Fundamental constants play a central role in the laws of physics. Any detection of the variation of these constant would signal a violation of the Einstein equivalence principle, and thus the need to go beyond general relativity. After recalling the links between fundamental constants and theories of gravity, I will focus on recent developments to constrain their time variation, mostly...
Varying constants theories in several guises may be essential for the resolution of a number of impasses in cosmology and quantum gravity. Perhaps the most radical of them all – varying c theories – may be the clue to extracting phenomenology from quantum gravity theories, finally rendering the field properly a branch of science. I will review this possibility, with particular emphasis on the...
The precision of atomic clocks improves at a rapid pace: While caesium clocks now reach relative uncertainties of a few $10^{-16}$, several optical clocks based on different atoms and ions are now reported with systematic uncertainties in the low $10^{-18}$ range [1]. The Yb$^+$ optical clock at PTB has recently reached this uncertainty [2], following Hans Dehmelt’s seminal ideas of using ...
I will present two new high-precision measurements of the deuterium abundance from absorbers along the line of sight to the quasar PKS1937–1009. The absorbers have lower column densities (N(HI)$ \approx 18\mathrm{cm}^{-2}$) than for previous high-precision measurements, boding well for further extensions of the sample due to the plenitude of low column density absorbers. The total...
We try to convince the reader that the categorical version of differential geometry, called Synthetic Differential Geometry (SDG), offers valuable tools which can be applied to work with some unsolved problems of general relativity. We do this with respect to the space-time singularity problem. The essential difference between the usual differential geometry and SDG is that the latter enriches...
Astronomical observations provide constraints on the time variation of the fundamental constants, the proton to electron mass ratio and the fine structure constant. These constants are dependent on particular combinations of the Quantum Chromodynamic Scale, the Higgs Vacuum Expectation Value and the Yukawa Couplings. The coefficients of these particle physics parameters are model dependent...
On this talk, we will present classical dark energy models that induces abrupt cosmic events in the future. These events are intrinsic to phantom-like matter, we will as well present the cosmological pertubations of these models. We will also briefly comment on the quantisations of these models. Mariam Bouhmadi-López will give more details on the quantum cosmology of these models.
We create a model independent mock dataset to test the viability and possible properties of the cosmological redshift drift, also known as Sandage-Loeb test. The redshift of a given object will exhibit a specific variation through time due to the expansion of the universe. This mechanism was predicted by Sandage in 1962, but with the technology of that epoch it was impossible to detected the...
Diatomic molecules are very promising probes for variation of fundamental constants (VFC), as their spectra can be very sensitive to both α and μ, making it possible to look for change in both constants in a single experiment [1].
Nearly degenerate levels with different sensitivity to VFC may provide huge enhancements of the relative variation, since δω/ω tends to infinity when the distance...
On this talk, we will present a review on dark energy singularities and abrupt events. We will start with a classical description of several models. On the second part of the talk, we will focus on the quantum analysis of these singularities/abrupt events. The analysis will encompass also modified theories of gravity.
The talk will focus on different observation strategies that might be used for wide field telescope surveys in order to find electromagnetic (EM) counterpart to gravitational wave (GW) event, and possible implication of finding such counterpart. Information carried by GW and EM bands are complementary. GW brings information about acceleration of the mass in the source when EM carries the...
We discuss the classical and quantum cosmology of a universe filled
with a tachyon condensate and other Born-Infeld type fields. We analyse,
in particular, the cases with a constant potential and with an
inverse square potential. We apply the Wheeler-DeWitt equation of
canonical quantum gravity to these models and show how it can be
appropriately reformulated as a difference equation.
Main foundations of the standard Lambda-CDM model of Cosmology are:
1) The redshifts of the galaxies are due to the expansion of the Universe plus the peculiar motions;
2) The cosmic microwave background radiation and its anisotropies come from the high energy primordial Universe when matter and radiation become decoupled;
3) The abundance pattern of the light elements is to be explained in...
