits are its greater

mass relative to typical standard particles. It doesn’t

absorb or emit any sort of electromagnetic radiation

(Caltech, 2002). All evidence on WIMPs has been

indirect.

2.2 MACHOS

Another theory of dark matter is abbreviated as

MACHOs, or massive compact halo object. Little is

known about MACHOs due to their lack of

luminosity (Caltech, 2002). However, there are

several MACHOs candidates, black holes, neutron

stars, brown dwarfs, and potentially planets that drift

through space without a proper planetary system all

can be categorized as candidates.

2.3 NEUTRINOS

A neutrino is a fermion that only interacts with the

weak nuclear force and gravity. There are a few

distinctive traits of neutrinos. Neutrinos are

electromagnetically neutral, and thus do not interact

with electromagnetic forces, adding on to its already

elusive nature. The neutrino also has an extremely

small mass. While unknown, it is predicted to be

significantly smaller than electrons. It has ½ unit of

spin. There are three leptonic flavors of neutrinos: the

electron neutrino, muon neutrino, and the tau

neutrino. Neutrinos are created because of radioactive

decay, examples such as beta decay, nuclear reactions

within a star, supernovae, and more. The three

leptonic flavors are potential candidates for dark

matter, specifically hot dark matter, meaning it moves

at nearly the speed of light at redshift z ~ 10

2.4 Leading Theories of Dark Energy

2.4.1 Cosmological Constant

The cosmological constant, a fundamental constant in

Einstein’s general relativity is associated with dark

energy. In Einstein’s equation E = mc

, mass and

energy are relative to one another, indicating this

energy has a gravitational effect. The cosmic

microwave background does not rule neutrinos as a

candidate for dark energy, but sterile neutrinos, those

that exclusively interact with gravity and no

fundamental forces, could potentially make up hot

dark matter.

2.4.2 Quintessence

Quintessence is a hypothetical candidate for dark

energy, an attempt to explain the constant expansion

of the universe, a form of vacuum energy. Its

variation in space and time differs it from the

cosmological constant (Caldwell, 2019).

Quintessence is predicted to be a scalar field. It is

spatially inhomogeneous, thus varies in different

locations. It is predicted to have a negative pressure,

which can be associated with the accelerating

expansion of the universe.

3 OBSERVATIONAL EVIDENCE

3.1 Dark Matter Evidence

3.1.1 Galactic Rotation Curve

In galaxies, the arms rotate around the center, and this

rotation is solid evidence of the existence of dark

matter. Rotation curves are calculated via rotational

velocity of stars along the length of the galaxy. When

studying galactic rotation curves, it can be found that

stellar rotational velocity remains constant, even

when the stars are further away from the center of the

galaxy. Based on Newton’s law of universal

gravitation, rotational velocity should theoretically

decrease as the distance from the center increases, yet

it remains constant. In the solar system, planets that

are further away rotate around the sun at a slower rate.

Unveiling the Invisible: The Interplay Between Dark Matter and Dark Energy in Cosmic Evolution

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Based on Kepler’s laws, this is clearly different for

galaxies, indicating that there is a halo of abundant

dark matter surrounding galaxies. Through studying

gas clouds near the edge of galaxies, one can

conclude that there is no concentrated mass

distribution in galaxies.

3.1.2 Gravitational Lensing

Gravitational lensing is a phenomenon where massive

objects bend light between said object and an

observer. Since it is known that although direct

observation of dark matter is impossible, dark matter

does still distort light. When light passes through

dense amounts of dark matter, these distortions can be

observed on galaxies. There are three types of

gravitational lensing, strong gravitational lensing,

weak gravitational lensing and microlensing. Strong

gravitational lensing involves a large mass acting as

the lens, with favourable geometry, and a large

deflection, usually capable of producing multiple

copies of images. Weak gravitational lensing involves

a large mass with less favourable geometry, with

distorted imagery. Microlensing involves smaller

masses, such as stars, and despite favourable

geometry, it is difficult to fix distortions in images.

