Sabine Hossenfelder

Nordic Institute for Theoretical Physics | Nordita · High energy physics

Do the laws of quantum physics still hold for macroscopic objects - this is at the heart of Schrödinger’s cat paradox - or do gravitation or yet unknown effects set a limit for massive particles? What is the fundamental relation between quantum physics and gravity? Ground-based experiments addressing these questions may soon face limitations due to...

We show that analog gravity systems exist for charged, planar black holes in asymptotic Anti-de Sitter space. These black holes have been employed to describe, via the gauge-gravity duality, strongly coupled condensed matter systems on the boundary of AdS-space. The analog gravity system is a different condensed matter system that, in a suitable li...

It is demonstrated that Maxwell's demon can be used to allow a machine to extract energy from a heat bath by use of information that is processed by the demon at a remote location. The model proposed here effectively replaces transmission of energy by transmission of information. For that we use a feedback protocol that enables a net gain by stimul...

Tests of Bell's theorem rule out local hidden variables theories. But any theorem is only as good as the assumptions that go into it, and one of these assumptions is that the experimenter can freely chose the detector settings. Without this assumption, one enters the realm of superdeterministic hidden variables theories and can no longer use Bell's...

Whether or not space-time is fundamentally discrete is of central importance for the development of the theory of quantum gravity. If the fundamental description of space-time is discrete, typically represented in terms of a graph or network, then the apparent smoothness of geometry on large scales should be imperfect -- it should have defects. Her...

The idea that Lorentz-symmetry in momentum space could be modified but still remain observer-independent has received quite some attention in the recent years. Motivated by Loop Quantum Gravity, this modified Lorentz-symmetry is being used as a phenomenological model to test possibly observable effects of quantum gravity. The most pressing problem...

We study the question whether disentanglement of Hawking radiation can be achieved with any local operation. We assume that the operation we look for is unitary and can be described by a Bogoliubov transformation. This allows to formulate requirements on the operation of disentanglement. We then show that these requirements can be fulfilled by a ti...

If space-time is emergent from a fundamentally non-geometric theory it will generically be left with defects. Such defects need not respect the locality that emerges with the background. Here, we develop a phenomenological model that parameterizes the effects of nonlocal defects on the propagation of particles. In this model, Lorentz-invariance is...

We propose a phenomenological model for the scattering of particles on space-time defects in a treatment that maintains Lorentz-invariance on the average. The local defects considered here cause a stochastic violation of momentum conservation. The scattering probability is parameterized in the density of defects and the distribution of the momentum...

I argue that it is possible for a theory to be neither quantized nor classical. We should therefore give up the assumption that the fundamental theory which describes gravity at shortest distances must either be quantized, or quantization must emerge from a fundamentally classical theory. To illustrate my point I will discuss an example for a theor...

Recently, it has been argued that black hole complementarity is inconsistent by showing that, for an infalling observer, it would lead to the existence of a firewall near the black hole horizon, thereby violating the equivalence principle. If true, this would necessitate to give up on at least one of the postulates of black hole complementarity. In...

It is generally believed that quantum gravity is necessary to resolve the known tensions between general relativity and the quantum field theories of the standard model. Since perturbatively quantized gravity is non-renormalizable, the problem how to unify all interactions in a common framework has been open since the 1930s. Here, I propose a possi...

While it has often been proposed that, fundamentally, Lorentz-invariance is not respected in a quantum theory of gravity, it has been difficult to reconcile deviations from Lorentz-invariance with quantum field theory. The most commonly used mechanisms either break Lorentz-invariance explicitly or deform it at high energies. However, the former opt...

It was recently claimed that the Planck length is not a limit to the precision by which we can measure distances, but that instead it is merely the Planck volume that limits the precision by which we can measure volumes. Here, we investigate this claim and show that the argument does not support the conclusion.

We review the question of whether the fundamental laws of nature limit our ability to probe arbitrarily short distances. First, we examine what insights can be gained from thought experiments for probes of shortest distances, and summarize what can be learned from different approaches to a theory of quantum gravity. Then we discuss some models that...

It is explained why the argument in arXiv:1104.2019 does not answer the question how to describe multi-particle states in models with a deformed Lorentz-symmetry in momentum space.

It is argued that it is possible to give operational meaning to free will and the process of making a choice without employing metaphysics.

We calculate the particle spectra of evaporating self-dual black holes that are potential dark matter candidates. We first estimate the relevant mass and temperature range and find that the masses are below the Planck mass, and the temperature of the black holes is small compared to their mass. In this limit, we then derive the number-density of th...

