{"id":{"repo_id":"freiburg-diss","oai_identifier":"oai:freidok.uni-freiburg.de:1159"},"canonical_url":"https://search.dev.ndltd.org/etd/freiburg-diss/oai:freidok.uni-freiburg.de:1159","repository":{"repo_id":"freiburg-diss","name":"University of Freiburg","base_url":"https://freidok.uni-freiburg.de/oai/oai2.php"},"display":{"title":"Die Methode der nichtlokalen effektiven Wirkung in höherdimensionalen Raumzeitmodellen","abstract":"Among the most promising candidates for a unified description of quantum
theory and gravitation is superstring theory. It predicts the existence of
multidimensional stable objects called \"branes\" (short for membranes). On
these branes open strings can end, which also means that the gauge fields
associated with the ends of a string reside on the branes. Gauge fields,
rather than spreading through the entire ten-dimensional spacetime of
superstring theory, are thus confined to these lower-dimensional objects. This
led to the proposal that the universe we inhabit could be a three-dimensional
brane on which all matter consisting of gauge fields is trapped. In string
theory, gravity is mediated by the exchange of closed strings and therefore is
not restricted to the branes but propagates through the whole
higher-dimensional spacetime, commonly called bulk. The shape of the bulk can
be constrained because no deviations from four-dimensional gravity have yet
been observed.
The study concentrates on a specific type of such \"braneworld\" models, the
Randall-Sundrum two-brane model. In this model the bulk is a slice of five
dimensional anti-de Sitter space having an orbifold at the position of both
branes. The brane tensions have the same magnitude but opposite signs and are
fine-tuned to the bulk cosmological constant in such a way that a flat metric
is induced on the branes. For this model the nonlocal braneworld action is
constructed in a holographic setup alternative to Kaluza-Klein description:
the action is written as a functional of the two metric and radion fields on
the branes. This action effectively describes the dynamics of the
gravitational field both on branes and in the bulk in terms of brane
geometries directly accessible for observations. The nonlocal form factors of
the action incorporate a cumulative effect of the bulk Kaluza-Klein
modes. Also the reduced version of this action is considered which is obtained
by integrating out the fields on the negative-tension brane invisible from the
viewpoint of an observer on the positive tension brane, \"our universe\". This
effective action features a nontrivial transition (anti-de Sitter flow)
between the local and nonlocal phases of the theory associated with the limits
of small and large brane separation. The results confirm a braneworld scenario
with diverging (repulsive) branes and suggest possible new implications of
this phase transition in brane cosmology. The relation of the nonlocal method
to the holographic description of braneworlds with an anti-de Sitter bulk by
means of the Graham-Feffermann coordinate system is examined.
Using the Randall-Sundrum model as an example a phenomenologically important
generic aspect of braneworld models is revealed. Braneworld models with
non-factorizable geometries can feature extremely light massive gravitons. If
astrophysical objects have quadrupole moments oscillating at high frequencies
they might therefore produce gravitational waves which are a superposition of
the massless and one or more massive modes. As the massive components have
propagation speeds below the speed of light, the superposition of the modes
will show an interference pattern. This interference will manifest itself as
oscillations in the intensity of a gravitational wave. The oscillation length
depends on the brane distance parameterized by the non-linear radion
field. This led to the name radion-induced graviton oscillations for the
predicted effect. In the Randall-Sundrum model in particular waves from the
negative tension brane exhibit strong oscillations on the positive tension
brane. Although these waves seem strongly suppressed at first sight by the
geometry of the bulk M-theory scaling arguments suggest that oscillations of
gravitational waves from the negative-tension brane may actually become a
relevant effect for gravitational wave astronomy. Other simple braneworld
models are discussed which show a strong mixing of modes and large amplitude
modulations although connected with oscillation lengths of cosmological
scales, which remain therefore unobservable. Graviton oscillations are treated
both in a derivative expansion of the effective action and in an expansion of