Microlensing can be used to indirectly observe

MACHOs, using the duration of certain events to

predict lens mass, which in turn can be used to predict

the halo model. This permits measurement of cluster

mass without needing velocity.

Two galaxy clusters collided onto one another,

and specifically the smaller cluster traveling away

from the collision was designated 1E 0657-56, better

known as the Bullet cluster. It is strong evidence for

the existence of dark matter. Dark matter was

detected indirectly by using gravitational lensing. In

accordance with MOND, the gravitational lensing

should follow baryonic matter, yet it doesn’t, and is

instead separated into 2 parts. And with the

knowledge that dark matter interacts with gravity

exclusively, it can be predicted that the 2 areas with

the strongest gravitational concentration is dark

matter. Other modified theories cannot otherwise

explain this displacement in its center of mass.

3.1.3 Velocity Dispersion

Stellar velocity dispersion is shown to be related to

dark matter halos. In accordance with the Virial

theorem, it is possible to measure distribution of mass

within a system, such as a galaxy cluster. Scattering

in radial velocity of galaxies can help with mass

estimation (Yang et al., 2011). Velocity dispersion is

different from observed mass distribution, which can

only be explained by dark matter.

3.1.4 Linear Structure Formation

Dark matter is important for linear structure

formation, since it permits the formation of compact

structures without the influence of radiation pressure

due its property of only interacting with gravity. Dark

matter halos form through gravitational collapse,

creating the familiar astronomical web (Frenk &

White, 2012), which reveals all kinds of structures

like galaxies, galaxy clusters and more (Nadler,

2022).

3.1.5 Non-Linear Structure Formation

Dark matter is also proposed to be crucial in non-

linear structure formation. Dark matter overdensities

help with structure formation, as baryonic

fluctuations are smaller (Mina et al., 2022). This

results in dark matter being the dominant force of

structure formation.

3.1.6 Lyα Forest

The Lyα forest is an absorption feature in

astronomical spectroscopy, specifically from distant

quasars’ spectra. It is caused by photons’ interactions

with neutral hydrogen in the intergalactic medium.

There are thousands of absorption systems from these

high-redshift quasars. The Lyα forest can be used to

constrain cosmological models that are related to dark

matter and constrain its properties.

3.2 Dark Energy Evidence

3.2.1 Type Ia Supernovae Observation

A method of observing dark energy involves

comparing distance measurements with predicted

redshift, which helped conclude that the universe had

expanded more in later stages, indicating an

acceleration. Type Ia supernovae are good cosmic

landmarks for observing things, called Standard

Candles. Observations of Type Ia Supernovae at

redshifts where z > 0.5 demonstrates the acceleration

of the universe, which disagrees with the common

belief that the universe’s expansion rate is

decelerating.

3.2.2 Baryon Acoustic Oscillations

Similarly to how Type Ia supernovae are crucial as

standard candles, BAO can be used as standard rulers

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to provide a length scale (Harvard). The lengths of

these hypothetical rulers is the distance between the

peaks of galaxy distribution. It is given that dark

energy is the reason for the universe’s accelerating

expansion. Understanding dark energy means

understanding and successfully measuring the rate of

acceleration, which BAO can help with, since it

provides information about the current sound horizon

to that of different time periods. BAO can help

measure the distance-redshift relations, in particular

the expansion history of the universe, something

commonly associated with dark energy. Having BAO

data can make different test models for dark energy

possible.

3.2.3 Large-Scale Structures

Large-scale structures contribute to the formation of

all kinds of astronomical objects, and observations

point to the matter of such structures is up to 30% of

the universe’s density, which is constant with the idea

that 71.3% of the universe if dark matter while 27.4%

of it is dark matter and baryonic matter (NASA).

3.2.4 Cosmic Microwave Background

According to CMB anisotropies, the universe is

generally flat, which means mass-energy density has

to be equal to critical density, which gives scientists

the measurement of the ratio of matter to energy,

needing dark energy to fill the void that is the 70%

remaining (Harvard).

