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The Theory of Measurements - VIB


the 5th?

 
4th June 2025



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From my description of the goal one can perhaps see some of the difficulties.
Since quantum gravity should be background-free, the geometrical structures defining the causal structure of spacetime should themselves be local degrees of freedom propagating causally.  This much is already true in general relativity.  But because quantum gravity should be a quantum theory, these degrees of freedom should be treated quantum-mechanically.  So at the very least, we should develop a quantum theory of some sort of geometrical structure that can define a causal structure on spacetime.


- John C. Baez, Higher-Dimensional Algebra
and Planck-Scale Physics, 1999.














































"Thus, the conclusion is that new ideas have arisen in loop quantum gravity which have some hope of resolving the problem of time and the problem of quantum cosmology.  Further, as a well formulated background independent quantum theory, loop quantum gravity allows older ideas about these problems to be precisely formulated and tested.  Meanwhile, while
string theory apparently does not offer so far anything new to resolve these problems, it is striking that a few string theorists have put forward proposals that appear to be inspired by
the ideas coming from loop quantum gravity. ”

- Lee Smolin, How far are we from the quantum theory of gravity?, 2003
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"This distinction between classical and quantum geometry is dramatically augmented by the
realization that topology change — an operation which by fundamental definition in classical geometry is discontinuous — can be perfectly continuous and smooth in the quantum geometry of string theory. "

-
Brian R. Greene, String Theory on Calabi-Yau
Manifolds, 1997.















































































































































































































































































































































































































 












































   
    
We continue our discussion of the measurement of a path PQ being measured with a stack of measurement circuits.  The path PQ represents an information δδ-function which is either singular or complex in nature.  The information contained within the Path PQ, is extracted by the observer using Mckts.  If all the information is extracted, the observer has arrived at the point Q from the starting point P.  The observer stays in the state of measurement until the measurement is complete.1


   
It is important to note that the measurement circuits Mckt, corresponds to the measurement capability of Obs1/1 (Obsc).  The system in the state of the measurement i.e. the electron orbiting around a proton, corresponds to the measurement capability of the Obs1/137 (Obselec). 

    Equivalently, the vector space V corresponds to Obs1/1, and the covector space V* corresponds to Obs1/137, such that V*:V .  We note that Lorentz Invariance / Möbius Invariance along with Locality and Unitarity, is implicit.  All the physical measurements, are made and interpreted in S-frame. 

     Let us quickly review the relativistic wave equation or Klein-Gordon equation first.




    We have a rather simple homemade criterion in j-space, based on the fact whether the measurement circuit Mckt can be completed or not, while making a measurement. 

 
     If the measurement circuit can be completed then we can write a relativistic wave equation for a spin-less particle, known as the Klein-Gordon equation.

    The idea is fairly straightforward.  We set up a field based on oscillations (harmonic).  We then write Lagrangian density of the field.  Next, we use Euler-Lagrange equation to derive the equation of motion, which is the Klein-Gordon equation.  An important point to note, is that mass appearing in this equation is based on interactions between oscillators. We provide a quick summary as follows.
 

   
Consider a pair of coupled (interacting) harmonic oscillators as shown.  We can write the Kinetic Energy T, Potential Energy V, and then the Lagrangian for the configuration as,

T=12mx1˙2+12mx2˙2T = \frac{1}{2}m{\dot{{x}_{1}}}^{2}+\frac{1}{2}m{\dot{{x}_{2}}}^{2},
V=12kx12+12kx22+12κ(x1x2)2,  and
L=TVL=T-V
    =12mx1˙2+12mx2˙212kx1212kx2212κ(x1x2)2.=\frac{1}{2}m{\dot{{x}_{1}}}^{2}+\frac{1}{2}m{\dot{{x}_{2}}}^{2}-\frac{1}{2}k{x}_{1}^{2}-\frac{1}{2}k{x}_{2}^{2}-\frac{1}{2}κ({x}_{1}-{x}_{2})^{2}.

    Now, suppose we place these oscillators infinitesimally close together i.e. (x2x1=0j)\left({x}_{2}-{x}_{1}={0}_{j}\right).  ( The value of the 0j is based on the measurement capability of the observer Obs1/1, i.e. The locality condition.  Therefore the precise measurement of 0j is not possible for Obs1/137, which has a lower measurement capability than Obs1/1.)

We select coordinate axes as,
(i)  x - the separation between the oscillators, and
(ii)  ϕ(x) - their respective vertical displacements also known as the field amplitudes.
  
    
    Imagine that we have infinite many of these oscillators infinitesimally close to each other. In this case, x is a continuous variable.


 And, rather than calculating total energy of the configuration, we write the Kinetic Energy Density 𝒯(t,x)𝒯, Potential Energy Density 𝒱(t,x)𝒱, and the Lagrangian density ℒ(t,x),  for the unit area of the configuration.

𝒯=12mφ˙2𝒯=\frac{1}{2}m{\dot{φ}}^{2}, and
𝒱=12kφ2+12κxφ2𝒱=\frac{1}{2}k{φ}^{2}+\frac{1}{2}κ{{∂}_{x}φ}^{2}.

