scholarly journals Brane Gases on K3 and Calabi–Yau Manifolds

2003 ◽  
Vol 18 (23) ◽  
pp. 4295-4314 ◽  
Author(s):  
Damien A. Easson
Keyword(s):  
String Theory ◽  
Particle Physics ◽  
Thermal Equilibrium ◽  
Initial Singularity ◽  
Superstring Theory ◽  
Initial State ◽  
Four Dimensions ◽  
Cosmological Context ◽  
Spatial Dimensions ◽  
The Universe

We initiate the study of Brane Gas Cosmology (BGC) on manifolds with nontrivial holonomy. Such compactifications are required within the context of superstring theory in order to make connections with realistic particle physics. We study the dynamics of brane gases constructed from various string theories on background spaces having a K3 submanifold. The K3 compactifications provide a stepping stone for generalizing the model to the case of a full Calabi–Yau threefold. Duality symmetries are discussed within a cosmological context. Using a duality, we arrive at an N=2 theory in four dimensions compactified on a Calabi–Yau manifold with SU(3) holonomy. We argue that the Brane Gas model compactified on such spaces maintains the successes of the trivial toroidal compactification while greatly enhancing its connection to particle physics. The initial state of the universe is taken to be a small, hot and dense gas of p-branes near thermal equilibrium. The universe has no initial singularity and the dynamics of string winding modes allow three spatial dimensions to grow large, providing a possible solution to the dimensionality problem of string theory.

Interstellar Overdrive

2020 ◽  
pp. 58-66
Author(s):  
Nicholas Mee
Keyword(s):  
String Theory ◽  
Laws Of Nature ◽  
Platonic Solids ◽  
Symmetrical Shape ◽  
Regular Arrangement ◽  
Spatial Dimensions ◽  
The Universe

Kepler sought patterns and symmetry in the laws of nature. In 1611 he wrote a booklet, De Niva Sexangular (The Six-Cornered Snowflake), in which he attempted to explain the structure of familiar symmetrical objects. Almost 300 years before the existence of atoms was definitively established, he concluded that the symmetrical shape of crystals is due to the regular arrangement of the atoms of which they are formed. He also investigated the structure of geometrical objects such as the Platonic solids and the regular stellated polyhedra, known today as the Kepler–Poinsot polyhedra. Like Kepler, today’s theoretical physicists are seeking patterns and symmetries that explain the universe. According to string theorists, the universe includes six extra hidden spatial dimensions, forming a shape known as a Calabi–Yau manifold. No-one knows whether string theory will revolutionize physics like Kepler’s brilliant insights, or whether it will turn out to be a red herring.

scholarly journals Geography of fields in extra dimensions: String theory lessons for particle physics

2015 ◽  
Vol 30 (10) ◽  
pp. 1530008 ◽  
Author(s):  
Hans Peter Nilles ◽  
Patrick K. S. Vaudrevange
Keyword(s):  
String Theory ◽  
Particle Physics ◽  
Extra Dimensions ◽  
Model Building ◽  
Unified Theory ◽  
Fundamental Interactions ◽  
Spatial Dimensions ◽  
Physics Model ◽  
String Theories

String theoretical ideas might be relevant for particle physics model building. Ideally one would hope to find a unified theory of all fundamental interactions. There are only a few consistent string theories in D = 10 or 11 spacetime dimensions, but a huge landscape in D = 4. We have to explore this landscape to identify models that describe the known phenomena of particle physics. Properties of compactified six spatial dimensions are crucial in that respect. We postulate some useful rules to investigate this landscape and construct realistic models. We identify common properties of the successful models and formulate lessons for further model building.

scholarly journals Dimensions of Space

2020 ◽  
Vol 3 (11) ◽  
pp. 74-79
Author(s):  
Kedar Pansare ◽  
Meghraj Parab ◽  
Vrushabh Parmar ◽  
Yashwantrao Mitnasala ◽  
Rajni Bahuguna
Keyword(s):  
Quantum Gravity ◽  
Loop Quantum Gravity ◽  
Higher Dimensions ◽  
Superstring Theory ◽  
Unified Theories ◽  
Spatial Dimensions ◽  
The Universe ◽  
Dimensions Of Space

The existence and the mysteries of the universe could not be explained by using just 3 spatial dimensions. There was a need to think of higher dimensions as a tool to explain the phenomena happening in our universe. Therefore, unified theories such as Loop Quantum Gravity and Superstring Theory were proposed. We will be taking an overview of these theories in order to get some idea about each.