3.3 Combined Observation

Gravitational lensing is one of the most universally

useful methods for both dark matter and dark energy

observation. Gravitational lensing provides evidence

of objects' existence that can’t be detected normally.

This combined with measurements from the CMB

and large-scale structure formation are consistent

with the λCDM model of the universe (Harvard).

4 METHODOLOGY

4.1 Data Methods

There are many methods for detecting dark matter

and dark energy. Starting with dark matter, there are

numerous ways of direct and indirect detection.

Direct means of detection are very challenging, but

there are attempts, such as using SuperCDMS

(Cryogenic Dark Matter Search) SNOLAB, which

uses germanium and silicon detectors to find low-

mass dark matter particles, or WIMPs, or the LUX-

ZEPLIN, which utilizes liquid xenon to detect

interactions between dark and normal atomic matter.

As a result, scientists typically directly detect

dark matter and dark energy by observing changes in

movement in other objects, such dark matter decay.

Gamma-ray telescopes look for extra gamma-ray

emissions from high-density regions, such as the

center of a galaxy. Other methods involve the use of

particle accelerators in an attempt to create dark

matter via particle collisions. The most reliable way

is simply to observe things.

4.2 Analytical Techniques

A model was developed and then improved upon to

demonstrate the accretion of dark matter subhalos.

The function has many purposes, allowing the

prediction of un-evolved subhalo mass functions, the

mass function of subhalo accretions, accretion

distributions after being given a starting mass, and

frequency of mergers. Testing this with N-body

simulations reveals that the predictions of this

analytical model match up well with the simulations

(Yang et al., 2011).

5 RESULTS

5.1 Effects of Dark Matter on Cosmic

Structures

Dark matter plays a crucial role in the formation of all

cosmic structures. Its properties state it is exclusively

affected by gravity, and thus the effects of radiation

do nothing to it. Normal matter collapses later and

accelerates structure formation. From a technical

“bird’s eye view” of the universe, it can be seen that

all large-scale cosmic structures, galaxies, galaxy

clusters all seem to be arranged in a web-like structure

as a result of dark matter’s gravitational influence,

whether it be observed with linear and non-linear dark

matter structures.

5.2 Effects of Dark Energy on Cosmic

Expansion

Dark energy can be held accountable for the

unexpected accelerating rate of expansion of the

universe. Dark energy is proposed to exert a negative

pressure. Originally, the universe was predicted to

have stopped expanding and should slowly collapse,

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as gravity brings cosmological objects together,

which is no longer the case. It can be thought of as a

cosmological tug-of-war, where gravity originally

slower the expansion, only to be overpowered by dark

energy. Dark energy is also thought of as the force

that pushes galaxies and other large scale

astronomical objects apart. In most models of the

universe, the universe is “flat”. Dark energy’s

existence explains this as well.

6 CONCLUSIONS

Dark matter and dark energy are both unable to be

directly observed but extremely critical for cosmic

evolution, impacting numerous things, such as

galaxies, galaxy clusters, the distribution of

astronomical objects across the universe, formation of

large-scale linear and nonlinear structures, as well as

playing a role in the expansion of the universe itself.

Despite having similar names and overlapping areas

where it’s influence comes together, there are no

direct interactions between dark matter and dark

energy. The biggest problem with dark matter is that

it has not been directly reproduced or directly

observed, since it is known to not interact with

electromagnetic radiation. It only interacts with

gravity. Numerous other attempts at explaining

cosmological phenomena have been tried, usually

without inventing a completely different form of

matter, the best known being MOND, Modified

Newtonian Dynamics. Other problems with dark

matter is there is no understanding of its mass ranges,

which makes testing these theories impossible. One

of the most accepted models of dark matter, WIMPs,

have inconsistencies between its predicted abundance

in comparison to the dark matter density in the

universe. Current theories also struggle to give truly

accurate predictions of galactic rotation curves.

Similarly, dark energy faces several limitations

regarding its proposed theories. For example, there

are no set properties of dark energy, which prevents

good development of models. There are no real

constraints for dark energy modelling.

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