the effective four-dimensional Green function.","abstract_html":"Among the most promising candidates for a unified description of quantum <br>theory and gravitation is superstring theory. It predicts the existence of <br>multidimensional stable objects called "branes" (short for membranes). On <br>these branes open strings can end, which also means that the gauge fields <br>associated with the ends of a string reside on the branes. Gauge fields, <br>rather than spreading through the entire ten-dimensional spacetime of <br>superstring theory, are thus confined to these lower-dimensional objects. This <br>led to the proposal that the universe we inhabit could be a three-dimensional <br>brane on which all matter consisting of gauge fields is trapped. In string <br>theory, gravity is mediated by the exchange of closed strings and therefore is <br>not restricted to the branes but propagates through the whole <br>higher-dimensional spacetime, commonly called bulk. The shape of the bulk can <br>be constrained because no deviations from four-dimensional gravity have yet <br>been observed. <br> <br>The study concentrates on a specific type of such "braneworld" models, the <br>Randall-Sundrum two-brane model. In this model the bulk is a slice of five <br>dimensional anti-de Sitter space having an orbifold at the position of both <br>branes. The brane tensions have the same magnitude but opposite signs and are <br>fine-tuned to the bulk cosmological constant in such a way that a flat metric <br>is induced on the branes. For this model the nonlocal braneworld action is <br>constructed in a holographic setup alternative to Kaluza-Klein description: <br>the action is written as a functional of the two metric and radion fields on <br>the branes. This action effectively describes the dynamics of the <br>gravitational field both on branes and in the bulk in terms of brane <br>geometries directly accessible for observations. The nonlocal form factors of <br>the action incorporate a cumulative effect of the bulk Kaluza-Klein <br>modes. Also the reduced version of this action is considered which is obtained <br>by integrating out the fields on the negative-tension brane invisible from the <br>viewpoint of an observer on the positive tension brane, "our universe". This <br>effective action features a nontrivial transition (anti-de Sitter flow) <br>between the local and nonlocal phases of the theory associated with the limits <br>of small and large brane separation. The results confirm a braneworld scenario <br>with diverging (repulsive) branes and suggest possible new implications of <br>this phase transition in brane cosmology. The relation of the nonlocal method <br>to the holographic description of braneworlds with an anti-de Sitter bulk by <br>means of the Graham-Feffermann coordinate system is examined. <br> <br>Using the Randall-Sundrum model as an example a phenomenologically important <br>generic aspect of braneworld models is revealed. Braneworld models with <br>non-factorizable geometries can feature extremely light massive gravitons. If <br>astrophysical objects have quadrupole moments oscillating at high frequencies <br>they might therefore produce gravitational waves which are a superposition of <br>the massless and one or more massive modes. As the massive components have <br>propagation speeds below the speed of light, the superposition of the modes <br>will show an interference pattern. This interference will manifest itself as <br>oscillations in the intensity of a gravitational wave. The oscillation length <br>depends on the brane distance parameterized by the non-linear radion <br>field. This led to the name radion-induced graviton oscillations for the <br>predicted effect. In the Randall-Sundrum model in particular waves from the <br>negative tension brane exhibit strong oscillations on the positive tension <br>brane. Although these waves seem strongly suppressed at first sight by the <br>geometry of the bulk M-theory scaling arguments suggest that oscillations of <br>gravitational waves from the negative-tension brane may actually become a <br>relevant effect for gravitational wave astronomy. Other simple braneworld <br>models are discussed which show a strong mixing of modes and large amplitude <br>modulations although connected with oscillation lengths of cosmological <br>scales, which remain therefore unobservable. Graviton oscillations are treated <br>both in a derivative expansion of the effective action and in an expansion of <br>the effective four-dimensional Green function.","abstract_has_math":false,"creators":["Rathke, Andreas"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Römer, Hartmann"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":null,"date_issued":"","date_published":null,"updated_at":"2026-07-24T02:22:03Z","subjects":["cosmology","effective action","brane","extra dimensions","gravitational wave"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://freidok.uni-freiburg.de/data/1159","outbound_label":"Repository record","outbound_source":"source_url"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Römer, Hartmann"]},{"key":"dc:creator","label":"Author","values":["Rathke, Andreas"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:type","label":"Dc Type","values":["DoctoralThesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["cosmology","effective action","brane","extra dimensions","gravitational wave"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Among the most promising candidates for a unified description of quantum