We give a brief introduction to the recent idea of Large eXtra Dimensions (LXDs). We give a motivation for the existence of a minimal length scale and show how to incorporate it into quantum theory. We derive first order corrections to high precision measurements such as transition frequencies in He+ and the muon gyromagnetic moment. The results cl...

We propose to experimentally test non-deterministic time evolution in quantum mechanics by consecutive measurements of non-commuting observables on the same prepared state. While in the standard theory the measurement outcomes are uncorrelated, in a super-deterministic hidden variables theory the measurements would be correlated. We estimate that f...

The question of how to measure and aggregate happiness is more than a century old. In recent years, its relevance has risen due to efforts to replace the GDP with an index more indicative of well-being, though such efforts are fraught with serious conceptual problems. After briefly recalling these problems, we suggest to address them by using inste...

We offer a brief survey of existent and planned experimental tests for quantum gravity.First, we outline the questions we wish to address, and then introduce some of thephenomenological models that are currently used in quantum gravity, both with andwithout a lowered Planck scale. After that, we summarize experimental areas wherethese models can be...

By studying the notion of a fundamentally minimal length scale in asymptotically safe gravity we find that a specific version of deformed special relativity (DSR) naturally arises in this approach. We then consider two thought experiments to examine the interpretation of the scenario and discuss similarities and differences to other approaches to D...

In a recent paper it was suggested a novel interpretation of deformed special relativity. In that new approach, nonlocal effects that had previously been shown to occur and be incompatible with experiment to high precision, are interpreted as coordinate artifacts that do not lead to real physical consequences. It is argued here that if one follows...

It was previously shown that models with deformations of special relativity that have an energy-dependent yet observer-independent speed of light suffer from nonlocal effects that are in conflict with observation to very high precision. In a recent preprint it has been claimed that this conclusion is false. This claim was made by writing down expre...

It was previously shown that models with deformations of special relativity that have an energy-dependent yet observer-independent speed of light suffer from nonlocal effects that are in conflict with observation to very high precision. In a recent paper it has been proposed that these paradoxa arise only in the classical limit and can be prevented...

We show that models with deformations of special relativity that have an energy-dependent speed of light have nonlocal effects. The requirement that the arising nonlocality is not in conflict with known particle physics allows us to derive strong bounds on deformations of special relativity and rule out a modification to first order in energy over...

We offer some, hopefully clarifying, comments on Verlinde's recent claim that gravity is an entropic force. A suitable identification of quantities shows that both formulations of Newtonian gravity, the classical and the thermodynamical one, are actually equivalent. It turns out that some additional assumptions made by Verlinde are unnecessary. How...

We study the formation of a black hole and its subsequent evaporation in a model employing a minisuperspace approach to loop quantum gravity. In previous work the static solution was obtained and shown to be singularity-free. Here, we examine the more realistic dynamical case by generalizing the static case with the help of the Vaidya metric. We tr...

At any time, there are areas of science where we are standing at the frontier of knowledge, and can wonder whether we have reached a fundamental limit to human understanding. What is ultimately possible in physics? I will argue here that it is ultimately impossible to answer this question. For this, I will first distinguish three different reasons...

We examine the transformation of particle trajectories in models with deformations of Special Relativity that have an energy-dependent and observer-independent speed of light. These transformations necessarily imply that the notion of what constitutes the same space-time event becomes dependent on the observer's inertial frame. To preserve observer...

If the history of science has taught us anything, it's that persistence and creativity makes the once impossible possible. It has long been thought experimental tests of quantum gravity are impossible. But during the last decade, several different approaches have been proposed that allow us to test, if not the fundamental theory of quantum gravity...

We discuss why there are no negative gravitational sources in General Relativity and show that it is possible to extend the classical theory such that repulsive gravitational interaction occurs.

Authors Hohmann and Wohlfarth have put forward a no-go theorem for bimetric gravity with positive and negative mass in arXiv:0908.3384v1 [gr-qc]. This comment shows that their no-go theorem does not apply to arXiv:0807.2838v1 [gr-qc]. In a recent paper [1] authors Hohmann and Wohlfarth present a no-go theorem for bimetric gravity with positive and...

We review the different options for resolution of the black hole loss of information problem. We classify them first into radical options, which require a quantum theory of gravity which has large deviations from semi-classical physics on macroscopic scales, such as non-locality or endowing horizons with special properties not seen in the semi-clas...

Atlanta Conference on Science and Innovation Policy 2009 This presentation was part of the session : Organizations of Science and Innovation The scientific community makes for an interesting case study for the emergence of social phenomena from individual interests. As a community of practice with only peripheral external interactions, researchers...

We propose an extension of general relativity with two different metrics. To each metric we define a Levi-Cevità connection and a curvature tensor. We then consider two types of fields, each of which moves according to one of the metrics and its connection. To obtain the field equations for the second metric we impose an exchange symmetry on the ac...