ON THE HEISENBERG INDETERMINACY PRINCIPLE AND THE FORMATION OF STRUCTURE IN THE UNIVERSE

1995 ◽  
Vol 10 (07) ◽  
pp. 539-547 ◽  
Author(s):  
M. D. POLLOCK
Keyword(s):  
Background Radiation ◽  
Density Fluctuations ◽  
Internal Space ◽  
Superstring Theory ◽  
Scale Invariant ◽  
Classical Action ◽  
Four Dimensions ◽  
Dimensionless Constant ◽  
Microwave Background Radiation ◽  
The Universe

The Heisenberg indeterminacy principle ΔpaΔqa ~ ħ, relating canonically conjugate variables pa and qa, is quantified for the classical action obtained by the reduction of the ten-dimensional heterotic superstring theory to four dimensions, in the mini-superspace (Friedmann space-time) [Formula: see text]. There are two coordinates, α and [Formula: see text], representing position and velocity, respectively, the canonical momenta being [Formula: see text] and [Formula: see text]. In both cases, the result can be expressed as an indeterminacy in the time, (Δt/t)2. The fluctuations connecting position and velocity decrease with time and are always undetectably small, Δt/t ≲ 10−44. But the fluctuations involving velocity and acceleration increase with time, and are evaluated at the time te of equipartition of radiation and matter in the universe. Translated first into a metric fluctuation [Formula: see text], this is equivalent to a Gaussian, scale-invariant spectrum of density fluctuations of magnitude [Formula: see text], where the dimensionless constant B depends only on the compactification scheme. For a Calabi–Yau internal space, the estimate B ≈ 3 implies that ζ ≈ 2 × 10−4, which is sufficient for the creation of galaxies and in approximate agreement with observations of the anisotropy of the cosmic microwave background radiation by COBE and at Tenerife.

Inflation, dark matter, and dark energy

2019 ◽  
pp. 423-464
Author(s):  
Malcolm S. Longair ◽  
Chris Smeenk
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Power Spectrum ◽  
Early Universe ◽  
Particle Physics ◽  
Large Scale ◽  
Initial State ◽  
Large Scale Structures ◽  
Initial Power ◽  
The Universe

The success of the ΛCDM model has raised a number of challenging problems for the origin of structure in the universe and the initial state from which it evolved. The origins of these basic cosmological problems are described. The dark matter must be non-baryonic, but its nature has not been established. Likewise, the nature of the dark energy is not understood. The inflationary model for the very early universe has had some undoubted successes in accounting for the initial power-spectrum of fluctuations from which large-scale structures formed but there is no physical realization of the inflaton field. Defects formed during phase transitions in the early universe cannot account for the initial power spectrum of fluctuations, but may have some part to play in structure formation. The origin of the baryon-antibaryon asymmetry in the early universe is not understood in terms of theories of particle physics.

scholarly journals The String Theory Landscape

Universe ◽  
2019 ◽  
Vol 5 (7) ◽  
pp. 176 ◽  
Author(s):  
Michael R. Douglas
Keyword(s):  
String Theory ◽  
Cosmological Constant ◽  
Particle Physics ◽  
Cosmological Constant Problem ◽  
Grand Unified Theories ◽  
Eternal Inflation ◽  
The Standard Model ◽  
Unified Theories ◽  
Spatial Dimensions ◽  
M Theory

String/M theory is formulated in 10 and 11 space-time dimensions; in order to describe our universe, we must postulate that six or seven of the spatial dimensions form a small compact manifold. In 1985, Candelas et al. showed that by taking the extra dimensions to be a Calabi–Yau manifold, one could obtain the grand unified theories which had previously been postulated as extensions of the Standard Model of particle physics. Over the years since, many more such compactifications were found. In the early 2000s, progress in nonperturbative string theory enabled computing the approximate effective potential for many compactifications, and it was found that they have metastable local minima with small cosmological constant. Thus, string/M theory appears to have many vacuum configurations which could describe our universe. By combining results on these vacua with a measure factor derived using the theory of eternal inflation, one gets a theoretical framework which realizes earlier ideas about the multiverse, including the anthropic solution to the cosmological constant problem. We review these arguments and some of the criticisms, with their implications for the prediction of low energy supersymmetry and hidden matter sectors, as well as recent work on a variation on eternal inflation theory motivated by computational complexity considerations.

