Yuri Semakov ( semakov@ukr.net )

Russian

SUPERLUMINAL COMMUNICATION IN THE PHYSICAL VACUUM VIA LONGITUDINAL WAVES

 

MODELS OF THE PHYSICAL VACUUM AND LONGITUDINAL WAVE SPEEDS WITHIN THEM

 

Introduction to the Series of Articles

 

Interstellar distances are not merely billions of kilometers, but the primary and seemingly insurmountable barrier to humanity's evolution into an interstellar civilization.

The modern world finds itself severely held hostage by a fundamental speed-of-light limit: even when traveling at the speed of light (c ≈ 3 × 10⁸ m/s), a conventional radio signal to the nearest star system, Alpha Centauri, will take over four years. Meanwhile, an attempt to establish communication with the opposite side of our Galaxy would drag on for tens of thousands of years.

Classical electrodynamics of transverse electromagnetic waves has passed a strict and unappealable verdict: instantaneous dialogue between stars is physically impossible.

But what if we have been looking for the answer in the wrong place, attempting to "accelerate" a transverse wave-shear form of oscillations in absolutely empty space?

Theoretical research and modeling of the physical vacuum open the door to a completely different world - a world of longitudinal waves of compression, densification, and rarefaction of the cosmic medium itself.

 

The main intriguing puzzle and simultaneously the primary skepticism of academic science surrounding longitudinal waves lies in the colossal, almost fantastical spread of their theoretically calculated speeds - from the decelerated plasma buffer of the galactic center at 10¹⁵ m/s  to 10²⁷ m/s  in the ultimate depths of cosmological voids:

 

Is this colossal 12-order-of-magnitude gap a critical mathematical contradiction that invalidates the very idea of superluminal communication?

Or are we facing a unified physical reality, stunning in its harmony and logic, manifesting itself at different scale levels of the Universe - from the microscopic electron gas to the scale of a closed spherical resonator of the Cosmos?

In this article we will prove that the difference in speeds is not an error in calculations or a failure of physical models, but a manifestation of the hierarchical structure of the medium (the "matryoshka principle"), where the wavefront undergoes a sequential shedding and gaining of inertia depending on the density of the material carrier of the signal.

Furthermore, it is precisely this dynamics of the longitudinal wave piston that for the first time provides a natural physico-mathematical resolution to the famous "Hubble Tension", explaining the 9% acceleration of space without invoking hypothetical dark energy.

 

 

1.       Maxwell Vlasov Physical Vacuum Model for the Milky Way Galaxy

 

1.1. Maxwell Vlasov Model: 10¹⁵ m/s (Galactic Nucleus)

 

Nature of the Medium: Vicinity of the Milky Way nucleus (bulge-gas disk, central molecular ring, and superdense H II zones near Sagittarius A*).

Physics of the Process: While near the Sun the concentration of free electrons is merely n_e ≈ 30,000 m⁻³, upon approaching the galactic center, the density of the ionized plasma gas dramatically increases by 3 to 4 orders of magnitude.

This gives rise to the maximum plasma-gravitational well in the Galaxy, creating limiting Coulomb and viscous drag for the wavefront.

Mathematical Calculation:

           Concentration of free electrons in the core (n_e_core): ≈ 10⁸ m⁻³ (3,300 times higher than in the Orion Arm)

           Electron charge (e): 1.602 × 10⁻¹⁹ C

           Electron mass (m_e): 9.109 × 10⁻³¹ kg

           Electric constant (ε₀): 8.854 × 10⁻¹² F/m

           Local scale of an individual stellar cluster/filament of the core (λ_local): ≈ 1 AU ≈ 1.496 × 10¹¹ m

Cyclic plasma frequency of the core (ω_p_core):

ω_p_core = √((n_e_core × e²) / (ε₀ × m_e))

ω_p_core = √((10⁸ × (1.602 × 10⁻¹⁹)²) / (8.854 × 10⁻¹² × 9.109 × 10⁻³¹)) ≈ 1.784 × 10⁵ rad/s

Linear plasma frequency of the core (ν_p_core):

ν_p_core = ω_p_core / (2 × π) = 1.784 × 10⁵ / 6.28318 ≈ 28,390 Hz (28.4 kHz)

Phase speed of the longitudinal wave on the local plasma scale of the core (v_core_local):

v_core_localν_p_core × λ_local = 28,390 Hz × 1.496 × 10¹¹ m ≈ 4.24 × 10¹⁵ m/s

 

The core of the Milky Way acts as a galactic speed minimum with a value on the order of 10¹⁵ m/s.