Substitute κ=mκ=m and Φ=mφΦ=\sqrt{m}φ and then 𝓂2=km{𝓂}^{2}=\frac{k}{m}  to obtain,

𝒯=12(tΦ)2𝒯=\frac{1}{2}({∂}_{t}Φ{)}^{2}, and
𝒱=12𝓂2Φ2+12(xΦ)2𝒱=\frac{1}{2}{𝓂}^{2}{Φ}^{2}+\frac{1}{2}{({∂}_{x}Φ)}^{2}.

We note that by using the condition κ=mκ=m, we have made the mass measured in the unit area, purely interaction dependent.  We can write the Lagrangian density as,

(t,x)=𝒯(t,x)𝒱(t,x)==12(tΦ)212𝓂2Φ212(xΦ)2ℒ(t,x)=𝒯(t,x)-𝒱(t,x)==\frac{1}{2}({∂}_{t}Φ{)}^{2}-\frac{1}{2}{𝓂}^{2}{Φ}^{2}-\frac{1}{2}{({∂}_{x}Φ)}^{2}.

The Euler-Lagrange equation for field in terms of the Lagrangian density (t,x)ℒ(t,x), is given as,

Φi=μ((μΦi))\frac{∂ℒ}{{∂Φ}^{i}}={∂}_{μ}\left(\frac{∂ℒ}{∂({∂}_{μ}{Φ}^{i})}\right).

Substituting for (t,x)ℒ(t,x), we get Klein-Gordon equations in 1-dimension and 3-dimensions as,

(t2x2+𝓂2)Φ=0\left({∂}_{t}^{2}-{∂}_{x}^{2}+𝓂^{2}\right)Φ=0  (1-D),
(t2x2y2z2+𝓂2)Φ=0 (3-D).\left({∂}_{t}^{2}-{∂}_{x}^{2}-{∂}_{y}^{2}-{∂}_{z}^{2}+𝓂^{2}\right)Φ=0
 
Here the quantity 𝓂𝓂 represents, the interaction based mass density (mass for a unit area/volume), in the field Φ(t,x)Φ(t,x).        


     
    The objection to Kaluza's theory, was with his assumption of the existence of the 5th dimension, which was cylindrical.   For Kaluza, it was a mathematical construct which unified General Relativity with Electromagnetism.  However if the 5th dimension exists then it must be observed experimentally. 

    An attempt was made by Oscar Klein to introduce the quantum mechanics to explain the 5th dimension as follows:

Define a scalar field Φ(xM)=Φ(xμ,x5)
Φ({x}^{M})=Φ({x}^{μ},{x}^{5})


    Write Klein-Gordon equation in 5-D as

(t2x2y2z2+52+𝓂02)Φ=0\left({∂}_{t}^{2}-{∂}_{x}^{2}-{∂}_{y}^{2}-{∂}_{z}^{2}+{∂}_{5}^{2}+{𝓂}_0^{2}\right)Φ=0.

Introduce a boundary condition for the scalar field Φ(xM)Φ({x}^{M}) as

Φ(xμ,x5)=Φ(xμ,x5+2πa)Φ({x}^{μ},{x}^{5})=Φ({x}^{μ},{x}^{5}+2πa).

(aa is called compatification scale, assumed to be of the order of Planck's length)


Assume a sinusoidal dependence for ΦΦ on x5 and use harmonic expansion to obtain decoupled 4D Klein-Gordon Equation as,

(t2x2y2z2+𝓂n2)Φ(xμ)=0\left({∂}_{t}^{2}-{∂}_{x}^{2}-{∂}_{y}^{2}-{∂}_{z}^{2}+{𝓂}_{n}^{2}\right)Φ({x}^{μ})=0,
where 𝓂n2=𝓂02+n2a2.{𝓂}_{n}^2={𝓂}_{0}^2+\frac{{n}^{2}}{{a}^{2}}.

The problem immediately arose as the value of the mass of the 1st mode m1 would have been around 1019 GeV.  The verification of such a high value of mass is not possible.

    However, as we discussed earlier the mass 𝓂𝓂 in Klein-Gordon equation represents the interaction between oscillators, rather than the inertial mass of a particle (boson). 

    Perhaps the extrapolation of the classic 4-D Klein-Gordon equation to 5-D equation, based on the theory proposed by Kaluza, is not so straightforward.  We simply can not go on adding space dimensions into a relativistic field equation beyond 3-D, while keeping t{∂}_{t}, or et^\widehat{{e}_{t}}, unchanged. 
 


 

     The more fundamental issue is the independence of 4-D geometry from x5.  At present, there is no satisfactory explanation for this independence. 

  
Let us review the role of the metric tensor in geometric space.  We have two descriptions, we can call bird's eye view of space-time (extrinsic view for the observer) and bug's eye view of space-time (intrinsic view of the observer in S-frame). 




    In General Relativity the space-time is curved (extrinsic view), however the observer measures the space as flat and time as linear (intrinsic view or S-frame). The metric tensor gμν{g}_{μν} provides the relationship between both, so that the equations of motion can be derived in the flat-space. 

