Physics Days 2017 Archive
Black Holes and Child Universes
by Eduardo GUENDELMAN
Evidence to the case that classical gravitation provides the clue to make sense out of quantum gravity is presented. The key observation is the existence in classical gravitation of child universe solutions or "almost" solutions, "almost" because of some singularity problems. The difficulties of these child universe solutions due to their generic singularity problems will be very likely be cured by quantum effects, just like for example "almost" instanton solutions are made relevant in gauge theories with breaking of conformal invariance. Some well motivated modifcations of General Relativity where these singularity problems are absent even at the classical level are discussed. High energy density excitations, responsible for UV divergences in quantum field theories, including quantum gravity, are likely to be the source of child universes which carry them out of the original space time. This decoupling could prevent these high UV excitations from having any influence on physical amplitudes. Child universe production could therefore be responsible for UV regularization in quantum field theories which take into account semiclassically gravitational effects. Child universe production in the last stages of black hole evaporation, the prediction of absence of tranplanckian primordial perturbations, connection to the minimum length hypothesis and in particular the connection to the maximal curvature hypothesis are discussed.
Interacting Diffusive Unified Dark Energy and Dark Matter from Scalar Fields
by Eduardo GUENDELMAN
Here we generalize ideas of unified Dark Matter Dark Energy in the context of Two Measure Theories and of Dynamical space time Theories. In Two Measure Theories one uses metric independent volume elements and this allows to construct unified Dark Matter Dark Energy, where the cosmological constant appears as an integration constant associated to the equation of motion of the measure fields. The Dynamical space time Theories generalize the Two Measure Theories by introducing a vector field whose equation of motion guarantees the conservation of a certain Energy Momentum tensor, which may be related, but in general is not the same as the gravitational Energy Momentum tensor. We propose two formulations of this idea: I - by demanding that this vector field be the gradient of a scalar, II - by considering the dynamical space field appearing in another part of the action. Then the Dynamical space time Theory becomes a theory of Diffusive Unified Dark Energy and Dark Matter. These generalizations produce non conserved energy momentum tensors instead of conserved energy momentum tensors which leads at the end to a formulation of interacting DE-DM dust models in the form of a diffusive type interacting Unified Dark Energy and Dark Matter scenario. We solved analytically the theories for perturbative solution and asymptotic solution, and we show that the Λ CDM is a fixed point of these theories at large times. Also a preliminary argument about the good behavior of the theory at the quantum level is proposed for both theories.
A Big Bang in a Little Room
by Zeeya MERALI
My new book, A Big Bang in a Little Room (Basic Books, 2017), discusses how it may one day be possible for humans to make their own "baby universe" in the lab — a DIY cosmos complete with (possibly) its own stars, planets and people. The book is based on extensive interviews that I carried out with physicists located around the globe. Some of their ideas have fed directly into the blueprints of this "little bang theory", while others form the basis of related theories about the origins of space and time, and the possibility that our cosmos is one of many in a multiverse of parallel universes. In this talk, I will discuss what drives these diverse personalities — including a KGB-blacklisted physicist who published science papers while working as a zookeeper, a cosmologist who once investigated telepathy, a scientist who sees resonances between his Buddhist meditation practices and the origins of space, time and consciousness, and an Evangelical Christian physicist who has developed a theological framework of parallel universes. Beyond simply explaining the physics of how scientists might one day achieve the feat of baby-universe creation, I will discuss the ethical and philosophical implications of such act.
From Everyday Physics Problems to Very Big Problems
by Mustafa HALİLSOY
The Physics of football. From car crashes to JFK's assassination and particle collisions near Black Holes. The poor man's interpretation of BICEP and LIGO. And the Biggest Problem: God, the Conscious Mind of the Universe.
Why nerve fibers do not buckle?
by Habib MAZHARIMOUSAVI
In this study I give a theoretical model which explains the smoothness of nerve fibers. We show that a nerve fiber may encounter large curvature due to the possible bending which could cause the fiber to buckle. However, its membrane's structure provides a mechanism to avoid it.
A Soap Operon: 'SOME JUST GET TOO ATTACHED,' starring mRNAs and the membrane
by Elgin Gülpınar KORKMAZHAN
Unlike their eukaryotic counterparts, bacterial cells have little to no internal compartmentalization. This allows many rapidly diffusing macromolecules, such as proteins and mRNAs, to be evenly distributed in the cell. Important exceptions are proteins embedded in the cell membrane, which transport material and information across the membrane. Often these proteins attach to the membrane before their translation is complete, anchoring their mRNAs to the vicinity of the membrane. This coupling between translation and localization suggests that the dynamics of translation may shape the spatial organization. In this work a canonical model of non-equilibrium statistical physics is employed to characterize this connection, and show how tunable kinetic properties allow the cell to regulate the spatial organization of both mRNAs and proteins. I show that a combination of the rate of translation initiation, the availability of secretory apparatuses, and the composition of the coding region determines the abundance of mRNAs near the membrane, as well as their residence time. I discuss implications to regulation of mRNA levels in the cell and to couplings with chromatin dynamics. In the light of my results, I propose and justify a novel mechanism for the formation and regulation of membrane protein clusters and membrane domains enriched in proteins, through the association of proteins that are translated from a single mRNA during a single stay near the membrane. Once verified experimentally, such a mechanism could pave the path to a better understanding of bacterial regulation and bacterial membrane organization as well as to an effective way of synthetically manipulating protein organization in bacterial membranes, which has been relatively out of reach in biology so far.