The aim of this note is to address the low energy limit of quantum field theories with a minimal length scale. The essential feature of these models is that the minimal length acts as a regulator in the asymptotic high energy limit which is incorporated through an infinite series of higher order derivatives. If one investigates a perturbative expan...

MARCH 13th 2008: Until Wednesday, the Presidential candidate (insert name here) scored high in the polls. Then a Google search for his name showed up as first hit a report on an alleged child abuse committed by the candidate, published by Mary S. (name changed) on her personal website. The story was backed up by the following highly ranked hits tha...

We investigate the properties of multiparticle states in deformed special relativity (DSR). Starting from the Lagrangian formalism with an energy dependent metric, the conserved Noether current can be derived which is additive in the usual way. The integrated Noether current had previously been discarded as a conserved quantity, because it was corr...

We investigate how deformations of special relativity in momentum space can be extended to position space in a consistent way, such that the dimensionless contraction between wave-vector and coordinate-vector remains invariant. By using a parametrization in terms of an energy dependent speed of light, and an energy dependent Planck's constant, we a...

In models with large extra dimensions, the Planck scale can be lowered to values soon accessible at the LHC. These models predict a vast number of quantum gravitational effects at the lowered Planck scale, among them the production of TeV-mass black holes and gravitons. Since the Planck length is expected to set a fundamental limit to the resolutio...

Planck scale physics represents a future challenge, located between particle physics and general relativity. The Planck scale marks a threshold beyond which the old description of spacetime breaks down and conceptually new phenomena must appear. In the last years, increased efforts have been made to examine the phenomenology of quantum gravity, eve...

In models with large extra dimensions (LXDs) the Planck scale can be lowered to values that are within the reach of the next generation of particle colliders. Those models predict the production of TeV mass black holes and therefore a new era in short distance physics. However, the details of the black hole evaporation process especially in the fin...

Higher-dimensional models of neutrino physics with one or more right-handed neutrinos in the bulk have attracted considerable attention in recent years. However, a critical issue for such models is to find a way of introducing the required flavor dependence needed for generating neutrino oscillations. In this paper, we point out that a natural ``mi...

The dynamics of a universe with an anti-gravitating contribution to the matter content is examined. The modified Friedmann equations are derived, and it is shown that anti-gravitating radiation is the slowest component to dilute when the universe expands. Assuming an interaction between both kinds of matter which becomes important at Planckian dens...

It has been proposed that the incorporation of an observer independent minimal length scale into the quantum field theories of the standard model effectively describes phenomenological aspects of quantum gravity. The aim of this paper is to interpret this description and its implications for scattering processes.

The aim of this note is to clarify the relation between three different approaches of theories with a minimal length scale: a modification of the Lorentz group in the 'deformed special relativity', theories with a 'generalized uncertainty principle' and those with 'modified dispersion relations'. It is shown that the first two are equivalent, how t...

Collider produced black holes are the most exciting prediction from models with large extra dimensions. These black holes exist in an extreme region, in which gravity meets quantum field theory, particle physics, and thermodynamics. An investigation of the formation and decay processes can therefore provide us with important insights about the unde...

The possibility of a symmetry between gravitating and anti-gravitating particles is examined. The properties of the anti-gravitating fields are defined by their behavior under general diffeomorphisms. The equations of motion and the conserved canonical currents are derived, and it is shown that the kinetic energy remains positive whereas the new fi...

Large extra dimensions lower the Planck scale to values soon accessible. The production of TeV mass black holes at the {\sc LHC} is one of the most exciting predictions. However, the final phases of the black hole's evaporation are still unknown and there are strong indications that a black hole remnant can be left. Since a certain fraction of such...

Within the scenario of large extra dimensions, the Planck scale is lowered to values soon accessible. Among the predicted effects, the production of TeV mass black holes at the {\sc LHC} is one of the most exciting possibilities. Though the final phases of the black hole's evaporation are still unknown, the formation of a black hole remnant is a th...

The existence of a minimal length scale, a fundamental lower limit on spacetime resolution is motivated by various theories of quantum gravity as well as string theory. Classical calculations involving both quantum theory and general relativity yield the same result. This minimal length scale is naturally of the order of the Planck length, but can...

Large extra dimensions could lower the Planck scale to experimentally accessible values. Not only is the Planck scale the energy scale at which effects of modified gravity become important. The Planck length also acts as a minimal length in nature, providing a natural ultraviolet cutoff and a limit to the possible resolution of spacetime.In this Le...

Black holes merge together different field of physics. From General Relativity over thermodynamics and quantum field theory, they do now also reach into the regime of particle and collider physics. In the presence of additional compactified dimensions, it would be possible to produce tiny black holes at future colliders. We would be able to test Pl...