In recent years the idea that not only the configuration space of particles, i.e. spacetime, but also the corresponding momentum space can have a nontrivial geometry has attracted significant attention, especially in the context of quantum gravity. The aim of the talk is to discuss extension of this concept to the domain of field theories, the so-called Nonlinear Field Space Theory (NFST)....
We formulate the basic framework of thermodynamical entropic force cosmology which allows variation of the gravitational constant G and the speed of light c. Some cosmological solutions are given and tested against combined observational data (supernovae, BAO, and CMB). We observationally test that the fit of the data is allowed for the speed of light c growing and the gravitational constant G...
The power spectrum of inflationary gauge-invariant perturbations is computed in the context of canonical quantum gravity for generic slow-roll models. A semiclassical approximation, based on an expansion on inverse powers of the Planck mass, is applied to the complete Wheeler-DeWitt equation describing a perturbed inflationary universe. This expansion leads to a hierarchy of equations at...
The all presentation is an updated version of my paper printed in Annalen der Physik (Leipzig , 11 (2002) 441-455. (ArXiv: gr-qc.0102072). In this paper I have considered exact, non-linear gravitational waves in the framework of general relativity and showed that they transfer energy-momentum and angular momentum.
Using the method of regularization of singularities due to varying constants, I will first discuss some proposals to construct the cyclic models of the universe which can be connected by standard and non-standard singularities. Then, on the footing of thermodynamics and the 2nd law I will discuss the cyclic multiverse models having different values of the fundamental constants which can...
We discuss the primordial power spectra for both scalar and tensor perturbations in a inflationary model quantized by means of the hybrid quantization in Loop Quantum Cosmology. In order to compute the primordial power spectra we use the effective dynamics coming from the quantum theory and we neglect backreactions. As expected, the primordial power spectra obtained depend crucially in the...
An exact, plane wave solution of the gravitational field equations is investigated. The source stress tensor is represented by an anisotropic null fluid with energy flux to which the energy density $\rho$ and the pressure $p_{z}$ are negative but finite throughout the spacetime. They depend on a constant length (taken of the order of the Planck length) and acquire Planck values close to the...
In the talk I will focus on quantum cosmology minisuperspace models based on the Wheeler–DeWitt equation which apart from standard matter and 3-geometry configuration degrees of freedom allow those related to the variability of physical constants – varying speed of light (VSL) c and varying gravitational constant G. The probability of tunneling of the universe “from nothing” to the Friedmann...
The quantum bounce a priori connects several (semi)classical epochs of Universe evolution,
however determining if and how well the semiclassicality is preserved in this transition
is highly nontrivial. We review the present state of knowledge in that regards in the
isotropic sector of loop quantum cosmology. This knowledge is next extended by studies
of an isotropic universe admitting...
Optical lattice clocks benefit from a low quantum-projection noise by simultaneously interrogating a large number of atoms, which are trapped in an optical lattice tuned to the “magic wavelength” to largely cancel out light shift perturbation in the clock transition. About a thousand atoms enable the clocks to achieve $10^{-18}$ instability in a few hours of operation, allowing intensive...
The spectroscopy of molecular hydrogen can be used for a search into physics beyond the Standard Model. Differences between the absorption spectra of the Lyman and Werner bands of H$_2$ as observed at high redshift and those measured in the laboratory can be interpreted in terms of possible variations of the proton-electron mass ratio $\mu=m_p/m_e$ over cosmological history. Investigation of...
Several recent proposals to measure α-variation use highly-charged ions, in which the effects of a possible variation are enhanced [1]. These systems include potential new clocks that are predicted to have extraordinarily high accuracy [1-4]. In systems where the transitions are available due to level crossings, the clocks can have extremely high sensitivity to variation of the fine-structure...
I will briefly introduce MTMG, and discuss its phenomenology for both the self-accelerating and normal branch.