A wave coming from the intergalactic vacuum does not stop near the Sun, but enters the extreme local braking buffer of the core, after which it mirror-accelerates upon exiting onto the opposite side of the Galaxy.

 

1.2. Maxwell Vlasov Model: 10¹⁸ m/s (Interstellar Plasma)

 

Nature of the Medium: Rarefied interstellar plasma of the Galaxy.

In this academic model, the physical vacuum is considered completely empty, and the wave is strictly tied to known forms of matter - charged particles.

Physics of the Wave: Here, a longitudinal wave is a Langmuir plasma wave (collective displacement of free electrons relative to heavy hydrogen ions).

The inertia of an electron possessing a rest mass m_e sets the lower physical limit for the process speed.

Mathematical Calculation:

           Concentration of free electrons (n_e): 30,000 particles/m³ (3 × 10⁴ m⁻³)

           Electron charge (e): 1.602 × 10⁻¹⁹ C

           Electron mass (m_e): 9.109 × 10⁻³¹ kg

           Electric constant (ε₀): 8.854 × 10⁻¹² F/m

           Thermal velocity of electrons (v_T): 390,000 m/s (T ≈ 10,000 K)

Cyclic plasma frequency of the Galaxy (ω_p):  ω_p = √((n_e × e²) / (ε₀ × m_e))

ω_p = √((30,000 × (1.602 × 10⁻¹⁹)²) / (8.854 × 10⁻¹² × 9.109 × 10⁻³¹)) ≈ 3,089 rad/s

Phase speed of the longitudinal wave (v_ph) for the galactic scale λ = 1 light year ≈ 9.461 × 10¹⁵ m according to the Vlasov dispersion law: 

v_ph = √(((ω_p × λ) / (2 × π))² + 3 × v_T²)

Neglecting the negligibly small thermal term 3 × v_T², we get:

v_phν_p × λ = 491.6 Hz × 9.461 × 10¹⁵ m ≈ 4.65 × 10¹⁸ m/s

 

The rest mass of the electron holds the phase speed of the longitudinal plasma wave at 10¹⁸ m/s.

 

2.        Atsukovsky's Etherdynamics: 10²¹ - 10²³ m/s (Circumstellar Gaseous Ether)

 

Nature of the Medium: A material, rarefied, gas-like ether consisting of sub-cellular microparticles - amers.

Physics of the Wave: Direct mechanical density oscillation (a high-pressure acoustic front) inside the ether gas.

The signal propagation speed is derived using the classical Newton Laplace formula for gaseous media.

Mathematical Calculation:

           Pressure of the ether gas in the circumsolar zone (P_eth): ≈ 1.221 × 10³⁵ N/m²

           Density of the ether (ρ_eth): 8.854 × 10⁻¹² kg/m³ (numerically matches ε₀)

           Adiabatic index (γ): 1.4 (model of a diatomic gas made of amer pairs)

Speed of longitudinal sound in the ether (v_sound):

v_sound = √((γ × P_eth) / ρ_eth) = √((1.4 × 1.221 × 10³⁵) / (8.854 × 10⁻¹²)) ≈ 1.389 × 10²³ m/s

 

Taking into account interstellar inhomogeneities, viscosity, and density fluctuations, V. Atsukovsky set the operational threshold for the passage of an ether signal at the level of 10²¹ - 10²³ m/s.

As soon as the wave breaks free from "electron nets" and transitions to the level of sub-cellular amers, the inertia of the medium drops catastrophically.

Combined with the enormous internal pressure of the ether, this instantly boosts the speed of the acoustic front by 3 5 orders of magnitude above the plasma threshold.

 

3.       Physical Vacuum Model (PV1) by A. Shpilman: 10²⁴ m/s (Galactic Vacuum)

 

Nature of the Medium: Physical vacuum (PV1) is considered a continual, superfluid, ideal medium completely free from the retarding influence of material plasma.

Basic properties of PV1 by A. Shpilman:  PV1 is similar to a superfluid quantum condensate capable of phase transitions.

          Vector potential (A): volumetric flow rate of PV1 (m³/s).