Planck scale physics represents a future challenge, located between particle physics and general relativity. The Planck scale marks a threshold beyond which the old description of spacetime breaks down and conceptually new phenomena must appear. Little is known about the fundamental theory valid at Planckian energies, except that it necessarily see...

Large extra dimensions lower the Planck scale to values soon accessible. Motivated by String Theory, the models of large extra dimensions predict a vast number of new effects in the energy range of the lowered Planck scale, among them the production of TeV-mass black holes and gravitons. But not only is the Planck scale the energy scale at which ef...

The existence of extra dimensions and a minimal length scale are modifications of our spacetime which are suggested by string theory. In models with additional dimensions, the Planck scale can be lowered to values accessible by future colliders and in ultra high energetic cosmic rays. Effective theories which extend beyond the standard-model by inc...

In models with large additional dimensions, the GUT scale can be lowered to values accessible by future colliders. Due to modification of the loop corrections from particles propagating into the extra dimensions, the logarithmic running of the couplings of the Standard Model is turned into a power law. These loop-correction are divergent and the st...

Large extra dimensions lower the Planck scale to values soon accessible. Motivated by string theory, the models of large extra dimensions predict a vast number of new effects in the energy range of the lowered Planck scale, among them the production of TeV-mass black holes. But not only is the Planck scale the energy scale at which effects of modif...

We discuss modifications of the gyromagnetic moment of electrons and muons due to a minimal length scale combined with a modified fundamental scale $M_f$. First-order deviations from the theoretical standard model value for $g-2$ due to these String Theory-motivated effects are derived. A constraint of $M_f>577 GeV$ for the new fundamental scale is...

String theory suggests modifications of our spacetime such as extra dimensions and the existence of a mininal length scale. In models with addidional dimensions, the Planck scale can be lowered to values accessible by future colliders. Effective theories which extend beyond the standart-model by including extra dimensions and a minimal length allow...

The Casimir force in a system consisting of two parallel conducting plates in the presence of compactified universal extra dimensions (UXD) is analyzed. The Casimir force with UXDs differs from the force obtained without extra dimensions. A new power law for the Casimir force is derived. By comparison to experimental data the size R of the universa...

Modifications of the gyromagnetic moment of electrons and muons due to a minimal length scale combined with a modified fundamental scale M_f are explored. Deviations from the theoretical Standard Model value for g-2 are derived. Constraints for the fundamental scale M_f are given. Comment: 4 pages

String theory suggests the existence of a minimum length scale. An exciting quantum mechanical implication of this feature is a modification of the uncertainty principle. In contrast to the conventional approach, this generalised uncertainty principle does not allow to resolve space–time distances below the Planck length. In models with extra dimen...

Recent calculations applying statistical mechanics indicate that in a setting with compactified large extra dimensions a black hole might evolve into a (quasi-)stable state with mass close to the new fundamental scale Mf. Black holes and therefore their relics might be produced at the LHC in the case of extra-dimensional topologies. In this energy...

We compute the production of particles from the gravitational field of an expanding mass shell. Contrary to the situation of Hawking radiation and the production of cosmological perturbations during cosmological inflation, the example of an expanding mass shell has no horizon and no singularity. We apply the method of `ray-tracing', first introduce...

The production of black holes at Tevatron and LHC in spacetimes with compactified space-like large extra dimensions is studied. Either black holes can already be observed in p collisions at ?s = 1.8 TeV or the fundamental gravity scale has to be above 1.4 TeV. At LHC the creation of a large number of quasi-stable black holes is predicted, with life...

The production of black holes in large extra dimensions is studied for Tevatron energies. We find that black holes may have already been created in small abundance in collisions at TeV. For the next Tevatron run ( TeV) large production rates for black holes are predicted.

We address the production of black holes at LHC in space times with compactified space-like large extra dimensions (LXD). Final state black hole production leads to suppression of high-P_T jets, i.e. a sharp cut-off in the cross section for pp->jet+X. This signal is compared to the jet plus missing energy signature due to graviton production in the...

We adress the production of black holes at LHC and their time evolution in space times with compactified space like extra dimensions. It is shown that black holes with life times of hundred fm/c can be produced at LHC. The possibility of quasi-stable remnants is discussed.

We adress the production of black holes at LHC and their time evolution in space times with compactified space like extra dimensions. It is shown that black holes with life times of at least 100 fm/c will be produced in huge numbers at LHC. We discuss also the possibility of quasi-stable remnants. An outstanding problem in physics is to understand...

Frankfurt (Main), Universiẗat, Diss., 2003. Computerdatei im Fernzugriff.