The ratio of two atomic transition frequencies is by definition independent of the unit of frequency and therefore its value depends only on fundamental constants such as the fine-structure constant $\alpha$ or fundamental properties of particles like for instance the electron mass. Repeated measurements of frequency ratios performed in the laboratory, with suitable atomic structure...
Atomic dysprosium (Dy) and ytterbium (Yb) have proved to be valuable systems to study fundamental problems in modern physics. Their high atomic mass and their rich energy-level structure, which results in accidental degeneracies of opposite-parity energy states, make them ideal candidates for investigating parity-violating (PV) interactions. Dysprosium is particularly well-suited for searches...
We consider the finite interactions of the generalized Proca theory
including the sixth-order Lagrangian and derive the full linear perturbation
equations of motion on the flat Friedmann-Lema\^{i}tre-Robertson-Walker background
in the presence of a matter perfect fluid.
By construction, the propagating degrees of freedom (besides the matter perfect fluid)
are two transverse vector...
Keywords:
- Eternal inflation
- Bubble nucleation
- de Sitter space
- Entanglement
Precision spectroscopy is a driving force for the development of our physical understanding. A prime example is the search for variation of fundamental constants in laboratory experiments through the repeated frequency comparison of highly accurate frequency standards. It is advantageous to compare standards with a large difference in sensitivity of their transitions to a change in these...
Recently, quantum entanglement in the context of cosmology has been widely discussed. There are many quantities which characterize quantumness of a state.Among such quantities, quantum discord is often mentioned as the best one. In this talk, we discuss the quantum discord in de Sitter spacetime.
The time variation of the equation of state $w$ for quintessence scenario with a scalar field as dark energy is studied up to the third derivative ($d^3w/da^3$) with respect to the scale factor $a$, in order to predict the future observations and specify the scalar potential parameters. The third derivative of $w$ for general potential $V$ is derived and applied to several types of...
The latest cosmological observations by the Planck collaboration (and combined with others) are compatible with a phantom like behavior $(w<-1)$ for the dark energy equation of state that drives the current acceleration of the Universe. With this mindset we look into models where dark energy is described by a 3-form field minimally coupled to gravity. These models have the advantage, when...
One of possible scenarios predicts that the dark matter (DM) may have a form of stable topological defects [1]. For nonzero DM coupling to standard-model particles, the encounter with such object would effectively result in temporary variation of fundamental constants. Recently it was proposed by Derevianko and Pospelov [2] that the networks of correlated atomic clocks may be used for such...
On a warped five-dimensional Friedmann-Lema\^{\i}tre-Robertson-Walker(FLRW) spacetime, dark energy can be induced by a U(1) scalar-gauge field on the brane. We consider a zero effective cosmological constant, i.e., the Randall-Sundrum(RS) fine-tuning and no bulk matter fields. The standard model fields interact via the bulk Weyl tensor and cause brane fluctuations. Due to the warp factor,...
In the present article, we have addressed the following points:
Firstly we have briefly reviewed Bell's inequality in quantum mechanics and its implications. For this we reviewed the proof of Bell's inequality.
Further we have discussed the violation of Bell's inequality in the context of quantum mechanics. Also we have given the explanation for such violation, which finally give rise to new...
- Vacuum dark fluid presented by variable cosmological term
[I. Dymnikova, Phys. Lett. B 472 (2000) 33; I. Dymnikova, Class. Quant. Grav. 19 (2002) 725 (Honorable Mention-2001 of the Gravity Research Foundation); I. Dymnikova and E. Galaktionov, Phys. Lett. B 645 (2007) 358; I. Dymnikova, Int. J. Mod. Phys. A 31 (2016) 1641005]
- Regular Cosmologies with Vacuum Dark Energy
...
- One-horizon spacetimes.
- Holographic principle.
- Spacetime singled out by evaporation of the cosmological horizon.
- Lemaitre class model for relaxing cosmological constant.