theory and gravitation is superstring theory. It predicts the existence of
multidimensional stable objects called \"branes\" (short for membranes). On
these branes open strings can end, which also means that the gauge fields
associated with the ends of a string reside on the branes. Gauge fields,
rather than spreading through the entire ten-dimensional spacetime of
superstring theory, are thus confined to these lower-dimensional objects. This
led to the proposal that the universe we inhabit could be a three-dimensional
brane on which all matter consisting of gauge fields is trapped. In string
theory, gravity is mediated by the exchange of closed strings and therefore is
not restricted to the branes but propagates through the whole
higher-dimensional spacetime, commonly called bulk. The shape of the bulk can
be constrained because no deviations from four-dimensional gravity have yet
been observed.
The study concentrates on a specific type of such \"braneworld\" models, the
Randall-Sundrum two-brane model. In this model the bulk is a slice of five
dimensional anti-de Sitter space having an orbifold at the position of both
branes. The brane tensions have the same magnitude but opposite signs and are
fine-tuned to the bulk cosmological constant in such a way that a flat metric
is induced on the branes. For this model the nonlocal braneworld action is
constructed in a holographic setup alternative to Kaluza-Klein description:
the action is written as a functional of the two metric and radion fields on
the branes. This action effectively describes the dynamics of the
gravitational field both on branes and in the bulk in terms of brane
geometries directly accessible for observations. The nonlocal form factors of
the action incorporate a cumulative effect of the bulk Kaluza-Klein
modes. Also the reduced version of this action is considered which is obtained
by integrating out the fields on the negative-tension brane invisible from the
viewpoint of an observer on the positive tension brane, \"our universe\". This
effective action features a nontrivial transition (anti-de Sitter flow)
between the local and nonlocal phases of the theory associated with the limits
of small and large brane separation. The results confirm a braneworld scenario
with diverging (repulsive) branes and suggest possible new implications of
this phase transition in brane cosmology. The relation of the nonlocal method
to the holographic description of braneworlds with an anti-de Sitter bulk by
means of the Graham-Feffermann coordinate system is examined.
Using the Randall-Sundrum model as an example a phenomenologically important
generic aspect of braneworld models is revealed. Braneworld models with
non-factorizable geometries can feature extremely light massive gravitons. If
astrophysical objects have quadrupole moments oscillating at high frequencies
they might therefore produce gravitational waves which are a superposition of
the massless and one or more massive modes. As the massive components have
propagation speeds below the speed of light, the superposition of the modes
will show an interference pattern. This interference will manifest itself as
oscillations in the intensity of a gravitational wave. The oscillation length
depends on the brane distance parameterized by the non-linear radion
field. This led to the name radion-induced graviton oscillations for the
predicted effect. In the Randall-Sundrum model in particular waves from the
negative tension brane exhibit strong oscillations on the positive tension
brane. Although these waves seem strongly suppressed at first sight by the
geometry of the bulk M-theory scaling arguments suggest that oscillations of
gravitational waves from the negative-tension brane may actually become a
relevant effect for gravitational wave astronomy. Other simple braneworld
models are discussed which show a strong mixing of modes and large amplitude
modulations although connected with oscillation lengths of cosmological
scales, which remain therefore unobservable. Graviton oscillations are treated
both in a derivative expansion of the effective action and in an expansion of
the effective four-dimensional Green function.","Unter den vielversprechendsten Kandidaten für eine vereinheitlichte
Beschreibung von Quantentheorie und Gravitation ist die Superstringtheorie.