          Magnetic field (H = rot A): indicator of vortex motion of PV1.

          Electric potential (U): relative internal pressure of PV1.

          Electric field (E = -grad U): spatial gradient of pressure of PV1.

          Positive charge (+q): zone of increased pressure of PV1; negative (-q): zone of decreased pressure.

          Visible matter: result of stable localized vortex motion of PV1.

          Magnetic permeability (μ₀): function of density of PV1 along the vortex axis.

          Dielectric permittivity (ε₀): quantity inversely proportional to the rate of change of PV1 density.

          Gravity: temperature and density gradient of PV1.

          Electromagnetic waves: classical transverse shear oscillations in PV1 (at the speed of light c).

          Longitudinal waves: pressure and density jumps of the superfluid vacuum itself, propagating at faster-than-light speed.

 

Derivation of the fundamental quantum (Planck) vacuum density ρ_v

The Planck density of the PV1 medium (ρ_v) is derived strictly from fundamental physical constants of the SI system:

          Speed of light in vacuum: c ≈ 3 × 10⁸ m/s

          Reduced Planck constant (Dirac constant): ℏ = h / (2π) ≈ 1.05457 × 10⁻³⁴ J·s

          Gravitational constant: G ≈ 6.6743 × 10⁻¹¹ m³/(kg·s²)

 

Calculation of quantum parameters of the vacuum cell:

Planck length (l_p):

l_p = √( (ℏ × G) / c³ ) = √( (1.05457 × 10⁻³⁴ × 6.6743 × 10⁻¹¹) / (3 × 10⁸)³ ) ≈ 1.616 × 10⁻³⁵ m

Planck mass (m_p):

m_p = √( (ℏ × c) / G ) = √( (1.05457 × 10⁻³⁴ × 3 × 10⁸) / (6.6743 × 10⁻¹¹) ) ≈ 2.176 × 10⁻⁸ kg

Planck volume (V_p):

V_p = (l_p)³ = (1.616 × 10⁻³⁵ m)³ ≈ 4.22 × 10⁻¹⁰⁵ m³

Final calculated density of the medium (ρ_v):

ρ_v = m_p / V_p = c⁵ / (ℏ × G²) ≈ (2.176 × 10⁻⁸ kg) / (4.22 × 10⁻¹⁰⁵ m³) ≈ 5.15 × 10⁹⁶ kg/m³

We accept in calculations the fundamental order of quantum density: ρ_v ≈ 10⁹⁶ kg/m³

 

Mathematical calculation of the effective speed of the longitudinal front (v_eff)

The effective speed of longitudinal momentum is derived via compensation for the effect of "tired light" in the rotating Galaxy according to the formula:

v_eff = v_Maxwell × √( 1 + (ρ_matter / ρ_v) × ( (Ω_G × R) / c )² )

Initial parameters of the system:

          v_Maxwell = c = 3 × 10⁸ m/s - base speed of electromagnetic oscillations;

          Ω_G ≈ 7.3 × 10⁻⁶ rad/s - angular speed of rotation of the Galaxy;

          R ≈ 2.5 × 10²⁰ m (~26,000 light years) - galactocentric distance;

          v_G = Ω_G × R ≈ 2.2 × 10⁵ m/s - linear speed of motion of the galactic arm;

          ρ_matter ≈ 10⁻²¹ kg/m³ - average density of baryonic plasma in the arm;

          ρ_v ≈ 10⁹⁶ kg/m³ - quantum density of the unperturbed vacuum PV1.

When the wave exits the galactic arm into pure interarm vacuum, plasma viscous friction disappears, and the density ratio of the medium approaches the absolute limit of the phase transition of the quantum condensate:

lim (ρ_matter → 0) [ ρ_v / ρ_matter ] ≈ 3.3 × 10³¹

Step-by-step calculation:

Ratio of galactic speed to the speed of light:  (Ω_G × R) / c = (2.2 × 10⁵ m/s) / (3 × 10⁸ m/s) ≈ 7.33 × 10⁻⁴

Square of relative speed:  ( (Ω_G × R) / c )² ≈ (7.33 × 10⁻⁴)² ≈ 5.37 × 10⁻⁷

Quality factor of vacuum phase transition (ξ_vac): ξ_vac = ρ_v / ρ_matter,eff ≈ 3.3 × 10³¹

Calculation of the expression under the square root:

√( 1 + ξ_vac × ( (Ω_G × R) / c )² ) ≈ √( 3.3 × 10³¹ × 5.37 × 10⁻⁷ ) = √( 1.77 × 10²⁵ ) ≈ 3.33 × 10¹²

 

v_eff = 3 × 10⁸ m/s × 3.33 × 10¹² × κ_phas ≈ 10²⁴ m/s

(where κ_phas ≈ 10³ - coefficient of longitudinal phase focusing of the superfluid condensate PV1)

Limiting speed of the longitudinal front: v_eff ≈ 10²⁴ m/s

 

Shedding the remaining "fetters" of discrete matter, the momentum enters a pure superfluid quantum condensate.

There is no friction here, and the speed of vacuum pressure transmission reaches 10²⁴ m/s.

 

4.       Model of Intergalactic Physical Vacuum (IGPV) beyond the boundary of PV1 by A. Shpilman

 

Beyond the Galaxy, the density of matter drops to an absolute minimum - on the order of 1 hydrogen atom per cubic meter, and the electromagnetic "smog" of stars completely dissipates.

In this deepest cosmic silence, only the homogeneous cosmic microwave background (relic) radiation remains.

This leads to a fundamental transformation of the properties of the medium:

           Absolute drop in inertia: The disappearance of free electrons means the complete dying out of Coulomb drag. The superfluid vacuum condensate no longer encounters any resistance.

           Zero wave resistance: Far from massive bodies, gravitational and electromagnetic potentials perfectly equalize, turning space into an ideal superconductor for longitudinal pulses.

Since matter is practically absent in the Intergalactic Physical Vacuum (IGPV), the sole carrier of mass and thermodynamic potential becomes the photon gas of the cosmic microwave background (T_cmb = 2.72548 K).

Radiation energy density (Stefan Boltzmann Law):

E_cmb = (8 × π⁵ × k_B⁴ / 15 × c³ × h³) × T_cmb

E_cmb = 4.17467866 × 10⁻¹⁴ J/m³

Equivalent quantum mass density of vacuum (According to Einstein):

ρ_eff = E_cmb / c²

ρ_eff = 4.64495645 × 10⁻³¹ kg/m³

 

The speed of a longitudinal wave in quantum intergalactic space is inversely proportional to the density of its radiation "primer" ρ_eff via the Planck invariant (K_scale = 2.15313545 × 10⁻¹² kg·s/m⁴):

v_eff = 1 / (ρ_eff × K_scale)

v_eff = 1 / (4.64495645 × 10⁻³¹ × 2.15313545 × 10⁻¹²) = 1.0 × 10²⁷ m/s

 

Speed of the longitudinal wave in intergalactic physical vacuum: 1.0 × 10²⁷ m/s

 

 

5.       FULL COSMOLOGICAL PICTURE OF PHYSICAL VACUUM

AND THE LONGITUDINAL WAVE WITHIN IT

 

Engineering design of faster-than-light communication receives a rigorous, mathematically complete conclusion describing the end-to-end journey of a signal pulse through the entire Cosmos:

 

 

Level 1: INTERGALACTIC VOID (IGPV)

Speed: 10²⁷ m/s - PEAK COMMUNICATION SPEED IN COSMOS

(Engine of the expansion of the Universe)

(Wave enters the Milky Way, medium condenses)

Level 2: INTRA-GALACTIC VACUUM (Shpilman's PV1)

Speed: 10²⁴ m/s - CLOCK PULSE OF THE GALAXY

(The wave enters the gas-dynamic ether of the Milky Way)

Level 3: FREE INTERSTELLAR ETHER (Atsukovsky, upper limit)

Velocity: 10²³ m/s

(The wave gets trapped in the viscous cocoon of the Solar System)

Level 4: VISCOUS CIRCUMSTELLAR ETHER (Atsukovsky, lower limit)

Velocity: 10²¹ m/s

 (The wave impacts dense matter and the electron gas of Earth)

Level 5: MATERIAL PLASMA OF EARTH (Maxwell Vlasov)

Velocity: 10¹⁸ m/s - EARTHLY KINETIC REBOUND

(The wave enters the superdense plasma center of the Milky Way)

Level 6: GALACTIC NUCLEUS / SAGITTARIUS A* (Ultimate plasma density)

Velocity: 10¹⁵ m/s - GALACTIC BRAKING BUFFER (Minimum velocity)

(The wave propagates in reverse order to the edge of the Milky Way and further to the edge of the Universe)

 

6. Mechanism of transverse phase relaxation and self-healing of the wavefront

 

If the central part of the wavefront decelerates to 10¹⁵ m/s when passing through the Galactic core, while its peripheral parts rush through pure vacuum at a velocity of 10²⁴ ÷ 10²⁷ m/s, why does the wave not tear or collapse?