- Cosmological evolution.
- Anisotropy.
Detection of gravitational waves from mergers of two black holes is one
of the greatest discoveries of this century. It will open a new window on the Universe.
I shall describe observations of these signals in the data of LIGO detectors
by consortium of LIGO Scientific Collaboration and Virgo Collaboration.
I shall present several aspects of this dicovery: gravitational wave detectors,...
I will discuss how quantum mechanics makes the vacuum energy very sensitive to the values of physical parameters and how this exacerbates the cosmological constant problem in theories with varying 'constants'. Models of "interacting dark energy" in which the masses of dark matter states depend on the dark energy sector provide a striking example of this: in some models the finetuning of the...
Previous evidence for time and space variations in the fine-structure constant (alpha) emerged from large samples of quasar spectra observed with the Very Large Telescope and Keck telescope. I will first review this evidence in light of our work that identified systematic wavelength calibration errors in these telescopes. These errors are subtle, complex and still not fully understood; they...
The observational evidence for the recent acceleration of the universe demonstrates that canonical theories of cosmology and particle physics are incomplete (and possibly incorrect) and that new physics is out there, waiting to be discovered. The most fundamental task for the next generation of astrophysical facilities is to search for, identify and ultimately characterize this new physics. I...
In the last 15 years, studies of velocity shifts between metal transitions observed in high-resolution quasar spectra with the largest optical telescopes identified possible evidence for variation in the fine-structure constant, $\alpha$. Recent ‘supercalibration’ techniques have shown that these spectra likely have significant systematic distortions in their wavelength scales that undermine...
Motivated by the cosmological setup, we investigated the influence of the gravity induced terms on the Higgs field effective action. Using the heat kernel approach we obtained the one-loop effective action in the classical curved spacetime. Specializing to the standard cosmological metric, we studied the effect of gravitational field of this form on the behavior of the Higgs effective...
A new and fully-automated method is presented for the analysis of high-resolution absorption spectra (GVPFIT). The method has broad application but here we apply it specifically to the problem of measuring the fine structure constant at high redshift. For this we need objectivity and reproducibility. Three numerical methods are unified into one ``artificial intelligence'' process: a genetic...
In single field slow-roll inflation, one expects that the spectral index $n_s -1$ is first order in slow-roll parameters. Similarly, its running $\alpha_s = \mathrm d n_s/\mathrm d \log k$ and the running of the running $\beta_s = \mathrm d \alpha_s/\mathrm d \log k$ are second and third order and therefore expected to be progressively smaller, and usually negative. Recent analyses hinting...
ESPRESSO is a high-resolution-ultra-stable spectrograph for the VLT, whose commissioning will start in early 2017. One of its key science goals is to test the stability of nature’s fundamental couplings with unprecedented accuracy and control of possible
systematics. A total of 27 nights of the ESPRESSO Consortium’s guaranteed time observations (GTO) will be spent in testing the stability of...
Constraining variation in fundamental constants offers an important test for physics beyond the Standard Model.
The fine-structure constant (α) might not be constant throughout the universe. Models involving scalar fields coupled to α, the scalar charge depending on environment (e.g. on gravitational potential) naturally lead to α variation. White dwarf photospheres, where the...
We propose an improved methodology to constrain spatial variations of the fine structure constant using clusters of galaxies. We use the Planck 2013 data to measure the thermal Sunyaev-Zeldovich effect at the location of 618 X-ray selected clusters. We then use a Monte Carlo Markov Chain algorithm to obtain the temperature of the Cosmic Microwave Background at the location of our galaxy...
We construct models of dark matter with suppressed spin-independent scattering cross section utilizing the existing simplified model framework. Even simple combinations of simplified models can exhibit interference effects that cause the tree level contribution to the scattering cross section to vanish, thus demonstrating that direct detection limits on simplified models are not robust when...