   We keep in mind that what we are calling extrinsic view or phase space , acts on every point (j-pixel) in the measurement space.  Therefore the value of metric tensor may change from j-pixel to j-pixel in S-frame, for a curved phase space.   And subsequently if we want a metric which is coupled to every j-pixel of space-time in GR, the metric must not change across j-pixels underlying the geometry in S-frame. 

    There is only one possibility as shown below, and it corresponds to Kaluza's cylindrical condition x5=0\frac{∂}{{∂x}^{5}}=0.

   

    Therefore in a discrete measurement space, the structure formed by the measurement circuits in the abstract gauge space, must be cylindrical.  Only then they can describe the geometry in the observer's frame of reference.

  Furthermore since the structure represents the progression of measurements, it will have its own time axis ττ  along the path PQ, which is likely to be below Planck's scale.  (Looks like we just contradicted quantum mechanics, which does not allow another intrinsic space-time description within S-frame, possibly because of the unitarity condition.)3

    We also note that since there is a displacement within this gauge space, it will result in establishing a 2D charge space, represented by Mckt.  The completed measurement in this charge space, i.e. completion of measurement for the path PQ, will result in the measurement of a unit of charge in the intrinsic space of the observer in S-frame. 

    Additionally, a displacement in the phase space is likely to cause the physical motion in the intrinsic space of the observer in S-frame.

   Keeping in mind that xx in phase space corresponds to its own time axis ττ in phase space, the physical dimension aa used in Kaluza-Klein theory and time τ, τ both are well below the measurement capability of the observer Obs1/137.  Symbolically, we can write the scalar field as,

ϕ(xμ,x5)=ϕ(xμ,x5+2π0j),a=0j.
ϕ\left({x}^{μ},{x}^{5}\right)=ϕ\left({x}^{μ},{x}^{5}+2π{0}_{j}\right), \;a={0}_{j}.


The quantity 2π0j2π{0}_{j}, is measurable in intrinsic phase space, but below the measurement threshold in S-frame. 

   The property of invariance under U(1) transformation eiθx{e}^{iθx}(Electromagnetic Field), is satisfied by each measurement circuit in the phase space. 

x5=x5+θ(x),{x}^{5} = {x}^{5}+θ(x),
    ψψ,=U(x)ψ,
ψ→{ψ}^{,}=U(x)ψ,

    andU(x)=eiθx.and\;U(x)={e}^{iθx}.
 
     When we look for invariance of a wave-function under a gauge transformation, the space xx refers to the intrinsic phase space in S-frame of the observer Obs1/137.  Thus the quantity ds2{ds}^{2} remains unchanged with Kaluza ansatz. 

   The cylindrical structure proposed by Kaluza corresponds to Mckt in discrete measurement space.  It reflects the capacity of the maximum efficiency observer Obs1/1 to make a measurement in a given field.     

    Since 4D-space is independent of variation in x5{x}^{5}, no internal structure for the cylindrical path PQ, can be measured in the flat-space or the intrinsic space of the macroscopic observer.


 
    The methodology proposed by Klein, is an important one.  We will be discussing its implications in the discrete measurement space next.
 
  ....to be continued   
______________

1.  If the observer travels the path PQ in one step, i.e. all the information contained within the path PQ is extracted by a single measurement, it is called zero-entropy measurement.  The time-axis has no physical significance in this case as loge1 = 0.

2. The Klein-Gordon equation describes the relativistic motion of composite particles with spin 0,  or equivalently the measurements of a composite information δδ-function in j-space.  So the equation of motion of a Higgs boson can be described by Klein-Gordon equation.

3. Lochlainn O'Raifeartaigh, The Dawning of Gauge Theory,  Princeton Series in Physics, 1997, page 68.




 

 




 




 

Previous Blogs:


The Theory of Measurements - VIA


The Theory of Measurements - V


The Theory of Measurements - IV


The Theory of Measurements - III


The Theory of Measurements - II


The Theory of Measurements - I


An Ecosystem of δ-Potentials - IVB
 
An Ecosystem of δ-Potentials - IVA

An Ecosystem of δ-Potentials - III

An Ecosystem of δ-Potentials - II

An Ecosystem of δ-Potentials - I

Nutshell-2019

Stitching Measurement Space - III

Stitching Measurement Space - II

Stitching Measurement Space - I

Mass Length & Topology

A Timeless Constant

Space Time and Entropy

Nutshell-2018

Curve of Least Disorder

Möbius & Lorentz Transformation - II

Möbius & Lorentz Transformation - I

Knots, DNA & Enzymes

Quantum Comp - III

Nutshell-2017

Quantum Comp - II

Quantum Comp - I

Insincere Symmetry - II

Insincere Symmetry - I

Existence in 3-D

Infinite Source

Nutshell-2016

Quanta-II

Quanta-I

EPR Paradox-II
 
EPR Paradox-I

De Broglie Equation

Duality in j-space

A Paradox

The Observers
 
Nutshell-2015
 
Chiral Symmetry

Sigma-z and I

Spin Matrices

Rationale behind Irrational Numbers

The Ubiquitous z-Axis

 

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