Sie sagt die Existenz von mehrdimensional stabilen Objekten sogenannten Branes
(kurz für Membranes) voraus. Auf diesen Branes können offene Strings enden,
was gleichzeitig bedeutet, daß die Eichfelder, die mit den String-Enden
verknüpft sind, auf den Branes sitzen. Anstatt sich durch die gesamte
zehndimensionale Raumzeit der Superstringtheorie auszubreiten, sind Eichfelder
daher auf diese niedrigerdimensionalen Objekt eingeschränkt. Diese Beobachtung
führte zu der Idee, daß unser Universum eine dreidimensionale Brane sein
könnte, auf der alle aus Eichfeldern bestehende Materie gefangen ist. In der
Stringtheorie wird die Gravitation durch geschlossene Strings beschrieben und
ist daher nicht auf die Branes eingeschränkt sondern propagiert durch die
gesamte höherdimensionale Raumzeit, die meist als Bulk (Hauptteil) bezeichnet
wird. Die mögliche Form des Bulk ist dadurch erheblich eingeschränkt, daß
bislang keinerlei Abweichung der Gravitation vom vierdimensionalen Verhalten
beobachtet wurden.
Die vorliegende Untersuchung konzentriert sich auf einen bestimmten Typ
solcher Branewelten, das Randall-Sundrum-zwei-Brane-Modell. In diesem Modell
ist der Bulk ein Abschnitt eines fünfdimensionalen Anti-de Sitter-Raums, der
an der Position beider Branes einen Orbifold hat. Die Brane-Spannungen sind
gleichgroß mit entgegengesetztem Vorzeichen und so auf die kosmologische
Konstante des Bulk abgestimmt, daß auf die Branes eine flache Metrik induziert
wird. Für dieses Modell wird die nichtlokale Branewelt-Wirkung in einem
holographischen Zugang konstruiert, der eine Alternative zur
Kaluza-Klein-Beschreibung bietet: Die Wirkung wird als Funktional der beiden
Metriken und Radion-Feldern auf den Branes dargestellt. Diese Wirkung
beschreibt erfolgreich die Dynamik des Gravitationsfeldes auf den Branes und
im Bulk mit Hilfe der Brane-Geometrien, die der Beobachtung direkt zugänglich
sind. Die nichtlokalen Formfaktoren der Wirkung umfassen den kumulativen
Effekt der Kaluza-Klein-Moden des Bulk. Zusätzlich wird die reduzierte Version
dieser Wirkung untersucht. Sie ergibt sich, wenn man die Felder auf der Brane
mit negativer Spannung ausintegriert, die aus der Sicht eines Beobachters auf
der Brane mit positiver Spannung, \"in unserem Universum\", unbeobachtbar
sind. Diese effektive Wirkung zeigt einen nichttrivialen Phasenübergang
(Anti-de Sitter-Fluß) zwischen der lokalen und der nichtlokalen Phase der
Theorie, die mit den Grenzfällen kleinen und großen Brane-Abstands verbunden
sind. Die Resultate bestätigen ein Branewelt-Szenario mit
auseinanderstrebenden (repulsiven) Branes und legen neue Implikationen dieses
Phasenübergangs für die Brane-Kosmologie nahe. Die Beziehung der nichtlokalen
Methode zur holographischen Beschreibung von Branewelten in einem Anti-de
Sitter-Bulk mit Hilfe des Feffermann-Graham Koordinatensystems wird
beleuchtet.