We investigate a new method to recover (if any) a possible varying speed of light (VSL) signal from cosmological data on an extended redshift range. We use mock cosmological data from future galaxy surveys (BOSS, DESI, WFirst-2.4 and SKA): the sound horizon at decoupling imprinted in the clustering of galaxies (BAO) as an angular diameter distance, and the expansion rate derived from those...
General relativity (GR) is the current tour de force of gravitation that passes all experimental scrutinies with great precision. However, the difficult in incorporating quantum principles motives alternative theories beyond GR. Some of these theories predict the breakdown of local Lorentz invariance. Standard-model extension (SME) is a convenient effective-theoretic framework to study such...
For 56 years astronomers have been sweeping the skies with radio telescopes in the hope of stumbling across a message from an extraterrestrial civilization. So far, nothing. Now the Search for Extraterrestrial Intelligence (SETI) has received a huge fillip with a $100 million donation by the philanthropist Yuri Milner. However, is the current search strategy misconceived? Should we abandon...
In scalar-tensor theories the gravitational sector is extended by including an additional scalar degree of freedom. The most general metric that can be built in such a theory includes disformal terms so that standard model fields move on a metric which is the sum of the space time metric and a tensor constructed from first derivatives of the scalar. In such a theory gravitational waves and...
The standard model of cosmology features three key theoretical paradigms:
1) Inflation
2) Dark Matter
3) Dark Energy (accelerated expansion of the universe)
Inflation has severe fine-tuning problems and the need for eternal inflation and a multiverse. The alternative model Variable Speed of Light Cosmology (VSL) can avoid these problems and fit available observational data. The CMB is...
In trying to understand the selection of the initial state of the universe, physics is experiencing a paradigm shift on the last decade. A multiverse extension of the standard model of cosmology is now a promising and active direction of research. I will provide a brief introduction of various efforts in extending cosmic inflation to a multiverse origin. I will then describe in some detail how...
The discovery, in 1998, that the Universe is currently undergoing an
accelerated expansion is one of the greatest milestones in all physics.
Naturally, over the last 17 years, many proposals to explain this
evolution have been brought forward. Most ideas involve scalar field
dark energy or extensions of Einstein's gravity. These proposals are
essentially phenomenological without any...
We present the nucleation of a false vacuum bubble in curved space, which have compact geometries. The analytic computations for the radius and nucleation rate of a vacuum bubble are evaluated using the thin-wall approximation. We discuss possible cosmological implications of our new solutions.
We consider a massive vector field with derivative interactions that propagates only the 3 desired polarizations (besides two tensor polarizations from gravity) with second-order equations of motion in curved space-time. The cosmological implications of such generalized Proca theories are investigated for both the background and the linear perturbation by taking into account the Lagrangian up...
We will present a recent result [1] regarding the cosmological constant problem. In the framework of the piecewise-linear approaches to the construction of the gravitational path integral, there are three contributions to the total cosmological constant (CC): the bare term, the matter vacuum fluctuations term, and the quantum gravity term. The existence of the quantum gravity term is necessary...
I will introduce a geometrical framework with a connection that is fully determined by a vector field as a generalization of Weyl geometry. Within these geometries, it is possible to formulate gravitational theories that lead to interesting vector-tensor theories with non-minimal couplings and derivative self-interactions such that the vector only propagates the 3 polarizations corresponding...
The paradigm of an interacting multiverse opens the door to a new wide variety of cosmic phenomena to be explored. In this talk, we shall show that the interactions among the universes of the multiverse may change the global properties of the universes without violating their notion of causal closure (in the local sense). These changes would eventually have observational consequences on the...
Cosmology papers arXiv:1003.1686, 1006.1246, 1112.5308, 1411.1947, 1511.03933;
PPN papers arXiv:1309.0031, 1607.?????.
