scholarly journals Semiclassical Length Measure from a Quantum-Gravity Wave Function

Technologies ◽  
2017 ◽  
Vol 5 (3) ◽  
pp. 56
Author(s):  
Orchidea Lecian
Keyword(s):  
Wave Function ◽  
Quantum Gravity ◽  
Gravity Wave ◽  
Length Measure

scholarly journals Gravity-wave interferometers as quantum-gravity detectors

Nature ◽  
10.1038/18377 ◽  
1999 ◽  
Vol 398 (6724) ◽  
pp. 216-218 ◽  
Author(s):  
Giovanni Amelino-Camelia
Keyword(s):  
Quantum Gravity ◽  
Gravity Wave

scholarly journals Semi-classical approximations based on Bohmian mechanics

2020 ◽  
Vol 35 (14) ◽  
pp. 2050070 ◽  
Author(s):  
Ward Struyve
Keyword(s):  
Wave Function ◽  
Quantum Theory ◽  
Quantum Gravity ◽  
Quantum Electrodynamics ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Bohmian Mechanics ◽  
Expectation Values ◽  
Usual Approach ◽  
Classical Approximation

Semi-classical theories are approximations to quantum theory that treat some degrees of freedom classically and others quantum mechanically. In the usual approach, the quantum degrees of freedom are described by a wave function which evolves according to some Schrödinger equation with a Hamiltonian that depends on the classical degrees of freedom. The classical degrees of freedom satisfy classical equations that depend on the expectation values of quantum operators. In this paper, we study an alternative approach based on Bohmian mechanics. In Bohmian mechanics the quantum system is not only described by the wave function, but also with additional variables such as particle positions or fields. By letting the classical equations of motion depend on these variables, rather than the quantum expectation values, a semi-classical approximation is obtained that is closer to the exact quantum results than the usual approach. We discuss the Bohmian semi-classical approximation in various contexts, such as nonrelativistic quantum mechanics, quantum electrodynamics and quantum gravity. The main motivation comes from quantum gravity. The quest for a quantum theory for gravity is still going on. Therefore a semi-classical approach where gravity is treated classically may be an approximation that already captures some quantum gravitational aspects. The Bohmian semi-classical theories will be derived from the full Bohmian theories. In the case there are gauge symmetries, like in quantum electrodynamics or quantum gravity, special care is required. In order to derive a consistent semi-classical theory it will be necessary to isolate gauge-independent dependent degrees of freedom from gauge degrees of freedom and consider the approximation where some of the former are considered classical.

QUANTUM COSMOLOGY IN R1×S1×S2 TOPOLOGICAL SPACE

1991 ◽  
Vol 06 (34) ◽  
pp. 3123-3131 ◽  
Author(s):  
SUBENOY CHAKRABORTY
Keyword(s):  
Wave Function ◽  
Topological Space ◽  
Critical Point ◽  
Gravity Wave ◽  
Path Integral ◽  
Infinite Number ◽  
Quantum Cosmology ◽  
Autonomous System ◽  
Saddle Points ◽  
Field Equations

We have discussed classical and quantum cosmological phenomena for anisotropic Kantowski–Sachs model. The classical Lorentzian field equations are reduced to an autonomous system and are analyzed near critical point. The minisuperspace path-integral reduces to a single ordinary integration over the lapse, and we study this integral by lapse method. We find that the integral has an infinite number of saddle points, each one has identical contribution to the integral. Also matter-gravity wave function is considered for this metric.

scholarly journals Spacetime has a “thickness”

2017 ◽  
Vol 26 (12) ◽  
pp. 1742002 ◽  
Author(s):  
Samir D. Mathur
Keyword(s):  
Black Hole ◽  
Quantum Gravity ◽  
Gravity Wave ◽  
Hawking Radiation ◽  
Finite Thickness ◽  
Low Energy ◽  
Leading Order ◽  
Curved Spacetime ◽  
Thickness Parameter

Suppose we assume that (a) information about a black hole is encoded in its Hawking radiation and (b) causality is not violated to leading order in gently curved spacetime. Then, we argue that spacetime cannot just be described as a manifold with a shape; it must be given an additional attribute which we call “thickness.” This thickness characterizes the spread of the quantum gravity wave functional in superspace — the space of all three-geometries. Low energy particles travel on spacetime without noticing the thickness parameter, so they just see an effective manifold. Objects with energy large enough to create a horizon do note the finite thickness; this modifies the semiclassical evolution in such a way that we avoid horizon formation and the consequent violation of causality.