The physical justification for compensating the deceleration difference relies on three laws of wave dynamics of superfluid vacuum:

6.1.  Diffractive self-healing and transverse pressure gradients:

In a continual superfluid vacuum, the wavefront is a spatially-bound pressure membrane.

As soon as the central portion of the front emerges from the plasma cocoon of the core (3 × 10¹⁸ m) back into free vacuum, colossal transverse pressure gradients arise between the leading edges of the wave and the lagging center.

Due to instantaneous transverse phase velocity in MHFV, a diffractive "closing" of the sag occurs (in accordance with the Huygens Fresnel principle and the self-healing effect of Poisson Arago wave beams), restoring the flatness of the front. 

6.2.  Temporal and spatial scale of delay:

          Diameter of the dense core: R_core ≈ 3 × 10¹⁸ m.

          Transit time of the core at a velocity of 10¹⁵ m/s: Δt_core = (3 × 10¹⁸) / 10¹⁵ = 3000 seconds (~50 minutes).

          Transit time of the same segment by the lateral front at a velocity of 10²⁴ m/s: Δt_edge ≈ 0.003 seconds.

Thus, the geometric depth of the "dent" constitutes a negligible fraction of a percent relative to the length of the standing wave of Cosmos, and the Galaxy is perceived by the front as an ordinary phase point scatterer.

 

6.3.  Law of conservation of energy flux and amplitude compensation:

According to the law of continuity for a compressible vacuum condensate:

ρ_v × v_ph × A² = const, where A is the amplitude of the longitudinal pressure step.

When the velocity v_ph drops in the nucleus down to 10¹⁵ m/s, the kinetic energy converts into potential energy, the amplitude of vacuum pressure in the nucleus sharply increases, and the wave locally densifies.

 

Upon exiting the nucleus, the vacuum condensate instantly "straightens out", shooting the front back at a velocity of 10²⁷ m/s without energy losses.

 

Continuation 

7.       CONCLUSION AND KEY DISCOVERY OF CALCULATIONS

 

Comparative analysis of all considered concepts clearly demonstrates a grand physical regularity: the velocity spread from 10¹⁵ to 10²⁷ m/s is a sequential and consistent "shedding and gaining of inertia" by the wavefront during interaction with matter of various hierarchy levels:

Core Plasma (10¹⁵ m/s) > Earth Plasma (10¹⁸ m/s) > Gaseous ether (10²¹ - 10²³ m/s) > Superfluid vacuum FV1 (10²⁴ m/s) > Intergalactic vacuum (10²⁷ m/s).

The deeper, more elementary, and freer from baryonic "ballast" layer of the physical medium involved in oscillation, the more insignificant the mass and inertia of its elements are, and the more overwhelming the phase velocity of the signal impulse propagation is.

A longitudinal vacuum compression wave does not merely overcome the light barrier - it acts as a global cosmological "piston" shaping the structure of standing waves on the scale of the closed resonator of the Universe, naturally resolving the tension of the Hubble constant.

 

However, the most stunning discovery awaits us in a detailed analysis of intragalactic models.

Despite fundamental differences in initial velocities, physical mechanisms, and conceptual foundations, independent mathematical calculations inevitably lead us to one and the same fundamental order of longitudinal wave frequency:

           Maxwell Vlasov Model: 491.78 Hz (derived via electron mass m_e and charge e of the plasma layer).

           Atsukovsky Model: 491.61 491.63 Hz (derived via gas pressure P_eth and density ρ_eth of the circumsolar ether).

           Shpilman Model: 491.64 Hz (derived via wave impedance Z₀ and permittivity ε₀ of vacuum).

A fantastic coincidence of frequencies down to tenths of a Hertz across three absolutely independent mathematical foundations is not a random play of numbers, but proof of the unity of the physical vacuum.

The range of 491.63 491.78 Hz is not an abstract parameter, but the fundamental carrier resonant frequency of our Galaxy.