scholarly journals Discrete Model of Electron

2019 ◽  
Vol 11 (6) ◽  
pp. 36
Author(s):  
Jose Garrigues-Baixauli
Keyword(s):  
Discrete Model ◽  
Fundamental Constants ◽  
Planck Length ◽  
Intrinsic Properties ◽  
Electron Wave ◽  
Electron Model ◽  
Four Dimensions ◽  
Rotational Movement ◽  
Spatial Dimensions ◽  
The Universe

An electron model is developed based on a 4D sphere with a diameter of the Planck length. This model allows us to explain and calculate the intrinsic properties of the electron, such as its mass, charge, spin, etc., from the fundamental constants. Using this Planck sphere in four dimensions, we reach the conclusion that the electron particle has a size that is fixed by the Planck dimensions. The rotation of the Planck sphere generates the electron wave, the size of which depends on its wavelength. Our hypothesis is that the universe is composed of Planck spheres in four spatial dimensions, with two possible states: a rest state and rotational movement.

ON THE COSMOLOGY OF THE AXION IN THE HETEROTIC SUPERSTRING THEORY

1992 ◽  
Vol 01 (02) ◽  
pp. 407-425 ◽  
Author(s):  
M.D. POLLOCK
Keyword(s):  
Dark Matter ◽  
Gravitational Constant ◽  
Energy Scale ◽  
Supersymmetric Particle ◽  
Closed Universe ◽  
Coupling Constant ◽  
Superstring Theory ◽  
Four Dimensions ◽  
Upper Limit ◽  
The Universe

The heterotic superstring theory, after reduction to four dimensions, is known to contain two axions, found by Witten, and studied further by Choi and Kim. One combination of these can be identified with the axion of Peccei and Quinn, whose energy scale is then given by the formula [Formula: see text], where [Formula: see text] is the ratio of the two separate energy scales, g s is the strong-interaction coupling constant and M P ≡G−1/2 is the Planck mass, G being the Newton gravitational constant. This agrees with the result obtained by Choi and Kim, apart from a factor of [Formula: see text], which is explained. For a supersymmetric theory, Steinhardt and Turner have shown, developing an idea by Weinberg, that the upper limit on this parameter, corresponding to a closed Universe today, is f a ≲1013ζ9/11≈4×1016 GeV , where ζ≲3×104 is the entropy enhancement accompanying the decay of a supersymmetric particle, presumed to be the gravitino of mass M g ≈104 GeV . These two calculations of f a differ only by a factor of 15 (agreement is obtained for M g ≈106−107 GeV ), suggesting that axions may constitute the dark matter of the Universe. Some further aspects of superstring axions are discussed, including their rôle in the formation of wormholes.

An Interview with the Physicist that Her Head in the Universe and Both Feet on the Earth

2019 ◽  
Author(s):  
Adib Rifqi Setiawan
Keyword(s):  
Standard Model ◽  
Particle Physics ◽  
Space Time ◽  
Additional Dimension ◽  
The Earth ◽  
The Standard Model ◽  
The Universe

Put simply, Lisa Randall’s job is to figure out how the universe works, and what it’s made of. Her contributions to theoretical particle physics include two models of space-time that bear her name. The first Randall–Sundrum model addressed a problem with the Standard Model of the universe, and the second concerned the possibility of a warped additional dimension of space. In this work, we caught up with Randall to talk about why she chose a career in physics, where she finds inspiration, and what advice she’d offer budding physicists. This article has been edited for clarity. My favourite quote in this interview is, “Figure out what you enjoy, what your talents are, and what you’re most curious to learn about.” If you insterest in her work, you can contact her on Twitter @lirarandall.

An Interview with the Physicist that Her Head in the Universe and Both Feet on the Earth

2019 ◽  
Author(s):  
Adib Rifqi Setiawan
Keyword(s):  
Standard Model ◽  
Particle Physics ◽  
Space Time ◽  
Additional Dimension ◽  
The Earth ◽  
The Standard Model ◽  
The Universe

Put simply, Lisa Randall’s job is to figure out how the universe works, and what it’s made of. Her contributions to theoretical particle physics include two models of space-time that bear her name. The first Randall–Sundrum model addressed a problem with the Standard Model of the universe, and the second concerned the possibility of a warped additional dimension of space. In this work, we caught up with Randall to talk about why she chose a career in physics, where she finds inspiration, and what advice she’d offer budding physicists. This article has been edited for clarity. My favourite quote in this interview is, “Figure out what you enjoy, what your talents are, and what you’re most curious to learn about.” If you insterest in her work, you can contact her on Twitter @lirarandall.

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