Blackbody radiation contains (on average) an entropy of 3.9+-2.5 bits per photon. This applies not only to provervial case of “burning a lump of coal”, but also to the Hawking radiation from black holes. The flip side of this observation is the information budget: If the emission process is unitary, as it certainly is for normal physical burning, then this entropy is exactly compensated by the...
The talk will be based on a joint work with M. Eckstein (arXiv:1510.06386), in which we propose and study an extension of the causal precedence relation onto the space of Borel probability measures on a given spacetime. The developed formalism draws from the mathematical theory of optimal transport and rigorously codifies the intuition of a subluminal probability flow. This will be illustrated...
We derive a formula for the post-Newtonian parameter $\gamma$ in $f(R)$ gravity in a straightforward manner without using a scalar-tensor representation or the transformation to the Einstein frame.
The post-Newtonian parameters, defined in the parametrized post-Newtonian formalism, have been used in placing observational constraints on modified theories of gravity with local gravity tests....
Drawing from the mathematical richness of noncommutative geometry, I will introduce the concept of an "almost commutative space-time" and show that it admits a sensible notion of causality. The latter does not affect classical causal relations in the space-time component, but it does induce highly non-trivial constraints on the "motion" in the "inner space". I will illustrate the general...
ABSTRACT: We show that a significant correlation (up to 5σ) emerges between the bulge index, defined to be larger for a larger bulge/disk ratio, in spiral galaxies with similar luminosities in the Galaxy Zoo 2 of the Sloan Digital Sky Survey and the number of tidal-dwarf galaxies in the catalog by Kaviraj et al. In the standard cold or warm dark matter cosmological models, the number of...
Recently we proposed a cosmological model based on smooth 4-manifolds admitting non-standard smoothness structures. The manifolds are so-called exotic versions of $\mathbb{R}^4$ ($R^4$) and $S^3\times \mathbb{R}$. This model has been developed further and we have shown how to derive some realistic cosmological parameters from these exotic smoothings in a new way. Besides, we indicated the...
The talk is devoted to the discussion why modern fundamental physics is closer to the objective idealism of Plato than to the Aristotelian empiricism, after more than 2 thousand years of the domination of the latter in classical physics.
Since the time of Newton, the laws of physics have generally been regarded as absolute, universal, eternal and immutable. In the era of modern cosmology, early versions of the big bang theory assumed the laws were magically imprinted on the universe at the moment of its origin. Quantum cosmology, however, requires the laws to transcend the physical universe, while eternal inflation cosmology...
On the occasion of the 300. anniversary of the death of G.W. Leibniz
Einstein once said: "What really interests me is whether God could have
created the world any differently." Our existence depends on a variety
of constants which appear to be extremely fine tuned to allow for the
existence of Life. These include the number of spatial dimensions, the
strengths of the forces, the masses...
The laws of physics not only allow for, but also enforce, in a sense, the origin of structures, even of such complex structures as living organisms. However, they mercilessly watch the balance: the grow must remain in agreement with the second law of thermodynamics – everything has to tend to the thermodynamical equilibrium, that is to say to the thermal death. Even the most stable structures...
The anthropic principle says that the universe is extremely fine-tuned to host the life. To explain the fine-tuning of the constants of nature, mainly we have three ways. The first way is to explain that with a more fundamental theory. But the important problem is that how far we can move towards a more fundamental theory? The second way of explaining the fine-tuning of the constants of nature...
Variation in fundamental constants provide an important test of theories of grand unification. Potentially, white dwarf spectra allow us to directly observe variation in fundamental constants at locations of high gravitational potential. We study hot, metal polluted white dwarf stars, combining far-UV spectroscopic observations, atomic physics, atmospheric modelling and fundamental physics, in...
As finite observers stationed here and now at the center of our universe, we observe ourselves and our nearby present world as being in a state of rest or low-velocity and conditioned by linear time. The geometry of our present world (space-time) appears to be approximately Euclidean, verifying Euclidean laws and analytic principles of organization. In this Euclidean zero-force world, any...