FALLING INTO A BLACK HOLE

2008 ◽  
Vol 17 (03n04) ◽  
pp. 583-589 ◽  
Author(s):  
SAMIR D. MATHUR
Keyword(s):  
Field Theory ◽  
Black Hole ◽  
Wave Function ◽  
String Theory ◽  
Quantum Gravity ◽  
Definition Of

String theory tells us that quantum gravity has a dual description as a field theory (without gravity). We use the field theory dual to ask what happens to an object as it falls into the simplest black hole: the two-charge extremal hole. In the field theory description the wave function of a particle is spread over a large number of "loops," and the particle has a well-defined position in space only if it has the same "position" on each loop. For the infalling particle we find one definition of "same position" on each loop, but there is a different definition for outgoing particles and no canonical definition in general in the horizon region. Thus the meaning of "position" becomes ill-defined inside the horizon.

scholarly journals Does Compton–Schwarzschild duality in higher dimensions exclude TeV quantum gravity?

2018 ◽  
Vol 27 (16) ◽  
pp. 1930001 ◽  
Author(s):  
Matthew J. Lake ◽  
Bernard Carr
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Wave Function ◽  
Quantum Gravity ◽  
Extra Dimensions ◽  
Planck Length ◽  
Compton Wavelength ◽  
Planck Mass ◽  
Higher Dimensional ◽  
Spatial Dimensions

In three spatial dimensions, the Compton wavelength [Formula: see text]) and Schwarzschild radius [Formula: see text]) are dual under the transformation [Formula: see text], where [Formula: see text] is the Planck mass. This suggests that there could be a fundamental link — termed the Black Hole Uncertainty Principle or Compton–Schwarzschild correspondence — between elementary particles with [Formula: see text] and black holes in the [Formula: see text] regime. In the presence of [Formula: see text] extra dimensions, compactified on some scale [Formula: see text] exceeding the Planck length [Formula: see text], one expects [Formula: see text] for [Formula: see text], which breaks this duality. However, it may be restored in some circumstances because the effective Compton wavelength of a particle depends on the form of the [Formula: see text]-dimensional wave function. If this is spherically symmetric, then one still has [Formula: see text], as in the [Formula: see text]-dimensional case. The effective Planck length is then increased and the Planck mass reduced, allowing the possibility of TeV quantum gravity and black hole production at the LHC. However, if the wave function of a particle is asymmetric and has a scale [Formula: see text] in the extra dimensions, then [Formula: see text], so that the duality between [Formula: see text] and [Formula: see text] is preserved. In this case, the effective Planck length is increased even more but the Planck mass is unchanged, so that TeV quantum gravity is precluded and black holes cannot be generated in collider experiments. Nevertheless, the extra dimensions could still have consequences for the detectability of black hole evaporations and the enhancement of pair-production at accelerators on scales below [Formula: see text]. Though phenomenologically general for higher-dimensional theories, our results are shown to be consistent with string theory via the minimum positional uncertainty derived from [Formula: see text]-particle scattering amplitudes.

Genetic quantum gravity and quantum Darwinism

2019 ◽  
Author(s):  
Vitaly Kuyukov
Keyword(s):  
Wave Function ◽  
Quantum Gravity ◽  
Dominant Gene ◽  
Space Time ◽  
Mathematical Form ◽  
Time Axis ◽  
Quantum Darwinism ◽  
Braid Theory ◽  
Concept Of Information ◽  
Selection Of

The nature of quantum mechanics has various interpretations. In this paper we consider the hypothesis of quantum Darwinism. Quantum theory is closely connected with the concept of information. Perhaps there is an analogue of the genetic code for quantum Darwinism. Here the attempt of the genetic formulation of quantum gravity. It is based on the idea of the quantum of the DNA helix in space-time , directed along the time axis. Twisting together all of the genetic spirals creates the very fabric of space-time. Such a mathematical form exists in braid theory. Matter how information is encoded in the genetic DNA structure of space-time. Natural and artificial selection of quantum Darwinism leads to the collapse of the wave function and the identification of a dominant gene.

scholarly journals HOW FAST CAN A BLACK HOLE RELEASE ITS INFORMATION?

2009 ◽  
Vol 18 (14) ◽  
pp. 2215-2219 ◽  
Author(s):  
SAMIR D. MATHUR
Keyword(s):  
Black Hole ◽  
Wave Function ◽  
String Theory ◽  
Quantum Gravity ◽  
Linear Combination ◽  
Evaporation Time ◽  
Simple Estimate ◽  
Semiclassical Physics ◽  
Gravity Effects ◽  
Spreading Time

When a shell collapses through its horizon, semiclassical physics suggests that information cannot escape from this horizon. One might hope that nonperturbative quantum gravity effects will change this situation and avoid the information paradox. We note that string theory has provided a set of states over which the wave function of the shell can spread, and that the number of these states is large enough that such a spreading would significantly modify the classically expected evolution. In this article we perform a simple estimate of the spreading time, showing that it is much shorter than the Hawking evaporation time for the hole. Thus information can emerge from the hole through the relaxation of the shell state into a linear combination of fuzzballs.

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