Auch ein generischer Aspekt von Branewelt-Modellen von phänomenologischer
Bedeutung wird anhand des Randall-Sundrum-Modells offengelegt. Die Grundlage
dafür bietet das mögliche Auftreten von extrem leichten massiven Gravitonen in
Branewelt-Modellen mit nicht-faktorisierbarer Geometrie. Falls
astrophysikalische Objekte Quadrupolmomente aufweisen, die mit großer Frequenz
oszillieren, könnten sie daher Gravitationswellen erzeugen, die eine
Superposition der masselosen und einer oder mehrerer massiver Moden
darstellen. Da die massiven Komponenten Ausbreitungsgeschwindigkeiten
unterhalb der Lichtgeschwindigkeit haben, würde die Superposition der Moden
ein Interferenzmuster zeigen. Diese Interferenz würde sich als Oszillation in
der Intensität der Gravitationswelle niederschlagen. Die Oszillationslänge
hängt vom Brane-Abstand ab, der durch das nichtlineare Radion-Feld
parametrisiert ist. Dies legt den Namen Radion-induzierte
Graviton-Oszillationen für den vorhergesagten Effekt nahe. Im
Randall-Sundrum-Modell zeigen insbesondere Wellen, die auf der Brane mit
negativer Spannung entstehen, auf der Brane positiver Spannung starke
Oszillationen. Obwohl diese Wellen auf den ersten Blick durch die Geometrie
des Bulks stark unterdrückt erscheinen, legen M-Theorie-motivierte
Skalierungsargumente nahe, daß Oszillationen in Gravitationswellen von der
Brane mit negativer Spannung tatsächlich ein relevanter Effekt für die
Gravitationswellen-Astronomie sein könnten. Andere einfache Branewelt-Modelle
mit einer starken Mischung der Moden bei gleichzeitiger starker
Amplitudenmodulation, die allerdings mit Oszillationslängen von kosmologischer
Größenordnung einhergeht und daher unbeobachtbar bleibt, werden
diskutiert. Graviton-Oszillationen werden sowohl in einer Reihenentwicklung
der effektiven Wirkung als auch in einer Entwicklung der effektiven
vierdimensionalen Greenfunktion behandelt."]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Die Methode der nichtlokalen effektiven Wirkung in höherdimensionalen Raumzeitmodellen","The method of the nonlocal effective action in higher-dimensional spacetime models"]}]}],"canonical_facts":{"dc:contributor":["Römer, Hartmann"],"dc:creator":["Rathke, Andreas"],"dc:description.abstract":["Among the most promising candidates for a unified description of quantum
theory and gravitation is superstring theory. It predicts the existence of
multidimensional stable objects called \"branes\" (short for membranes). On
these branes open strings can end, which also means that the gauge fields
associated with the ends of a string reside on the branes. Gauge fields,
rather than spreading through the entire ten-dimensional spacetime of
superstring theory, are thus confined to these lower-dimensional objects. This
led to the proposal that the universe we inhabit could be a three-dimensional
brane on which all matter consisting of gauge fields is trapped. In string
theory, gravity is mediated by the exchange of closed strings and therefore is
not restricted to the branes but propagates through the whole
higher-dimensional spacetime, commonly called bulk. The shape of the bulk can
be constrained because no deviations from four-dimensional gravity have yet
been observed.
The study concentrates on a specific type of such \"braneworld\" models, the
Randall-Sundrum two-brane model. In this model the bulk is a slice of five
dimensional anti-de Sitter space having an orbifold at the position of both
branes. The brane tensions have the same magnitude but opposite signs and are
fine-tuned to the bulk cosmological constant in such a way that a flat metric
is induced on the branes. For this model the nonlocal braneworld action is
constructed in a holographic setup alternative to Kaluza-Klein description:
the action is written as a functional of the two metric and radion fields on
the branes. This action effectively describes the dynamics of the
gravitational field both on branes and in the bulk in terms of brane
geometries directly accessible for observations. The nonlocal form factors of
the action incorporate a cumulative effect of the bulk Kaluza-Klein
modes. Also the reduced version of this action is considered which is obtained
by integrating out the fields on the negative-tension brane invisible from the
viewpoint of an observer on the positive tension brane, \"our universe\". This
effective action features a nontrivial transition (anti-de Sitter flow)
between the local and nonlocal phases of the theory associated with the limits
of small and large brane separation. The results confirm a braneworld scenario
with diverging (repulsive) branes and suggest possible new implications of
this phase transition in brane cosmology. The relation of the nonlocal method
to the holographic description of braneworlds with an anti-de Sitter bulk by
means of the Graham-Feffermann coordinate system is examined.