Cosmic censorship and black hole thermodynamics
by Koray DÜZTAŞ
Hawking's area theorem is known to pre-assume the validity of cosmic censorship conjecture. Here, we argue that Israel's proof of the third law of black hole dynamics pre-assumes the area theorem; therefore it indirectly pre-assumes cosmic censorship, contrary to general acceptance. Since this is equivalent to postulating the result, the third law still lacks a rigorous mathematical proof. In the same sense, individual tests of cosmic censorship are non-trivial even if the relevant energy momentum tensor satisfies the weak energy condition.
Search For Pair Produced Heavy Quarks Decaying Into a Z Boson and a Light Generation Jet With The Atlas Detector At Cern
by Serhat IŞTIN
There are many models extending beyond the well established Standard Model predicting additional massive quarks on top of the existing quark list. One of them is the grand unified theory (GUT) having the exceptional E6 as its symmetry group. This model predicts an additional iso-singlet down type quark for each existing Standard Model (SM) family with possible decay channels involving W ± , Z and Higgs bosons. Assuming that the similar mass structure as in the SM is also valid for these massive quarks, the lightest of them denoted by letter D would be the first one to be discovered at the ATLAS experiment. In addition to such theoretical motivations, we will present our past and ongoing heavy quark searches while briefly describing some of the technical work carried out at the ATLAS.
Hawking Radiation of Rotating Hairy Black Holes with Scalar Hair
by Huriye GÜRSEL
This talk will be on Hawking radiation emitted from a rotating black hole with scalar hair within the context of three dimensional Einstein gravity and non-minimally coupled scalar field theory. Prior to Hawking's discovery, black holes were considered to be fully black. What made his discovery so enterprising is that it brought forth a linkage between thermodynamics and gravity. Digging into Hawking's remarkable theory can lead us to a precise explanation of what gravity actually is. Since Hawking proposed his theory, many explanatory approaches aroused with the aim of finding alternative ways of explaining the Hawking radiation process. Throughout this talk, I will be focusing on the quantum tunneling approach, which is just one of the many promising hypothetical explanations behind this process. The particles being emitted will be fermions and scalar particles. During the speech, not only the questions below will be answered, but also Klein Gordon equation and tetrad formalism (Dirac Equation) will be investigated in detail, as they were the methodologies used in the article to be presented. Combining the quantum tunneling approach with WKB approximation, the tunneling rates of the particles will be obtained. These tunnelling rates will then be used to evaluate the Hawking temperature of the 3D RSHBH.
- Is Hawking temperature dependent on the spin value of the particles being tunneled through the event horizon?
- How about Information Loss Paradox?
- How does Hawking radiation provide information regarding quantum gravity?
Theoretical studies of Lipid membrane
by Niloufar ABTAHI
In the recent past, there has been a good explanation for the morphology of cells in terms of their geometrical diversity. We investigate the theoretical studies of fluid membrane. Moreover, we have modeled the shape equation of a deformed cylindrical symmetric lipid membrane, assuming the membrane is spontaneous-curvature-free and the deformation is along radial axis. Furthermore, the linearized shape equation is solved analytically under the certain boundary conditions and an example is discussed.
Energy and Stress of Lipid Bilayers
by Danial FORGHANI
A brief review of the energy and the stress tensor of a lipid bilayer, in an approach mainly offered by J. Guven and R. Capovilla in a series of articles during 2000's, will be presented. As it will be discussed, the behavior of a lipid bilayer - the membrane that separates the interior of a biological cell from its environment - can
be precisely captured by its geometrical degrees of freedom. The variation of the energy of such membranes, given in general by a functional in terms of the first and second fundamental forms, can be applied imposing certain constraints, to identify its stress tensor which is covariantly conserved under translation. The normal
projection of this conservation is nothing but the well-known "shape equation" which determines the configuration of the lipid bilayer in equilibrium.
Stationary scalar clouds around maximally rotating linear dilaton black holes
by Gülnihal TOKGÖZ
We investigate the wave dynamics of a charged massive scalar field propagating in a maximally rotating (extremal) linear dilaton black hole geometry. We prove the existence of a discrete and infinite family of resonances describing non-decaying stationary scalar configurations (clouds) enclosing these rapidly
rotating black holes. The results obtained signal the potential stationary scalar field distributions (dark matter) around the extremal linear dilaton black holes. In particular, we analytically compute the effective heights of those clouds above the center of the black hole.
Spectroscopy of rotating linear dilaton black holes from boxed quasinormal modes
by Izzet SAKALLI
Numerical studies of the coupled Einstein-Klein-Gordon system have recently revealed that confined scalar fields generically collapse to form caged black holes. In the light of this finding, we analytically study the characteristic resonance spectra of the confined scalar fields in rotating linear dilaton black hole geometry. Confining mirrors (cage) are assumed to be placed in the near-horizonregion of a
caged rotating linear dilaton black hole. The radial part of the Klein-Gordon equation is written as a
Schrödinger-like wave equation, which reduces to a Bessel differential equation around the event horizon. Using analytical tools and proper boundary conditions, we obtain the boxed-quasinormal mode frequencies of the caged rotating linear dilaton black hole. Finally, we employ Maggiore's method, which evaluates the transition frequency in the adiabatic invariant quantity from the highly damped quasinormal modes, in order to investigate the entropy/area spectra of the rotating linear dilaton black hole.