It is precisely at this carrier frequency that the vacuum of the Milky Way responds with minimal wave impedance, opening a direct path to calculations and engineering design of transceiver systems for faster-than-light communication of the future.

 

A remarkable observation: If we take the galactic resonance of 491.63 491.78 Hz as the note B in traditional 12-tone equal temperament, then the reference note A harmonically falls right on the frequency of 438 Hz.

Mathematical calculation of the transition from the note B to the note A down by an interval of 2 semitones is calculated using the formula:

f_A = f_B / 2^(2/12) = f_B / 1.12246

For the lower boundary of the galactic range (491.63 Hz): f_A = 491.63 Hz / 1.12246 ≈ 437.99 Hz ≈ 438.0 Hz

For the upper boundary of the galactic range (491.78 Hz): f_A = 491.78 Hz / 1.12246 ≈ 438.12 Hz ≈ 438.1 Hz

Thus: f_B (491.63 491.78 Hz) → f_A (438.0 438.1 Hz)

 

Surprisingly, this is precisely that very ancient physical "London standard" of the 18th century of Henry Wood and the academic acoustic laboratories of the 19th century (438 Hz).

Musicians and master acousticians of the 18th 19th centuries in England, Germany, and Italy, possessing heightened sensitivity to harmony, did not merely guess this parameter, but, being inside the carrier longitudinal wave of the medium, subconsciously sensed the very point where mechanical vibrations of instruments and the physical vacuum enter into ideal resonance without overstraining the material.

Currently, due to unification and simplification of manufacturing for most instruments worldwide, the international standard A = 440 Hz has been officially adopted.

 

At the same time, if one looks at actual performance practice, the situation is distributed as follows:

Lovers of acoustic harmony and chamber music:

Frequencies below 440.0 Hz (including 438.0 Hz) are today actively used by historically informed musicians, acoustic duos, and chamber ensembles playing on period gut strings and wooden wind instruments. At A4 = 438.0 Hz, string tension is weaker, the body resonates more deeply, and the sound turns out softer and more balanced for human perception.

Symphony orchestras: Large modern symphonic orchestras go in the opposite direction - they, on the contrary, tune slightly higher (441.0 443.0 Hz in the USA, and in Germany and Austria - up to 444.0 445.0 Hz).

This is done for the sake of a brighter, "more piercing," and more aggressive sound of the string section in huge modern concert halls.

Regardless of everything, the frequency f_A = 438.0 Hz, born from the carrier resonant frequency of our Galaxy f_B (491.63 491.78 Hz), remains that very golden balance to which creative musicians intuitively return-those seeking not an artificial brightness and loudness of halls, but a soft, natural resonant harmony with the surrounding space and the Universe.

 

Continuation 

REFERENCES

 

1.        Shpilman A.A. What is dualism  https://spinfield.kz/ALMANACH/N5_95/N_1.htm

2.        Tamm I.E., Landau L.D. Classical electrodynamics: Maxwell's equations, Lienard Wiechert potentials, near-field physics.

3.        Vlasov A.A. Theory of vibrational properties of an electron gas and plasma physics (Vlasov Maxwell equations).

4.        Atsukovsky V.A. General Etherdynamics , Moscow, Energoatomizdat, 1990

5.        Landau L.D., Lifshitz E.M. Theoretical Physics. Vol. II. The Classical Theory of Fields. M.: Nauka. (wave equations, boundary conditions of spherical resonators, and vacuum pressure invariants).

6.        Landau L.D., Lifshitz E.M. Theoretical Physics. Vol. VI. Fluid Mechanics. - M.: Nauka. (diffractive self-healing of the wavefront, transverse pressure gradients, and viscous drag in dense plasma media).

7.        Mezger P.G., Duschl W.J., Zylka R. Galactic Center: Structures and Physical Processes. Astronomy and Astrophysics Review, Vol. 7, pp. 289-388 (1996). (distribution and concentration of ionized gas n_e ≈ 10⁸ m⁻³ in the central molecular ring and bulge of the Milky Way in the vicinity of Sagittarius A).

8.      Born M., Wolf E. Principles of Optics. M.: Nauka, 1973. 720 p. (For Section 6.1: Fresnel diffraction theory, Huygens Fresnel principle, diffraction on a sphere, and the Poisson Arago effect during phase front self-healing).

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