Using the Randall-Sundrum model as an example a phenomenologically important
generic aspect of braneworld models is revealed. Braneworld models with
non-factorizable geometries can feature extremely light massive gravitons. If
astrophysical objects have quadrupole moments oscillating at high frequencies
they might therefore produce gravitational waves which are a superposition of
the massless and one or more massive modes. As the massive components have
propagation speeds below the speed of light, the superposition of the modes
will show an interference pattern. This interference will manifest itself as
oscillations in the intensity of a gravitational wave. The oscillation length
depends on the brane distance parameterized by the non-linear radion
field. This led to the name radion-induced graviton oscillations for the
predicted effect. In the Randall-Sundrum model in particular waves from the
negative tension brane exhibit strong oscillations on the positive tension
brane. Although these waves seem strongly suppressed at first sight by the
geometry of the bulk M-theory scaling arguments suggest that oscillations of
gravitational waves from the negative-tension brane may actually become a
relevant effect for gravitational wave astronomy. Other simple braneworld
models are discussed which show a strong mixing of modes and large amplitude
modulations although connected with oscillation lengths of cosmological
scales, which remain therefore unobservable. Graviton oscillations are treated
both in a derivative expansion of the effective action and in an expansion of
the effective four-dimensional Green function.","Unter den vielversprechendsten Kandidaten für eine vereinheitlichte
Beschreibung von Quantentheorie und Gravitation ist die Superstringtheorie.
Sie sagt die Existenz von mehrdimensional stabilen Objekten sogenannten Branes
(kurz für Membranes) voraus. Auf diesen Branes können offene Strings enden,
was gleichzeitig bedeutet, daß die Eichfelder, die mit den String-Enden
verknüpft sind, auf den Branes sitzen. Anstatt sich durch die gesamte
zehndimensionale Raumzeit der Superstringtheorie auszubreiten, sind Eichfelder
daher auf diese niedrigerdimensionalen Objekt eingeschränkt. Diese Beobachtung
führte zu der Idee, daß unser Universum eine dreidimensionale Brane sein
könnte, auf der alle aus Eichfeldern bestehende Materie gefangen ist. In der
Stringtheorie wird die Gravitation durch geschlossene Strings beschrieben und
ist daher nicht auf die Branes eingeschränkt sondern propagiert durch die
gesamte höherdimensionale Raumzeit, die meist als Bulk (Hauptteil) bezeichnet
wird. Die mögliche Form des Bulk ist dadurch erheblich eingeschränkt, daß
bislang keinerlei Abweichung der Gravitation vom vierdimensionalen Verhalten
beobachtet wurden.
Die vorliegende Untersuchung konzentriert sich auf einen bestimmten Typ
solcher Branewelten, das Randall-Sundrum-zwei-Brane-Modell. In diesem Modell
ist der Bulk ein Abschnitt eines fünfdimensionalen Anti-de Sitter-Raums, der
an der Position beider Branes einen Orbifold hat. Die Brane-Spannungen sind
gleichgroß mit entgegengesetztem Vorzeichen und so auf die kosmologische
Konstante des Bulk abgestimmt, daß auf die Branes eine flache Metrik induziert
wird. Für dieses Modell wird die nichtlokale Branewelt-Wirkung in einem
holographischen Zugang konstruiert, der eine Alternative zur
Kaluza-Klein-Beschreibung bietet: Die Wirkung wird als Funktional der beiden
Metriken und Radion-Feldern auf den Branes dargestellt. Diese Wirkung
beschreibt erfolgreich die Dynamik des Gravitationsfeldes auf den Branes und
im Bulk mit Hilfe der Brane-Geometrien, die der Beobachtung direkt zugänglich
sind. Die nichtlokalen Formfaktoren der Wirkung umfassen den kumulativen
Effekt der Kaluza-Klein-Moden des Bulk. Zusätzlich wird die reduzierte Version
dieser Wirkung untersucht. Sie ergibt sich, wenn man die Felder auf der Brane
mit negativer Spannung ausintegriert, die aus der Sicht eines Beobachters auf
der Brane mit positiver Spannung, \"in unserem Universum\", unbeobachtbar
sind. Diese effektive Wirkung zeigt einen nichttrivialen Phasenübergang
(Anti-de Sitter-Fluß) zwischen der lokalen und der nichtlokalen Phase der
Theorie, die mit den Grenzfällen kleinen und großen Brane-Abstands verbunden
sind. Die Resultate bestätigen ein Branewelt-Szenario mit
auseinanderstrebenden (repulsiven) Branes und legen neue Implikationen dieses
Phasenübergangs für die Brane-Kosmologie nahe. Die Beziehung der nichtlokalen
Methode zur holographischen Beschreibung von Branewelten in einem Anti-de
Sitter-Bulk mit Hilfe des Feffermann-Graham Koordinatensystems wird
beleuchtet.
Auch ein generischer Aspekt von Branewelt-Modellen von phänomenologischer
Bedeutung wird anhand des Randall-Sundrum-Modells offengelegt. Die Grundlage
dafür bietet das mögliche Auftreten von extrem leichten massiven Gravitonen in
Branewelt-Modellen mit nicht-faktorisierbarer Geometrie. Falls
astrophysikalische Objekte Quadrupolmomente aufweisen, die mit großer Frequenz
oszillieren, könnten sie daher Gravitationswellen erzeugen, die eine
Superposition der masselosen und einer oder mehrerer massiver Moden
darstellen. Da die massiven Komponenten Ausbreitungsgeschwindigkeiten
unterhalb der Lichtgeschwindigkeit haben, würde die Superposition der Moden
ein Interferenzmuster zeigen. Diese Interferenz würde sich als Oszillation in
der Intensität der Gravitationswelle niederschlagen. Die Oszillationslänge
hängt vom Brane-Abstand ab, der durch das nichtlineare Radion-Feld
parametrisiert ist. Dies legt den Namen Radion-induzierte
Graviton-Oszillationen für den vorhergesagten Effekt nahe. Im
Randall-Sundrum-Modell zeigen insbesondere Wellen, die auf der Brane mit
negativer Spannung entstehen, auf der Brane positiver Spannung starke
Oszillationen. Obwohl diese Wellen auf den ersten Blick durch die Geometrie
des Bulks stark unterdrückt erscheinen, legen M-Theorie-motivierte
Skalierungsargumente nahe, daß Oszillationen in Gravitationswellen von der
Brane mit negativer Spannung tatsächlich ein relevanter Effekt für die
Gravitationswellen-Astronomie sein könnten. Andere einfache Branewelt-Modelle
mit einer starken Mischung der Moden bei gleichzeitiger starker
Amplitudenmodulation, die allerdings mit Oszillationslängen von kosmologischer
Größenordnung einhergeht und daher unbeobachtbar bleibt, werden
diskutiert. Graviton-Oszillationen werden sowohl in einer Reihenentwicklung
der effektiven Wirkung als auch in einer Entwicklung der effektiven
vierdimensionalen Greenfunktion behandelt."],"dc:format.medium":["application/pdf"],"dc:subject":["cosmology","effective action","brane","extra dimensions","gravitational wave"],"dc:title":["Die Methode der nichtlokalen effektiven Wirkung in höherdimensionalen Raumzeitmodellen","The method of the nonlocal effective action in higher-dimensional spacetime models"],"dc:type":["DoctoralThesis"]},"updated_at":"2026-07-24T02:22:03Z"}